Tartrazine clearing of the tympanic membrane for improved visualization of the middle ear

Biological tissues intrinsically scatter light, which limits the depth of penetration of optical imaging. Optical coherence tomography (OCT) is a non-invasive, label-free imaging modality that generates real-time 2- and 3- dimensional in vivo images with high spatial resolution (<10 µm). While OCT has been used in nascent otologic studies to noninvasively diagnose otitis media, distinguish cholesteatoma from normal middle ear mucosa, and identify vascular tumors of the middle ear, the intrinsic light scattering of the tympanic membrane (TM) limits OCT penetration depth. Optical clearing agents (OCAs) are known to improve optical transparency by decreasing the refractive index mismatch between cellular and extracellular components of biological tissue, thereby increasing the amount of light penetration. Tartrazine (Yellow 5) is an absorbable FDA-approved food-grade dye that has been shown to make biological tissue transparent in in vivo and ex vivo animal models. In this study, we investigated the application of tartrazine to optically clear the TM of human cadaveric specimens using a custom-built 1310 nm swept-source OCT system. We demonstrate that tartrazine is an effective OCA for the TM and improves the quality of visualization for OCT imaging into the middle ear, highlighting the potential clinical application of tartrazine to improve the noninvasive diagnosis of middle ear pathologies using OCT.