The light does not penetrate deeply into the skin tissue because of tissue turbidity. Light penetration depth in skin tissue can be increased by using optical clearing agents such as glycerol, glucose and dimethyl sulfoxide(DMSO). The stratum corneum prevents most optical skin clearing agent from diffusing into the tissue. Previous studies demonstrated the optical tissue clearing effect using optical clearing agents and presented several physical methods to improve transdermal delivery of optical clearing agents. In previous study, we introduced a micro-needling method to enhance optical clearing efficacy against skin barrier and suggested quantitative analysis method to evaluate the optical tissue clearing efficacy. In this study, we present a new physical micro-needling method combined with sonophoresis to further enhance the optical tissue clearing efficacy. The optical tissue clearing effect was quantitatively evaluated with a modulation transfer function target placed under ex-vivo porcine skin samples. To improve transdermal delivery of glycerol, 70% glycerol solution as optimal concentration was topically applied. In conclusion, the samples treated with micro-needling method and sonophoresis resulted in noticeable optical tissue clearing effect.
Light scattering in biological tissues can be reduced by using optical clearing agents. Various physical methods in conjunction with agents have been studied to enhance the optical clearing efficacy of skin for diagnostic and therapeutic applications. In this study, we propose a new physical method to enhance the optical clearing potential of topically applied glycerol. A microneedle roller is used to easily create numerous transdermal microchannels prior to glycerol application. The optical clearing efficacy of skin is quantitatively evaluated with the use of a modulation transfer function target placed underneath ex vivo porcine skin samples. From cross-polarized images acquired at various time points after glycerol application, we find that samples treated with the microneedle roller resulted in an approximately two-fold increase in contrast compared to control samples 30 min after glycerol application. In conclusion, our data suggest that the microneedle roller can be a good physical method to enhance transdermal delivery of optical clearing agents, and hence their optical clearing potential over large regions of skin.
Laser speckle imaging modality is one of widely used methods to evaluate blood flow because of its simplicity.
However, laser speckle image has a limitation in the evaluation of subcutaneous blood flow due to its low contrast
perfusion image. Various methods have been tried to enhance the perfusion image contrast. Such methods presented
positive results in some degree. However, it could not be fundamental solutions due to low penetration depth of lasers
restricted by optical tissue scattering property. This study suggests a method to enhance the perfusion image contrast of
laser speckle imaging modality by increasing the penetration depth of lasers. An optical clearing agent (glycerol) was
topically applied on skin treated with micro-needle roller in order to reduce the time period of optical tissue clearing and
therefore, enhance the penetration depth of laser. In this study, we investigated the effect of glycerol and micro-needling
methods in the contrast enhancement of laser speckle perfusion skin image and presented the results of <i>in-vitro</i>
and <i>in-vivo</i> animal experiment.