324 JOURNAL OF COSMETIC SCIENCE In vitro drug release studies for microsponges. In vitro drug release for the developed microsponge formulation was carried out by Franz diffusion cell method. The release was found to be 52.42 ± 0.72 in 8 hours. FORMULATION AND EVALUATION OF GEL CONTAINING DRUG-LOADED MICROSPONGES Determination of pH. The pH of the developed gel (F1) was found to be 5.82 ± 0.18. Determination of spreadability. Bioavailability and therapeutic property of the topical formulation depends upon the spreadability. The spreadability is expressed of time in Figure 4. 3D graphic representation of entrapment efficiency %dependence from studied variables. Figure 5. Scanning electron microscopy.

325 Microsponge Loaded Topical Gel seconds based on the slip off from the gel by upper slide under a certain load (30). Time taken for the separation of the two slides is less, which indicates the topical formulation has better spreadability (31). Formulation F1, having optimum viscosity and spreadability of this formulation, is 5.9 ± 0.025 g.cm/sec. Measurement of viscosity. The viscosity values of the formulation F1 at various rpm with spindle 63 are shown in Table VI. Drug content study The percentage drug content of the prepared benzoyl peroxide gel formulations F1 was found to be 98.0 ± 0.417%. In vitro drug release study. In vitro drug release for the developed microsponges loaded topical gel formulation was carried out by Franz diffusion cell method. The release was found to be 50.12 ± 0.75 in 8 hours (shown in Table VII) the sustained release profile is shown in Figure 6. CONCLUSION Topical semi-solid dosage form microsponges loaded with benzoyl peroxide containing PLGA, for acne treatment, were developed. They were prepared by a qausi solvent evaporation method. Using central composite RS DOE, a number of formulations were designed with dependent variables of PLGA, span 80, and PVA. They were prepared and characterized in terms of entrapment efficiency and in vitro drug release. Derived mathematical models were used for subsequent formulation optimization. Optimal formulation was prepared and subjected to further characterization studies. A topical semi-solid dosage form was obtained by incorporating carbopol as a gelling agent. Topical gel was characterized in means of its rheological properties, spreadability, in vitro release profile, and stability. Experimental design results were validated using Design Expert software 11. No significant difference (p 0.05) between the two values was observed upon comparing predicted value with experimental value (%EE), thus specifying that the design had been validated. The presence of small spherical vesicles in SEM analysis revealed some agglomeration of microsponges, which might be due to the evaporation of water present in the formulation during sample preparation prior to SEM analysis. Optimized formulation upon storage was found to be physically stable. Further, carbopol gels were clear and transparent in appearance with a pH value close to normal physiological pH range of skin (3.0–9.0), suggesting their nonirritating nature upon application to the skin. Viscosity is thought to be an important characteristic in defining skin penetration. Table VI Viscosity Values of the Formulations RPM Viscosity (cp) at room temperature (formula 1) 10 5,670 20 3,324 30 2,472 40 1,870 50 1,253