Permeation-enhanced biocompatible tissue clearing for improving OCT imaging depth

OCT imaging depth is governed by tissue optical absorption and scattering (dominated by the latter, which results from refractive index (RI) mismatch). Recently, an FDA-approved food coloring dye, tartrazine, has been shown to achieve in vivo optical clearing of biological tissues. With a sharp absorption peak in the near-violet spectrum, a rise of RI of its aqueous solution at longer wavelengths was observed as governed by the Kramers-Kronig relations, promoting RI matching and therefore scattering mitigation. However, delivery of tartrazine into tissues were aided by prolonged physical massage, which is potentially damaging. In this study, we evaluate the utilization of Tween 80 as a non-irritating and effective chemical permeation enhancement agent for tartrazine delivery into tissues, laying the path for potential broad in vivo optical clearing applications to enhance imaging depth.