Molecular-Specific Optical Coherence Tomography Contrast Agents for High-Sensitivity <i>In Vivo</i> Detection of Corneal Injury

Optical coherence tomography (OCT) is a powerful tool for <i>in vivo</i> corneal imaging; however, its diagnostic precision is hampered by a lack of molecular specificity. To overcome this limitation, we designed and synthesized CD44 aptamer-conjugated gold nanoparticles (AP-GNPs) as a molecularly targeted OCT contrast agent for the quantitative assessment of corneal injury. AP-GNPs specifically bind to CD44, a biomarker overexpressed in injured corneal tissue, leading to enhanced signal intensity and prolonged retention at the lesion site compared to nontargeted nanoparticles. In the alkali burn mouse model, AP-GNP-enhanced OCT enabled noninvasive and highly sensitive detection of mild and severe injuries, demonstrating a significant increase in the signal-to-noise ratio from 12 to 24 h postinsult, a feat not achievable by conventional diagnostics such as fluorescein staining. This was quantified by a significant amplification of the signal-to-noise ratio at 12 h by 23.6% for mild injuries and 54.5% for severe injuries, relative to nonenhanced controls. Comprehensive safety profiling confirmed the excellent biocompatibility of the nanoprobes after topical administration. This study establishes an aptamer-based contrast enhancement strategy for OCT, providing the first demonstration of quantitative <i>in vivo</i> improvement in detection sensitivity for corneal pathology and offering a promising platform for both preclinical research and clinical diagnostics.