In vivo imaging of a new indocyanine green micelle formulation in an animal model of laser-induced choroidal neovascularization.

PURPOSE

We investigated a novel formulation of indocyanine green (ICG/HS 15) in an animal model of laser-induced choroidal neovascularization (CNV).

METHODS

The ICG was formulated with the nonionic solubilizer and emulsifying agent Kolliphor HS 15 to create ICG/HS 15 to improve the chemical stability and fluorescence efficacy. In vivo imaging was performed in rats that had undergone laser photocoagulation. Retinal uptake and fluorescence intensity of ICG and ICG/HS 15 were compared following intravenous injection of 3 dosages (0.05, 0.1, and 0.15 mg/kg body weight) at 7, 14, and 21 days following laser treatment. Postmortem analysis included histology with frozen sections and flat mounts.

RESULTS

Immediately following injection of ICG or ICG/HS 15, a strong fluorescence was visible in the retinal vasculature and at the site of laser lesions. Pixel intensity was higher for ICG/HS 15 compared to conventional ICG at 8 minutes after injection for all different injection days and dosages. Over time, a continuous decrease of the fluorescent signal was observed for up to 60 minutes to baseline level. Flow cytometry data showed an increased uptake of micellar dye of macrophages and endothelial cells. Histology revealed an accumulation of the micellar dye within the laser lesion.

CONCLUSIONS

Micelle formulated ICG can be visualized in the retinal vasculature and laser-induced CNV in vivo and ex vivo. Micellar ICG/HS 15 showed in vivo stronger signal intensity when compared to ICG for all tested dosages. Following further investigations, ICG/HS 15 may be evaluated in patients with retinal and choroidal diseases for more refined diagnosis.