Encapsulating insoluble antifungal drugs into oleic acid-modified silica mesocomposites with enhanced fungicidal activity

Abstract

Recently, with increasing medical practices, including organ transplantation and tumor chemotherapy, fungal infections, particularly the occurrence of drug-resistant fungal strains, remain a severe problem for the public health, which cause worse complications in the immunocompromised patients. The search for efficacious yet safe antifungal agents is in high demand in precision medicine. However, fungicides are often poorly water soluble for oral absorption, which is difficult for pharmaceutical efficacy evaluation. In this study, lipophilic oleic acid (OA)-grafted mesoporous silica (SBA-15) was facilely modified by cetyltrimethylammonium bromide (CTAB), which acts as an efficient antifungal drug matrix of itraconazole (ITZ). Characterized by physicochemical methods, the rod-like SBA-15-OA-CTAB/ITZ composite with retained mesostructural regularity shows that the loading amount of ITZ in the mesopore is ∼18%, contributing to the enhanced antifungal activity against Aspergillus fumigatus (A. fumigatus) and Candida albicans (C. albicans). The antimicrobial mechanism study suggests that the reactive oxygen species (ROS) were formed when fungal cells were incubated with the formulated ITZ, while there was no ROS formation in the presence of pure ITZ, which may result from the quaternary ammonium moieties of CTAB in the nanocomposites. Due to the potential toxicity of CTAB on mammalian cells, the as-synthesized mesoporous SBA-15-OA-CTAB/ITZ provides an alternative molecular design for the formulation improvement of a lipophilic antifungal drug applicable for external uses such as topical therapy.