Acemetacin-loaded bilosomal gel formulations prepared using different polymers for topical application: Box-Behnken design for bilosomes formulation optimization and in vitro evaluation of the formulations

Acemetacin (ACIN) is a poorly water-soluble nonsteroidal anti-inflammatory drug, which limits its effectiveness in topical therapeutic applications. This study aimed to enhance the delivery potential and dermal applicability of ACIN through the development of bilosome-loaded hydrogel formulations. Bilosomes were prepared using the thin-film hydration method and optimized using Box-Behnken Design (BBD). The amount of phosphotidylcholine (lecithin), cholesterol and sodium taurocholate were chosen as the formulation parameters and their effects were evaluated on the resulting vesicle size, zeta potential and entrapemnet efficiency percentage (EE%). The optimized formulation displayed a vesicle size of 137.3 nm, a zeta potential of -30.1 mV, a polydispersity index (PDI) of 0.384 and EE% of 84.5%. Bilosomes were incorporated into hydrogel bases containing hydroxypropyl methylcellulose (HPMC) or Carbopol. HPMC-based gels exhibited a favorable pH (~4) for skin application and were selected for further evaluation. These gels provided sustained drug release for up to eight hours. Cytocompatibility testing on L929 fibroblasts using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay demonstrated cell viability above 90% within the tested concentration range (0.05-2 µg/mL), indicating good biocompatibility. The bilosome-loaded HPMC gel formulation exhibited desirable physicochemical properties, sustained drug release, and excellent cytocompatibility, making it a promising vehicle for topical delivery of ACIN. Further anti-inflammatory and in vivo studies are recommended to confirm its potential for topical or anti-inflammatory applications.