Transient optical clearing with tartrazine with improved delivery kinetics

Light transport in biological tissue is fundamentally limited by scattering from refractive index heterogeneity. We present a transient, reversible tissue clearing approach that combines chemical and physical methods to reduce scattering and enhance optical visualization. Using the common food dye tartrazine to modulate the refractive index of the interstitial medium via Kramers–Kronig relations, we applied used different physical and chemical methods enhance tissue permeability and accelerate diffusion. These interventions promote near-homogeneous refractive index matching between lipid-rich and aqueous compartments, reducing scattering consistent with optical scattering models. Changes in tissue clarity were evaluated visually and quantified using camera-based imaging with machine learning algorithms to score visibility and quantify contrast changes. This framework links refractive index modulation, scattering theory, and transport physics with image-based analysis to enable controlled, reversible, and non-invasive deep-tissue imaging.