Sustainable superlubricity achieved by thermosensitive and degradable hydrogel under ocular conditions

Sustainable lubrication of biomedical hydrogels with high stability is important for their application in dry eye disease (DED) treatment but remains a challenge. We report a novel strategy to achieve sustainable superlubricity under ocular conditions on the basis of the degradation of a thermosensitive P-C_nPEG (polyethylene glycol (PEG)) hydrogel. First, by adjusting the composition and chemical structure of the P-C_nPEG complex, its aqueous solution undergoes an adaptive sol‒gel transition at 25.1 °C during heating, resulting in a gel state upon injection onto the ocular surface (35 °C). In addition, the P-C_nPEG hydrogel obtained at 35 °C also shows superior performance, such as shear resistance, high transmittance (> 80%), rapid swelling, self-healing, and Ca²⁺ responsiveness, making it suitable for ocular applications. In the tear environment of DED patients with high reactive oxygen species (ROS) content, the P-C_nPEG hydrogel degrades within 6 days through the breakage of crosslinking sites. The degradation solution of each day presents ultralow coefficients of friction (COFs) under ocular conditions through the hydration effect. Finally, the excellent biocompatibility of the hydrogel demonstrates its potential for ocular applications. This study systematically discusses the mechanism of sustainable degradation-induced superlubricity of P-C_nPEG hydrogels, introducing a novel and promising strategy for DED treatment.