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Patricia Fernandez-Robredo, Michael Powner, Senthil Selvam, Dawn A Sim, Pearse Andrew Keane, Marcus Fruttiger; Improvement of hyper reflective dots visualization on OCT by gold nanoparticles. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):5925. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
In previous work, we showed in a mouse model of choroidal neovascularisation (CNV) that circulating monocytes invading the retina can be labelled by indocyanine green (ICG) and imaged in vivo. Here we aimed to investigate the feasibility of using gold nanoparticles as contrast agents to label invading inflammatory cells on the OCT in the retina.
Gold nanoshells, nanorods, nanobypiramids and silver plates were pre-screened in a tissue phantom (agar sheets) to establish the best suitable contrast agent in OCT. Gold nanoshells (GNS) were selected for in vivo analyse in the mouse CNV model. Mice (n=5) were i.p. injected with GNS 3 days before the animals were lasered with a 532 nm diode laser (Micron III, Phoenix Research) and compared with control animals (n=5). Three to four laser spots were made close to the optic nerve in each eye. OCT images were taken on SD-OCT (Envisu R2200, Bioptigen), immediately after and 7 days post CNV induction. Fluorescein angiography was performed 7 days after laser. Animals were sacrificed, eyes flatmounted and subjected to lectin (IB4) staining and analysed using fluorescence microscopy.
Hyper reflective dots (HRDs) were visible in OCT images one week after the CNV induction, surrounding CNV lesion area. Those dots were brighter in animals injected with nanoshells compared to controls. The HRD observed in the OCT correlated with lectin positive cells observed in the flatmount samples with macrophage-like morphology.
This study shows that gold nanoparticles can improve the visualisation of inflammatory cells on OCT. HRDs in OCT are observed clinically, but it has been difficult to prove what cells the HRDs exactly represent. Further studies are needed to characterise these cells.
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