Topology effects in photodynamic therapy with phthalocyanine nanocarriers†

Two different amphiphilic copolymers, a random copolymer (RCP) and a block copolymer (BCP), have been used to encapsulate a far-red photosensitizing hydrophobic zinc phthalocyanine while forming self-assembled nanocarriers of different topology: self-folded single-chain nanoparticles (SCNPs) and star-like aggregates (SLAs), respectively. Different copolymer/phthalocyanine ratios have been tested to assess their effect on structural properties which were determined by small-angle X-ray scattering (SAXS) measurements. The relevance of these materials as photosensitizer nanocarriers for photodynamic therapy (PDT) has been studied against human breast cancer cells (MCF-7). A better PDT effect was found for the SCNP-Pc2_x (100 μg mL⁻¹) excited at 800 nm with a pulsed laser than for the SLA-Pc2_x under identical conditions. Conversely, irradiation at slightly lower wavelengths (740 nm) of MCF-7 cells incubated with SLA-Pc2_x resulted in a notorious PDT effect when compared to that observed for MCF-7 cells incubated with the SCNP-Pc2_x. These systems represent new strategies for the encapsulation of photosensitizers for photodynamic therapy.