3D Photoacoustic Microscopy and OCT Molecular Imaging of Choroidal Neovascularization using Gold Nanoparticle Clusters

Abstract

Purpose : Longitudinal visualization of choroidal neovascularization (CNV) in a rabbit laser-induced model using multimodal photoacoustic microscopy (PAM), optical coherence tomography (OCT), and fluorescence imaging (FI) system powered by ultraminiature chain-like gold nanoparticle clusters (GNC).

Methods : Six New Zealand rabbits were used to create CNV using laser photocoagulation. After 28 days post laser treatment (300 mW, 75 µm, and 0.5 s), CNV developed, and the rabbits received an intravenous injection of 400 µL GNC conjugated with RGD at a mass concentration of 2.5 mg/mL. The location and margin of CNV were observed using multimodal PAM, OCT, and FI imaging. PAM images were achieved using two different wavelengths of 578 nm to visualize retinal microvasculature and 650 nm to distinguish CNV from the surrounding retina vessels. All the animal experiments were implemented under a protocol approved by the UM IACUC.

Results : In vitro studies showed that the fabricated ultraminiature GNC are biocompatible with high targeting efficiency. Renal clearance test demonstrates that GNC can be excreted via urine after intravenous injection (IV) into rabbits through a marginal ear vein. In vivo data illustrates that CNV developed at day 28 post laser treatment and observed on the late phase fluorescence images. By acquiring PAM at 578 nm and 650 nm, the margin of CNV were differentiated from the surrounding retinal vessels after IV administration of GNC with strong signal and high resolution. Three-dimensional PAM images demonstrate the CNV structure. OCT images provide supplementary information of retinal structure and location of CNV.

Conclusions : This study presents a novel multifunctional contrast agents for PAM, OCT, and FI imaging. The degree and margin of CNV can be monitored up to 28 days and precisely differentiated from the surrounding vasculature. This illustrates that contrast-enhanced multimodal molecular imaging can be a useful tool to study of ocular diseases.

This abstract was presented at the 2023 ARVO Imaging in the Eye Conference, held in New Orleans, LA, April 21-22, 2023.

 

Multimodal imaging of choroidal neovascularization in living rabbits: (A) color fundus at day 28 post laser photocoagulation. (B) Fluorescein angiography (FA) images. Late leakage indicates CNV (red dotted circle). (C-D) 2D OCT image pre and post administration of GNC. (E-H) PAM images obtained at 578 (E,G) and 650 nm (F,H). Pseudo-green color illustrates the location of GNC-targeted CNV. (i) Overlay 3D PAM images.