In Vitro Imaging of Animal Tissue with Upconversion Nanoparticles (UCNPs) as a Molecular Probing Agent Using Swept Source Optical Coherence Tomography (SSOCT)

Abstract

The aim of the current study is to demonstrate the potential of rare earth (RE) based upconversion nanoparticles (UCNPs) as molecular probing agents for non-invasive depth-resolved bioimaging technique, swept-source optical coherence tomography (SSOCT). The Na+ doped La2O3:Er3+/Yb3+ UCNPs were synthesized using a solution combustion route with characterization for emission spectra and morphological study. A custom made SSOCT system was also incorporated for tissue imaging with an A-scan rate of 100 kHz/s, the central wavelength of 1060 nm, an axial and lateral resolution of ~ 4.5 µm and ~ 13 µm in tissue, respectively. UCNPs are utilized as exogenous molecular probing agents to improve local scattering in inner tissue layers. In vitro imaging of chicken breast tissue is functioned with and without excited UCNPs. Time-dependent dynamic changes in scattering coefficients of local tissue and contrast to noise ratio (OCT B-scans) is presented with a new mathematical model. Substantial enhancement in OCT image contrast, local scattering coefficients, and depth range of OCT was observed. The penetration dynamics of excited and non-excited UCNPs with time is reported. Excitation of the UCNPs enhance the scattering coefficients which lead to high contrast OCT images. It also enables the tunable characteristics of UCNPs as targeted molecular probes.