Combined Effect of Ultrasound-SLS on Skin Optical Clearing

Our previous studies demonstrated the ultrasound-induced skin optical clearing enhancement with topical application of optical clearing agents on in vitro porcine skin and in vivo human skin. The objective of this study was to develop more effective methods by simultaneously using two kinds of skin permeation enhancers. The effect of ultrasound (SP) in combination with a chemical enhancer, sodium lauryl sulfate (SLS), on skin optical clearing was investigated. Light transmittance and imaging depth of in vitro porcine skin were measured with spectroscopy and optical coherence tomography (OCT). Three treatments were performed: 1) 60% glycerol (60% Gly); 2) 60% glycerol +15-min SP (Gly/SP); and 3) 60% glycerol + 1% SLS + 15-min SP (Gly/SLS/SP). We find that Gly/SLS/SP exhibits a most significant effect in increasing total transmittance and OCT imaging depth. Total transmittance increases by a factor of 1.9 (1276-nm light) to 3.4 (470-nm light) after 60 min. In addition, the effect after 30 min of Gly/SLS/SP exposure is almost the same as that after 60 min of Gly/SP exposure. Simultaneously, Gly/SLS/SP results in a 56% increase in OCT 1/e light penetration depth after 60 min, much better than 60% glycerol and Gly/SP.