Purpose: To improve the surface bio-properties of polyetheretherketone (PEEK)/nano magnesium silicate (n-MS) composite (PC). Materials and Methods: The surface of PC was firstly treated by particle impact (PCP) and subsequently modified by concentrated sulfuric acid (PCPS). Results: PCPS surface exhibited not only macropores with sizes of about 150 μm (fabricated by particle impact) but also micropores with sizes of about 2 μm (created by sulfonation of PEEK) on the macroporous walls, and sulfonic acid (-SO₃H) groups were introduced on PCPS surface. In addition, many n-MS nanoparticles were exposed on the microporous walls, which formed micro-nano structures. Moreover, the surface roughness and hydrophilicity of PCPS were obviously enhanced as compared with PC and PCP. Moreover, the apatite mineralization of PCPS in simulated body fluid (SBF) was obviously improved as compared with PC. Furthermore, compared with PC and PCP, PCPS exhibited antibacterial performances due to the presence of -SO₃H groups. In addition, the responses (eg, adhesion and proliferation as well as differentiation) of bone marrow mesenchymal stem cell of rat to PCPS were significantly promoted as compared with PC and PCP. Conclusion: PCPS with macro-microporous surface containing -SO₃H groups and micro-nano structures exhibited antibacterial activity and induced cell responses, which might possess large potential for bone substitute and repair.

Absorbable polymers have attracted increasing attention in the field of bone regeneration in recent years for their degradation. Compared with other degradable polymers, polypropylene carbonate (PPC) has several advantages such as biodegradation and relatively cheap raw materials. Most importantly, PPC can degrade into water and carbon dioxide totally which does not give rise to local inflammation and bone resorption in vivo. However, pure PPC has not presented excellent osteoinductivity properties. In order to enhance the osteoinductivity of PPC, silicon nitride (SiN) was employed due to its excellent mechanical properties, biocompatibility and osteogenesis compared with the other common materials such as hydroxyapatite and calcium phosphate ceramics. In this study, composites of PPC mixed with different contents of SiN were prepared successfully (PSN10 with 10 wt% SiN content, and PSN20 with 20 wt% SiN content). The characterization of the composites suggested that PPC mixed with SiN evenly and PSN composites presented stable properties. The results in vitro revealed that the PSN20 composite possessed satisfactory biocompatibility and exerted better osteogenic differentiation effects on adipose-derived stem cells (ADSCs). In particular, the PSN20 composite accelerated the healing of bone defects better and degraded with the process of bone healing in vivo. Overall, the PSN20 composite exhibited better biocompatibility, induced osteogenic differentiation of ADSCs and promoted healing of bone defects, due to which the PSN composite is considered as a potential candidate for treating bone defects in the field of bone tissue engineering.

A piezoelectric nanozyme is a novel biomaterial with the integration of piezoelectricity and nanozyme activity that has the capability of killing bacteria and promoting cell responses under a mechanical stimulus and exhibits great prospects in tissue regeneration. Herein, a piezoelectric nanozyme of bismuth sulfide (BS) with cationic vacancies (VBS) was synthesized, which exhibits enhanced piezoelectricity and nanozyme activities compared with BS. Moreover, a piezoelectric hydrogel of VBS and phenylboronic acid grafted sodium alginate-arginine (VBS-PSA) was prepared. Triggered by ultrasound (US) with high power (>0.5 W cm⁻²), VBS-PSA produces a large amount of reactive oxygen species (ROS) through both piezoelectricity-enhanced sonodynamic efficiency and peroxidase-like (POD-like) activity, thereby displaying the powerful antibacterial capability. However, under low-power US (≤0.5 W cm⁻²), the piezoelectric effect of VBS-PSA generates electrical signals that significantly stimulate the osteoblast responses (proliferation and osteoblast differentiation) and enhance catalase-like (CAT-like) activity for scavengers of ROS and generation of oxygen, thereby creating a favorable microenvironment for cell growth. Our study presents a novel strategy to apply the piezoelectric effect of hydrogels for enhancing sonodynamic efficiency and nanozyme activities that synergistically kill bacteria and stimulate osteoblast responses. The piezoelectric hydrogel would have great potential for the repair of infected bone defects.