1. INTRODUCTION:

Favipiravir is an antiviral medication that has shown potential in treating various RNA viruses, including influenza and certain strains of the coronavirus. To enhance its therapeutic efficacy, researchers have explored the use of nanoparticle drug delivery technologies, like PLGA nanoparticles, to encapsulate and deliver favipiravir¹. This approach offers several advantages, including improved drug stability, prolonged release, targeted delivery, and potentially reduced side effects. Because PLGA nanoparticles may contain both hydrophobic and hydrophilic medicines, they are a suitable polymer that is frequently employed as drug carriers.² When favipiravir is loaded into PLGA nanoparticles, it becomes entrapped within the polymer matrix. In order to maintain therapeutic levels in the body, this encapsulation protects against degradation and enables controlled discharge of the medication over a prolonged amount of time. The introduction of favipiravir loaded PLGA nanoparticles involves the preparation of these nanoparticles through various techniques such as solvent evaporation, emulsion-solvent evaporation, or nanoprecipitation. PLGA nanoparticles protect the encapsulated favipiravir from degradation caused by environmental factors or enzymatic breakdown, thus extending its shelf life. The slow and controlled release of favipiravir from the nanoparticles ensures a sustained therapeutic effect, reducing the frequency of dosing and improving patient compliance and can help minimize systemic exposure and potential side effect. Encapsulation within PLGA nanoparticles can enhance the solubility and bioavailability of favipiravir, which can improve its overall effectiveness.^3-5This study aimed to encapsulate the favipiravir in to PLGA polymer and subject it for pharmacokinetics behavior of formulated nanoparticle.

2. MATERIALS AND METHOD:

2.1. Materials:

Hetero Healthcare Ltd., India provided a complimentary sample of favipiravir (Pure material). We bought PLGA (lactide:glycolide (50:50), mol wt 30,000–60,000) from Labkart Scientific Solutions that is located in India. We bought Tween 60 and Dimethyl Sulfoxide (DMSO) from Finar Chemicals in India. The solvent medium and chemicals utilized in this study were all of High purity grade.

2.2. Method:

2.2.1. Formulation of Favipiravir nanoparticles:

The nanoprecipitation technique was used to produce the favipiravir-loaded mucoadhesive nanoparticle, with a minor modification of the technique suggested by Takeuchi et al. (2018) ⁶. About 100 mg of PLGA and 10 mg Favipiravir was separately made into solution in DMSO. The uniform was added drop by drop into twice the amount of aqueous solution containing 1% v/v of Tween 80. The mixture was subjected under Ultra-probe Q700 sonicator (Qsonica, Cole-Parmer India Pvt. Ltd, India) for 2 min. The resultant suspension was shaken for eight hours at room temperature while left exposed. The unentrapped medicines were separated from the produced nanoparticle by centrifuging it for 30 minutes at 1000 rpm at Remi, India. In order to get a dry powder form, the nanoparticle was ultimately freeze-dried at -20 ˚C using a laboratory Lyophilizer (Borg Scientific, India).

2.2.2. Investigations using DSC and XRD:

X-ray diffractometers have been utilized to identify the crystalline changes of Favipiravir in the nanoparticle and the physical status was tested by DSC analysis.

2.2.3. Calculating the encapsulation effectiveness:

The centrifugation technique was used to indirectly measure the percentage of Favipiravir loaded within the nanoparticles, and the RP-HPLC technique employed to determine the presence of amount of dispersed material in the supernatant.^7-9

2.2.4. Determination of size, Polydispersity index, zeta potential and surface morphology of nanoparticle:

Using the DSC approach, the particle size and PDI of the nanoparticle were determined¹⁰. The Malvern Analytical Ltd, UK was utilized to analyze the zeta potential based on electrophoretic mobility in an electric field. A SEM was applied to observe the nanoparticles' morphology. A conductive gold coated metal stub using the Hitachi 1010 ion beam sputter coater after a modest quantity of nanoparticles was added to it. Using the Hitachi 3000 N SEM (JSM 5610 LV SEM, JEOL, Japan) chamber, the prepared specimen was viewable. With a pressure of 0.6 mmHg and a voltage for acceleration of 20 kV, the picture was taken.

2.2.5. Research on In-vitro release kinetics:

The liberation drugs in the nanoparticles were measured by utilizing a cellulose separation tube (Braga and Oliveira, 2007) (Himedia laboratory, India). After being dissolved in 5 milliliters of water, nanoparticles (drug equivalent of 2 mg) were placed into a cellulose-based dialysis tube (molecular weight cut-off 35 kDa). After that, the dialysis tube was submerged in 300 cc of dissolving liquid at 37 °C while being stirred magnetically at a speed of 75 rpm. An adequate amount of the specimens was eluted then replenished with the same amount of fresh receptor fluid at different intervals. After centrifuging the eluted sample, the drug concentration of the supernatant was calculated using the HPLC method.^{11 – 12}

2.2.8. Determination of mucoadhesive binding efficiency of nanoparticle:

The nanoparticle-mucin interactions were evaluated by employing UV Spectrophotometric method¹³. In short, mucin was solubilized in a phosphate based buffer solution (pH 6.5) to yield 0.5% v/v. Following this, 10 mg of nanoparticles suspended in 2 ml of distilled water and 1 ml of mucin solution were combined. The resultant was centrifuged for two hours at 20°C and 35,000 rpm after being incubated for two hours at 37 °C. After extracting the supernatant and calculating the amount of free mucin, the spectra were taken at 255 nm using a UV-Visible spectrophotometer (Jasco, Japan). A comparison was made between the Favipiravir nanoparticle and PLGA and blank nanoparticles. The following formula was used to calculate the mucin binding efficiency.

Supernatant containing free mucin

Mucin Binding = -------------------------------------- x 100

Efficiency (%) Total mucin

2.2.9 Statistical study:

The mean and SD were determined for the whole data set. GraphPad Prism 5 software was utilized to perform Dunnett's test and one-way ANOVA, with significance defined as p < 0.05.

3. RESULTS AND DISCUSSION:

Administering drugs through inhalation is a safe and effective approach for treating respiratory conditions like cystic fibrosis, asthma, COPD, and lung infections¹⁴. Several inhalation devices have shown effectiveness in managing pulmonary route issues¹⁵. DPI is one of the most well-known devices for pulmonary medication administration among them. Numerous investigations have been conducted using various techniques to create mucoadhesive nanoparticles of polymeric material that are suitable for pulmonary distribution ^6,16. It has been formulated by nanoprecipitation technique with the help of the Ouzo effect¹⁷. The effect has been processed by organic solvent containing components that were precipitated in aqueous solution to produce nanoparticles and this process would be enhanced by low frequency in the ultra-probe sonicator. When both the phases are mixed properly, the organic phase is back to back dispersed as drops within the non-solvent phase produce nanoparticle precipitate. It is caused by inter facial agitation and thermal variability in the mixture.¹⁸Fig 1. displays the Favipiravir nanoparticles X-ray diffraction patterns. Six distinct peaks were visible in the XRD spectra of Favipiravir at (2 theta) 5.37°, 8.45°, 12.61°, 14.45°, 16.05°, and 22.20°. These strong peaks demonstrated the drug's absolute crystalline nature. Similarly, chitosan showed two distinguished peaks at 9.63 and 20.53 (2 theta), which would be the proof of semi-crystalline nature. In the Favipiravir nanoparticle spectra that have less intense peaks, that reference Favipiravir is encapsulated as an amorphous form. The drug loading and co-solvent type had no effect on the morphology of Favipiravir in nanoparticles. The nanoparticles are smaller in size and it causes broad peaks in the diffraction. The peaks have broadened by a low number of crystalline planes and its turn to cause a disappearance of intensity in the diffraction patterns.¹⁹During the nanoprecipitation, Favipiravir was completely embedded in the network structure of PLGA. In the Favipiravir nanoparticle which was observed, three sharp peaks disappeared as it was with pure Favipiravir, due to conversion of crystallinity to amorphous nature. Amorphous nature of Favipiravir showed excellent absorption, and drug release kinetics.

The DSC spectrum was used to estimate the temperature of glass transition (Tg) of Favipiravir within product. The thermograms of Favipiravir and nanoparticles were shown in Fig 2. Favipiravir showed two exothermic peaks at 135.7 and 173.5 °C and three endothermic peaks at 31.3, 121.7 and 132.6 °C. These sharp peaks confirmed that the Favipiravir is . On the other hand, the nanoparticle showed a broader exothermic peak at 138.1 °C and no other sharp peaks were observed, which concludes that Favipiravir was a matrix in polymeric network structure as an amorphous form. Favipiravir nanoparticles provide better dissolution properties in lung fluid that provide enhancement in the drug bioavailability and efficacy, when it’s administered through pulmonary route²⁰.

Fig. (1). XRD spectra of favipiravir mucoadhesive

Fig. (2). DSC spectra of favipiravir mucoadhesive nanoparticles

nanoparticles.

The surface morphology of nanoparticle was characterized by SEM technique and it showed that the formulated nanoparticle has spherical shape with smooth surface (Fig. 3). When a nanoparticle was added to a biological fluid, it was smoothly encircled by bio-macromolecules, which changed every biological characteristic and were later removed from the biological system by the operation of opsonin²¹. The nanoprecipitation technique formed uniform shape and size of nanoparticles by Ouzo effect, which was enhanced by ultrasonication technique.

Fig. (3). SEM image of favipiravir mucoadhesive nanoparticles

The nanoparticle size, Zeta potential and PDI of Favipiravir nanoparticles were analyzed by Zetasizer. These properties could be the main factor in drug diffusion, permeation and stability of the nanoparticle²². The prepared nanoparticle has the size of 104.6 nm with PDI of 0.02 (Fig 4 and 5).According to Guadarrama-Escobar et al. (2021)²³, a significant contributing factor to particle-particle aggregation is the nanoparticles zeta potential. The synthesized Favipiravir nanoparticles displayed -12.7 mV (Fig. 5), which is more stable and does not exhibit any aggregation. The ideal Zeta potential value of the most stable nanoparticle would be in the range between ±10 to 30 mV. The negative zeta potential value was higher in the nanoparticle preparation as a consequence of terminal Carboxyl functional groups in the polymers. Lowering the negative zeta potential value directly proportional to nanoparticle stability, hence the prepared mucoadhesive Favipiravir nanoparticle was found to be stable.

Fig. (4). Particle size of favipiravir mucoadhesive

Fig. (5). Zetapotential of favipiravir mucoadhesive nanoparticles. nanoparticles.

The entrapment of Favipiravir in the nanoparticle showed 72.06 ± 0.2 % and it confirmed that a satisfied quantity of drug would reach the lung to prevent the viral replication. The % Entrapment efficiency would be dependent on concentration of PLGA and Chitosan. Since, the polymer shows more entrapment efficiency than polymeric chains. More hydrocarbon chains might be the reason for high entrapment efficiency.²⁴

The drug release profile of Favipiravir mucoadhesive nanoparticle was evaluated by Cellulose dialysis tube and the released Favipiravir was analyzed by HPLC technique. The precipitated mucoadhesive nanoparticle has a strong matrix network structure of polymer and the Favipiravir has been entrapped in the matrix that showed significant sustained release. Approximately 16.2 ± 1.02% of the medication was released at the beginning after two hours (Fig. 6), which indicates that the reason for a small proportion of medication being released was the polymeric lacto-glycolic-acid linkage that formed a more solid wall around the drug²⁵ which provides prolonged release. At the end of 48 h, a significant amount (85.1 ± 4.18%) of drug has been released and it confirms that sustained release over the period and it stretches satisfied bioavailability. The release follows zero order kinetic mechanism (R² = 0.9095) and Higuchi's equation linearity showed drug release would be a diffusion mechanism. Peppa’s linearity showed non-Fickian anomalous transport from the polymeric matrix into diffusion medium.

Fig. (6). In-vitro release profile of Favipiravir nanoparticles

Fig. (7). Mucin binding efficiency of mucoadhesive nanoparticles

There are several well-established techniques for assessing mucoadhesion strength of dosage forms such as pills, gels, and films. Texture analysis is one of the procedures used to measure the mucoadhesive strength of dosage form in mucous membranes. This technique, although accurate and dependable, might not be ideal for examining particles at the nanoscale.²⁶ As a result, the emphasis has shifted to other methodologies and is able to measure the mucoadhesive strength by using various methods and to evaluate the strength of nanoparticles in mucin. Spectroscopic investigation is the easiest approach for analyzing the assessing adhesion and behavior in mucosal environments.

The mucoadhesive nature of Favipiravir nanoparticles would be compared with plain drug and PLGA nanoparticles respectively (Fig 7). PLGA nanoparticles showed lowest binding capacity as 32.2 ± 1.2% . PLGA polymer was used to create this mucoadhesive nanoparticle, which forms a hydrogen bond with the hydrophilic functional groups (-OH- & -NH2-) in mucin. The polymer's positive charge interacts with the negative charge of sialic acid, which is present in mucin²⁷

Despite the fact that the nanoparticles displayed mucosal binding effectiveness, which depends on type of the polymer charge and hydrogen bonding. According to Chatterjee et al. (2017), the perfect mucoadhesive polymers would be those that adhere quickly to the mucosal layer without altering their physical makeup, minimize drug release interference, degrade naturally without releasing any harmful byproducts, and improve the penetration of active agents.

4. CONCLUSION:

We approached the delivery of Favipiravir mucoadhesive nanoparticle by dry powder inhaler. In this attempt, the prepared nanoparticles have appropriate particle size to reach lungs and significant mucoadhesive strength on pulmonary tract with substantial DPI dispersion properties. Therefore, Favipiravir mucoadhesive nanoparticle loaded dry powder inhaler could be the best and alternative route of administration during the epidemic situation.

5. CONFLICT OF INTEREST:

There are no conflicts of interest among the writers, and each one contributed equally.

6. ACKNOWLEDGEMENT:

The authors are thank full to Mr. P.V.V.Siva Krishna, Assistant Professor, Department of Pharmaceutics, Vignan Pharmacy College, Vadlamudi, Guntur. Andhra Pradesh helped us by giving PLGA polymer for this research work.

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Received on 13.08.2024 Revised on 06.12.2024

Accepted on 07.03.2025 Published on 01.10.2025

Available online from October 04, 2025

Research J. Pharmacy and Technology. 2025;18(10):4635-4640.

DOI: 10.52711/0974-360X.2025.00666

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