Fabrication of Au-polydopamine blackspheres-loaded PLLA-(silk fibroin) scaffold with photothermal conversion in NIR-II biowindows for deep nerve regeneration

Near infrared second region (NIR II) is applied in deep tissue imaging and tumor therapy. TRPV1 ion channels in cell membrane are widely distributed in nerve tissue, and opened with thermal stimulation, inducing Ca2+ influx. Gold-polydopamine (PDA) blackspheres (AuPBs) with good NIR II absorption and photothermal conversion were prepared by self-oxidation–reduction of dopamine and chlorauric acid, and then loaded on PLLA-SF parallel films (PSPF), which were then curved into nerve scaffolds (PSPF@AuPBs). After this scaffold implantation in sciatic nerve injury site (a depth of more than 1 cm under the skin), PDA in AuPBs relieved inflammatory response in injury site, leading to higher VEGF expression and new-vessels formation; furthermore, TRPV1 ion channels in Schwann cells (SCs) were periodically opened under NIR II irradiation to achieve effect of Ca2+ influx, activating SCs to highly express BDNF and NGF, and then promoting arrangement and myelination of SCs, nerve regeneration and functional recovery. These results suggested that our fabricated PSPF@AuPBs, as an effective NIR II adsorption platform, could provide a good photothermal conversion therapy to improve deep tissue regeneration.