Assessment of the effects of ultrasound-mediated alcohols on skin optical clearing.

Our previous studies have shown the ultrasound-induced skin optical clearing enhancement with topical application of glycerol on in vitro porcine skin and in vivo human skin. The objective of this study was to find more effective ultrasound-alcohol combinations on skin optical clearing. The effect of sonophoretic delivery (SP) in combination with a series of alcohols such as glycerol, propylene glycol, butanediol, butanol, polyethylene glycol (PEG200, PEG400) 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). Sixty percent alcohols and ultrasound (SP) with a frequency of 1 MHz and a power of 0.75 W over a 3-cm probe was simultaneously applied for 15 min. Optical clearing capability of alcohols was much improved with the simultaneous application of ultrasound compared with alcohols alone. Light transmittance at 1276 nm increased by 31% (butanol) to 57% (PEG200) at 60 min, respectively. PEG200 with ultrasound exhibited 1.8-fold the clearing capability of PEG200 alone, which was the highest enhancement by ultrasound among the six alcohols. Sixty minutes of PEG200/SP exposure resulted in a significantly increased 1e light penetration depth of 1.43 mm compared to 0.95 mm for control in OCT measurement.