Photosensitizer-Conjugated Albumin−Polypyrrole Nanoparticles for Imaging-Guided In Vivo Photodynamic/Photothermal Therapy

Conjugated polymers with strong absorbance in the near‐infrared (NIR) region have been widely explored as photothermal therapy agents due to their excellent photostability and high photothermal conversion efficiency. Herein, polypyrrole (PPy) nanoparticles are fabricated by using bovine serum albumin (BSA) as the stabilizing agent, which if preconjugated with photosensitizer chlorin e6 (Ce6) could offer additional functionalities in both imaging and therapy. The obtained PPy@BSA‐Ce6 nanoparticles exhibit little dark toxicity to cells, and are able to trigger both photodynamic therapy (PDT) and photothermal therapy (PTT). As a fluorescent molecule that in the meantime could form chelate complex with Gd3+, Ce6 in PPy@BSA‐Ce6 nanoparticles after being labeled with Gd3+ enables dual‐modal fluorescence and magnetic resonance (MR) imaging, which illustrate strong tumor uptake of those nanoparticles after intravenous injection into tumor‐bearing mice. In vivo combined PDT and PTT treatment is then carried out after systemic administration of PPy@BSA‐Ce6, achieving a remarkably improved synergistic therapeutic effect compared to PDT or PTT alone. Hence, a rather simple one‐step approach to fabricate multifunctional nanoparticles based on conjugated polymers, which appear to be promising in cancer imaging and combination therapy, is presented. Bovine serum albumin (BSA) preconjugated with the photosensitizer chlorin e6 (Ce6) is used as the stabilizing agent to facilitate the synthesis of polypyrrole (PPy), obtaining PPy@BSA‐Ce6 nanoparticles by a simple one‐step method. Utilizing such nanoparticles, an in vivo multimodal imaging‐guided combined photodynamic and photothermal therapy is carried out, achieving a remarkably improved synergistic therapeutic effect compared to the respective mono‐therapy.