Black phosphorus nanosheets and gemcitabine encapsulated thermo-sensitive hydrogel for synergistic photothermal-chemotherapy.

The purpose of this study was to propose a thermosensitive hydrogel incorporating black phosphorus (BP) nanosheets and gemcitabine for chemo-photothermal combination therapy against cancer. The BP nanosheets were prepared by liquid exfoliation method and the thermo-sensitive hydrogel was prepared by "cold method" with Pluronic F127 as hydrogel matrix for intratumoral injection. BP nanosheets and the hydrogel were characterized by particle size, morphology, phase transition feature, near infrared photothermal conversion performance, photothermal stability and biodegradation. The in vitro release behaviors of gemcitabine were assessed. Moreover, the photothermal efficacy, and photothermal-chemotherapy combination were evaluated in mice bearing tumors. The BP nanosheets displayed uniform 2D sheet-like morphology with a diameter of about 200 nm. The hydrogel showed phase translation at near body temperature, great photothermal efficacy in vitro and good biodegradability. The hydrogel exhibited good photothermal effect in BALB/c mice bearing 4T1 xenograft tumors. The combination of photothermal therapy and chemotherapy displayed superior antitumor effect compared to chemotherapy alone.