Cell labeling using hybrid lipid coated gold nanorods.

Abstract

Purpose : Cell transplantation is a promising prospective therapy for retinal degenerative diseases and is currently being evaluated in clinical trials for the treatment of advanced Age-related Macular Degeneration (AMD). However, there remains no objecive method to conclusively identify and track cells following implantation. Gold nanorods (GNR) have previously been demonstrated to provide sufficient contrast for detection using optical coherent tomography (OCT) imaging inferring their potential as a label for therapeutic cells. The purpose of this study was to test whether, and under what conditions, lipid-coated GNR could be internalized into cells and potentially used as a cell labeling technique.

Methods : GNR with an aspect ratio of 69x12nm were purchased from a commercial vendor (Nanopartz). The surface architecture of the gold nanorods was modified to improve their stability and enhance cellular internalization into cells through the addition of a hybrid lipid-coating. Lipid-coated GNR were then labeled with rhodamine to allow fluorescence identification of internalized GNR within cells. Lipid coated GNR were incubated with baby-hampster kidney (BHK) and human retinal pigmented epithelial cells (RPE) at 37C at concentrations ranging from none to ~3x10¹¹ GNR/ml for between 4 and 24 hours.

Results : Incubation of GNR with BHK and RPE cells resulted in a dose and time-dependent internalization of the GNR. Internalized GNR could readily be visualized under fluorescent microscopic conditions at concentrations ranging between ~1x10⁹ to 1x10¹⁰ GNR/ml. GNR could not be visualized in cells at concentrations lower than 1x10⁹ even when applied for up to 24 hours. Toxicity was observed as loss of cell adhesion to the culture dish and cell lysing was only occasionally evident and only at the highest concentrations. A significant number of GNR had been internalized by 4 hours incubation, with only slight increase in internalization up to 24 hours.

Conclusions : Lipid-coated GNR readily internalize into BHK and RPE cells. Use of fluorescence as a detection method for internalized GNR lacked sensitivity to visualize internalized GNR at the lower concentrations. Future use of quantitative methods such as ICP-MS will provide higher accuracy detection of intracellular GNR. These studies suggest that with further refinement, lipid–coated GNR could be used as a cell labeling technique for use with high-resolution in vivo retinal imaging.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.