Bonding heterostructure mediated “photo-thermo-electric” implant: NIR-II photothermal and thermoelectric therapy for bone tumor defects

Recurrence of solid tumors after surgical resection is a major barrier to tissue regeneration. As an emerging treatment strategy, photo-thermo-electric therapy ablates tumor cells via photothermal effects and generates reactive oxygen species (ROS) via thermoelectric effects to disrupt heat shock proteins, thereby suppressing their protective function in tumor cells. However, conventional materials suffer from low thermoelectric efficiency and weak tissue penetration ability. In this study, we fabricated iodine-doped bismuth sulfide (I-Bi2S3) nanorods with bonding heterostructures to improve thermoelectric performance. The approach employed iodine doping to introduce additional electrons, thereby regulating the band structure of Bi2S3 and exploiting the dual low-energy vibration effect of the heterostructures to reduce thermal conductivity. More importantly, controlling the type of heterostructure modulated the bandgap width, thereby expanding the light absorption range to the higher-penetration near-infrared (NIR)-II region for deep tissue treatment. The I-Bi2S3 nanorods were incorporated into poly-l-lactic acid (PLLA) scaffolds to confer antitumor functionality. According to the results, the bonding heterostructures enhanced the conductivity of Bi2S3 and reduced its thermal conductivity, significantly enhancing thermoelectric efficacy. The heterostructures reduced the bandgap of Bi2S3 from 1.23 to 0.88 eV, enabling optical absorption in the NIR-II region. The ROS tests showed that the PLLA/I-Bi2S3 scaffold exhibited good photothermal effects and ROS generation under 1064-nm laser irradiation. The antitumor efficacy of the PLLA/I-Bi2S3 scaffold reached 84.6% against MG-63 cells, demonstrating its exceptional potential in cancer treatment.