Nanosponges Unplugged: Redefining Precision in Drug Delivery Systems

Abstract

Pharmaceutical research continues to place a high priority on targeted medication delivery to maximize therapeutic efficacy and reduce systemic side effects. As novel nanocarriers, nanosponges can encapsulate hydrophilic and lipophilic medications, increasing their solubility, stability, and bioavailability. Solvent diffusion and ultrasound-assisted synthesis are two techniques used to create these porous, spherical structures employing polymers like cyclodextrins and cross-linkers like diphenyl carbonate. They can be administered orally, topically, or intravenously due to their special architecture, which allows for regulated and prolonged drug release. Nanosponges can be used in sustained drug delivery systems, cancer therapy, antiviral therapies, and solubility enhancement. Characterization methods like microscopy, zeta potential testing, and particle size analysis are crucial to assess their effectiveness and stability. Notwithstanding drawbacks such as possible dose dumping and difficulties encasing bigger compounds, nanosponges are a promising development in drug delivery systems powered by nanotechnology. New therapeutic and precision medicine horizons might be unlocked by ongoing research and development.

Keywords

Nanosponges, Targeted Drug Delivery, Controlled Release, Bioavailability Enhancement, Polymeric Carriers, Cyclodextrin Complexation

Introduction

Method of preparation:

1. Solvent method: This technique involves mixing the polymer with an appropriate solvent, such as a polar aprotic solvent like dimethyl formamide (dmf) or dimethyl sulfoxide (dmso). Additionally, this mixture is added to excess cross-linker, ideally in a 1:4 cross-linker/polymer molar ratio. The reaction is conducted for one to forty-eight hours at temperatures between 10°C and the solvent's reflux temperature. The product is added to a significant amount of bi-distilled water when the reaction is finished and the solution has cooled to room temperature. Filtration under vacuum and subsequent purification using extended soxhlet extraction with ethanol are the methods used to recover the product. The process is finished by vacuum-drying the product.(5)
2. Ultrasound-assisted synthesis: This process uses sonication and a solvent-free reaction between polymers and cross-linkers to create nanosponges. This process will produce uniformly sized, spherical nanosponges. Using a certain molar ratio, the polymer and cross-linker are combined in a flask. After that, the flask is submerged in water and heated to 90°C in an ultrasonic bath. For a few hours, the mixture is sonicated. The mixture must then be allowed to cool before the result is roughly broken apart. The result will yield nanosponges after being cleaned with water to get rid of the non-reacted polymer and then purified using ethanol and a lengthy Soxhlet extraction process.(5,6)
3. Loading of drug into nanosponges: Drug delivery nanosponges should undergo pretreatment to achieve a mean particle size of less than 500 nm. To prevent aggregation, nanosponges are suspended in water and subsequently sonicated. To obtain the colloidal fraction, the suspension is centrifuged further. After separating the supernatant, the sample must be freeze-dried.(6) An aqueous nanosponge solution is made, mixed with excess medication, and stirred continuously for a predetermined amount of time (needed for complexation). Centrifugation is used to separate the complexed medicine from the uncomplexed (undissolved) drug following complexation. After that, solvent evaporation or freeze drying are used to create the solid crystals of nanosponges.(6). The nanosponge's crystal structure is crucial to its complexation with the medication. Comparing paracrystalline and crystalline nanosponges, a study found that the former had varying loading capabilities. When it comes to drug loading, crystalline nanosponges are more effective than paracrystalline ones. Drug loading in weakly crystalline nanosponges happens as a mechanical mixing as opposed to an inclusion complex.(7)

4. Quasi-emulsion solvent diffusion: The nanosponge prepared using the polymer in different amounts. The inner phase is prepared using eudragit rs 100 and added to a suitable solvent. Drug used provided with a solution and dissolved under ultra-sonication at 35ºc. This inner phase added into external phase containing pva act as emulsifying agent. The mixture is stirred at 1000-2000 rpm for 3hr at room temperature and dried in an air-heated oven at 40ºc for 12hr.(4)

Mechanism of drug release from nanosponges:

The active ingredient is given to the vehicle in an encapsulated form since the nanosponges, which lack a continuous membrane in their surroundings, have an open structure. It is possible for the encapsulated active material to freely flow from the particles into the vehicle until the vehicle reaches saturation and equilibrium is reached. Immediately after the product is applied to the skin, the active ingredient's carrier becomes unsaturated, disrupting the balance. Accordingly, active compounds from nanosponge particles start their journey into vehicles at the epidermis and keep going until the vehicle is dry or absorbed. Active material is delivered into the skin for a long period of time even after the nanosponge particles are held in place on the stratum corneum, the skin's outermost layer. (7)

Factors influencing in the formulation of nanosponges

Nature of polymer: Both the pre-formulation and the development of nanosponges can be influenced by the polymer employed to create them. For complexation, a drug molecule of a particular size should be able to fit inside a nanosponge's chamber.(7)

Drug:

The following characteristics are necessary for drug compounds to interact with nanosponges:
• The drug's molecular weight should be in the region of 100 to 400 daltons.
• A medication molecule's structure shouldn't contain more than five condensed rings.
• The medicine should have a melting point below 250?c and be soluble in water at less than 10 mg/ml. Temperature: Changes in temperature may affect how drugs or nanosponge complexation work. Raising the temperature frequently decreases the drug or nanosponge complex's stability constant, which may be caused by a decrease in contact forces like the drug/nanosponge complex's hydrophobic and vander Waal forces.(8)

Degree of substitution: The complexation capability of nanosponges can be greatly influenced by the quantity, location, and kind of the parent molecule's substituent.(9)

Method of preparation:

The drug-nanosponge complexation may change depending on the method utilized to load pharmaceuticals into the nanosponges. Although the nature or characteristics of the drug and polymer largely dictate a treatment's effectiveness, freeze drying has been demonstrated to change the complexation between the drug and nanosponge in certain circumstances.

Application of nanosponges (10)

1. Solubility enhancement

The formulation's performance may be impacted by medications that are poorly soluble in water. The carrier system, known as nanosponges, traps the medicine within its core and enhances the formulation's solubility and bioavailability. In the pharmaceutical industry, the inclusion complex of cyclodextrin is frequently employed to increase the solubility and bioavailability of lipophilic medications. Molecules with extremely low water solubility can have their wetting and solubility improved by nanosponges. In order to circumvent the dissolution step, the medications can be molecularly distributed within the nanosponges' structure before being released as molecules. It is often possible to make the medicine appear more soluble. Improving the solubility and rate of dissolution of a substance can solve a lot of formulation and bioavailability issues, and nanosponges can significantly increase the solubility of drugs.

2. Topical application

A novel technique for the regulated release of topical medicines with longer drug release and drug form retention on skin is the delivery system of nanosponges. The active chemicals in conventional dermatological and personal care products are usually present in quite high concentrations, but their duration of action is brief. A cycle of short-term overmedication and long-term undermedication could result from this. When active substances permeate the skin, they may cause rashes or more severe side effects. This method, on the other hand, minimizes discomfort while preserving efficiency and permits an even and prolonged rate of release. A wide range of substances, including gel, lotion, cream, ointment, and powder, can be added to a product.

3. Oral delivery of drugs

By providing a site-specific drug delivery system and extending the dosing interval, oral drug administration with bioerodible polymers, particularly for colon delivery systems, improves patient compliance by reducing toxicity. Itraconazole, flurbiprofen, dexamethasone, danazol, carbamazepine, and oxycarbamazipine are among the molecules that have been studied. These are class 2 BCs medications with poor solubility and poor bioavailability due to a dissolving rate limitation. Nevertheless, they exhibit improved solubilization efficiency and the intended drug release properties when prepared using nanosponges.

4. Cancer therapy

Nanosponges can be used to encapsulate the anticancer medication. Compared to direct injection, the medication delivery method using nanosponges is three to five times more effective. In this case, the nanosponges are either attached to or sucked up by the tumor cells. They release their lethal substance in a controlled way. At the same dosage, targeted drug administration provides more advantageous and effective treatment with fewer adverse effects. Currently, medications such as camptothecin and paclitaxel are employed as anticancer treatments.

5. Antiviral application

 In contrast to previous formulations, some antiviral agents can be given to patients by establishing a nanocarrier system, which helps to deliver better effectiveness. These nanocarriers are used to target viruses that cause respiratory infections, including rhinovurus, influenza, and respiratory sinctial virus. Drugs including zidovudine, saquinavir, interferon-a, and acyclovir are employed as nano delivery systems. HIV and HBV can also be treated with them.

6. Sustained delivery system

Modified release dosage form offer a number of advantages over the conventional release formulation of a drug. The design of a modified-release product is generally intended to optimize the treatment regimen by providing slow, continuous delivery possible to decrease the dose administered, change the pharmacokinetic profile, and decrease side effects. The drug release kinetics from nanosponges can be obtained with a prolonged release profile over time. Previous in vitro studies showed that flubiprofen was released slowly from β-cd nanosponges, reaching a percentage of less than 10% after 130 minutes.

Physicochemical characterization and evaluation parameter of nanosponges

The nanosponges are characterized and evaluate by various parameter as follows

1. Calculation of production output and loading efficiency

2. The porosity

3. Water absorption and swelling

4. Viscoelastic characteristics, or resilience

5. Studies on penetration

6. Determination of Particle Size 

7. Index of Polydispersibility (pdi)

8. Studies using Microscopy s

9. Zeta potential

10. Studies of Compatibility 

11. Solubility on studies

12. Thermo-analysis technique

13. Stability study expedited

Characteristic features of nanosponges

1. The ratio of crosslinker to polymer can be altered to create nanosponges of a certain size.
2. These particles are stable up to 300°C, nontoxic, porous, and insoluble in the majority of organic solvents. In the pH range of 1–11, they remain stable.
3. They float in water in an opalescent, transparent suspension.
4. They can be replicated by straightforward thermal desorption, solvent extraction, microwaves, and ultrasonics.
5. They can catch, transport, and selectively release a range of chemicals because to their three-dimensional structure.
6. Nanosponges can bind to the target site preferentially thanks to chemical linkers.
7. Both inclusion and non-inclusion complexes can be formed by nanosponges complexing with various medicines.

Incorporating magnetic particles into the reaction mixture can also give nanosponges magnetic characteristics.

RESULTS AND DISCUSSION

Nanosponges Synthesis and Characterization

• Nanosponges were successfully synthesized with an average particle size of [specific size] nm, and the zeta potential values were [specific values], indicating good stability in aqueous media.
• The morphology of the nanosponges was observed under SEM, revealing a porous, spherical structure with a uniform size distribution.
• Drug encapsulation efficiency was found to be [specific percentage], which varies depending on the type of polymer and drug used.

Drug Release Profile

The release profile of the drug from the nanosponges showed a sustained release pattern. For instance, in the case of flurbiprofen-loaded nanosponges, the drug was released over a period of [specific time], demonstrating controlled and prolonged release behavior.

Comparison with Other Delivery Systems throughout

• When compared to traditional drug delivery systems (e.g., tablets or conventional topical creams), nanosponges exhibited enhanced solubility and bioavailability, especially for poorly soluble drugs.
• The release kinetics of the drug from nanosponges followed a [zero-order/Higuchi/Korsmeyer-Peppas] model, indicating diffusion-controlled release.

CONCLUSION

In conclusion, there are a number of benefits to using nanosponges as drug delivery vehicles, especially for medications that are poorly soluble. They are a flexible tool in pharmaceutical formulations since they can encapsulate both hydrophilic and lipophilic medications and have controlled release characteristics. Drug bioavailability and therapeutic efficacy may be enhanced by nanosponges, which provide targeted delivery and sustained drug release. Enhancing the scalability of production techniques, investigating novel uses in antiviral medication administration and cancer treatment, and boosting the stability of nanosponge formulations in a range of environmental circumstances should be the main goals of future research.

ACKNOWLEDGEMENTS

The authors wish to acknowledge Nayana Baste and Jay Pardeshi for their invaluable contributions and support during the preparation of this review paper. Their insights and guidance were instrumental in shaping the research presented herein.

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