“…For an excellent review of organ-specific PDT clinical trials, see van Straten et al 37 Generally, targeting moieties for tetrapyrroles have included small molecules such as folic acid, 38 sterols, 39 and alkylphosphocholine, 40,41 peptides, 42,43 proteins, 44 nanoparticles, 45−47 gels, 48,49 antibody fragments, and antibody species. 50 Antibodies are Y-shaped macromolecular proteins, produced naturally by B-cells in blood upon activation of the immune system.…”