Tumour-homing chimeric polypeptide-conjugated polypyrrole nanoparticles for imaging-guided synergistic photothermal and chemical therapy of cancer

Near-infrared (NIR)-absorbing conjugated polymer nanoparticles are interesting for imaging-guided combination therapy, especially for synergistic photothermal therapy and chemotherapy; however, most of them target tumours passively through the enhanced permeability and retention (EPR) effect, leading to low utilization efficiency. To address this problem, we report an active tumour-targeting strategy of tumour-homing chimeric polypeptide-conjugated NIR-absorbing conjugated-polymer nanoparticles as a new class of drug nanocarriers for imaging-guided combination therapy of cancer. Methods: A tumour-homing chimeric polypeptide C-ELP-F3 was genetically engineered, and chemoselectively conjugated to polypyrrole (PPy) nanoparticles via a facile thiol-maleimide coupling reaction to form ELP-F3 conjugated PPy (PPy-ELP-F3) nanoparticles. Doxorubicin (DOX) was physically adsorbed onto PPy-ELP-F3 nanoparticles to yield DOX-loaded PPy-ELP-F3 (DOX/PPy-ELP-F3) nanoparticles. The physicochemical properties of DOX/PPy-ELP-F3 were characterized. The pharmacokinetics of DOX/PPy-ELP-F3 was studied in a mouse model. The photoacoustic imaging and photothermal imaging of tumours were tested in a melanoma-bearing mouse model. The photothermal-chemical combination therapy of tumours was investigated by using melanoma cells in vitro and in a melanoma-bearing mouse model. Results: DOX/PPy-ELP-F3 nanoparticles showed enhanced cytotoxicity to melanoma cells in vitro and improved tumour-targeting efficiency in vivo, as compared with both DOX/PPy-ELP nanoparticles without the tumour-homing function and free DOX. The photothermal effect of DOX/PPy-ELP-F3 nanoparticles could accelerate the release of DOX from PPy-ELP-F3. Under the guidance of photoacoustic and photothermal imaging, the synergy of photothermal and chemical therapy could completely abolish tumours without detectable systemic toxicity. Conclusion: Tumour-homing chimeric polypeptide-conjugated NIR-absorbing conjugated-polymer nanoparticles are promising as a new multifunctional drug delivery platform for highly-efficient imaging guided combination therapy.