Nano-Confined Hydrogel Microspheres with Programmable Mechanics and Molecular Lubricity

The simultaneous integration of high elasticity and lubricity-hallmarks of biological tissues-remains a fundamental challenge in synthetic hydrogels due to the intrinsic trade-off between "dehydration-induced" elasticity and "hydration-dependent" lubrication. Herein, inspired by the dynamic architecture of living systems, the construction of "living" biodegradable hydrogel microspheres is reported that reconcile this contradiction through internal nano-reinforcement and external molecular lubrication. Crystalline disc-like Laponite nanosheets are intercalated within GelMA networks, acting as dynamic, spatially confining crosslinkers that inhibit water infiltration and preserve network cohesion. Concurrently, zwitterionic brushes are grafted onto the microsphere surface, forming a robust hydration layer via dynamic charge-dipole interactions to enable long-lasting lubrication. This synergistic design endows the microspheres with tunable elasticity (14-4000 Pa) and adjustable friction coefficients (0.12-0.04), achieving a functional convergence of mechanical resilience and surface lubricity. Experimental evaluations confirm their efficacy in inhibiting excessive mechanical stress-induced calcium ion influx and downstream calcium signaling to prevent chondrocyte damage. This work offers a universal strategy to overcome the elasticity-lubrication paradox in hydrogels, unlocking their potential in biomedical engineering, drug delivery, and soft robotic interfaces.

cartilage lubrication; microfluidic microspheres; nano enhancement; osteoarthritis; spatial confinement.