Formulation, Optimization and In vitro Characterization of Pioglitazone - Glimepiride Nanosuspension for Enhanced Type 2 Diabetes Therapy

Diabetes Mellitus is a chronic metabolic disorder characterized by persistent hyperglycemia resulting from defects in insulin secretion, insulin action, or both. It represents a spectrum of metabolic abnormalities affecting carbohydrate, lipid, and protein metabolism, which can lead to long-term microvascular and macrovascular complications. The disease is globally recognized as one of the most significant public health challenges due to its increasing prevalence, morbidity, and mortality. This condition impairs the body's ability to regulate blood glucose levels, resulting in long-term damage, dysfunction, and failure of various organs, particularly the eyes, kidneys, nerves, heart, and blood vessels. The pathophysiology of diabetes involves impaired glucose uptake by cells, leading to elevated blood sugar levels, which can cause both acute and chronic complications. Acute manifestations include polyuria, polydipsia, weight loss, and fatigue, while chronic complications range from neuropathy and retinopathy to nephropathy and cardiovascular disease⁽¹⁾. Risk factors include genetic predisposition, obesity, sedentary lifestyle, and poor dietary habits. Diagnostic criteria typically involve elevated fasting blood glucose levels, abnormal oral glucose tolerance test results, or increased glycated hemoglobin (HbA1c) levels. Management of diabetes mellitus includes lifestyle modification, dietary regulation, regular physical activity, and pharmacological interventions such as oral hypoglycemic agents or insulin therapy, depending on the severity and progression of the condition⁽²⁾. Despite advances in treatment, diabetes remains a major public health concern globally due to its increasing prevalence and associated healthcare burden. Early detection, continuous monitoring, and patient education play a vital role in controlling disease progression and minimizing complications. Ongoing research is also focused on improving therapeutic approaches, including the development of novel drugs and regenerative medicine techniques aimed at restoring pancreatic function or enhancing insulin sensitivity.

According to the International Diabetes Federation (IDF), more than 530 million people worldwide are currently living with diabetes, and the number is projected to rise to 643 million by 2030 and 783 million by 2045⁽³⁾. India is among the leading countries with the highest burden of diabetic patients, often referred to as the "Diabetes Capital of the World."

TYPES OF DIABETIC MELLITUS:

Diabetes mellitus is a group of metabolic disorders characterized by chronic hyperglycemia resulting from defects in insulin secretion, insulin action, or both. It is broadly classified into several types, with the most common being Type 1, Type 2, and gestational diabetes mellitus (GDM) Monogenic Diabetes, Secondary Diabetes.

Type 1 Diabetes Mellitus (T1DM) is a chronic autoimmune disorder characterized by the destruction of insulin-producing β-cells in the pancreas, leading to an absolute insulin deficiency. It typically manifests in childhood or adolescence but can occur at any age. The exact cause of T1DM is multifactorial, involving a combination of genetic predisposition and environmental triggers such as viral infections, diet, or toxins. Human leukocyte antigen (HLA) genes play a significant role in susceptibility to T1DM, especially HLA-DR3 and DR4 alleles. The autoimmune response leads to a gradual depletion of β-cells, which results in elevated blood glucose levels (hyperglycemia)⁽⁴⁾. Clinical symptoms often appear suddenly and include excessive thirst (polydipsia), frequent urination (polyuria), weight loss, fatigue, and sometimes diabetic ketoacidosis (DKA), a life-threatening condition. Diagnosis is confirmed through blood tests showing hyperglycemia, low or undetectable levels of insulin and C-peptide, and the presence of autoantibodies such as GAD65, IA-2, or ZnT8. Management of T1DM requires lifelong insulin therapy, either through multiple daily injections or continuous subcutaneous insulin infusion via a pump⁽⁵⁾. Blood glucose monitoring, carbohydrate counting, regular physical activity, and patient education are essential for optimal glycemic control and prevention of complications. Despite advances in insulin delivery and glucose monitoring technologies, achieving normoglycemia remains challenging for many patients. Ongoing research focuses on immune modulation, β-cell regeneration, and artificial pancreas systems to improve quality of life and potentially cure the disease.

Type 2 Diabetes Mellitus (T2DM) is a chronic metabolic disorder characterized by insulin resistance and relative insulin deficiency, leading to elevated blood glucose levels. It is the most common form of diabetes, accounting for over 90% of all diabetes cases globally. The condition develops gradually, often associated with lifestyle factors such as physical inactivity, poor diet, obesity, and genetic predisposition. Unlike Type 1 diabetes, where there is an absolute deficiency of insulin due to autoimmune destruction of pancreatic β-cells, T2DM results from the body's inability to use insulin effectively, known as insulin resistance, along with a progressive decline in insulin secretion⁽⁶⁾. T2DM is commonly diagnosed in adults, but its prevalence in younger populations is rising due to increasing rates of childhood obesity. The disease often remains asymptomatic in its early stages, making early detection challenging. Common symptoms, when present, include increased thirst, frequent urination, fatigue, blurred vision, and slow-healing wounds. If left uncontrolled, T2DM can lead to serious complications such as cardiovascular disease, nephropathy, neuropathy, and retinopathy. Management of T2DM includes lifestyle interventions like regular physical activity, dietary modifications, and weight loss. Pharmacological treatments, including metformin, sulfonylureas, DPP-4 inhibitors, GLP-1 receptor agonists, and insulin therapy, are used based on individual needs and disease progression. Early diagnosis and comprehensive management are crucial to preventing complications and improving quality of life⁽⁷⁾.

Pathophysiology of Type 2 Diabetes Mellitus:

• T2DM is a multifactorial disease characterized by:
• Insulin resistance in skeletal muscle, liver, and adipose tissue.
• β-cell dysfunction with progressive decline in insulin secretion.
• Increased hepatic glucose output.
• Dysregulation of incretin hormones and adipokines⁽⁸⁾.

These alterations lead to chronic hyperglycemia, oxidative stress, and inflammatory changes, contributing to vascular complications.

Gestational Diabetes Mellitus (GDM) is a form of glucose intolerance that is first recognized during pregnancy, typically in the second or third trimester. It arises when the body cannot produce enough insulin to meet the increased demands during pregnancy, leading to elevated blood glucose levels. GDM is one of the most common pregnancy complications, affecting approximately 7–10% of pregnancies worldwide. Risk factors include obesity, advanced maternal age, family history of type 2 diabetes, previous GDM, and belonging to certain ethnic groups with higher diabetes prevalence. The pathophysiology of GDM involves a combination of insulin resistance and inadequate pancreatic beta-cell function. Placental hormones such as human placental lactogen, progesterone, and cortisol contribute to insulin resistance, while genetic and environmental factors may impair insulin secretion. If untreated, GDM can result in adverse outcomes such as macrosomia, preeclampsia, neonatal hypoglycemia, and increased risk of cesarean delivery. Moreover, both mother and child face an elevated long-term risk of developing type 2 diabetes and metabolic syndrome later in life. Management of GDM includes lifestyle modifications, such as dietary changes and regular physical activity. If glycemic targets are not met through these means, insulin therapy or oral hypoglycemic agents may be required. Early diagnosis through glucose tolerance testing and proper glycemic control are essential to minimize complications. Postpartum follow-up is also crucial for monitoring and preventing progression to chronic diabetes⁽⁹⁾.

Monogenic diabetes is a rare form of diabetes caused by a single gene mutation, unlike the more common forms like Type 1 and Type 2 diabetes, which are influenced by multiple genetic and environmental factors. It typically results from mutations in genes involved in insulin production or beta-cell function, leading to impaired insulin secretion. The most common forms of monogenic diabetes are neonatal diabetes and maturity-onset diabetes of the young (MODY). Neonatal diabetes occurs in infants under six months, while MODY usually manifests before the age of 25. Both types are distinct from type 1 diabetes as they do not involve an autoimmune process. Early diagnosis is crucial, as the condition can often be managed with oral medications rather than insulin. Genetic testing can help identify the specific mutations and guide treatment decisions. Monogenic diabetes accounts for a small percentage of all diabetes cases but highlights the importance of genetic factors in the development of the disease. The identification of monogenic diabetes has significant implications for personalized medicine, offering a more targeted and effective approach to treatment compared to conventional diabetes management strategies.

Secondary diabetes refers to a form of diabetes that is caused by another underlying condition or factor. Unlike primary diabetes, such as Type 1 or Type 2 diabetes, secondary diabetes is the result of another disease or medication that disrupts the normal functioning of insulin or glucose metabolism⁽¹⁰⁾. Conditions like pancreatitis, cystic fibrosis, or hormonal disorders (such as Cushing’s syndrome) can lead to secondary diabetes. Certain medications, especially glucocorticoids, can also induce secondary diabetes by impairing insulin sensitivity or secretion. The pathophysiology of secondary diabetes varies based on the underlying cause, but it often involves insulin resistance or a reduction in insulin production. Managing secondary diabetes typically requires addressing the root cause, whether it's through managing the underlying disease or adjusting medication. Insulin therapy and other diabetic medications may also be necessary to regulate blood sugar levels. Early detection and treatment are crucial to prevent long-term complications, including cardiovascular disease, neuropathy, and retinopathy. Unlike primary diabetes, secondary diabetes can be reversed or improved once the underlying cause is treated. However, it is essential to regularly monitor blood glucose levels to assess the effectiveness of treatment.

CAUSE OF DIABETIC MELLITUS:

Diabetes mellitus is a complex metabolic disorder characterized by high blood glucose levels resulting from either insufficient insulin production or poor cellular response to insulin. The root cause of diabetes can be broadly categorized into type 1 and type 2 diabetes. Type 1 diabetes is primarily an autoimmune disorder where the immune system mistakenly attacks and destroys insulin-producing beta cells in the pancreas, leading to insulin deficiency. Genetic factors and environmental triggers, such as viral infections, contribute to the onset of type 1 diabetes. On the other hand, type 2 diabetes is mainly caused by insulin resistance, where the body’s cells become less responsive to insulin. Over time, the pancreas cannot produce enough insulin to compensate for the resistance, leading to elevated blood glucose levels. Type 2 diabetes is strongly linked to lifestyle factors such as obesity, physical inactivity, and poor diet, alongside genetic predisposition. In both types, the body’s inability to maintain normal blood sugar levels can result in long-term complications, such as cardiovascular disease, kidney failure, and nerve damage. Understanding the root causes of diabetes is crucial for early prevention, diagnosis, and management of the disease. Rapid industrialization, urbanization, and modernization have led to major lifestyle transitions that significantly increase the risk of Type 2 Diabetes Mellitus (T2DM)⁽¹¹⁾.

LIFESTYLE MODIFICATIONS CONTRIBUTING TO DIABETES MELLITUS:

• Unhealthy Diet & Excessive consumption of refined carbohydrates, saturated fats, sugary beverages, and processed foods.
• Low intake of dietary fiber, whole grains, fruits, and vegetables.
• Frequent fast-food consumption promotes obesity and insulin resistance.
• Physical Inactivity
• Sedentary lifestyle due to desk jobs, increased screen time, and lack of regular physical activity.
• Reduced energy expenditure promotes central obesity, a major risk factor for metabolic syndrome and T2DM.
• Obesity and Central Adiposity
• Obesity, especially visceral fat deposition, is closely linked with insulin resistance.
• Adipose tissue secretes free fatty acids and pro-inflammatory cytokines (TNF-α, IL-6), impairing insulin signaling.
• Psychological Stress and Sleep Disturbance
• Chronic stress increases cortisol and catecholamine levels, leading to hyperglycemia.
• Poor sleep quality and sleep apnea alter glucose metabolism and insulin sensitivity.
• Excessive alcohol consumption contributes to hepatic steatosis and insulin resistance.
• Tobacco smoking accelerates oxidative stress and increases the risk of T2DM and its complications.
• Urbanization and Socioeconomic Transition
• Shift from traditional diets to high-calorie western diets.
• Reduced occupational physical activity due to mechanization.
• Increased prevalence of childhood and adolescent obesity⁽¹²⁾.

THE TREATMENT APPROACH FOR DIABETES MELLITUS (DM)

Lifestyle modifications are a cornerstone in managing Diabetes Mellitus (DM) and play a crucial role in controlling blood sugar levels, improving overall health, and preventing complications. A healthy diet is essential, focusing on foods with low glycemic indexes, high fiber content, and balanced carbohydrates, while avoiding processed sugars and refined grains. Regular physical activity, such as walking, cycling, or resistance training, enhances insulin sensitivity and helps control blood glucose levels. The American Diabetes Association (ADA) recommends at least 150 minutes of moderate-intensity exercise per week. Additionally, weight management is critical, as reducing excess weight can significantly improve insulin sensitivity, especially in Type 2 DM. Stress management techniques, such as mindfulness or relaxation exercises, can also be beneficial, as stress can affect blood sugar levels. These lifestyle changes, when combined with consistent blood glucose monitoring, are integral in achieving long-term glycemic control and minimizing complications⁽¹³⁾.

Involves managing blood sugar levels, preventing complications, and improving quality of life.

• Preventive Role of Lifestyle Modifications
• Extensive clinical trials, such as the Diabetes Prevention Program (DPP) and the Finnish Diabetes Prevention Study, have demonstrated that lifestyle interventions can significantly reduce the incidence of T2DM among high-risk individuals. Key recommendations include:
• Adoption of a balanced diet rich in fiber, low in glycemic index foods, lean proteins, and healthy fats.
• Engaging in at least 150 minutes of moderate physical activity per week (e.g., brisk walking, cycling, swimming).
• Maintaining a healthy body weight (BMI < 25 kg/m²).
• Stress management through yoga, meditation, and adequate sleep.
• Avoid smoking and limit alcohol consumption.

Education and Support in the Treatment of Diabetes Mellitus

Education and patient support are vital components in the comprehensive treatment approach to Diabetes Mellitus (DM). While pharmacological therapy (insulin, oral hypoglycemic agents, and newer antidiabetic drugs) remains essential, long-term success in managing diabetes relies heavily on patient knowledge, self-care practices, and continuous psychosocial support.

1. Role of Diabetes Education

• Understanding the disease: Educating patients about the pathophysiology of diabetes, its complications, and the importance of glycemic control helps improve treatment adherence. Self-monitoring skills: Patients must learn how to monitor blood glucose levels, interpret readings, and take corrective actions.
• Medication adherence: Proper education ensures patients understand the dosage, timing, and possible side effects of medications, reducing non-compliance.
• Dietary guidance: Education empowers patients to make informed food choices, count carbohydrates, and follow individualized meal plans.
• Exercise knowledge: Patients are taught safe and effective ways to incorporate physical activity into daily routines⁽¹⁴⁾.

2. Importance of Support Systems

• Healthcare Team Support: Regular counseling by physicians, pharmacists, dietitians, and diabetes educators helps reinforce healthy behaviors.
• Family Support: Family members play a key role in providing emotional encouragement, helping with diet preparation, and reminding patients about medication and checkups.
• Peer Support Groups: Interactions with other diabetic patients reduce feelings of isolation, enhance coping skills, and promote shared learning.
• Technology Support: Mobile health apps, glucose monitors, and telemedicine platforms provide real-time feedback and motivation.

3. Psychosocial and Behavioral Support

• Addressing stress, anxiety, and depression is crucial since these factors negatively affect glycemic control.
• Structured support programs improve self-efficacy, motivation, and long-term commitment to lifestyle modifications.
• Behavioral counseling helps prevent burnout and promotes consistent adherence to therapy.

Medication Treatment Approach for Diabetes Mellitus⁽¹⁵⁾

The pharmacological management of Diabetes Mellitus (DM) is a cornerstone in achieving optimal glycemic control, preventing acute and chronic complications, and improving the quality of life of patients. The treatment approach is individualized and depends on the type of diabetes, severity of hyperglycemia, presence of comorbidities, age, body weight, and patient preferences. In Type 1 Diabetes Mellitus (T1DM), characterized by absolute insulin deficiency due to autoimmune destruction of pancreatic β-cells, insulin therapy is mandatory. Regimens may include multiple daily injections using basal and bolus insulins or continuous subcutaneous insulin infusion via pumps, aiming to mimic physiological insulin secretion and maintain target glycemic levels while minimizing hypoglycemia.

In Type 2 Diabetes Mellitus (T2DM), which accounts for the majority of cases, pharmacological therapy is often initiated after lifestyle modifications fail to achieve adequate glycemic control. Metformin, a biguanide, is the preferred first-line therapy due to its ability to reduce hepatic glucose production and improve insulin sensitivity, along with benefits of weight neutrality and cardiovascular protection. When monotherapy is insufficient, combination therapy with other classes of drugs may be employed. Sulfonylureas such as glimepiride stimulate pancreatic insulin secretion but carry a risk of hypoglycemia and weight gain. Thiazolidinediones (e.g. pioglitazone) improve peripheral insulin sensitivity but are associated with fluid retention and potential cardiac risks. Dipeptidyl peptidase-4 (DPP-4) inhibitors and glucagon-like peptide-1 (GLP-1) receptor agonists enhance incretin action, increasing glucose-dependent insulin release while reducing postprandial hyperglycemia, with GLP-1 agonists also promoting weight loss and cardiovascular benefits. Sodium-glucose co-transporter-2 (SGLT2) inhibitors lower blood glucose by promoting renal glucose excretion and additionally provide benefits in weight reduction, blood pressure control, and cardiovascular protection. Other agents such as alpha-glucosidase inhibitors and meglitinides are used to specifically control postprandial hyperglycemia through inhibition of intestinal carbohydrate digestion or rapid insulin stimulation, respectively.

In cases of advanced T2DM, when oral antidiabetic agents fail to maintain glycemic targets, insulin therapy is introduced, either alone or in combination with oral drugs, to achieve optimal glucose control. For gestational diabetes mellitus (GDM), insulin remains the standard therapy when lifestyle interventions are inadequate, though select oral agents like metformin may be used cautiously under supervision. Combination therapy, such as the co-administration of pioglitazone and glimepiride, targets both insulin resistance and inadequate insulin secretion, providing synergistic effects in glycemic control. The medication treatment approach for DM emphasizes individualized therapy, integrating patient-specific factors, pharmacodynamics, and safety profiles of drugs. Pharmacological therapy is most effective when combined with lifestyle modifications, patient education, and continuous monitoring, enabling sustained glycemic control, reducing the risk of complications, and improving long-term outcomes in diabetes management. The pharmacological classification of antidiabetic drugs is primarily based on their mechanism of action and their effect on glucose metabolism. This classification helps clinicians select appropriate therapy tailored to the patient’s pathophysiology, disease severity, and comorbid conditions. Antidiabetic drugs are divided into oral hypoglycemic agents and insulin therapy, with each category containing subclasses with distinct mechanisms⁽¹⁶⁾.

• Biguanides: The most commonly prescribed biguanide is metformin, which primarily reduces hepatic glucose production by inhibiting gluconeogenesis, while also enhancing insulin sensitivity in peripheral tissues such as muscle and adipose tissue. Metformin is considered first-line therapy for type 2 diabetes mellitus (T2DM) due to its efficacy, low risk of hypoglycemia, weight-neutral effect, and favorable cardiovascular outcomes.
• Sulfonylureas: These drugs, including glimepiride, glibenclamide, and gliclazide, act by stimulating pancreatic β-cells to secrete insulin. Sulfonylureas are effective in lowering both fasting and postprandial blood glucose levels. However, their use is associated with potential hypoglycemia and weight gain. They are often used as second-line therapy or in combination with other agents.
• Meglitinides (Glinides): Drugs such as repaglinide and nateglinide are short-acting insulin secretagogues that enhance postprandial insulin release. They are particularly useful for controlling postprandial hyperglycemia and offer flexibility in dosing with meals, with a lower risk of prolonged hypoglycemia compared to sulfonylureas⁽¹⁷⁾.
• Thiazolidinediones (Glitazones): Pioglitazone and rosiglitazone improve insulin sensitivity in peripheral tissues by activating peroxisome proliferator-activated receptor gamma (PPAR-γ). These agents primarily reduce insulin resistance and improve glycemic control in T2DM. Their adverse effects include fluid retention, weight gain, and potential cardiovascular concerns, which require careful patient monitoring.
• Dipeptidyl Peptidase-4 (DPP-4) Inhibitors: Drugs like sitagliptin, vildagliptin, and linagliptin inhibit the enzyme DPP-4, prolonging the action of incretin hormones such as GLP-1. This results in glucose-dependent insulin secretion and reduced glucagon release. These drugs are generally well-tolerated, weight-neutral, and carry a low risk of hypoglycemia.
• Glucagon-Like Peptide-1 (GLP-1) Receptor Agonists: Liraglutide, dulaglutide, and exenatide mimic endogenous GLP-1, enhancing insulin secretion in a glucose-dependent manner, suppressing glucagon, slowing gastric emptying, and promoting satiety. GLP-1 receptor agonists are effective in glycemic control, weight reduction, and have demonstrated cardiovascular benefits.
• Sodium-Glucose Co-Transporter 2 (SGLT2) Inhibitors: Drugs such as dapagliflozin, empagliflozin, and canagliflozin act on the kidneys to inhibit glucose reabsorption in the proximal tubules, leading to urinary glucose excretion. These agents provide additional benefits, including weight loss, blood pressure reduction, and cardiovascular and renal protection, but may increase the risk of urinary tract and genital infections⁽¹⁸⁾.
• Alpha-Glucosidase Inhibitors: Acarbose and miglitol inhibit intestinal alpha-glucosidase enzymes, delaying the breakdown and absorption of complex carbohydrates. This primarily reduces postprandial hyperglycemia and is often used as an adjunct to other antidiabetic agents.
• Insulin Therapy: Insulin replacement remains essential for type 1 diabetes mellitus and advanced type 2 diabetes mellitus. Insulin preparations include rapid-, short-, intermediate-, and long-acting formulations, as well as premixed combinations and insulin analogs. Therapy can be individualized using basal, bolus, or basal-bolus regimens to mimic physiological insulin secretion and achieve optimal glycemic control while minimizing hypoglycemia.

Classification of Anti-diabetic drugs based on their Pharmacological action^(19,20):

Figure 1 .Classification of Anti-diabetic drugs based on their Pharmacological action

Nanotechnology in drug delivery systems⁽²¹⁾:

Nanotechnology in drug delivery systems involves the use of nanoscale materials (1–100 nm) to improve the delivery, efficacy, and safety of therapeutic agents. By reducing particle size, nanocarriers enhance the solubility and bioavailability of poorly water-soluble drugs and allow for targeted delivery to specific tissues or cells, minimizing off-target effects. Nanocarriers also enable controlled or sustained drug release, improving therapeutic outcomes and reducing dosing frequency. Common nanocarriers include liposomes, polymeric nanoparticles, solid lipid nanoparticles (SLNs), nanostructured lipid carriers (NLCs), dendrimers, nanoemulsions, micelles, carbon-based nanoparticles, and quantum dots. These carriers can be administered via oral, intravenous, transdermal, pulmonary, ocular, or nasal routes, and have applications in cancer therapy, diabetes management, ocular delivery, vaccines, gene therapy, and antimicrobial treatments. Despite their advantages, challenges such as stability, toxicity, scale-up, and regulatory hurdles remain. Overall, nanotechnology offers a promising approach to delivering drugs more efficiently, safely, and precisely.

Common Nano formulations used in drug delivery systems (DDS)⁽²²⁾:

1. Liposomes:

Liposomes are spherical vesicles composed of one or more phospholipid bilayers surrounding an aqueous core. They are biocompatible and capable of encapsulating both hydrophilic (in the core) and hydrophobic (within the bilayer) drugs. Liposomes enhance drug stability, reduce toxicity, and allow targeted delivery, making them widely used in cancer therapy, vaccines, and antimicrobial treatments. Their size, surface charge, and composition can be tailored for controlled release and improved bioavailability.

2. Polymeric Nanoparticles

Polymeric nanoparticles are submicron-sized drug carriers made from biodegradable and biocompatible polymers such as PLGA, PEG, or chitosan. They can encapsulate a wide range of drugs and provide controlled and sustained release. These nanoparticles protect drugs from degradation, enhance solubility, and allow targeted delivery by surface modification. Their versatility makes them suitable for applications in cancer therapy, gene delivery, and treatment of chronic diseases.

3. Solid Lipid Nanoparticles (SLNs):

SLNs are made from solid lipids and stabilized by surfactants. They offer controlled drug release, improved stability, and high biocompatibility. SLNs are ideal for delivering poorly water-soluble drugs and are used in topical, oral, and injectable formulations.

4. Nanostructured Lipid Carriers (NLCs):

NLCs are advanced lipid-based nanoparticles combining solid and liquid lipids. They offer better drug loading, reduced drug leakage, and enhanced stability compared to SLNs. NLCs are effective for targeted and sustained drug delivery.

5. Dendrimers:

Dendrimers are highly branched, nanosized synthetic polymers with multiple functional groups. They allow precise drug attachment, targeted delivery, and controlled release. Dendrimers are used in cancer therapy, gene delivery, and diagnostics.

6. Nanoemulsions:

Nanoemulsions are kinetically stable emulsions with droplet sizes in the nanometer range. They enhance solubility and bioavailability of lipophilic drugs and are used in oral, topical, and intravenous drug delivery.

7. Carbon Nanotubes (CNTs):

CNTs are cylindrical nanostructures made of carbon atoms. They can penetrate cells and deliver drugs directly to the target site. Functionalized CNTs are used mainly in cancer treatment and gene delivery, though concerns about toxicity remain.

8. Gold and Silver Nanoparticles:

These metallic nanoparticles are used for targeted drug delivery, imaging, and diagnostics. Gold nanoparticles are valued for their stability and ease of functionalization, while silver nanoparticles have strong antimicrobial properties.

9. Magnetic Nanoparticles:

Magnetic nanoparticles (e.g., iron oxide) can be directed to specific body sites using external magnetic fields. They are used for targeted drug delivery, magnetic hyperthermia therapy, and as contrast agents in MRI.

10. Nanogels:

Nanogels are soft, swollen polymer networks capable of holding large amounts of water. They are responsive to stimuli like pH or temperature and allow controlled, localized drug release, making them useful in cancer and inflammation treatments.

NANO SUSPENSION

A nanosuspension is a submicron colloidal dispersion of pure drug particles, typically ranging from 1 to 1000 nm, stabilized by surfactants or polymers in a liquid medium. Unlike other Nano formulations, nanosuspensions do not require the drug to be solubilized, making them ideal for poorly water-soluble drugs in either crystalline or amorphous form. By reducing particle size, nanosuspensions increase the surface area, enhancing solubility, dissolution rate, and bioavailability, which allows for lower dosing and potentially fewer side effects. They are stabilized using surfactants (e.g., Tween 80, Poloxamer 188) or polymers (e.g., PVP, HPMC) and can be administered orally, parenterally, ocularly, or via inhalation. Preparation methods include top-down approaches like high-pressure homogenization and media milling, or bottom-up techniques such as solvent-antisolvent precipitation. Despite their advantages, challenges like aggregation, sedimentation, stabilizer selection, and scale-up must be carefully managed to ensure long-term stability and therapeutic efficacy⁽²³⁾.

ADVANTAGE OF NANO SUSPENSION

Nano Suspensions offer several advantages in drug delivery, particularly for poorly water-soluble drugs. By reducing drug particle size to the nanometer range, Nano Suspensions significantly increase surface area, leading to enhanced dissolution rate and improved bioavailability. This is especially beneficial for Biopharmaceutical Classification System (BCS) Class II and IV drugs. Nano Suspensions provide a versatile formulation platform for various routes of administration including oral, parenteral, ocular, and pulmonary. They enable uniform drug distribution, minimize dosing frequency, and reduce variability in absorption. Moreover, Nano Suspensions are physically stable and can be prepared without the need for toxic organic solvents. Their ability to bypass first-pass metabolism in some cases also enhances systemic availability. Additionally, Nano Suspensions can be sterilized and lyophilized for improved shelf-life, making them suitable for large-scale production. The simplicity of formulation using high-pressure homogenization or wet milling methods contributes to their industrial applicability. Overall, Nano Suspensions provide an efficient and adaptable approach to improve therapeutic efficacy, especially for hydrophobic drugs⁽²⁴⁾.

1. Enhanced Solubility and Dissolution Rate

Nanosuspensions reduce the particle size of poorly water-soluble drugs to the nanometer range, increasing the surface area. According to the Noyes–Whitney equation, smaller particles dissolve faster, leading to improved dissolution rate and enhanced bioavailability. This is particularly beneficial for BCS Class II and IV drugs, which have poor solubility but high permeability or both low solubility and low permeability.

2. Improved Bioavailability

The increased dissolution rate and greater surface area allow for faster and more complete absorption in the gastrointestinal tract. For drugs with poor oral bioavailability, nanosuspensions can significantly increase systemic exposure, reducing the required dose.

3. Reduction in Dose and Side Effects

Enhanced bioavailability means that a lower drug dose can achieve the desired therapeutic effect. This can minimize dose-dependent side effects and improve patient safety.

4. Flexibility in Administration Routes

Nanosuspensions can be formulated for oral, parenteral, ocular, pulmonary, or topical delivery. They enable injectable formulations of hydrophobic drugs without using organic solvents, which reduces toxicity risks.

5. Targeted and Controlled Delivery Potential

Nanosuspensions can be surface-modified with ligands or polymers to target specific tissues or cells. They also allow for sustained or controlled drug release, reducing dosing frequency and improving patient compliance.

6. Stability and Versatility

Properly stabilized nanosuspensions prevent aggregation, sedimentation, and crystallization, ensuring long-term stability. They can be converted into solid dosage forms (e.g., tablets, capsules, pellets) for enhanced convenience and shelf-life⁽²⁵⁾.

7. Improved Therapeutic Efficacy

By enhancing solubility, absorption, and bioavailability, nanosuspensions can increase the therapeutic effect of poorly soluble drugs. They are particularly useful for drugs with narrow therapeutic windows, ensuring consistent plasma levels.

8. Applicability to a Wide Range of Drugs

Suitable for hydrophobic drugs, poorly soluble new chemical entities (NCEs), and herbal extracts. Can be used in combination therapies, potentially reducing pill burden and improving adherence. Nanosuspensions improve drug delivery by enhancing solubility, bioavailability, and therapeutic efficacy, while reducing doses and side effects. Their versatility in administration and potential for targeted delivery makes them a promising strategy for poorly soluble drugs.

DISADVANTAGE OF NANO SUSPENSION

Nano Suspensions, although advantageous for enhancing the solubility and bioavailability of poorly water-soluble drugs, have certain limitations that can impact their practical application. One major disadvantage is the physical instability of the nanoparticles, which are prone to aggregation or crystal growth over time, especially during storage, leading to changes in particle size distribution and reduced therapeutic efficacy. Additionally, Nano Suspensions may require the use of stabilizers or surfactants in relatively high concentrations to maintain particle stability, which could potentially lead to toxicity or undesirable side effects⁽²⁶⁾. Another concern is the cost and complexity of production techniques like high-pressure homogenization or media milling, which can be resource-intensive and difficult to scale up for industrial use. Furthermore, sterilization of Nano Suspensions poses challenges, as conventional methods like autoclaving may affect particle integrity or lead to chemical degradation of the drug. Finally, the regulatory pathways for Nano Suspension based formulations are still evolving, which can delay product approval and commercialization. Despite their potential in drug delivery, these drawbacks necessitate further optimization in formulation, production, and regulatory compliance for broader clinical application⁽²⁷⁾.

NANO SUSPENSION FORMULATION

Nano Suspension formulation is an advanced drug delivery approach designed to enhance the solubility and bioavailability of poorly water-soluble drugs. It involves the dispersion of nanosized drug particles (typically less than 1 µm) in a suitable liquid medium stabilized by surfactants or polymers. The reduction in particle size leads to an increased surface area, which significantly improves the dissolution rate and absorption of the drug. Nano Suspensions can be prepared using techniques such as high-pressure homogenization, media milling, and precipitation methods. This formulation strategy is particularly beneficial for Biopharmaceutics Classification System (BCS) Class II and IV drugs⁽²⁸⁾, which have low solubility and/or permeability. Stabilizers like poloxamers, Tween 80, or HPMC are commonly used to prevent aggregation and maintain the physical stability of the suspension. Moreover, Nano Suspensions can be administered through various routes, including oral, parenteral, ocular, and pulmonary, offering formulation flexibility. They are also advantageous for targeting specific tissues or enhancing drug uptake by cells. Overall, Nano Suspension technology provides a promising  platform for delivering challenging drug molecules and improving therapeutic outcomes. Nano Suspensions for the formulation of poorly soluble drugs⁽²⁹⁾.

NANO SUSPENSION FORMULATION METHODS:

Nano Suspensions are prepared to reduce particle size and improve drug solubility.

• High-Pressure Homogenization
• Milling (Wet Media Milling)
• Solvent Evaporation
• Supercritical Fluid Technology
• Spray Drying

1. High-Pressure Homogenization⁽³⁰⁾:

High-Pressure Homogenization is a widely used method for producing Nano Suspensions. It involves forcing a drug suspension through a small orifice at very high pressures (500–2000 bar). This results in intense mechanical shear forces that break down large drug particles into the nanoscale range. The process is often followed by stabilization with surfactants or polymers to prevent particle aggregation. This method is efficient for achieving uniform particle sizes and is commonly used for water-insoluble drugs, improving their solubility and bioavailability.

Figure 2: High-Pressure Homogenization

2. Milling (Wet Media Milling):

Milling is a widely used technique for preparing Nano Suspensions, where the drug is ground in a liquid medium with the help of grinding media (e.g., ceramic or glass beads). The process involves the mechanical breakdown of drug particles into nanoscale sizes through high shear forces and collisions between the beads and drug particles. The drug is stabilized using surfactants or polymers to prevent aggregation after milling. This method is efficient for producing Nano Suspensions of poorly water-soluble drugs and is scalable for industrial production.

Figure 3: Milling (Wet Media Milling)

3. Solvent Evaporation⁽³¹⁾:

Solvent Evaporation is a method used to prepare Nano Suspensions by dissolving the drug in a volatile solvent, followed by the controlled evaporation of the solvent. The drug particles precipitate out in nanoscale size when the solvent is removed, usually under reduced pressure or through a solvent exchange process. Stabilizers like surfactants or polymers are added to prevent particle aggregation during precipitation. This method is commonly used for poorly soluble drugs and allows for precise control over particle size and drug loading, though solvent selection and evaporation conditions are critical for optimal results.

Figure 4: Solvent Evaporation

4. Supercritical Fluid Technology:

Supercritical Fluid Technology utilizes supercritical fluids, commonly supercritical carbon dioxide (CO?), to dissolve and precipitate drug particles at the nanoscale. In this process, the drug is dissolved in the supercritical fluid, and then, through rapid depressurization, the drug precipitates as nanoparticles. Supercritical CO? is favored because it is non-toxic, environmentally friendly, and allows for precise control over particle size. This method eliminates the need for organic solvents, making it an eco-friendly and efficient option for preparing Nano Suspensions, particularly for sensitive drugs. It is widely used for high-purity formulations in pharmaceutical applications.

Figure 5: Supercritical Fluid Technology

5. Spray Drying:

Spray Drying is a technique used to prepare Nano Suspensions by converting a drug solution or suspension into a dry powder form. The drug solution is sprayed into a hot gas stream, causing rapid evaporation of the solvent and resulting in the formation of fine, nanosized particles. During the process, stabilizers are added to prevent particle aggregation. Spray drying is efficient, scalable, and can produce particles with controlled size, making it ideal for encapsulating poorly soluble drugs. However, careful control of temperature and drying conditions is essential to avoid drug degradation.

Figure 6: Spray Drying

Nano suspension characterization parameters⁽³²⁾:

1. Particle Size and Zeta Potential
2. Polydispersity Index (PDI)
3. Morphology and Surface Structure (e.g., SEM, TEM)
4. Drug Content and Loading Efficiency
5. Saturation Solubility
6. Dissolution Rate
7. pH and Viscosity
8. Stability (physical and chemical)
9. Redispersibility (for dried formulations)
10. In-vitro Drug Release Profile

1. Particle Size and Zeta Potential

Particle size is a critical factor in nanosuspensions as it directly influences solubility, dissolution rate, bioavailability, and physical stability. Smaller particles have a higher surface area, leading to faster dissolution and better absorption. Zeta potential measures the surface charge of nanoparticles and indicates the electrostatic stability of the suspension. A high absolute zeta potential (typically ±30 mV or more) helps prevent aggregation and ensures long-term stability of the nanosuspension⁽³³⁾.

Figure 7: Particle Size and Size Distribution

2. Polydispersity Index (PDI)

The polydispersity index (PDI) indicates the uniformity of particle size distribution in a nanosuspension. A low PDI value, generally below 0.3, suggests a homogeneous particle population, which is essential for consistent drug release and stability. Higher PDI values indicate heterogeneity, increasing the risk of aggregation and inconsistent therapeutic performance.

3. Morphology and Surface Structure (SEM, TEM)

Morphological analysis using Scanning Electron Microscopy (SEM) or Transmission Electron Microscopy (TEM) provides information on the shape, surface characteristics, and size of nanoparticles. This evaluation helps confirm whether particles are spherical, rod-shaped, or irregular and allows detection of aggregation or surface defects, which can impact dissolution and bioavailability.

4. Drug Content and Loading Efficiency⁽³³⁾

Drug content refers to the actual amount of active pharmaceutical ingredient present in the nanosuspension, while loading efficiency indicates the proportion of drug successfully incorporated into the nanoparticles relative to the total drug used. High drug content and loading efficiency ensure that the formulation delivers the intended therapeutic dose effectively without wastage or overdosing.

5. Saturation Solubility

Saturation solubility measures the maximum concentration of a drug that can dissolve in a particular solvent under equilibrium conditions. Nanosuspensions often exhibit enhanced saturation solubility due to the increased surface area and higher surface energy of nanoparticles, which improves dissolution and absorption of poorly water-soluble drugs.

6. Dissolution Rate

The dissolution rate reflects how quickly the drug dissolves from the nanosuspension into the surrounding medium. Smaller particle size and greater surface area in nanosuspensions enhance the dissolution rate, leading to improved bioavailability and faster onset of therapeutic action compared to conventional formulations.

7. pH and Viscosity

The pH of a nanosuspension influences drug stability, solubility, and compatibility with excipients, while viscosity affects the flow properties, ease of administration, and redispersibility of the formulation. Optimizing both pH and viscosity is essential to ensure physical stability, patient compliance, and proper drug delivery⁽³⁴⁾.

8. Stability (Physical and Chemical)

Physical stability refers to the prevention of particle aggregation, sedimentation, or crystal growth over time, whereas chemical stability ensures the drug maintains its molecular integrity without degradation. Both aspects are critical to preserve the efficacy, safety, and shelf-life of the nanosuspension.

9. Redispersibility (for Dried Formulations)

For dried nanosuspension formulations, such as freeze-dried or spray-dried powders, redispersibility is a key parameter. It measures the ability of the nanoparticles to return to their original size and dispersion state upon reconstitution with a suitable medium, ensuring consistent dosing and therapeutic performance.

10. In-vitro Drug Release Profile

The in-vitro drug release profile evaluates the rate and extent of drug release from the nanosuspension under simulated physiological conditions. This parameter helps predict in-vivo performance, including absorption, onset of action, and sustained release potential, which are critical for designing effective and safe drug delivery systems.

AIM:

To formulate and evaluate a Pioglitazone and Glimepiride nano suspension to enhance its solubility, dissolution rate, and bioavailability for improved therapeutic efficacy in the management of type 2 diabetes mellitus.

OBJECTIVES:

• To formulate a nanosuspension of Pioglitazone and Glimepiride using anti solvent precipitation technique.
• To optimize the formulation parameters,  Drug and stabilizer ratio, type and concentration of surfactants/polymers, pH, and process variables for maximum stability and efficiency.
• To evaluate the physicochemical characteristics of the nanosuspension, including particle size, zeta potential, polydispersity index (PDI) and surface structure.
• To assess the in-vitro dissolution rate and drug release profile to ensure enhanced solubility and controlled release compared to conventional formulations.
• To evaluate the stability of the nanosuspension under different storage conditions, including physical, chemical, and redispersibility studies.

DRUG PROFILE

DRUG PROFILE:  PIOGLITAZONE⁽³⁵⁾

Table 1. Drug Profile:  Pioglitazone

PIOGLITAZONE :

Pioglitazone is an oral antidiabetic agent belonging to the thiazolidinedione class, primarily used to manage type 2 diabetes mellitus. It acts as a selective agonist for the peroxisome proliferator-activated receptor gamma (PPAR-γ), enhancing insulin sensitivity in adipose tissue, skeletal muscle, and the liver. Besides glycemic control, pioglitazone has been investigated for its potential effects in neurodegenerative diseases, cancer, and cardiovascular conditions due to its anti-inflammatory and antioxidant properties. It has also been associated with favorable effects on lipid profiles, including increased HDL cholesterol and decreased triglycerides. However, pioglitazone use is not without risks; it has been linked to weight gain, fluid retention, and a potential risk of heart failure and bladder cancer with long-term use. Despite these concerns, pioglitazone remains a valuable option in combination therapy for achieving glycemic control in patients inadequately managed by other antidiabetic medications⁽³⁶⁾.

DRUG PROFILE: GLIMEPIRIDE⁽³⁷⁾

Table 2. Drug Profile: Glimepiride

GLIMEPIRIDE:

Glimepiride is a second-generation sulfonylurea widely used for the management of type 2 diabetes mellitus. It lowers blood glucose levels by stimulating insulin secretion from pancreatic β-cells through binding to sulfonylurea receptors on ATP-sensitive potassium channels. Glimepiride is poorly water-soluble, highly protein-bound (>99%), and metabolized in the liver via CYP2C9. Standard dosing begins at 1 mg once daily, which can be titrated up to 8 mg based on glycemic response. Common adverse effects include hypoglycemia and weight gain. It is available in oral tablet forms (1, 2, 4 mg) and is frequently used in combination with drugs like Pioglitazone or Metformin to achieve better glycemic control. Due to its poor solubility, Glimepiride is a suitable candidate for nano-formulations aimed at improving bioavailability and therapeutic efficacy⁽³⁸⁾.

5. EXCIPIENT  PROFILE

TWEEN – 80 ⁽³⁹⁾

Table 3. Excipient  Profile  Tween – 80

Tween 80, also known as Polysorbate 80, is a non-ionic surfactant and emulsifier widely used in pharmaceutical and cosmetic formulations. Physically, it appears as a yellowish viscous liquid that is nearly odorless and is soluble in water, ethanol, and propylene glycol, forming micelles in aqueous solutions. With a hydrophilic-lipophilic balance (HLB) of around 15, Tween 80 is strongly hydrophilic, making it effective in stabilizing oil-in-water emulsions and enhancing the solubility of hydrophobic drugs. It functions as a solubilizer, stabilizer, emulsifier, and wetting agent, preventing particle aggregation and improving colloidal stability in formulations, particularly in nano-drug delivery systems such as nanosuspensions, nanoparticles, and liposomes. Tween 80 is generally regarded as safe (GRAS) at recommended concentrations.

Sodium Lauryl Sulphate ⁽⁴⁰⁾

Table 4. Excipient  Profile   Sodium Lauryl Sulphate

Sodium Lauryl Sulphate (SLS), also known as Sodium Dodecyl Sulfate, is an anionic surfactant widely used in pharmaceutical formulations. It lowers surface and interfacial tension, improving wetting, solubility, and dispersion of poorly water-soluble drugs. In nanosuspension formulations, SLS acts as a stabilizer and wetting agent, preventing particle aggregation and enhancing drug dissolution. It is freely soluble in water, with a high Hydrophilic-Lipophilic Balance (HLB ~40), making it suitable for forming micelles and promoting uniform dispersion. Typically used in concentrations of 0.1–2%, SLS is compatible with many excipients but should be used cautiously with cationic compounds due to potential incompatibility. It is generally regarded as safe within pharmacopeial limits but may cause mild irritation at higher concentrations.

Ethanol ⁽⁴¹⁾

Table 5. Excipient Profile Ethanol

PLAN OF WORK

Pre formulation Studies

• Characterise the drugs in terms of solubility, melting point, particle size.
• Analysis of the UV Spectrum of API and the Calibration curve.
• Perform drug-drug and drug-excipient compatibility studies using technique (FT- IR)

Formulation of Nanosuspension

• Optimize formulation parameters, Drug concentration, type and concentration of stabilizer/surfactant, pH, and process variables.
• Prepare trial batches of Pioglitazone and Glimepiride nanosuspension.

Characterization of Nanosuspension

• Determine particle size, zeta potential, and polydispersity index (PDI).
• Measure drug content, saturation solubility, and viscosity.
• Conduct pH measurement and stability studies.

In-vitro Studies

• Perform dissolution testing to compare the nanosuspension with conventional formulations
• Assess the in-vitro drug release profile for drugs.

Stability Studies

• Conduct physical and chemical stability studies under different temperature and humidity conditions.

METHODOLOGY

Solubility of the drug

The solubility of the drug was determined by the shake-flask method. An excess quantity of the drug was accurately weighed and added to a fixed volume of different solvents and buffer media (such as distilled water, phosphate buffer pH 1.2, 4.5, 6.8, and 7.4) in tightly closed glass vials. The vials were placed in a thermostatically controlled water bath shaker and agitated continuously at 37 ± 0.5 °C for 24 hours to attain equilibrium. After shaking, the samples were centrifuged at 10,000 rpm for 10 minutes to remove undissolved drug particles and the supernatant was carefully filtered through a 0.45 µm membrane filter. The filtrate was suitably diluted, and the concentration of drug dissolved was determined by UV–Visible spectrophotometry at its λ max using a previously prepared calibration curve. The solubility of the drug in each medium was expressed in mg/mL and compared to evaluate solvent and pH dependency(42).

Determination of Melting Point

The melting points of pioglitazone and glimepiride were determined using the capillary fusion method on a digital melting point apparatus. A small amount of each drug was finely powdered and packed into separate capillary tubes (≈ 2 - 3 mm column of powder). The capillaries were placed in the instrument alongside a certified calibration standard and heated at a rate of 1 -  2 °C/min in the expected melting range. The temperature at which the first sign of liquefaction appeared was recorded as the onset and the temperature at which the substance became a clear liquid was recorded as the end; the melting point was reported as the range (onset - end °C). Each measurement was performed in triplicate and the apparatus was checked with a standard reference to ensure accuracy(43).

Compatibility Studies (FTIR)

The drug - drug and drug - excipient compatibility of pioglitazone and glimepiride was evaluated using Fourier Transform Infrared (FTIR) spectroscopy. Pure samples of pioglitazone, glimepiride, their physical mixture (1:1 ratio), and drug - excipient mixtures (1:1 ratio) were prepared by triturating with dry potassium bromide (KBr) and compressed into transparent pellets under hydraulic pressure. Each pellet was scanned in the range of 4000–400 cm?¹ using an FTIR spectrophotometer at a resolution of 4 cm?¹. The obtained spectra were analyzed for the presence of characteristic functional group peaks of both drugs, such as C=O stretching, N–H stretching, and C- H bending vibrations. Any major shifts, disappearance, or appearance of new peaks in the mixture spectra compared with the spectra of pure drugs indicated possible chemical interactions. The absence of significant changes confirmed compatibility between pioglitazone, glimepiride, and the excipients (44).

Excipients used for the formulation of Nano Suspension:

Table 6. Excipients used for the formulation of Nano Suspension

Table 7. Preparation of Nanosuspension

Pioglitazone and glimepiride were formulated as a combined nanosuspension using the antisolvent precipitation method followed by probe sonication. The drugs (total 10 mg/mL; pioglitazone: glimepiride ratio 1:1 w/w) were dissolved in a minimal volume of ethanol to form the organic phase. An aqueous phase containing stabilizer (Tween 80) with sodium lauryl sulphate at the concentration was prepared and chilled to 4 -10 °C. The organic phase was injected rapidly into the aqueous phase under high-speed magnetic stirring (1000 - 1500 rpm). Immediately after injection, probe sonication was applied (amplitude 40–60%, pulse mode 10s on / 5s off), while the suspension was kept in an ice bath to avoid overheating. The organic solvent was removed under reduced pressure by rotary evaporation to evaporate ethanol. The resulting nanosuspension was centrifuged at low speed to remove large aggregates, characterized (Particle size, PDI, zeta potential), and lyophilized to obtain dry nanosuspension powder. Formulations were stored at 2 - 8°C for short-term stability testing and characterized for particle size (DLS) and in vitro dissolution⁽⁴⁵⁾.

Procedure:

Figure 8. Preparation of Nanosuspension^(46,47)

Drug Solution Preparation & Antisolvent Preparation:

• Dissolve the drug in a suitable organic solvent to form a clear solution.
• Prepare the antisolvent containing the stabilizer (e.g., 0.1–1% Tween 80 in water).

Precipitation:

• Slowly add the drug solution to the antisolvent under continuous stirring (magnetic or high-speed homogenizer).
• Rapid mixing causes supersaturation, leading to nucleation and formation of drug nanoparticles.

Stabilization:

• The surfactant molecules adsorb on the particle surface, preventing aggregation. Continue stirring for 30–60 minutes for uniform particle formation Size Reduction & Homogenization.

Figure 9. Preparation of Nanosuspension process

Evaluation of Nano Suspension:

Physical Characterization of Nanosuspension

• Particle size distribution (PSD)
• Polydispersity index (PDI)
• Zeta potential
• Crystallinity / Solid-state nature (XRD, DSC)
• Saturation solubility
• In-vitro dissolution profile
• Sedimentation rate and sedimentation volume

Particle size distribution (PSD)

The procedure for determining Particle Size Distribution (PSD) begins with the preparation of a representative sample. The sample is dispersed in a suitable medium that does not dissolve or react with the material, and a wetting agent may be added if required. Proper dispersion is ensured using gentle stirring and, if necessary, short bursts of sonication to break down agglomerates while avoiding overheating. Entrapped air bubbles are allowed to escape before measurement. Depending on the particle size range, appropriate techniques are chosen: laser diffraction is used for a wide range of powders and suspensions, dynamic light scattering (DLS) for submicron colloids, and sieve analysis for coarse powders. In laser diffraction or DLS methods, the dispersion is transferred into the instrument cell, while for dry powder measurement or sieving, samples are processed under controlled conditions. Instrument calibration and blank measurements with the medium alone are carried out to prevent contamination and ensure accuracy. Multiple replicate measurements are then performed under the same instrument settings, including refractive index, measurement time, and detector sensitivity. The resulting data provides PSD values such as D10, D50 (median), D90, and the span, which are analysed to assess particle uniformity and detect any multimodal distributions that may indicate agglomeration or heterogeneous populations. Finally, all results are reported with details of the method, dispersion medium, sonication conditions, and measurement parameters for reproducibility and reliability(48).

Figure 10. Particle size analyzer

Polydispersity Index (PDI)

The Polydispersity Index (PDI) is a dimensionless parameter that indicates the width or uniformity of particle size distribution in a nanosuspension or colloidal system. It is obtained from Dynamic Light Scattering (DLS) measurements and reflects how homogeneous or heterogeneous the particle population is. A PDI value close to 0 indicates a highly uniform (monodisperse) system, while values approaching 1 represent a broad and heterogeneous distribution. In general, PDI < 0.1 suggests a very narrow size distribution, 0.1–0.3 indicates moderate uniformity and is acceptable for most pharmaceutical nanosuspensions, while >0.5 indicates high polydispersity, often due to aggregation or poor formulation control. The PDI is calculated by the instrument software based on the cumulants analysis of the autocorrelation function of scattered light intensity. Since it strongly influences formulation stability and performance, controlling factors such as proper dispersion, stabilizer concentration, and processing method is essential to achieve a desirable PDI(49,50).

Zeta potential

Zeta potential is a measure of the surface charge of particles in a suspension and indicates the stability of colloidal systems, including nanosuspensions. It reflects the electrostatic repulsion between particles: high absolute values (typically > ±30?mV) suggest strong repulsion and good physical stability, whereas low values (< ±20?mV) indicate weak repulsion, which may lead to aggregation or sedimentation. Zeta potential is measured using electrophoretic light scattering (ELS), where an electric field is applied to the dispersion, causing charged particles to move. The instrument calculates the particle velocity (electrophoretic mobility) and converts it into zeta potential using the Smoluchowski equation for aqueous systems. Factors affecting zeta potential include pH, ionic strength, stabilizer type, and particle surface properties. Reporting zeta potential along with polydispersity index (PDI) and particle size helps assess the overall stability and uniformity of nanosuspensions(51,52).

Figure 11. Malvern Zeta potential analyzer

Differential Scanning Calorimetry (DSC)

Differential Scanning Calorimetry (DSC) is an analytical technique used to study the thermal behavior of substances, including drugs, excipients, and formulations. It measures the heat flow into or out of a sample as it is heated, cooled, or held isothermally, compared to an inert reference. DSC provides information about melting point, crystallinity, glass transition temperature (Tg), polymorphic transitions, and drug–excipient compatibility. In a typical procedure, a small amount of accurately weighed sample (usually 2–10?mg) is placed in a sealed aluminum pan, and an empty pan serves as a reference. The instrument is programmed to heat at a controlled rate (e.g., 5–10?°C/min) over a specified temperature range. Endothermic or exothermic events are recorded as peaks on a thermogram, where peak onset indicates transition temperature and peak area corresponds to enthalpy change (ΔH). DSC is widely used in preformulation studies to detect possible interactions in drug formulations and to evaluate the physical state of nanosuspensions, helping to ensure stability and efficacy(53).

Figure 12. Differential Scanning Calorimetry (DSC)

Saturation Solubility of the Drug

An excess amount of the drug is added to a known volume of solvent and the mixture is continuously stirred or shaken at a controlled temperature until equilibrium is reached, usually   24 - 48?hours. After equilibrium, the solution is filtered or centrifuged to remove undissolved particles. The clear supernatant is then analyzed for drug concentration using a suitable method, typically UV - Vis spectrophotometry. The measured concentration represents the saturation solubility of the drug in that solvent(54).

In-Vitro Dissolution Profile

The in-vitro dissolution profile is a method used to evaluate the rate and extent of drug release from a formulation under controlled laboratory conditions, providing insight into its potential bioavailability and performance. The in vitro drug release study assessed the release kinetics of the nano suspension over time. A dialysis membrane diffusion technique was used to measure drug release, with cumulative release (%) determined at set intervals. In this procedure, the formulation is placed in a dissolution apparatus, typically USP Apparatus II (paddle), containing a suitable dissolution medium maintained at 37?±?0.5?°C with constant stirring(55,56). At predetermined time intervals, samples of the medium are withdrawn, filtered to remove undissolved particles, and analyzed for drug content using an appropriate analytical method such as UV - Vis spectrophotometry. The volume withdrawn is replaced with fresh medium to maintain constant conditions. The cumulative percentage of drug released is then plotted against time to generate the dissolution profile. Comparing this profile with that of the pure drug or marketed formulation allows assessment of dissolution enhancement, which is particularly relevant for nanosuspensions where particle size reduction and stabilizers improve drug release(57).

Figure 13. A dialysis membrane diffusion technique

pH Measurement

The pH analysis of a nano suspension formulation is essential for evaluating its stability, compatibility, and biological suitability. A calibrated digital pH meter is used to measure the pH at room temperature. Ideally, the pH should range between 5.5 and 7.5 to ensure physiological acceptability, minimizing irritation and enhancing interaction with biological membranes(58,59).            

Figure 14. Digital pH Meter

Drug Content Analysis

The drug content analysis was performed to determine the actual amount of Pioglitazone and Glimepiride present in the formulated nanosuspension and to ensure uniform distribution of the drug within the formulation. A known quantity of the nanosuspension equivalent to a specific drug dose was accurately measured and diluted with methanol to dissolve the drug completely. The solution was then filtered or centrifuged to obtain a clear supernatant, and the absorbance was measured using a UV-Visible spectrophotometer at the respective wavelengths of Pioglitazone (269 nm) and Glimepiride (228 nm)(60). The concentration of each drug was determined from their respective standard calibration curves, and the percentage of drug content was calculated using the ratio of actual to theoretical drug content. The results indicated that the drug content of all formulations was within the acceptable range of 95–105%, confirming uniform dispersion, minimal drug loss during processing, and reproducibility of the formulation process. Thus, the analysis established that the prepared nanosuspensions contained the expected amount of both drugs, ensuring formulation accuracy and consistency(61).

Appearance (Colour, Opacity, Turbidity, Phase separation)

The appearance of a nanosuspension is a simple but important parameter that provides initial insight into its quality, stability, and uniformity. This evaluation includes observing the color, opacity, turbidity, and any phase separation of the formulation. Colour changes may indicate chemical degradation or interaction with excipients, while opacity or turbidity reflects particle concentration, size, and dispersion uniformity. Phase separation, such as sedimentation or creaming, suggests instability or inadequate stabilization(60). The assessment is usually performed visually against a white and black background under normal lighting conditions, and any changes are recorded over time to monitor physical stability. Consistent appearance is crucial for patient acceptability and for ensuring reproducible dosing in pharmaceutical nanosuspensions(62).

RESULT AND  DISCUSSION

PREFORMULATION STUDIES:

• The melting point of pure Pioglitazone shows 192°C. The melting point is closer with the reported  range of  Pioglitazone 193 °C – 195 °C.
• The melting point of pure Glimepiride shows 207 °C.  The melting point range of  Glimepiride  is  207 °C – 209 °C.

Solubility of drugs:

• Solubility of Pioglitazone
• In soluble in water
• Soluble in Organic solvents: Soluble in ethanol.
• Class: BCS Class II (low solubility, high permeability)

Solubility of Glimepiride

• In soluble in water
• Soluble in Organic solvents: Soluble in ethanol
• Class: BCS Class II

UV Spectrum Analysis:

The UV spectrum of both drugs is characterized by their absorption maxima (λmax), which are used for identification and quantitative analysis. The Pioglitazone Exhibits a distinct absorption peak at about 269 -270 nm in solvents as phosphate buffer (pH 7.4) and the Glimepiride Shows a strong absorption maximum at around 228- 230 nm in buffer solution.

UV Calibration Curve Analysis

The calibration curve shows a clear linear relationship between concentration (Con) and absorbance (abs). The regression equation, y = 0.0174x + 0.1723, and the correlation coefficient (R² = 0.9655) indicate a strong positive correlation. This means that as the concentration increases, the absorbance also increases consistently, which confirms the reliability of the method for quantitative analysis

Figure 16. UV Calibration Curve of Pioglitazone

Figure 17. UV Calibration Curve of Glimepiride

Fourier Transform Infra-Red spectroscopy analysis (FTIR)

FT-IR Analysis data Interpretation for Pioglitazone:

Figure 18. FT- IR Spectra for Pioglitazone

Table 8. FT- IR Spectra for Pioglitazone

FT- IR Analysis data Interpretation for Glimepiride:

Figure 19. FT- IR Spectra for Glimepiride

Table 9. FT- IR Spectra for Glimepiride

FT- IR Analysis data Interpretation for Tween - 80:

Figure 20. FT- IR Spectra for Tween - 80

Table 10. FT- IR Spectra for Tween – 80

FT-IR Data Interpretation for formulation

Figure 21. FT- IR Spectra for the Formulation

RESULT INTERPRETATION:

The FT-IR spectral analysis revealed a broad absorption at 3309.47 cm?¹, indicating the presence of O–H or N–H stretching vibrations, suggestive of alcohols or amines. Peaks observed at 2923.05 cm?¹ and 2853.40 cm?¹ correspond to C–H stretching of methylene and methyl groups, typical of aliphatic chains commonly found in lipids, waxes, or hydrocarbons. A strong, sharp peak at 1742.44 cm?¹ signifies the presence of a carbonyl group (C=O), pointing towards esters, ketones, or acids. The absorption at 1645.29 cm?¹ may be attributed to C=C stretching or N–H bending, indicating unsaturation or the presence of amide groups, possibly related to proteinaceous materials. Additional bands at 1463.47 cm?¹ and 1377.30 cm?¹ reflect CH? and CH? bending, confirming aliphatic structures. Prominent peaks between 1221.57 and 1059.80 cm?¹ are characteristic of C–O and C–N vibrations, typically associated with esters, ethers, alcohols, or amines, suggesting the presence of oxygenated compounds. Bending vibrations at 917.32 cm?¹ and 823.13 cm?¹ are indicative of =C–H or aromatic out-of-plane bending, reflecting alkenes or aromatic systems. The peak at 721.73 cm?¹ represents (CH?)n rocking, consistent with long-chain alkanes. Finally, the region between 623.97 and 513.18 cm?¹ shows peaks corresponding to C–Br stretching or skeletal vibrations, hinting at the presence of alkyl halides or complex molecular frameworks.

Table 11. FT- IR Spectra for the Formulation