Purpose

Avobenzone is a broad-spectrum sun-protective agent widely used in the form of creams and lotions. However, it is highly photo-unstable and causes irritation and systemic absorption which needs to be addressed. Microsponges are porous, polymeric carriers that are designed to deliver a pharmaceutical/cosmetic ingredient efficiently at the minimum dose and also to modify the drug release (sustained release) while reducing the skin toxicity problems pertaining to the drug. An attempt was made to formulate avobenzone-loaded microsponge gel.

Method

The microsponges for the delivery of avobenzone were successfully prepared by quasi-emulsion solvent diffusion method. The formulated microsponges were characterized for production yield, particle size, SEM, % entrapment efficiency, % drug release, FTIR and DSC. The optimized microsponges were further incorporated in hydrogel (HPMC K4M) in different ratios and evaluated for pH, viscosity, homogeneity, spreadability, stability testing, skin irritation study and sun protection factor (SPF) testing.

Results

The results showed that microsponge were spherical in shape with pore size in the range 0.10–0.30 μm. The production yield was between the range of 47 and 91.81%. The particle size was obtained within the range of 200 to 399 μm, indicating that increase in solvent (DCM) concentration reduces the particle size. Entrapment efficiency of formulation was ranging between 60 and 77.40%. In vitro drug release showed prolonged release of the drug for a duration of 8 h, and the % CDR was in the range of 27.79 to 65.66%. The microsponge gel showed good homogeneity and viscosity in the range of 1556 to 2622 cps, and spreadability was between 4.1 and 5.9 g.cm/s. The gel was found to be stable at 40 °C temperature and 75% RH, for a duration of 60 days. Microsponge gel was non-irritant on the rat skin and showed controlled release.

Conclusion

The controlled release and barrier effect of gel from microsponge result in prolonged retention of avobenzone along with decreased permeation activity. Hence, in conclusion, the study revealed enhanced efficacy and reduced toxicity with prolonged release of drug. It also showed better sun protection factor of 25 compared to the marketed preparation which was sun protection factor 20.

中文翻译：

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微海绵凝胶法提高阿伏苯宗作为防晒剂的稳定性和功效

目的

阿伏苯宗是一种广谱防晒剂，广泛用于面霜和乳液形式。然而，它是高度光不稳定的，会引起刺激和全身吸收，需要加以解决。微海绵是多孔的聚合物载体，旨在以最小剂量有效地输送药物/化妆品成分，并改变药物释放（持续释放），同时减少与药物有关的皮肤毒性问题。尝试配制负载阿伏苯宗的微海绵凝胶。

方法

采用准乳液溶剂扩散法成功制备了阿伏苯宗缓释微海绵。对所配制的微海绵进行了产率、粒径、SEM、包封率百分比、药物释放百分比、FTIR 和 DSC 的表征。将优化后的微海绵以不同的比例进一步掺入水凝胶 (HPMC K4M) 中，并评估其 pH、粘度、均匀性、铺展性、稳定性测试、皮肤刺激研究和防晒系数 (SPF) 测试。

结果

结果表明，微海绵呈球形，孔径范围为0.10-0.30 μm。产率在 47% 和 91.81% 之间。获得的粒径在 200 至 399 μm 范围内，表明溶剂 (DCM) 浓度的增加会降低粒径。制剂的包封率在 60% 和 77.40% 之间。体外药物释放显示药物的缓释持续时间为8 h，%CDR在27.79~65.66%之间。微海绵凝胶在 1556 至 2622 cps 范围内表现出良好的均匀性和粘度，铺展性在 4.1 至 5.9 g.cm/s 之间。发现凝胶在 40 °C 温度和 75% RH 下稳定 60 天。微海绵凝胶对大鼠皮肤无刺激性并显示受控释放。

结论

微海绵凝胶的控释和阻隔作用导致阿伏苯宗的保留时间延长，同时渗透活性降低。因此，总而言之，该研究揭示了随着药物的延长释放而提高了疗效并降低了毒性。与市售的防晒系数 20 的制剂相比，它还显示出更好的防晒系数 25。