Efficient Chemo-Mechanical Actuator Driven by Generation of Prestress via Glycosaminoglycans Accelerating Intrafibrillar Mineralization of Calcium Carbonate

Abstract

Huge contractile stresses are generated in collagen-based matrices via the precipitation of various minerals within the collagen fibrils. However, how to regulate the level of prestress via intrafibrillar mineralization remains unclear. Here, it is demonstrated that both, the polymorph selection and the deposition rate of mineral, are modified by proteoglycans that are naturally present in native collagen fibrils. The results show a 50% higher mineralization rate, possibly due to a reduction in the interfacial energy between collagen and precursors. While calcite particles nucleate in pure collagen, the additional presence of glycosaminoglycans leads to the intrafibrillar nucleation of vaterite in both collagen films and native tendons, resulting in contractile stress of more than 10 MPa after 72 h in tendons. Moreover, the stress generation rate can be adjusted by changing the pH values, temperature, and concentration of the mineralizing solution. The conversion of chemical energy to mechanical energy endows tendons with an energy density of 90 J kg⁻¹, more than twice that of biological muscle. By controlling the generation and release of the contractile stress induced by mineralization and demineralization, the designed collagen-based actuator demonstrates excellent actuation performance. The observed chemo-mechanical effect is expected to inspire the design of prestress-reinforced high-performance composites.