Percutaneous absorption and antibacterial activities of lipid nanocarriers loaded with dual drugs for acne treatment

The aim of this study was to develop lipid nanocarriers that combine tretinoin and tetracycline for the efficient topical delivery to treat acne vulgaris. Two different nanocarriers, nanoemulsions (NEs) and nano-structured lipid carriers (NLCs), were prepared, and we examined their average size, zeta potential, drug encapsulation percentage, and drug permeation via the skin. The antibacterial activities of the nanosystems against Staphylococcus aureus, Pseudomonas aeruginosa, and Propionibacterium acnes were evaluated by an agar diffusion assay and the amount of total protein. A ca. 200-nm particle size was achieved with the prepared nanoparticles. The size increased when incorporating a cationic surfactant. Dual-drug loading did not largely affect the size of negatively charged nanoparticles, but significantly reduced the particle size of positively charged nanocarriers. NEs and NLCs exhibited high entrapment of tretinoin which ranged 60-100%. Tetracycline mainly resided in the aqueous phase, with ca. 10% of molecules located at the particulate interface. An in vitro skin permeation study showed that NLCs enhanced tetracycline flux by about 2-times over the control solution. Tretinoin permeation was generally unaffected after nanoparticulate encapsulation. There was no significant difference in tretinoin delivery before or after tetracycline incorporation, while tetracycline permeation significantly decreased by 2-fold in the dual-drug system. Nanoparticulate loading mostly maintained the antibacterial activity of tetracycline. Negatively charged NEs and NLCs even strengthened the antibacterial ability against S. aureus compared to the control solution. This is the first report examining skin permeation and antibacterial activities of dual-drug nanocarriers for acne treatment.