Nanosponges as a Novel Drug Delivery System for the Management of Schizophrenia: A Comprehensive Review

Schizophrenia is a debilitating and long-term complex mental illness that affects approximately 20 million people worldwide. It presents itself as perceptional, thinking, emotional regulation, and social disturbances. Its common symptoms are positive symptoms such as hallucinations and delusions, negative symptoms such as emotional flatness, social isolation, and lack of drive, and cognitive problems such as memory, attention, and executive functioning(1). Schizophrenia has a severe personal, social, and economic burden on the affected individuals, their families, and healthcare systems because of its chronicity and complexity of progression. Since the ancient times, pharmacological interventions especially antipsychotic drugs have been the most used form of treating schizophrenia. The action of these drugs is largely due to the effects on dopamine and serotonin transmission in the brain. The Antipsychotics are commonly divided into first generation (FGAs) and second-generation (SGAs)(2). The first options were FGAs such as haloperidol and chlorpromazine and these can be used to treat positive symptoms such as hallucinations and delusions. Nevertheless, due to their high dopamine receptor antagonism, they have serious side effects related to motions, low quality of life, and lack of therapy compliance. The SGAs, including risperidone, olanzapine, quetiapine, and clozapine, have a more extensive therapeutic action and fewer extrapyramidal adverse effects because they act upon both the dopamine and serotonin receptors. However, they have the risks of metabolic disruptions, which are weight gain, diabetes and lipid abnormalities(3). Although SGAs have a better side, both types of antipsychotics do not fully cover the complicated neurobiology of schizophrenia and do not provide full symptom reduction. The most significant disadvantage of the existing antipsychotics is their poor pharmacokinetic characteristics. Most of these drugs are not soluble in water, they undergo a high rate of first-pass metabolism, and have a low oral bioavailability and they have difficulty in penetration through the blood-brain barrier (BBB). BBB provides a challenge to drug delivery of CNS drugs because it closely monitors the drugs entry into the brain(4). Accordingly, the attainment of effective levels of drugs in CNS can frequently demand high doses of antipsychotics, exposing the individual to the risk of systemic side effects. This, subsequently, affects patient adherence in an adverse way; a very critical matter in the treatment of schizophrenia. It has been shown that as many as half of schizophrenic patients do not adhere to medication therapy, which leads to a relapse, repeated hospital admission, and poor clinical outcomes in general(5). To improve patient compliance, antipsychotics in long acting injectable (LAI) forms were developed in order to provide the drug in a continuous movement over a period of time, between weeks, months, to years. Despite such benefits, LAIs also have certain disadvantages, such as the possibility of injection site reactions, restrictions in dosage change, and high costs of treatment. The above challenges have highlighted how urgent the development of more sophisticated drug delivery methods that can achieve better precision on the CNS, enhance drug bioavailability, lower doses, and minimize side effects(6).

In the recent past, nanotechnology has been considered a groundbreaking technology in drug delivery, especially that of CNS related diseases. Nanosponges are one of the many nanoscale carriers that have attracted a lot of attention because of their unique structural and functional characteristics. These are porous, widely cross-linked polymeric nanoparticles, commonly on the basis of cyclodextrins or other biodegradable polymers, having a three-dimensional porous structure. They are capable of entrapping both hydrophilic and lipophilic drugs. Nanosponges have a diameter of 100-500 nanometers so they will be ideal in passive transport across cellular membranes, such as the BBB(7).

There are numerous advantages of nanosponges over conventional methods of drugs delivery. They are porous and possess large surface area which allows them to accommodate quite large drug loading capacities. They also come in handy to stabilize volatile drug compounds, enhance solubility and controlled and targeted release. This effect has a long-acting effect especially in the treatment of schizophrenia where consistency in drug concentrations is a crucial element in ensuring relapse prevention. Further, nanosponges may be liganded, peptided or antibodied to provide such affinity to the brain tissues and augment its therapeutic potential and minimize undesirable side effects(8). The Porous morphology of Nanosponges shown in Figure 1.

Figure 1: Nanosponges

A number of antipsychotic medications such as risperidone, olanzapine, clozapine, and aripiprazole have been explored using nanosponge-based delivery platforms. Preliminary preclinical research has yielded encouraging outcomes, including better solubility, enhanced penetration into the central nervous system, lower toxicity, and extended drug release profiles. These results underscore the promise of nanosponge technology in addressing the key limitations of current antipsychotic treatments for schizophrenia. While nanosponges hold significant promise, they are not without limitations(9). Challenges such as complex manufacturing processes, difficulties in large-scale production, potential toxicity, and the current scarcity of clinical trials remain hurdles to their widespread adoption. Nevertheless, ongoing advancements in materials science and pharmaceutical nanotechnology continue to refine their safety and efficacy. As research progresses, nanosponges have the potential to become transformative tools in the development of next-generation therapies for schizophrenia. Nanosponges offer a compelling alternative by enhancing brain-specific targeting, enabling controlled drug release, and improving absorption. This review underscores the promise of nanosponge-based delivery platforms in revolutionizing schizophrenia treatment by exploring their design, advantages, therapeutic roles, current challenges, and future directions(10). The major types of Nanosponges are depicted in Figure 2.

Figure 2: Types of Nanosponges

Current Treatment of Schizophrenia

Antipsychotic medications remain the primary treatment for schizophrenia, serving as the first-line approach to managing its positive, negative, and cognitive symptoms. These drugs mainly act by regulating dopamine and serotonin pathways in the brain. However, their effectiveness is often limited, and long-term use is complicated by adverse effects, poor patient adherence, and pharmacokinetic challenges. Current therapeutic options include FGAs, SGAs, LAI formulations. FGAs such as haloperidol, chlorpromazine, fluphenazine, and thioridazine primarily inhibit dopamine D₂ receptors, which helps alleviate positive symptoms like hallucinations and delusions. Despite their efficacy, this strong dopamine blockade frequently leads to extrapyramidal side effects (EPS), including akathisia, dystonia, parkinsonism, and tardive dyskinesia. These movement-related complications can severely affect quality of life and often result in poor compliance or discontinuation of therapy. Although FGAs are cost-effective and sometimes preferred for managing acute psychotic episodes, their long-term use is restricted due to safety concerns(11).

SGAs including risperidone, olanzapine, quetiapine, clozapine, ziprasidone, and aripiprazole were developed to reduce EPS by targeting both dopamine D₂ and serotonin 5-HT_2A receptors. These medications are effective in managing positive symptoms and, to some extent, negative symptoms, while generally offering improved tolerability compared to FGAs. However, SGAs are associated with a range of metabolic side effects, such as weight gain, high blood sugar, insulin resistance, abnormal lipid levels, and increased risk of cardiovascular disease. Although clozapine is considered the most effective option for patients with treatment-resistant schizophrenia, its use is restricted due to the risk of agranulocytosis, necessitating frequent blood monitoring. Moreover, the long-term effectiveness of SGAs is hindered by issues like poor solubility, variable absorption, and challenges in maintaining stable therapeutic drug levels(12).

To improve treatment adherence in schizophrenia, LAI antipsychotics were developed. Medications like haloperidol decanoate, fluphenazine decanoate, risperidone microspheres, paliperidone palmitate, and aripiprazole LAI offer extended drug release over periods ranging from two to three months. These formulations help enhance compliance and lower the risk of relapse and hospitalization. Despite these advantages, LAIs come with certain limitations, including potential injection-site discomfort, restricted dosing flexibility, higher costs, and the requirement for administration by healthcare professionals. Furthermore, they do not fully overcome challenges related to adverse effects or limited drug delivery to the brain(13).

Antipsychotic drugs, whether taken orally or injected, still pose a great pharmacokinetic challenge. A significant number of these drugs possess low water solubility, and high levels of first-pass metabolism in addition to having poor ability to bypass the BBB. This has led to the need to have high doses in order to reach therapeutic concentration in the brain resulting in a heightened systemic side effect. Individual variations in drug metabolism also contribute to inconsistent treatment outcomes and a high rate of therapeutic failure. Advanced drug delivery systems that can lower systemic side effects, improve drug solubility, enable efficient BBB crossing, and guarantee sustained and controlled release are desperately needed in light of these constraints. Researchers are looking into nanotechnology-driven strategies, especially nanosponges, as viable substitutes to address these issues and get around the pharmacological and therapeutic drawbacks of the antipsychotic medications currently used to treat schizophrenia(14).

Nanosponges: A Novel Drug Delivery System

A novel family of nanoscale drug delivery devices called nanosponges was created to overcome major drawbacks of conventional pharmaceutical formulations, especially when it comes to the treatment of illnesses of the CNS, such as schizophrenia. These porous, sponge-like nanocarriers are usually made of biodegradable polymers or cyclodextrins cross-linked into a three-dimensional network with nanoscale voids. Nanosponges are potential instruments for administering antipsychotic drugs because of their unique architecture, which enables the effective encapsulation, protection, and controlled release of diverse drug compounds(15). Enhancing the stability and solubility of antipsychotic medications with low water solubility, like clozapine, olanzapine, and risperidone, is one of their main benefits. These drugs frequently have poor bioavailability and inconsistent absorption. These medications can be incorporated into the matrix of nanosponges due to their high surface area and porous structure, which enhances dissolution and promotes better oral absorption. This may result in lower dosages needed and fewer systemic adverse effects, which are typical of long-term antipsychotic therapy(16).

The capacity of nanosponges to distribute medications in a regulated and extended way is another benefit. Drug molecules are gradually released through diffusion or polymer breakdown after being held in their internal cross-linked network. This extended release helps to maintain stable plasma medication levels by avoiding the peaks and troughs that could lead to therapeutic failure or adverse effects. In the treatment of schizophrenia, where adherence is sometimes challenging, these formulations can reduce the frequency of dosages and provide improved compliance. Another notable advantage is their ability to enhance medication transport across the BBB, a major barrier in CNS therapy. Because of their enormous surface area, modifiable surface characteristics, and particle sizes between 100 to 200 nanometers(17).

Application of Nanosponges in Schizophrenia Treatment

When it comes to delivering antipsychotic drugs for the treatment of schizophrenia, nanosponges, an emerging class of nanocarriers, offer significant advantages. High drug encapsulation, improved solubility, degradation protection, and controlled drug release are all made possible by their special three-dimensional, porous, cross-linked polymeric framework(18). The main drawbacks of conventional antipsychotic treatments, such as limited water solubility, poor BBB penetration, frequent dosing requirements, and dose-dependent side effects, are addressed by these characteristics. When added to nanosponge systems, a number of commonly used antipsychotics, including risperidone, olanzapine, clozapine, and aripiprazole, have shown enhanced therapeutic results. Better solubility and stability, as well as a regulated release profile that guarantees more stable plasma concentrations and less peak-related adverse effects, have been demonstrated by risperidone-loaded nanosponges(19).

Their tiny particle size makes BBB transit more effective, which improves medication delivery to the brain and alleviates symptoms. Olanzapine's high first-pass metabolism and poor solubility are mitigated with olanzapine nanosponges. These formulations promote longer therapeutic levels and lessen the need for frequent doses by facilitating sustained release and enhancing solubility. Additionally, they may help mitigate metabolic side effects by minimizing systemic drug exposure(19).

Nanosponges formulation improve solubility and enable reduced dose for clozapine, which is frequently saved for instances that are resistant to treatment. Without frequent dose adjustments, the controlled release mechanism encourages more consistent therapeutic levels, which may lower the risk of side effects like seizures and increase overall treatment efficacy. An effective substitute for LAI formulations is aripiprazole nanosponges. Patient compliance may be enhanced by their capacity to deliver prolonged medication release without the need for injections(20). Additionally, their improved BBB penetration facilitates long-lasting antipsychotic effects. In conclusion, by increasing solubility, nanosponge-based drug delivery methods greatly improve the pharmacokinetic and therapeutic qualities of antipsychotics, allowing for extended release and making brain targeting easier. Better long-term results, less systemic adverse effects, lower relapse rates, and more stable medication levels are all a result of these advancements. Although there is a lot of promise for using nanosponges to treat schizophrenia, further clinical studies are needed to ensure their safety and effectiveness in human populations(21).

Advantages of Nanosponges Over Traditional Therapy

Nanosponges, a cutting-edge nanocarrier system, have the potential to address a number of issues related to the administration of conventional antipsychotic drugs. Poor water solubility, limited BBB penetration, rapid excretion from the body, and dosage-related side effects are common issues with conventional formulations, whether oral or injectable. These limitations frequently lead to poor adherence, increased relapse rates, and poor treatment outcomes for schizophrenia. Because of their distinctive structural and physicochemical properties, nanosponges offer a flexible and promising alternative(22).

One of the primary benefits of nanosponges is their capacity to significantly improve the stability and solubility of antipsychotics that are poorly soluble in water, such as clozapine, olanzapine, and risperidone. Their highly porous, sponge-like structure allows for efficient drug loading while shielding the active ingredients from deterioration. Because of this, the medication is released more consistently and steadily, reducing the fluctuations in blood concentration levels that are common with traditional treatments(23).

Additionally, their adjustable surface properties and nanoscale size typically between 100 and 500 nanometers allow for improved BBB penetration. By connecting to receptors on the BBB's endothelial cells, functionalizing nanosponges with certain ligands can improve their capacity to target brain regions and increase drug delivery to the brain while reducing systemic exposure. Nanosponges also encourage controlled and extended medication release, which lowers the frequency of dose and aids in maintaining steady therapeutic levels (24). This reduces the chance of relapse while simultaneously improving adherence. Nanosponges can minimize the systemic side effects frequently linked to conventional antipsychotic treatments by lowering the necessary dosage through improved CNS medication delivery. In summary, nanosponges are a promising candidate for future developments in the treatment of schizophrenia because they offer a highly efficient drug delivery system that can improve therapeutic results, encourage improved patient compliance, and lessen side effects(25).

Table 1: Nanosponges vs. Traditional Antipsychotic Therapy

Nanosponges: Challenges and Limitations

Nanosponges have a lot of potential as drug delivery systems for schizophrenia, but before they can be successfully used in clinical practice, a number of important issues need to be fixed. Even though these nanoscale carriers have advantages like better solubility, better blood–brain barrier (BBB) penetration, and controlled drug release, a number of scientific, technical, legal, and safety-related obstacles still prevent them from being used in clinical settings. The development of nanosponge-based treatments for schizophrenia depends on identifying and resolving these challenges. Among the most important the intricacy of their synthesis presents obstacles. Cross-linking procedures involving polymers or cyclodextrins are commonly used to create nanosponges(29). These reactions need exact control over variables such as temperature, solvent type, cross-linker concentration, and reaction duration. Important features like particle size, porosity, drug-loading capacity, and release behavior can be greatly impacted by even small changes in these parameters. Replicating results and meeting regulatory requirements become more challenging as manufacturing is scaled up from laboratory to industrial levels. The absence of defined production procedures is another urgent problem. Inconsistencies in the final product's physicochemical characteristics result from different research groups using different solvents, cross-linkers, purification methods, and drying procedures. Changes in variables like zeta potential, Establishing global quality control criteria is difficult because to stability and pore size distribution, which impede reproducibility. A significant obstacle to industrial scalability and regulatory approval is this discrepancy(30). The Challenges and limitation associated with drug delivery system is shown in Figure 3.

Figure 3: Nanosponges with challenges and limitation