Different effect of polymer-incorporated nanoparticles of Au and Ag on hematoporphyrin interaction with graft polymers

One of the ways to improve the efficiency of photodynamic therapy is to enhance the accumulation of the photosensitizer (PS) in the tumor; for this, either polymers or metal nanoparticles (NP) could be used. Here we studied the effect of Au and Ag nanoparticles (AuNPs and AgNPs, respectively) synthesized in situ in solution of non-charged and anionic polymers on spectral properties of PS hematoporphyrin (HP) as well as on ¹O₂ generation by this compound (revealed by ¹O₂ emission at 1275 nm). The star-like copolymer Dextran-graft-Polyacrylamide (D-g-PAA) and its anionic form (D-g-PAAan) were used as polymer matrices for nanosystems preparation. Absorption and fluorescence spectra show that HP molecules bind to D-g-PAA and D-g-PAAan in water that leads to the destruction of HP aggregates; these changes are accompanied by increase of ¹O₂ generation. Meanwhile, in the presence of polymers with incorporated AgNPs (D-g-PAA/Ag and D-g-PAAac/Ag) the mentioned effect is stronger as compared to corresponding polymers without incorporated NPs. Thus AgNPs affect the graft polymers interaction with HP. Contrarily, the presence of both polymers with incorporated AuNPs enhances HP aggregation; besides, in the case of non-charged polymer with gold nanoparticles D-g-PAA/Au, Au nanoparticles induce appearing of different HP form, presumably protonated one. Effect of Ag and Au nanoparticles on fluorescent properties of HP is mainly determined by the effect of these NPs on aggregation of HP (and, in the case of D-g-PAA/Au, by appearing of different HP form). As for HP-sensitized singlet oxygen luminescence, effect of AgNPs is also mainly related to aggregation destruction, while this of Au nanoparticles could have other mechanisms as well