Selective photothermal and photodynamic capabilities of conjugated polymer nanoparticles

Abstract

We found out that the conjugated polymers with different molecular weights and fullerene addition selectively controlled the photothermal and photodynamic effects of conjugated polymer nanoparticles (CPNs). It turned out that the use of high molecular weight (MW) conjugated polymer increase near infrared absorption, resulting in more photothermal effect than photodynamic effect. The highest photothermal effect was achieved when the more molecular ordering was expected by using a high MW conjugated polymer, phase-separated film dispersion process and a phospholipid-polyethylene glycol with alkyl tails for dense association with alkyl side chains of a conjugated polymer. On the other hand, the photodynamic effect was generally enhanced when less-organized molecular assemblies were expected by using a low MW conjugated polymer, a nanoprecipitation process, and/or a surfactant without compact alkyl chain association with a conjugated polymer. It was notable that fullerene acted differently on the photophysical properties of CPNs, depending on the molecular ordering. With limited fluctuation in the photothermal effect, the fullerene addition into CPNs enhanced the photodynamic effect under situations that can disrupt molecular ordering. In the meantime, the fullerene in CPNs enhanced the photothermal effect while maintaining the photodynamic effect with higher molecular ordering. Our results show that the combination of fullerenes can selectively and significantly increase the phototherapeutic capabilities based on molecular ordering of CPNs, suggesting a strategic approach for efficiency enhancement in the phototherapeutic medicinal applications.