Construction of a layer-by-layer self-assembled rosemarinic acid delivery system on the surface of CFRPEEK implants for enhanced anti-inflammatory and osseointegration activities.

Carbon fiber-reinforced polyether ether ketone (CFRPEEK) implants have attracted widespread attention in the field of clinical bone defect repair. However, the surface bioinertness confines the application of CFRPEEK implants. Inspired by the study of rosmarinic acid (RA)-promoted osteogenic differentiation, a self-assembly surface modification method based on electrostatic interactions, involving deposition of sodium carboxymethyl cellulose/chitosan and rosmarinic acid layer by layer on the surface of poly-L-lysine modified hydroxy CFRPEEK (SCPP/CC@RA), is proposed to introduce RA on the surface of CFRPEEK for bioactivation. After layer-by-layer self-assembly (LBL), the surface of SCPP/CC@RA exhibits weak electrophoresis (11.43 eV), suitable hydrophilicity, and bioactivity. The results of studies indicate that the RA release behavior of SCPP/CC@RA effectively regulates the immune-inflammatory response and promotes the differentiation of osteoblasts. The rapid release of RA (0.17 μg mL) in the initial stage can downregulate the secretion of inflammation-related cytokines and significantly reduce oxidative stress levels; the sustained release of RA (0.06 μg mL) in the late stage can upregulate the expression of osteogenesis-related genes and induce mineralization of osteoblasts. Moreover, the rabbit tibia defect model demonstrates that the LBL technique can enhance the osseointegration of CFRPEEK implants. Compared with the control group, the bone trabecular thickness of the SCPP/CC@RA group increases by 1.36 times, and the maximum pushing force increases by 2.67 times. In summary, this study provides a promising LBL based RA delivery system for the development of a dual-functional CFRPEEK implant in the field of bone implant biomaterials.