Bi 2 S 3 /Ti 3 C 2 -TPP nano-heterostructures induced by near-infrared for photodynamic therapy combined with photothermal therapy on hypoxic tumors.

BACKGROUND: Photodynamic therapy (PDT) efficacy of bismuth sulfide (Bi2 S3 ) semiconductor has been severely restricted by its electron-hole pairs (e- -h+ ) separation inefficiency and oxygen (O2 ) deficiency in tumors, which greatly hinders reactive oxygen species (ROS) generation and further clinical application of Bi2 S3 nanoparticles (NPs) in biomedicine.

RESULTS: Herein, novel Bi2 S3 /titanium carbide (Ti3 C2 ) two-dimensional nano-heterostructures (NHs) are designed to realize multimode PDT of synchronous O2 self-supply and ROS generation combined with highly efficient photothermal tumor elimination for hypoxic tumor therapy. Bi2 S3 /Ti3 C2 NHs were synthesized via the in situ synthesis method starting from Ti3 C2 nanosheets (NSs), a classical type of MXene nanostructure. Compared to simple Bi2 S3 NPs, Bi2 S3 /Ti3 C2 NHs significantly extend the absorption to the near-infrared (NIR) region and enhance the photocatalytic activity owing to the improved photogenerated carrier separation, where the hole on the valence band (VB) of Bi2 S3 can react with water to supply O2 for the electron on the Ti3 C2 NSs to generate ·O2 - and ·OH through electron transfer. Furthermore, they also achieve 1 O2 generation through energy transfer due to O2 self-supply. After the modification of triphenylphosphium bromide (TPP) on Bi2 S3 /Ti3 C2 NHs, systematic in vitro and in vivo evaluations were conducted, revealing that the synergistic-therapeutic outcome of this nanoplatform enables complete eradication of the U251 tumors without recurrence by NIR laser irradiation, and it can be used for computed tomography (CT) imaging because of the strong X-ray attenuation ability.

CONCLUSION: This work expands the phototherapeutic effect of Bi2 S3 -based nanoplatforms, providing a new strategy for hypoxic tumor theranostics.