Executive Summary : | Research by the PI group has shown that rare earth-based frequency upconversion nanoparticles (UCNPs) can enhance the contrast of images recorded by optical coherence tomography (OCT), providing information at higher tissue depth. UCNPs act as contrast enhancers through two mechanisms: changing the scattering parameter when excited with a 980 nm source and generation of heat in UCNPs on 980 nm excitation, which changes the refractive index of the medium. The latter mechanism is stronger than the previous one and requires more attention. Gold nanoparticles can also work as an exogenous agent to enhance OCT imaging, but they need to be excited with shorter wavelength radiation, making them less practical for biological tissue imaging.
The 980 nm radiation falls within the therapeutic window (650-1000 nm) and is more favorable for biological tissues, allowing for more depth information to be obtained. OCT is a popular optical imaging tool in biomedical/medicine, and current versions of OCT are limited by poor contrast images. To address this, the PI group has tried UCNPs in OCT imaging and found that La2O3:Er3+/Yb3+ provides the most intense photo-acoustic signal but is not compatible for biological purposes. To achieve similar effects in biocompatible hosts, the group plans to synthesize multi rare earth ions with hosts such as La2O3, Ca3(PO4)2, CaWO4, and CaMO4, and conduct NIR (980 nm) to heat generation studies using photoacoustic spectroscopy and heat optimization. Upconversion emission studies and correlation studies with photoacoustic signals will also be conducted. |