Chronic wounds are a major health challenge that require new treatment strategies. Hydrogels are promising drug delivery systems for chronic wound healing because of their biocompatibility, hydration, and flexibility. However, conventional hydrogels cannot adapt to the dynamic and complex wound environment, which involves low pH, high levels of reactive oxygen species, and specific enzyme expression. Therefore, smart responsive hydrogels that can sense and respond to these stimuli are needed. Crucially, smart responsive hydrogels can modulate drug release and eliminate pathological factors by changing their properties or structures in response to internal or external stimuli, such as pH, enzymes, light, and electricity. These stimuli can also be used to trigger antibacterial responses, angiogenesis, and cell proliferation to enhance wound healing. In this review, we introduce the synthesis and principles of smart responsive hydrogels, describe their design and applications for chronic wound healing, and discuss their future development directions. We hope that this review will inspire the development of smart responsive hydrogels for chronic wound healing.

Background: The tumor microenvironment (TME) poses significant challenges to effective therapy, with cancer-associated fibroblasts (CAFs) playing a key role in tumor progression and drug resistance in triple-negative breast cancer (TNBC). Herein, a TME responsive nanocapsule, NPC-ABS/FDS, was developed utilizing baicalein, a CAFs modulator, and the cytotoxic drug doxorubicin to selectively target CAFs and tumor cells, respectively, in a stepwise manner. Methods: NPC-ABS/FDS was designed with CD13-mediated primary targeting for tumor accumulation and secondary targeting via σ-receptor binding (ABS nanoparticles) for CAFs and folate modification (FDS nanoparticles) for cancer cells. Physicochemical properties were assessed using TEM, particle size, and ζ-potential analyses. Fluorescence imaging evaluated tumor retention, while cellular uptake and TME modulation were analyzed in vitro and in vivo. Results: The successful preparation of NPC-ABS/FDS was demonstrated by its uniform morphology, stable characteristics, charge reversal, and increased particle size. Fluorescence imaging confirmed prolonged peritumoral retention. Cellular uptake increased 2.5-fold for baicalein in CAFs and 4.3-fold for doxorubicin in cancer cells. NPC-ABS/FDS downregulated α-SMA and FAP, reducing CAFs activation, improving intratumoral drug penetration, and enhancing CD8⁺ and CD4⁺ T cell infiltration while decreasing regulatory T cells. Conclusions: NPC-ABS/FDS effectively modulates multiple TME components, including CAFs and immune cells, and improves drug delivery in TNBC. These findings may support the development of improved therapeutic approaches for TNBC.