In Vivo Imaging of Mammalian Embryos By NIR-I Photoacoustic Tomography and NIR-II Optical Coherence Tomography Using Gold Nanostars as Multifunctional Contrast Agents

Background High resolution, strong contrast and multimodality visualization of live mammalian embryo is an important requirement for studying foetal development. Photoacoustic Tomography (PAT) and Optical Coherence Tomography (OCT) are two advanced imaging modalities that has been utilized for embryonic imaging. However, high contrast, multiscale and deep tissue visualization of live embryos remains challenging. Results Here, we demonstrate the use of gold nanostars (GNS) as multimodality contrast agents for the visualization and differentiation of embryos in vivo using NIR-I PAT and NIR-II OCT. We perform NIR-I PAT imaging to confirm in vivo GNS accumulation in the foetuses, and then use a customized NIR-II OCT system to further reveal deep, contrast-enhanced micro features of freshly harvested embryos. We investigate two different GNS administration pathways, i.e. intravenous and intravaginal injection, and significant enhancement of signal, image contrast, and imaging depth are achieved for both PAT and OCT. Conclusions These findings prove that PAT-OCT bi-modal imaging with GNS enhancement provides more accurate structural characteristic of live mammalian embryos, and thus reveal its potential for embryonic development visualization and early abnormality examination. These findings prove that PAT-OCT bi-modal imaging with GNS enhancement provides more accurate structural characteristic of live mammalian embryos, and thus reveal its potential for embryonic development visualization and early abnormality examination.