Application of self-powered hydrogel systems in cartilage tissue engineering
Articular cartilage possesses a very limited intrinsic capacity for repair due to its avascularity, low cellularity, and poor extracellular matrix turnover, making effective regeneration after injury-induced osteoarthritis particularly challenging. In recent years, hydrogel-based electroactive platforms, particularly self-powered hydrogels, have emerged as promising strategies for cartilage repair by integrating extracellular matrix mimetic hydration, mechanical compliance, and localized bioelectrical stimulation within a unified regenerative system. This review summarizes current advances of self-powered hydrogels for cartilage tissue engineering, with a focus on their material classification, underlying mechanisms, and translational potential. The fundamental concept of self-powered hydrogels is first outlined, and hydrogel-native electroactive systems are distinguished from hydrogel-enabled self-powered platforms. The major mechanistic categories are then discussed, including piezoelectric hydrogels, hydrogel-based triboelectric platforms, mechano-iontronic hydrogels, and other emerging self-powered systems such as thermoelectric, hydrovoltaic, and biofuel cell-based constructs. Particular emphasis is placed on the material basis, structural design, mechanoelectrical transduction pathways, and the current in vitro and in vivo evidence supporting their application in cartilage and osteochondral regeneration. This review also analyzes the major barriers to clinical translation, including insufficient mechanistic decoupling, lack of standardized electrical dose evaluation, signal attenuation in the hydrated joint environment, degradation-performance mismatch, and the limited availability of long-term, larger animal, and clinically relevant validation studies. Overall, self-powered hydrogels represent a rapidly evolving class of bioelectronic biomaterials capable of recapitulating the coupled mechanical, electrical, and ionic microenvironment of native cartilage. Future advances will depend on coordinated progress in material design, quantitative bioelectrical characterization, and translational evaluation.