Development of polypyrrole-methylene blue nanoparticles for the combination of photothermal and photodynamic therapies

Combined therapy can be a highly promising strategy efficacy in the treatment of cancer with minimum side effects. The combination of photothermal therapy (PTT) and photodynamic therapy (PDT) has recently gained much attention due to its selective and localized therapeutic effects by light irradiation. The contrast agents for photo-based therapy should have a large absorption coefficient in the near-infrared region (NIR) (700–2500 nm) where the light has its maximum depth of penetration in tissues. In this work, we reported a multifunctional nanoparticle that has strong NIR absorbing capability for the combination of PTT and PDT. Methylene blue (MB) is a common photosensitizer for PDT in clinical use. Polypyrrole (PPy) is a super material for PTT because of its superior inherent features including strong NIR absorption, photothermal stability, low cost, and biocompatibility. For the first time, methylene blue (MB) was conjugated with photothermal material polypyrrole (PPy) to form a novel NIR photo-absorber. A fast and cost-effective method was developed to prepare the MB-PPy nanoparticles. The in vitro test evidenced that PPy–MB NPs able to kill the cancer cells with the assistance of the NIR laser. Therefore, the novel PPy–MB NPs could be considered as promising single multifunctional nanoplatforms for further applications of photo-induced therapy.