There is herein described a nanovesicle comprising a bilayer of porphyrin-phospholipid conjugates. Each porphyrin-phospholipid conjugate comprises one porphyrin, porphyrin derivative or porphyrin analog covalently attached to a lipid side chain at one of the sn-1 or the sn-2 positions of one phospholipid. Further, the nanovesicle has a defined regioisomeric ratio of sn-1:sn-2 porphyrin-phospholipid conjugates.