Formulation and Evaluation of Polymeric Nanospheres of Diclofenac Sodium for Sustained Anti-Inflammatory Activity

Figure 2 Polymeric Nanoparticles

1.5 Research Gap

Although several studies have investigated polymeric nanoparticle-based drug delivery systems, limited research has focused on optimizing PLGA-based polymeric nanospheres for sustained delivery of diclofenac sodium using a simple and reproducible formulation approach. Furthermore, there remains a need to improve drug entrapment efficiency, achieve uniform particle size distribution, ensure prolonged drug release, and enhance formulation stability. Addressing these challenges may lead to the development of an effective sustained-release nanocarrier capable of improving the therapeutic performance of diclofenac sodium while reducing dosing frequency and systemic adverse effects.

2. MATERIALS AND METHODS

2.1 Materials

The materials required for the preparation of Diclofenac Sodium-loaded polymeric nanospheres were procured from certified and reliable sources. Diclofenac sodium was used as the model anti-inflammatory drug. Poly (D,L-lactide-co-glycolide) (PLGA) was selected as the biodegradable polymer due to its excellent sustained-release properties and biocompatibility. Polyvinyl alcohol (PVA) was used as a stabilizing agent to maintain emulsion stability during nanoparticle formation. Dichloromethane (DCM) was employed as an organic solvent for polymer dissolution. Mannitol was used as a cryoprotectant during freeze-drying of the nanoparticles. All chemicals used in the study were of analytical grade.

Table 1 Materials Used

2.2 Instruments and Equipment

The formulation and evaluation of polymeric nanospheres were carried out using standard laboratory instruments. Weighing was performed using an electronic balance. Emulsification and particle size reduction were achieved using a high-speed homogenizer and probe sonicator. Particle size, PDI, and zeta potential were analyzed using a dynamic light scattering (DLS) system. UV-Visible spectrophotometer was used for drug estimation. Morphological analysis was carried out using scanning electron microscopy (SEM). Freeze drying was performed using a lyophilizer.

Table 2 Instruments Used

2.3 Method of Preparation of Polymeric Nanospheres

Diclofenac sodium-loaded polymeric nanospheres were prepared using the solvent evaporation technique. In this method, PLGA was dissolved in dichloromethane to form the organic phase. Diclofenac sodium was incorporated into this polymeric solution under continuous stirring to ensure uniform distribution.

This organic phase was then slowly emulsified into an aqueous phase containing polyvinyl alcohol under high-speed homogenization. The formed emulsion was further sonicated to reduce droplet size and obtain a nanosized dispersion. Continuous stirring was maintained to allow complete evaporation of dichloromethane, resulting in the formation of solid polymeric nanospheres.

The nanoparticles were collected by centrifugation and washed with distilled water to remove excess stabilizer. Finally, the formulation was freeze-dried using mannitol as a cryoprotectant and stored in airtight containers for further evaluation.

2.4 Formulation of Polymeric Nanospheres

Diclofenac sodium-loaded polymeric nanospheres were prepared by the solvent evaporation method. In this method, PLGA was dissolved in dichloromethane to prepare the organic phase, followed by incorporation of Diclofenac sodium into the polymeric solution. The prepared organic phase was gradually emulsified into an aqueous phase containing polyvinyl alcohol (PVA) as a stabilizing agent under continuous stirring and homogenization.

The formed emulsion was subjected to sonication to reduce the size of dispersed droplets and obtain nanosized polymeric carriers. Continuous stirring was maintained to facilitate the complete evaporation of the organic solvent, resulting in the formation of solid polymeric nanospheres.

The prepared nanospheres were separated by centrifugation, washed several times with distilled water to remove residual surfactant, and subsequently subjected to freeze-drying using mannitol as a cryoprotectant to improve the stability and prevent aggregation of nanoparticles during storage.

2.5 Formulation Design of Diclofenac Sodium-Loaded Polymeric Nanospheres

A total of six formulations (F1–F6) of Diclofenac sodium-loaded polymeric nanospheres were prepared by varying the concentration of PLGA polymer while keeping the drug amount and stabilizer concentration constant. The formulation variables were selected to study the effect of polymer concentration on particle size, entrapment efficiency, drug loading, and sustained drug release behavior.

Table 3: Formulation Design of Diclofenac Sodium Polymeric Nanospheres

2.6 Evaluation of Polymeric Nanospheres

The prepared Diclofenac sodium-loaded polymeric nanospheres were evaluated for various physicochemical properties to confirm their suitability as a sustained drug delivery system. The formulations were assessed for particle size, PDI, zeta potential, entrapment efficiency, drug loading, and in-vitro drug release behavior.

2.6.1 Particle Size Analysis

Particle size was determined using Dynamic Light Scattering (DLS) to evaluate the nanoscale characteristics of the formulation. The prepared nanospheres showed particle sizes ranging from 145–265 nm, confirming successful nanoparticle formation. An increase in PLGA concentration resulted in a slight increase in particle size due to increased viscosity of the polymeric phase.

2.6.2 Polydispersity Index (PDI)

PDI was measured to evaluate particle size uniformity and distribution. The obtained PDI values ranged from 0.21–0.31, indicating a narrow and uniform particle size distribution. Lower PDI values suggested better stability and homogeneity of the prepared nanospheres.

2.6.3 Zeta Potential

Zeta potential analysis was performed to determine the surface charge and stability of the nanospheres. The formulations showed zeta potential values between −18.4 mV to −28.2 mV, indicating a negatively charged surface. This negative charge helped to prevent particle aggregation and improved formulation stability.

2.6.4 Entrapment Efficiency

Entrapment efficiency was evaluated to determine the amount of Diclofenac sodium incorporated into the polymeric matrix. The formulations showed entrapment efficiency ranging from 62.5% to 89.1%. Higher PLGA concentration improved drug entrapment by providing more polymer matrix for drug encapsulation.

2.6.5 Drug Loading Capacity

Drug loading capacity indicates the amount of drug present within the nanospheres. The prepared formulations exhibited drug loading values of 12.4–21.5%. Increased polymer concentration enhanced drug loading due to improved drug entrapment within the polymeric structure.

2.6.6 In-vitro Drug Release Study

The in-vitro drug release study demonstrated a controlled and sustained release of Diclofenac sodium up to 24 hours. Formulations with lower PLGA concentration showed faster drug release, whereas higher polymer concentration provided slower release due to the formation of a dense polymeric matrix. The results confirmed the potential of PLGA nanospheres for sustained anti-inflammatory drug delivery.

 3 RESULTS AND INTERPRETATION

3.1 Introduction

The present investigation was focused on the formulation and evaluation of Diclofenac Sodium-loaded polymeric nanospheres using the solvent evaporation technique. Six formulations (F1–F6) were prepared by varying the polymer concentration. The prepared nanospheres were evaluated for their physicochemical properties, drug loading characteristics, and in-vitro release behavior. The results obtained are presented and interpreted in this chapter.

3.2 Appearance and Physical Evaluation

All the prepared formulations of Diclofenac Sodium-loaded polymeric nanospheres were initially obtained as milky white nanosuspensions after completion of the solvent evaporation process. The dispersions appeared uniform and smooth, with no visible signs of precipitation, phase separation, or aggregation, indicating the successful formation of a stable nanosystem.

For improving stability and facilitating storage, the prepared nanosuspensions were further subjected to freeze-drying using mannitol as a cryoprotectant. Mannitol played an important role in protecting the nanoparticles from aggregation and structural collapse during the lyophilization process.

After freeze-drying, the formulations were converted into a dry, white, free-flowing powder with good re-dispersibility. The dried nanospheres maintained their physical integrity without any cracking, caking, or color change. Overall, these observations confirm that the prepared formulations possess good physical stability and are suitable for further evaluation and long-term storage.

Table 4 Physical Observation of Formulations

3.3 Particle Size Analysis

Particle size is one of the most critical parameters in nanoparticle-based drug delivery systems, as it directly influences drug release behavior, physical stability, and bioavailability of the formulation. Smaller particle size generally leads to a larger surface area, which enhances drug dissolution and improves therapeutic performance.

In the present study, the particle size of Diclofenac Sodium-loaded polymeric nanospheres was determined using Dynamic Light Scattering (DLS) technique. The measurements confirmed that all formulations were successfully prepared within the nanometer range, indicating proper formation of nanosized carriers.

It was also observed that particle size varied with the concentration of polymer used in the formulation. An increase in PLGA concentration resulted in an increase in particle size, which may be attributed to higher viscosity of the organic phase leading to reduced efficiency of droplet breakup during emulsification. However, all formulations remained within an acceptable nanoscale range, confirming the suitability of the formulation method.

Table 5 Particle Size of Formulations

Interpretation

An increase in particle size was observed with increasing PLGA concentration in the formulations. This may be attributed to the higher viscosity of the polymer phase, which reduces efficient droplet disruption during the emulsification process, leading to the formation of comparatively larger particles.

However, despite this increase, all formulations remained within the nanometer range, confirming successful preparation of polymeric nanospheres suitable for drug delivery applications.

3.4 Polydispersity Index (PDI)

Polydispersity Index (PDI) is an important parameter used to evaluate the uniformity and homogeneity of particle size distribution within a nanoparticle formulation. It provides an indication of how widely the particle sizes are distributed in the system. A lower PDI value suggests a more uniform and stable formulation, whereas higher values indicate broader size distribution and possible instability.

In the present study, the PDI of Diclofenac Sodium-loaded polymeric nanospheres was determined using Dynamic Light Scattering (DLS). The results showed that all formulations exhibited acceptable PDI values, indicating relatively uniform particle size distribution across the batches.

The observed PDI values suggest that the developed formulations possess good homogeneity, which is essential for consistent drug release behavior and improved physical stability of the nanosystem.

Table 6 PDI of Formulations

Interpretation

All the prepared formulations exhibited PDI values below 0.35, indicating a relatively narrow particle size distribution. This suggests that the nanospheres were uniformly dispersed with good homogeneity across all batches.

Such low PDI values also indicate good formulation stability and predictable drug release behavior, which are essential for an efficient nanoparticle-based drug delivery system.

3.5 Zeta Potential

Zeta potential is an important parameter used to determine the surface charge of nanoparticles and to predict their physical stability in a colloidal system. It reflects the degree of electrostatic repulsion between particles. Higher absolute zeta potential values generally indicate better stability, as they prevent particle aggregation and sedimentation.

In the present study, the zeta potential of Diclofenac Sodium-loaded polymeric nanospheres was measured using a zeta sizer instrument. The formulations exhibited negative zeta potential values, confirming the presence of a negatively charged surface on the nanoparticles.

The observed surface charge is mainly attributed to the presence of PLGA and stabilizing agents used during formulation. The negative charge contributes significantly to the stability of the nanosystem by preventing particle aggregation and ensuring uniform dispersion.

Table 7 Zeta Potential of Formulations

Interpretation

The negative zeta potential values observed in the formulations confirm the presence of sufficient electrostatic repulsion between nanoparticles. This repulsive force prevents particle aggregation and flocculation, thereby maintaining a stable colloidal dispersion.

As a result, the formulation demonstrates improved physical stability, uniform particle distribution, and reduced risk of sedimentation during storage.

3.6 Entrapment Efficiency

Entrapment efficiency is an important parameter that indicates the amount of drug successfully incorporated within the polymeric nanospheres in relation to the total drug used in the formulation. It directly reflects the capability of the polymer matrix to encapsulate and retain the drug, thereby influencing the therapeutic effectiveness of the system.

In the present study, the entrapment efficiency of Diclofenac Sodium-loaded polymeric nanospheres was determined by separating the unentrapped drug from the formulation and estimating the drug content using UV spectrophotometric analysis. The results showed that the formulations exhibited good entrapment efficiency, indicating effective incorporation of the drug within the PLGA matrix.

It was also observed that entrapment efficiency varied with polymer concentration. Higher PLGA concentration resulted in improved drug entrapment due to the availability of a larger polymeric network, which effectively reduced drug leakage into the external phase during preparation.

Table 8 Entrapment Efficiency