Tartrazine-based optical clearing to enable deep imaging of murine embryos with optical coherence tomography

Optical coherence tomography (OCT) enables non-invasive, label-free, three-dimensional imaging with micrometer-scale lateral resolution, and is widely used for developmental imaging in murine models. However, traditional approaches often require embryo extraction or invasive surgical procedures, limiting the ability to perform longitudinal in vivo imaging. A key limitation of OCT is its shallow imaging depth (~1 mm), primarily due to light scattering caused by the heterogeneous refractive indices (RIs) of tissue components such as water, lipids, and proteins. To address this, optical clearing techniques employing RI-matching solutions have been explored. Here, we exploited a novel clearing approach using tartrazine, a commercially available food dye with an RI of 1.418 at 1310 nm. Using a custom-built OCT system centered at 1300 nm, we performed in utero imaging of murine embryos. A tartrazine solution was topically applied to the pregnant dam’s skin, enabling OCT imaging through the skin, uterine wall, and yolk sac. Our preliminary results demonstrate that tartrazine significantly increased imaging depth by approximately 130%, enabling clear visualization of embryonic structures without invasive intervention. This technique offers a simple, effective strategy to improve OCT penetration depth for longitudinal developmental imaging in utero.