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  Bioactive Materials and Tissue Engineering Researc
Research Directions
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Research Directions

The group has creatively carried out both fundamental and applied research by systematically studying silicate-based bioactive ceramics, composite materials, tissue engineering materials and nanobiomaterials.

1.Fundamental and applied research for silicate-based bioactive ceramics, glasses and their composites.

Calcium phosphate bioceramics, as bone regenerative materials, have been used clinically. The shortcomings of this family bioceramics mainly include insufficient mechanical strength, bioactivity and uncontrollable degradation. To solve these problems, BTEG prepared a series of silicate-based bioceramics, bioglasses and inorganic/organic composites with varied compositions (e.g. Ca, Mg, Zn, Sr or Na-containing silicate ceramics, silicate/polymer composite and mesoporous bioglass/silk fibrin scaffolds). BTEG, for the first time, synthesized Mg/Zn-containing Akermanite (Ca2MgSi2O7), Bredigite (Ca7MgSi4O16) and Hardystonite (Ca2ZnSi2O7)silicate ceramics powders, and prepared their bulk ceramics. Followed the preparation of these novel bioceramics, the relationship of their compositions, mechanical strength, bioactivity and degradation has been systematically studied.

The relationships for the compositions of silicate ceramics/composites, ionic microenvironments, and the attachment, proliferation, differentiation and bone-related gene expression as well as protein secretion of different stem cells (e.g. bone marrow stromal cells, dental pulp stem cells, periodontal ligament stem cells and adipose stem cells) have been investigated. It is found that (1) silicate-based ceramics with specific compositions could significantly enhance the attachment, proliferation, differentiation of bone marrow stromal cells, (2) Mg-containing silicate bioceramics (akermanite) could stimulate the differentiation of several kinds of stem cells, in which ERK signalling pathway plays an important role to induce osteogenic differentiation of stem cells, and the released Mg and Si-containing ionic products could significantly stimulate angiogenesis, NO synthesis and the expression of KDR (VEGFR2), FGFR1 (bFGFR) and ACVRL1, indicating that silicate-based bioceramics have great potential for bone tissue engineering. The study is of great importance to develop new bioactive materials for bone regeneration both theoretically and practically, (3) Sr-containing silicate bioceramics could distinctly promote the proliferation and differentiation of osteoblasts through the synergistic effect of Sr, Si ions and alkaline microenvironment.

Further in vivo study has been conducted to evaluate the osteogenesis and angiogenesis of silicate bioceramics and their composite materials. The results have shown that they possess excellent in vivo biocompatitibility, osteo-stimulation ability, degradation and angiogenesis, in which bone-forming ability, degradation and angiogenesis of silicate-based biomaterials are superior to those of conventional β-tricalcium phosphate ceramics. Further study has indicated that Sr-containing silicate bioceramics could treat osteoporosis in an animal model through the release of Sr ions to stimulate bone regeneration. Therefore, silicate-based bioceramics have shown clearly stimulatory effect on osteogenesis and angiogenesis in vivo.

Silicate-based ceramics have been further used for orthopedic coating application. Silicate ceramic coatings showed excellent bonding strength with Ti alloys, bioactivity and osteointegration with host bone, indicating that silicate bioceramic coatings could be used for bioactive implants (e.g. artificial joints, dental implants and orthopedics fixed instruments).

The research results have been published in internationally top-ranking peer-review journals (Biomaterials 2006, 27:5651-5657; Biomaterials 2008;29:4792-4299; Biomaterials 2008;29:2588-2596; Biomaterials 2009,30:5041-5048; European Cells & Materials 2011,22:68-83; Biomaterials 2011,32(29):7023-7033; Acta Biomaterials.2012,8:341-349; Acta Biomaterialia.2012,8(1):350-360). The study is of great importance to establish new bioceramic system and develop functional biomaterial products for bone/tooth regeneration and bone tissue engineering application.

2.New methods and technology for preparing biomaterials with controllable nano/micro-meter structure

Nanomaterials have special characteristics due to nanostructure, which may endow biomaterials special functions. BTEG has studied a series of nano-sized bioceramics and bioglasses, including preparation and drug-delivery properties of nano-sized bioceramic powders and mesoporous bioglasses (MBG) with ordered channel structure. It is found that silicate-based MBG materials possess special pH-stimuli property for drug delivery, which is of great importance to further develop bioactive materials with controllable drug-delivery ability for tissue regeneration and osteomyelitis therapy.

A series of nano-sized hydroxyapatite with varied morphology (e. g. nanoparticles, nanorods, nanowires, nanosheets and hollow nanospheres) and compositions (e. g. Na, Si, Sr, Mg and CO32-) has been prepared by using calcium silicate ceramic or Ca-Si-Na-P bioglass templates; by combination of electron-spinning technique and hydrothermal method, hierarchically structured nanocrystalline hydroxyapatite assembled hollow fibers were successfully prepared, which could be used for protein carriers.

Further study has been conducted to investigate the effect of surface nano/micro structure of biomaterials on specific protein absorption, and the attachment, proliferation, differentiation of bone marrow stromal cells. It is found that the nano/micro-structure surface of biomaterials significantly stimulates the biological response of bone-forming cells and new bone formation through selective absorption of specific proteins in serum.

Porous scaffolds are one of key factors to influence tissue repair and regeneration. BTEG not only studied the composition of bioactive materials, but also explored new technology to construct scaffolds. Significantly advance in preparing electron-spinning tissue engineering scaffolds has been made in the group. Previous scaffolds prepared by electron-spinning technique showed an uncontrollable structure with irregular fiber distribution. We, for the first time, prepared nano-fiber scaffolds with controllable structure, fiber orientation/distribution and complex patterns. In 2007, this result was published in “Advanced Materials”, the top journal of materials sciences. Tube-like nanofiber materials with controllable microstructure were successfully prepared in 2008, which was then published in “Nano Letters” and highlighted by Nature China. Currently, BTEG is carrying out further study of electron spinning materials for artificial blood vessels, wound dressing, surgical anti-adhesion/anti-scars membranes.