1Research Scholar, Department of Pharmaceutics, Government College of Pharmacy, Karad.
2Associate Professor, Government College of Pharmacy, Karad.
Poor aqueous solubility remains a major limitation in the effective delivery of many therapeutic agents, often resulting in reduced bioavailability and inconsistent clinical outcomes. Among various nanocarrier systems, niosomes non-ionic surfactant-based vesicles have emerged as a promising platform for enhancing the solubility, stability, and therapeutic performance of poorly soluble drugs. This review critically examines the role of niosomes as versatile carriers, highlighting their structural characteristics, preparation methods, and mechanisms of drug encapsulation. Special emphasis is placed on the formulation challenges associated with niosomal systems, including vesicle instability, drug leakage, scalability issues, and variability in entrapment efficiency. The influence of formulation variables such as surfactant type, cholesterol content, hydration conditions, and preparation techniques on vesicle performance is systematically discussed. Furthermore, recent advancements aimed at overcoming these limitations are explored, including surface modification, ligand-mediated targeting, stimuli-responsive niosomes, and hybrid nanocarrier approaches. The review also summarizes current applications of niosomes in improving the delivery of hydrophobic drugs via various routes of administration, along with insights into their pharmacokinetic and pharmacodynamic benefits. By integrating conventional knowledge with emerging strategies, this article provides a comprehensive perspective on the potential of niosomes to address solubility-related challenges and outlines future directions for their successful translation into clinical practice.
The oral delivery of therapeutic agents remains the most preferred route of drug administration due to its convenience, patient compliance, and cost-effectiveness. However, a significant proportion of newly developed drug molecules exhibit poor aqueous solubility, which severely limits their dissolution rate and, consequently, their bioavailability. It has been estimated that nearly 40–70% of new chemical entities fall under the category of poorly water-soluble compounds, posing a major challenge in pharmaceutical development [1,2]. These drugs often demonstrate erratic absorption profiles, leading to suboptimal therapeutic efficacy and increased variability in clinical response. To overcome solubility-related limitations, several formulation strategies have been explored, including solid dispersions, micronization, lipid-based systems, and nanotechnology-driven approaches [3]. Among these, vesicular drug delivery systems have gained considerable attention due to their ability to encapsulate both hydrophilic and lipophilic drugs while improving drug stability and bioavailability. Niosomes, which are non-ionic surfactant-based vesicles, have emerged as a promising alternative to conventional liposomes due to their enhanced chemical stability, cost-effectiveness, and ease of storage [4].Niosomes are typically composed of non-ionic surfactants and cholesterol, forming bilayered structures capable of entrapping poorly soluble drugs within their hydrophobic domains. Their unique architecture allows for controlled drug release, protection of labile molecules, and improved permeation across biological membranes [5]. Additionally, niosomes offer flexibility in terms of formulation design, enabling optimization for different routes of administration, including oral, transdermal, ocular, and parenteral delivery [6].
Despite their advantages, the development of niosomal systems is associated with several formulation challenges. Issues such as vesicle aggregation, fusion, leakage of encapsulated drug, and limited physical stability can affect their performance and shelf life [7]. Furthermore, factors such as surfactant selection, cholesterol ratio, hydration conditions, and preparation techniques play a critical role in determining vesicle size, entrapment efficiency, and drug release characteristics [8]. These challenges necessitate a systematic understanding of formulation variables to ensure reproducibility and scalability. Recent advances in nanotechnology have led to the development of innovative strategies to enhance the performance of niosomes. These include surface functionalization for targeted drug delivery, incorporation of stimuli-responsive components, and the design of hybrid vesicular systems that combine the advantages of multiple nanocarriers [9]. Such advancements have significantly expanded the potential applications of niosomes, particularly in the delivery of poorly soluble drugs with complex pharmacokinetic profiles. In this context, the present review aims to provide a comprehensive overview of niosomes as carriers for poorly soluble drugs, focusing on formulation challenges and emerging strategies to overcome these limitations. By integrating current research findings and technological advancements, this article seeks to highlight the potential of niosomal systems in improving drug solubility and therapeutic outcomes.
Niosomes As Versatile Carriers For Poorly Soluble Drugs
1. Structural Characteristics of Niosomes
Niosomes are bilayered vesicular systems formed by the self-assembly of non-ionic surfactants in aqueous media. Their structure resembles liposomes; however, the use of non-ionic surfactants imparts greater chemical stability and reduces oxidative degradation [10]. The amphiphilic nature of surfactants leads to the formation of a bilayer, where hydrophilic head groups face the aqueous phase and hydrophobic tails align inward. This structural arrangement enables niosomes to encapsulate both hydrophilic and lipophilic drugs. Hydrophilic molecules are entrapped within the aqueous core, while lipophilic drugs are incorporated into the bilayer region [11]. Cholesterol is commonly added to improve membrane rigidity and reduce permeability, thereby enhancing vesicle stability and minimizing drug leakage [12].
Figure 1: Structure of Niosome
2. Preparation Methods of Niosomes
The method of preparation significantly influences vesicle characteristics such as size, lamellarity, and encapsulation efficiency [13]. The thin-film hydration method involves solvent evaporation to form a thin film followed by hydration, producing multilamellar vesicles [14]. The reverse-phase evaporation method provides higher encapsulation efficiency, particularly for hydrophilic drugs [15]. The ether injection method results in unilamellar vesicles formed by injecting surfactant solution into a heated aqueous phase [16]. Advanced methods such as microfluidization and sonication improve size uniformity, while proniosomes enhance storage stability and are hydrated prior to use [17].
Table 1: Comparison of Niosome Preparation Methods
General Process of Niosome Preparation
Figure 2: General Process of Niosome Preparation
3. Mechanisms of Drug Encapsulation
Drug encapsulation in niosomes depends on drug solubility and vesicle structure. Hydrophilic drugs are entrapped within the aqueous core, while lipophilic drugs are incorporated into the bilayer membrane [18]. Amphiphilic drugs may distribute between both regions. Encapsulation efficiency is influenced by surfactant type, cholesterol content, and preparation conditions. Surfactants with higher phase transition temperatures form more rigid bilayers, improving drug retention [19]. Advanced techniques such as pH gradient-based active loading enhance drug entrapment for ionizable compounds [20].
Factors Affecting Encapsulation Efficiency
Figure 3: Factors Affecting Encapsulation Efficiency
Formulation Challenges and Influencing Variables In Niosomal Systems
1. Formulation Challenges in Niosomal Drug Delivery
Despite their advantages, niosomes face several formulation-related challenges that can affect their stability, reproducibility, and therapeutic performance. One of the primary concerns is vesicle instability, which may arise due to aggregation, fusion, or sedimentation during storage. These phenomena can lead to changes in vesicle size distribution and compromise drug delivery efficiency [21]. The instability is often influenced by the physicochemical properties of surfactants and environmental conditions such as temperature and pH. Another critical issue is drug leakage, particularly during storage. Leakage occurs due to increased membrane permeability or disruption of the bilayer structure, resulting in premature drug release. This is more pronounced in formulations lacking adequate membrane stabilizers such as cholesterol [22]. Leakage not only reduces the effective drug dose but also affects reproducibility and shelf life. Scalability represents a major hurdle in the industrial translation of niosomal formulations. While laboratory-scale methods such as thin-film hydration are widely used, they often lack reproducibility when scaled up. Parameters such as mixing efficiency, solvent removal rate, and hydration uniformity become difficult to control on a large scale, leading to batch-to-batch variability [23]. Additionally, variability in entrapment efficiency poses a challenge in achieving consistent drug loading. Factors such as drug solubility, surfactant composition, and preparation method significantly influence encapsulation outcomes. Inconsistent entrapment can lead to unpredictable drug release profiles and reduced therapeutic efficacy [24].
Table 2: Instability and Leakage in Niosomes
|
Challenge |
Cause |
Impact |
|
Vesicle instability |
Aggregation, fusion |
Reduced shelf life |
|
Drug leakage |
Bilayer permeability |
Loss of drug content |
|
Scalability issues |
Process variability |
Poor reproducibility |
|
Entrapment variability |
Formulation factors |
Inconsistent drug delivery |
2. Influence of Formulation Variables on Niosome Performance
2.1 Surfactant Type
The choice of surfactant plays a crucial role in determining vesicle formation, stability, and drug encapsulation. Surfactants with appropriate hydrophilic-lipophilic balance (HLB) values and higher phase transition temperatures tend to form more stable bilayers with improved drug retention [25]. Longer alkyl chain surfactants generally enhance membrane rigidity, reducing permeability and drug leakage.
2.2 Cholesterol Content
Cholesterol is an essential component in niosomal formulations as it modulates membrane fluidity and permeability. An optimal concentration of cholesterol enhances bilayer rigidity and prevents drug leakage; however, excessive cholesterol may reduce entrapment efficiency by disrupting the regular packing of surfactant molecules [26].
2.3 Hydration Conditions
Hydration parameters, including temperature, time, and pH, significantly influence vesicle formation and size. Adequate hydration ensures complete swelling of the surfactant film and uniform vesicle formation. Elevated temperatures above the phase transition temperature facilitate better bilayer formation and drug encapsulation [27].
2.4 Preparation Techniques
The method of preparation directly impacts vesicle size, lamellarity, and drug loading efficiency. Techniques such as thin-film hydration produce multilamellar vesicles, while methods like microfluidization yield more uniform and smaller vesicles. The choice of technique must be aligned with the intended application and scalability requirements [28].
Table 3: Influence of Formulation Variables on Niosomal Properties
|
Variable |
Effect on Vesicle |
Outcome |
|
Surfactant type |
Determines bilayer formation |
Stability, encapsulation |
|
Cholesterol content |
Modulates rigidity |
Reduced leakage |
|
Hydration conditions |
Affects vesicle size |
Uniformity |
|
Preparation method |
Controls structure |
Reproducibility |
Advanced Strategies to Overcome Limitations of Niosomal Systems
Recent progress in nanotechnology has significantly improved the functional performance of niosomal drug delivery systems. To address challenges such as instability, non-specific distribution, and limited drug retention, several advanced strategies have been developed. These include surface engineering, targeted delivery approaches, stimuli-responsive systems, and hybrid nanocarrier designs.
Figure 4: Advanced Strategies to Overcome Limitations of Niosomal Systems
1. Surface Modification of Niosomes
Surface modification is an effective strategy to enhance the stability, circulation time, and bioavailability of niosomes. One of the most widely employed approaches is the coating of vesicles with hydrophilic polymers such as polyethylene glycol (PEG), a process commonly referred to as PEGylation. This modification creates a steric barrier around the vesicle surface, reducing opsonization and subsequent clearance by the mononuclear phagocyte system [29].
In addition to PEGylation, other polymers and biomolecules such as chitosan and polysaccharides have been used to improve mucoadhesion, enhance permeability, and provide controlled drug release [30]. Surface-modified niosomes demonstrate improved physical stability and prolonged systemic circulation, making them suitable for targeted and sustained drug delivery applications.
2. Ligand-Mediated Targeting
Ligand-mediated targeting enhances the specificity of drug delivery by attaching ligands to the surface of niosomes that can recognize and bind to specific receptors on target cells. Common ligands include antibodies, peptides, folic acid, and sugars, which facilitate receptor-mediated endocytosis [31]. This strategy is particularly useful in cancer therapy, where overexpressed receptors on tumor cells can be selectively targeted. By improving site-specific delivery, ligand-functionalized niosomes reduce systemic toxicity and enhance therapeutic efficacy [32]. The success of this approach depends on ligand density, binding affinity, and stability of the ligand–carrier conjugate.
3. Stimuli-Responsive Niosomes
Stimuli-responsive (smart) niosomes are designed to release their drug payload in response to specific internal or external triggers such as pH, temperature, enzymes, or light. These systems improve drug release control and minimize off-target effects [33]. For instance, pH-sensitive niosomes are particularly useful in tumor targeting, as the tumor microenvironment is more acidic than normal tissues. Similarly, temperature-sensitive systems can release drugs in response to localized hyperthermia. Enzyme-responsive niosomes exploit disease-specific enzymatic activity to trigger drug release [34].
4. Hybrid Nanocarrier Approaches
Hybrid nanocarriers combine niosomes with other nanostructures such as liposomes, nanoparticles, or polymeric systems to overcome individual limitations and enhance overall performance. These systems integrate the advantages of multiple delivery platforms, such as improved stability, higher drug loading, and controlled release [35].
For example, noisome polymer hybrids can provide enhanced mechanical strength and sustained drug release, while lipid niosome hybrids can improve biocompatibility and membrane fusion properties. Such systems are particularly beneficial for delivering poorly soluble drugs, as they enhance solubility and bioavailability [36].
Advancements In Niosomal Systems:
1. Stimuli-Responsive Patented Niosomes
A major advancement is the development of environment-responsive niosomes, designed to release drugs only under specific conditions.
These reduce systemic toxicity and improve therapeutic index [37].
2. Proniosomal Dry Powder Systems (Stability-Focused Patents)
Recent patents focus on proniosomes, which are dry formulations converted into niosomes upon hydration.
These are considered commercially viable patented systems for large-scale production [38].
3. Topical and Transdermal Niosomal Patents
Recent patent applications (e.g., US20240033213) describe topical niosomal formulations with controlled vesicle size and composition.
These systems are widely patented for:
4. Natural Compound-Loaded Niosomal Patents
Recent patented formulations include niosomal delivery of phytochemicals such as:
These systems address:
5. Nanospray-Dried Niosomal Systems
Integration of niosomes with nanospray drying produces dry, stable niosomal powders with improved shelf life [1].
6. Functionalized / Targeted Niosomal Systems
Represent a shift toward precision nanomedicine [42].
7. Niosomal In-Situ Gel Systems
Reduce dosing frequency and enhance patient compliance [43].
8. Vanillic Acid-Loaded Niosomes for Wound Healing
Niosomal delivery enhances therapeutic efficacy by providing controlled release and improved bioavailability
9. Chitosan-Coated Niosomes for Oral Delivery
Chitosan-coated niosomes are promising carriers for oral delivery of sensitive and poorly bioavailable drugs.
10. Cromolyn-Loaded Niosomes for Alzheimer’s Disease
This system represents a non-invasive nanocarrier approach for neurodegenerative disorders like Alzheimer’s disease
Future Perspectives, Market Trends & Commercial Aspects Of Niosomes
1. Rapid Growth of Global Niosomes Market
2. Increasing Adoption in Pharmaceutical Drug Delivery
3. Expansion in Cosmeceutical and Skincare Industry
4. Shift Toward Targeted and Personalized Medicine
5. Industrial Preference Due to Cost-Effectiveness and Stability
6. Integration with Advanced Nanotechnology Platforms
CONCLUSION:
Niosomes have emerged as a promising nanocarrier system for addressing the persistent challenge of poor aqueous solubility in drug delivery. Their unique bilayer structure enables the encapsulation of both hydrophilic and lipophilic drugs, enhancing solubility and bioavailability. Compared to conventional systems, niosomes offer advantages such as improved stability, cost-effectiveness, and formulation flexibility. Despite these benefits, several formulation challenges remain, including vesicle instability, drug leakage, and scalability issues. These limitations are strongly influenced by critical formulation variables such as surfactant type, cholesterol content, hydration conditions, and preparation techniques. A thorough understanding of these factors is essential for optimizing niosomal performance and ensuring reproducibility. Recent advancements in nanotechnology have significantly improved the functionality of niosomal systems. Strategies such as surface modification, ligand-mediated targeting, and stimuli-responsive designs have enhanced drug targeting, controlled release, and therapeutic efficacy. Hybrid nanocarrier approaches further expand their potential by combining the strengths of multiple delivery systems. Innovations like proniosomes, nanospray-dried formulations, and in-situ gel systems have addressed key stability and storage challenges, improving their suitability for large-scale production. Additionally, the successful incorporation of natural compounds and targeted therapies highlights the versatility of niosomes across various therapeutic applications.
From a commercial perspective, the growing demand for advanced drug delivery systems is driving increased interest in niosomes across pharmaceutical, cosmetic, and nutraceutical industries. Their role in enabling targeted and personalized medicine further strengthens their future potential. In conclusion, niosomes represent a highly adaptable and efficient platform for enhancing the delivery of poorly soluble drugs. Continued research focused on overcoming existing limitations and improving scalability will be crucial for their successful clinical translation and widespread industrial application.
REFERENCES.
Ruturaj Sapate*, Indrajit Gonjari, Prathamesh Thorat, Vaishnavi Punase, Pratiksha Kamble, Pradnya Jagtap, Niosomes in Enhancing Solubility of Poorly Soluble Drugs: Advancements and Future Perspectives, Int. J. of Pharm. Sci., 2026, Vol 4, Issue 5, 648-659. https://doi.org/10.5281/zenodo.20028368
10.5281/zenodo.20028368
