ABSTRACT
In order to enhance the optical transparency of biological tissues using topically applied optical clearing agents (OCAs), various chemical penetration enhancers (PEs) were used to promote the penetration of OCAs into tissues. This chapter mainly focuses on the PEs propylene glycol (PG), Thiazone, and liquid paraffin, each of which can enhance skin optical clearing efficacy. The results indicated that a mixture of OCA and PE can induce better skin optical clearing efficacy than pure OCA with the same treatment time. Both Thiazone and PG can promote the penetration of OCAs and enhance optical clearing efficacy, which permits laser speckle contrast imaging (LSCI) to depict blood flow distribution and allows access to deeper vascular structures using optical coherence tomography (OCT) angiography. By contrast, the enhancing ability of Thiazone is superior to PG for in vitro and in vivo skin optical clearing. Liquid paraffin, as a highly refined mineral oil, demonstrates a good synergistic optical clearing effect with glycerol on skin and esophagus tissues within a short treatment time.
