Poly-(D,L-lactide-co-glycolide) nanoparticles with covalently-bound porphyrins for efficient singlet oxygen photosensitization

With the aim of assessing the role of the chemical structure of the photosensitizer on the photophysical and photochemical properties of the final nanoparticle suspension, we have investigated a series of poly-(ethylene glycol)-poly-(D,L-lactide-co-glycolide) nanoparticles containing a hydrophobic or a hydrophilic porphyrin covalently conjugated to the nanoparticle. Covalent conjugation responded to the objective of trying to improve photosensitizer loading in these nanoparticles, especially for hydrophilic photosensitizers, but also enabled the porphyrins to remain attached to the nanoparticle without necessarily being inside the poly-(D,L-lactide-co-glycolide) core. This strategy has provided valuable information about the dependence of the photophysical and singlet oxygen photosensitizing properties of the suspensions on the nature of the photosensitizer. It is concluded that poly-(D,L-lactide-co-glycolide) nanoparticles with covalently-bound hydrophilic porphyrins show superior singlet oxygen photosensitizing ability.