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The Key Laboratory of Inorganic Coating Materials has long been engaged in the research and development of biomedical coatings on orthopedic implants for over 50 years. We conduct basic and applied research towards improving the bone/implant interface, with the aim of accelerating bone healing and improving bone anchorage to the implants, typically following two different approaches.

In the first strategy, we improve the interface by the architecture of surface topography for implants. In micron level, plasma sprayed Ti coatings with interconnected pores ranging between 100 and 500 μm (Fig. 1) were found to promote osteoblastic cells ingrowth and stimulate osteogenetic differentiation. At nanometer scale, plasma sprayed Ti coatings with a hierarchical topography where nanowires were superimposed in the micro-rough coating structure (Fig. 2), improved matrix protein adsorption, and thus increased filopodia generation, bone cell migration and differentiation, and finally osseointegration. Our work demonstrated that the hierarchical micro/nano structure activated integrin β1/ROCK/FAK/ERK signalling path, and besides, ROCK which was associated with cytoskeleton tension acted as an essential mediator of the stimulating effects on osteogenic differentiation.

Fig. 1 (a) Surface morphology and (b) cross-sectional image of micro-patterned Ti coatings

Fig. 2 Surface morphology of micro-rough Ti coating (a) and hybrid micro-nano structured Ti coating (b)

Fig. 3 Potential molecular mechanisms of the enhanced osteogenic differentiation of BMSCs on the hybrid micro-nano structured Ti coating

In the second strategy, we improve the bone/implant interface chemically by modifying the implant surface with different kinds of bio-ceramics, such as calcium phosphate and calcium silicate based ceramics. A series of Ca-Si based coating materials containing inorganic additives such as strontium, zinc, silver, zirconium, magnesium and iron have been developed in our group. The inorganic chemical modification was found to enhance the bone forming, angiogenesis, anti-inflammatory activity or antibacterial property of implant materials. Biochemical surface modification is a variant of this strategy and refers to the incorporation of organic molecules, such as proteins, enzymes or peptides, to induce bone cell responses. In our study, organic molecules type I collagen/hyaluronic acid coated Ti coating was observed to improve stem cell proliferation (Fig. 4), osteogenic differentiation and finally osseointegration (Fig. 5). 

Fig. 4 CLSM images of BMSCs cultured on the as-sprayed Ti coating (a-1, a-2), the alkali treated Ti coating (b-1, b-2) and biochemically modified Ti coating (c-1, c-2)

Fig. 5 Histological sections after 1 mon implantation: the as-sprayed Ti coating (a), the alkali treated Ti coating (b) and biochemically modified Ti coating (c)

More than 150 academic papers have been published in the scientific journals of biomaterials field including Biomaterials, Acta Biomaterialia, Journal of Biomedical Materials Research, Journal of Colloid and Interface Science, etc. Besides promoting basic research, we cooperated with the companies of orthopedic implants for the development of better human medical products. Our group successfully applied vacuum plasma spray (VPS) technology to manufacture porous Ti coating and bioactive HA coating on orthopedic implants and established production lines. More than 300,000 bone substitutes (artificial hip joints, spinal implants, etc.) with VPS Ti coating or/and HA coating have been manufactured and applied clinically in these years.