Fabrication of Stable and Well-Dispersed Polyaniline-Polypyrrolidone Nanocomposite for Effective Photothermal Therapy

Well-dispersed polyaniline (PANi) nanoparticles were successfully synthesized by simple oxidative polymerization of aniline in a two-phase system in the presence of poly(vinylpyrrolidone) (PVP) as a polymer shell agent, and citric acid was used as a doping acid instead of inorganic acids due to its better biocompatibility. TEM showed that the nanocomposites of PANi and PVP (PANi@PVP) assembled into core-shell like nanostructures uniformly. MTT results indicated that the PANi@PVP nanoparticles supported the survival of cells; IC50 could reach about 2.5 mg/mL, much higher than the IC50 value reported for PANi nanoparticles without PVP. Furthermore, in the presence of PVP, only exceeding PANi (>1.5 mg/mL) resulted in a comparable production of intracellular reactive oxygen species (ROS), the induction of apoptosis in PC-12 cells, and a weaker DNA fragmentation. TEM of PC-12 cell sections displayed that the cell morphological changes associated with the apoptosis were induced when exposed to a very high dose of PANi@PVP (3 mg/mL). The well-dispersed PANi@PVP combined with NIR irradiation achieved excellent photothermal conversion performance, which could kill cancer cell BEL-7402 in vitro effectively. Reflecting this well-dispersed property, the tumors in cancer bearing KM mice disappeared thoroughly after a single subcutaneous injection of PANi@PVP nanoparticles and subsequent NIR laser irradiation.