Tartrazine-enhanced visible-light OCT for deep-tissue imaging

Visible-light optical coherence tomography (vis-OCT) provides ultrahigh axial resolution and intrinsic spectroscopic contrast, but its performance in deep tissues is fundamentally limited by strong scattering and absorption at short wavelengths. Here, we report the use of tartrazine-an FDA-approved, water-soluble food dye-as a rapid, biocompatible contrast enhancer to improve vis-OCT penetration and structural visibility across multiple tissue types. We systematically evaluated tartrazine-assisted imaging in postmortem chicken muscle, optic nerve, and brain cortex, as well as in vivo at the ocular limbus and mouse ear. Topical or surface immersion with low-concentration tartrazine solutions significantly improved the vis-OCT signal in deep tissue with increased signal-to-noise ratio, extended penetration, and enhanced structure contrast. These results establish Tartrazine as an inexpensive, safe, and effective optical clearing and contrast-enhancing agent for vis-OCT, enabling deeper and higher-fidelity imaging of biological tissues both ex vivo and in vivo.