Evaluation of the interactions between human stratum corneum and liposome formulations using QCM-D

The interactions between human stratum corneum (SC) and two liposomal formulations, azithromycin (AZM)- and nisin-loaded liposomal formulations designed for topical/intradermal application, were investigated using quartz crystal microbalance with dissipation (QCM-D). SC isolated from cadaver skin was affixed onto the QCM sensor's surface. The liposome formulations were prepared using the thin-film rehydration method. The particle sizes of the blank liposome, nisin-loaded, AZMloaded, and combined-loaded liposomes were measured as 90.7 +/- 0.58 nm, 100.8 +/- 2.5 nm, 136.9 +/- 6.5 nm, and 174.3 +/- 9.8 nm, respectively. The frequency shifts with blank and drug-loaded liposomes were similar to 20 and similar to 25 Hz, respectively as a result of the formation of bilayers on gold surface in a two-step process, adsorption of intact vesicles followed by the formation of the bilayer upon rinsing with water. The frequency shifts for blank and drug-loaded liposomes on SC were similar to 8 and similar to 15 Hz, respectively. These results show that the liposomes are deposited as bilayers on SC with both the blank and drug-loaded liposomes. The increase in frequency shifts with drug-loaded liposomes indicate the deposition of drug along with lipids onto both the gold and SC surfaces. More significantly, the data showed much slower kinetics of liposome component spreading onto the SC than on gold. The changes in dissipation that accompanies these differences in frequency shifts show transformation of vesicle onto rigid bilayer on gold upon rinsing with water, but direct formation of lipid bilayers on SC. The findings of this study contribute to a better understanding of the interaction between SC and liposomes, such as adsorption, deformation, and rupture of liposomes on different substrates, paving the way for investigating topical and intradermal mechanisms of drug delivery and cosmetic products developed based on liposome formulations.