Formulation and Evaluation of Fluconazole-Loaded Polymeric Nanoparticles Prepared by Solvent Evaporation Method

Fungal infections remain a significant global health concern, particularly among immunocompromised patients and individuals with chronic illnesses. Superficial and systemic fungal infections such as candidiasis, onychomycosis, and aspergillosis are associated with considerable morbidity and, in severe cases, high mortality rates. ^1-2 Although several antifungal agents are available, their clinical effectiveness is often limited by poor solubility, inadequate tissue penetration, variable bioavailability, and drug-related toxicity. Therefore, the development of advanced drug delivery systems capable of improving the therapeutic efficacy of antifungal drugs is of considerable interest. ^3-5

Fluconazole is a widely used triazole antifungal agent effective against a broad spectrum of fungal pathogens, particularly Candida species. ⁶ It acts by inhibiting lanosterol 14-α-demethylase, a cytochrome P450–dependent enzyme essential for ergosterol biosynthesis in fungal cell membranes, leading to increased membrane permeability and fungistatic activity. ⁷ Despite its clinical utility, fluconazole exhibits certain formulation challenges, including limited solubility under physiological conditions and suboptimal penetration into infected tissues, which can reduce its therapeutic performance and necessitate higher or repeated dosing.⁸

Nanotechnology-based drug delivery systems have emerged as a promising strategy to overcome the limitations associated with conventional dosage forms. ⁹ Among various nanocarriers, polymeric nanoparticles have gained significant attention due to their small particle size, high surface area, biocompatibility, and ability to provide controlled and targeted drug delivery. ¹⁰ Polymeric nanoparticles typically exist as nanospheres or nanocapsules, in which the drug may be uniformly dispersed within the polymeric matrix or enclosed within a polymeric shell. These systems can protect drug molecules from degradation, enhance solubility, improve bioavailability, and reduce dose-related side effects.¹¹

Polyvinylpyrrolidone K30 (PVPK30) is a hydrophilic, biocompatible polymer extensively used in pharmaceutical formulations as a stabilizer and solubility enhancer. Its ability to form stable dispersions and prevent nanoparticle aggregation makes it a suitable candidate for nanoparticle formulation.¹² The solvent evaporation method is one of the most commonly employed techniques for preparing polymeric nanoparticles due to its simplicity, reproducibility, and ability to produce nanoparticles with controlled size distribution by varying formulation parameters such as polymer concentration and surfactant content.¹³

In the present study, fluconazole-loaded polymeric nanoparticles were formulated using the solvent evaporation method with PVPK30 as a stabilizer and Tween 20 as a surfactant. The effect of varying stabilizer concentration on particle size and stability was systematically evaluated.¹⁴ The prepared nanoparticles were characterized using ultraviolet–visible spectroscopy, particle size analysis, and zeta potential measurement. The objective of this research was to develop a stable polymeric nanoparticle system for fluconazole that could potentially enhance its therapeutic efficacy and provide a promising approach for antifungal drug delivery.¹⁵

2. MATERIALS AND METHODS

2.1 Drug and Excipients

Fluconazole was obtained as a gift sample from a reputed pharmaceutical company and was used as received. Polyvinylpyrrolidone K30 (PVPK30) was used as the polymeric stabilizer. Tween 20 was employed as a surfactant to enhance nanoparticle stability. Methanol and distilled water were used as solvents during formulation and analysis. All chemicals and reagents used in the study were of analytical grade.

2.2 Preparation of Fluconazole-Loaded Polymeric Nanoparticles

Fluconazole-loaded polymeric nanoparticles were prepared by the solvent evaporation method. Accurately weighed fluconazole was dissolved in methanol to form the organic phase. PVPK30 was dissolved in distilled water to prepare the aqueous phase, followed by the addition of Tween 20 as a surfactant. The organic phase containing the drug was added dropwise into the aqueous phase under continuous magnetic stirring to form an emulsion.

Table 1: Composition of Fluconazole-Loaded Polymeric Nanoparticle Formulations

The resulting dispersion was stirred continuously to allow evaporation of the organic solvent, leading to the formation of polymeric nanoparticles. The prepared nanoparticle suspension was further stirred until complete removal of the solvent was achieved. Different formulations (F1–F4) were prepared by varying the concentration of PVPK30 while keeping the drug concentration constant. The final nanoparticle dispersions were collected and stored in airtight containers for further characterization.

The organic phase containing fluconazole was added dropwise to the aqueous phase under continuous magnetic stirring. The formulation process was carried out using a magnetic stirrer, as shown in Figures 1 and 2, to ensure uniform mixing and complete evaporation of the organic solvent.

Figure 1: Preparation of Fluconazole Polymeric Nanoparticles Using Magnetic Stirrer (Initial Stirring Stage)

Figure 2: Continuous Magnetic Stirring During Solvent Evaporation Process

2.3 Characterization of Polymeric Nanoparticles

2.3.1 Determination of Drug Content

The drug content of the prepared polymeric nanoparticles was determined using ultraviolet–visible spectrophotometry. An accurately measured quantity of nanoparticle dispersion equivalent to a known amount of fluconazole was dissolved in methanol and suitably diluted. The absorbance was measured at the predetermined λmax of fluconazole using a UV visible spectrophotometer against a blank. Drug content was calculated using the calibration curve of fluconazole.

2.3.2 Particle Size Analysis

The mean particle size of the prepared polymeric nanoparticles was measured using dynamic light scattering (DLS) technique. The nanoparticle dispersion was suitably diluted with distilled water to avoid multiple scattering effects and analyzed at room temperature. The average particle size was recorded and expressed in nanometers (nm).

2.3.3 Zeta Potential Measurement

Zeta potential measurements were carried out to evaluate the surface charge and stability of the prepared nanoparticles. The nanoparticle dispersions were diluted with distilled water and analyzed using a zeta potential analyzer based on electrophoretic mobility. The zeta potential values were expressed in millivolts (mV).

3. RESULTS AND DISCUSSION

3.1 Physical Description and Organoleptic Properties

The prepared fluconazole-loaded polymeric nanoparticles were observed for physical appearance and organoleptic properties. All batches appeared as a white, free-flowing powder with an unpleasant taste and no detectable odor (Table 2). These observations indicate uniformity in physical form and suggest that the nanoparticles were successfully obtained without any visible signs of aggregation or degradation.

Figure 4: Prepared Fluconazole-Loaded Polymeric Nanoparticle Formulations (F1–F4)

Table 2: Physical Description and Organoleptic Properties of Fluconazole Nanoparticles

3.2 Melting Point

The melting point of the pure drug fluconazole was determined using a melting point apparatus and was found to be 139?°C. This value is consistent with literature reports, confirming the purity of the drug used for nanoparticle formulation. No significant change in melting point was observed after formulation, suggesting that the drug retained its crystalline properties during nanoparticle preparation.

3.3 UV-Visible Spectroscopy

The UV-visible spectroscopy was employed to evaluate the drug concentration and preliminary estimation of nanoparticle size in aqueous suspension. A calibration curve was constructed using fluconazole in phosphate buffer (pH 7.4) with concentrations ranging from 0 to 10 µg/mL.

Table 3: Calibration Data of Fluconazole in Phosphate Buffer (pH 7.4) Using UV-Visible Spectroscopy

Fig no. 5 Calibration curve of fluconazole in phosphate buffer Ph 7.4

3.4 Drug Content

The drug content of fluconazole-loaded polymeric nanoparticles was determined to evaluate the uniformity of drug distribution within the formulations. All prepared formulations (F1–F4) exhibited satisfactory drug content, indicating efficient incorporation of fluconazole into the polymeric matrix. Minor variations in drug content among different batches were observed, which may be attributed to differences in polymer concentration and emulsification efficiency. However, the overall results confirmed that the solvent evaporation method is suitable for achieving uniform drug loading in polymeric nanoparticles.

3.5 Particle Size Analysis

Particle size is a critical parameter influencing the stability, drug release behavior, and biological performance of nanoparticulate systems. The mean particle size of the prepared fluconazole-loaded polymeric nanoparticles was found to be in the nanometer range for all formulations, confirming successful nanoparticle formation.

An increase in the concentration of PVPK30 resulted in a significant reduction in particle size. Formulation F1 showed comparatively larger particle size, whereas formulation F4 exhibited the smallest mean particle size of 205.3 nm. This reduction in particle size may be attributed to the enhanced stabilizing effect of PVPK30, which prevents particle aggregation and promotes the formation of smaller droplets during emulsification. The nanoscale particle size achieved is expected to enhance surface area, improve drug dissolution, and facilitate better interaction with biological membranes, thereby improving antifungal efficacy.

Figure 6: Particle size distribution of fluconazole-loaded polymeric nanoparticles – Formulation F1 prepared by solvent evaporation method.

Figure 7: Particle size distribution of fluconazole-loaded polymeric nanoparticles – Formulation F2 prepared by solvent evaporation method.

Figure 8: Particle size distribution of fluconazole-loaded polymeric nanoparticles – Formulation F3 prepared by solvent evaporation method.

Figure 9: Particle size distribution of fluconazole-loaded polymeric nanoparticles – Formulation F4 prepared by solvent evaporation method.

3.6 Zeta Potential

Zeta potential measurement provides valuable information regarding the surface charge and stability of nanoparticle formulations. The zeta potential values of all formulations were found to be in the negative range, indicating the presence of surface charge sufficient to maintain colloidal stability.

Among all batches, formulation F4 showed an optimal zeta potential value of −19.8 mV, suggesting better electrostatic repulsion between nanoparticles and reduced risk of aggregation. The observed increase in zeta potential magnitude with higher polymer concentration may be due to improved surface coverage of nanoparticles by PVPK30. Although values around ±30 mV are generally considered ideal for long-term stability, the obtained zeta potential values indicate moderate stability suitable for short-term pharmaceutical applications.

Figure 10: Zeta potential distribution of fluconazole-loaded polymeric nanoparticles – Formulation F1 prepared by solvent evaporation method.

Figure 11: Zeta potential distribution of fluconazole-loaded polymeric nanoparticles – Formulation F2 prepared by solvent evaporation method.

Figure 12: Zeta potential distribution of fluconazole-loaded polymeric nanoparticles – Formulation F3 prepared by solvent evaporation method.

Figure 13: Zeta potential distribution of fluconazole-loaded polymeric nanoparticles – Formulation F4 prepared by solvent evaporation method.