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E. Peiretti, R.W. Flower, M. Fossarello; Human Erythrocyte–Ghost–Mediated Choroidal Angiography and Photocoagulation . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4282.
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Purpose: To demonstrate use of human erythrocyte ghosts as vehicles for indocyanine green (ICG) dye and conjugated substances for choroidal angiography and vessel photocoagulation enhancement. Methods: A three–step osmotic hemolysis procedure was developed for introducing ICG dye and conjugated substances into human erythrocyte ghost cells. Loaded cells were examined microscopically to validate shape normalcy and stability. Location of dye molecules within the ghost cells was validated by examination with a single molecule microscope (450 nm resolution). 0.05 ml boluses of packed ghost cells were injected into the marginal ear veins of Dutch belted rabbits (i.e., 0.005 % of total blood volume), and high–speed angiograms were recorded. For comparison, angiograms were made following intravenous injections of 0.05 ml boluses of 0.25 mg/ml ICG in aqueous solvent. Results: Compared to the rapid choroidal blood flows depicted by the single wavefront transits seen in conventional aqueous ICG angiograms, flow rates indicated by the erythrocyte ghosts appeared notably slower. In addition to the ghost cell wavefront transit, directionality of flow in individual vessels remained discernable for as long as 20 seconds. Small clusters of stalled erythrocytes (presumably in the choriocapillaris) were seen to form and then dissipate. As dye was entirely confined within the erythrocyte ghosts, build–up of background fluorescence associated with vessel wall staining was avoided. The rabbits exhibited no response to multiple injections of the human ghost cells. Conclusions: Compared to artificial lyposome encapsulation, erythrocyte ghost encapsulation provides enormous volume capacity and the shape flexibility needed to pass through capillaries. Since the greatest portion of vessel lumen cross section is occupied by erythrocytes rather than by serum, use of ICG–loaded autogolous ghosts could improve ICG dye–enhanced photocoagulation of CNV feeder vessels by delivering higher concentrations of ICG to targeted vessels as well as inhibitors of clot lysis.
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