In this study, gold nanoparticles (AuNPs) were synthesized in situ using chitin nanogels (CNGs) as templates to prepare composites (CNGs@AuNPs) with good photothermal properties, wherein their drug release properties in response to stimulation by near-infrared (NIR) light were investigated. AuNPs with particle sizes ranging from 2.5 nm to 90 nm were prepared by varying the reaction temperature and chloroauric acid concentration. The photothermal effect of different materials was probed by near-infrared light. Under 1 mg/mL of chloroauric acid at 120 °C, the prepared CNGs@AuNPs could increase the temperature by 32 °C within 10 min at a power of 2 W/cm². The Adriamycin hydrochloride (DOX) was loaded into the CNGs@AuNPs to investigate their release behaviors under different pH values, temperatures, and near-infrared light stimulations. The results showed that CNGs@AuNPs were pH- and temperature-responsive, suggesting that low pH and high temperature could promote drug release. In addition, NIR light stimulation accelerated the drug release. Cellular experiments confirmed the synergistic effect of DOX-loaded CNGs@AuNPs on chemotherapy and photothermal therapy under NIR radiation.

In order to achieve rapid and qualitative detection of soluble heavy metal ions, nitrogen-doped fluorescent carbon quantum dots (N-CQDs) were synthesized using chitin extracted from shrimp and crab shells as the carbon source. The structural, morphological, and optical properties of the synthesized N-CQDs were systematically characterized using transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FTIR), Raman, X-ray photoelectron spectroscopies (XPS), ultraviolet-visible (UV-Vis) absorption spectroscopy and fluorescence spectroscopy. The resulting N-CQDs exhibited a carbonization yield of 54.46% and a fluorescence quantum yield of 34.33%. Their morphology, structure and optical properties were thoroughly characterized using a range of analytical techniques. The synthesized N-CQDs exhibited excellent fluorescence properties, and remarkable stability. When applied for metal ion detection, the N-CQDs displayed a distinct and selective fluorescence quenching response exclusively toward Fe³⁺ ions. The detection limit for Fe³⁺ at room temperature was 4.04 μmol/L. Furthermore, due to the inherent nitrogen present in the acetyl amino groups of chitin, nitrogen doping was achieved without the need for external dopants during the hydrothermal synthesis process. Owing to their high stability, low cost and low toxicity, the N-CQDs synthesized in this study provide a promising fluorescence sensing platform with excellent selectivity for Fe³⁺ detection, achieved through precise control of surface functional groups.

Injectable self-healing hydrogels are promising biomaterials for wound management, as their ability to autonomously repair enables conformal sealing of irregular wounds. In this study, an injectable hydrogel was fabricated through Schiff base cross-linking of acrylamide-modified chitosan (AMCS) and 50% oxidized alginate (ADA). To enhance its mechanical robustness and hemostatic performance, chitin nanogels (CNGs) were incorporated as a reinforcing component. The structure-property relationships of the resulting hydrogel were characterized using infrared spectroscopy, field emission scanning electron microscopy, confocal laser scanning microscopy, and rheological analysis. Rheological studies confirmed that the composite hydrogel (AANGH) exhibited a superior storage modulus and more robust self-healing recovery compared to the base hydrogel (AAH3). MTT assays using L929 fibroblast cells demonstrated outstanding cytocompatibility, with cell viability maintained at over 100%. Furthermore, in vivo hemostatic assessment demonstrated effective hepatic hemorrhage control, characterized by significantly reduced blood loss, shortened hemostasis time, and favorable antibacterial properties. This work establishes that AANGH is an effective strategy for creating a mechanically robust, self-healing, and highly biocompatible chitosan-based hydrogel with strong potential for hemostatic applications.