This invention relates generally to minimally-invasive, in vivo methods of detecting one or more ligands on an intraluminal surface of a blood vessel using microparticles coated with one or more ligand binding partners. More particularly, in certain embodiments, the invention relates to minimally-invasive, in vivo methods of detecting endothelial and leukocyte antigens that are predictive of diabetic retinopathy (DR) and/or other conditions using protein-conjugated microparticles detectable by a non-invasive detection system, for example, a scanning laser ophthalmoscope. In other embodiments, the invention relates to targeted delivery of drugs or other substances to specific regions of an intraluminal surface of a blood vessel using drug-containing microparticles coated with one or more ligand binding partners.
