Anti-acne cinnamic acid bigel: a hybrid topical system for concurrent modulation of inflammation and microbial load

Acne vulgaris is a chronic inflammatory skin disease aggravated by Cutibacterium acnes (P. acnes). Conventional drug delivery treatments researchers reported irritation, resistance and poor efficacy. Poor skin permeability, along with oxidative degradation hindering its efficacy on Dermal drug delivery application.

In this study, the novel work was to incorporate and optimize cinnamic acid phytoconstituent within a bigel system to improve solubility, stability, permeation and achieve prolonged release.

Box-Behnken design was used to optimize formulation, independent variables (oleogel: hydrogel ratio, mixing time and mixing or rotation speed) with globule size, hardness and in vitro drug release as responses.

Cinnamic acid-loaded bigels were prepared by phase mixing of hydrogel and oleogel components at varying ratios and optimized using a Box-Behnken design. Formulations were evaluated for viscosity and drug content, and the optimized batch (F7) was further characterized by FTIR, DSC, SEM, rheological analysis, amplitude sweep stability, antibacterial activity against P. acnes and P. aeruginosa, anti-inflammatory activity, and ex vivo skin permeation.

The optimized formulation exhibited a globule size of 619 nm and a zeta potential of - 30.6 mV, indicating good stability. In vitro drug release reached 69.98 ± 0.534% over 6 h, compared to 95.02 ± 1.3% for the marketed formulation, following Korsmeyer-Peppas kinetics (R² = 0.9477 and 0.9321). SEM analysis confirmed a porous, interconnected structure. The formulation demonstrated notable antimicrobial activity against P. acnes (ZOI: 15.22 mm), comparable to erythromycin (14.22 mm). In vivo anti-inflammatory studies showed complete paw edema inhibition (100%) for F7, exceeding the marketed clindamycin gel (95%), with significant p-values (p = 0.0015 and p = 0.0071). Ex vivo studies indicated sustained drug release without skin irritation CONCLUSION: Cinnamic acid-loaded bigel represents a promising therapeutic approach for the management of acne-associated inflammation.