Highly temperature-sensitive, photothermal, and robust intelligent hydrogels tailored for the NIR-II biological window

Combining PNIPAM with a biocompatible NIR-II photothermal agent to prepare near-infrared-responsive hydrogels holds significant importance in the field of biomedical applications. In this study, PNIPAM/Bacterial cellulose (BC)/MXene composite hydrogels were prepared by in-situ polymerization, where Nb2C MXene serving as a near-infrared photothermal agent and BC acting as enhancing filler. The composite hydrogels possess a semi-interpenetrating network structure, where PNIPAM serves as the crosslinking network backbone, and BC act as a semi-interpenetrating network, which significantly enhances the mechanical strength of the composite hydrogels. The tensile strength and compressive strength reach 35 KPa and 500 KPa, respectively, which is an order of magnitude higher than that of pure PNIPAM hydrogel. The introduction of BC and MXene did not significantly affect the thermo-sensitivity of the composite hydrogel which can rapidly undergo a phase transition and release internal moisture above LCST. Morover, the composite hydrogel exhibits excellent photothermal performance, with its temperature rapidly increasing to around 70 °C under the irradiation of 1064 nm laser. The degree of temperature fluctuations can be accurately regulated by modifying the laser intensity and exposure time. Additionally, it demonstrates good photothermal cycling stability and significant potential for photothermal therapy.