Hongsong Fan

Fabrication and cellular biocompatibility of porous carbonated biphasic calcium phosphate ceramics with a nanostructure.

Microwave heating was applied to fabricate interconnective porous structured bodies by foaming as-synthesized calcium-deficient hydroxyapatite (Ca-deficient HA) precipitate containing H(2)O(2). The porous bodies were sintered by a microwave process with activated carbon as the embedding material to prepare nano- and submicron-structured ceramics. By comparison, conventional sintering was used to produce microstructured ceramics. The precursor particles and bulk ceramics were characterized by transmission electron microscopy (TEM), dynamic light scattering, scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FTIR) and mechanical testing. TEM micrographs and assessment of the size distribution showed that the needle-like precursor particles are on the nanoscale. SEM observation indicated that the ceramics formed by microwave sintering presented a structure of interconnective pores, with average grain sizes of approximately 86 and approximately 167nm. XRD patterns and FTIR spectra confirmed the presence of carbonated biphasic calcium phosphate (BCP), and the mechanical tests showed that the ceramics formed by microwave sintering had a compressive strength comparable to that obtained by conventional methods. Rat osteoblasts were cultured on the three kinds of BCP ceramics to evaluate their biocompatibility. Compared with the microscale group formed by conventional sintering, MTT assay and ALP assay showed that nanophase scaffolds promoted cell proliferation and differentiation respectively, and SEM observation showed that the nanoscale group clearly promoted cell adhesion. The results from this study suggest that porous carbonated biphasic calcium phosphate ceramics with a nanostructure promote osteoblast adhesion, proliferation and differentiation. In conclusion, porous carbonated BCP ceramics with a nanostructure are simple and quick to prepare using microwaves and compared with those produced by conventional sintering, may be better bone graft materials.

Preparation, bioactivity, and drug release of hierarchical nanoporous bioactive glass ultrathin fibers.

Hierarchical nanoporous bioactive glass ultrathin fibers with different pore diameters from 1.5-nm micropores up to 65-nm macropores are synthesized using P123-PEO co-templates and an electrospinning technique (see image). Experiments demonstrate that the prepared bioactive glass fibers are highly homogenous and bioactive and their nanopores can control drug release well.

Biomimetic interpenetrating polymer network hydrogels based on methacrylated alginate and collagen for 3D pre-osteoblast spreading and osteogenic differentiation

Hydrogels hold great promise for bone tissue engineering but their application is greatly limited by their low cell affinity and poor mechanical properties, as well as limited cell spreading ability for anchorage dependent cells such as osteoblasts. In this study, a series of hydrogels based on an interpenetrating polymer network (IPN) of methacrylated alginate (MAA) and collagen were developed to support pre-osteoblast spreading and proliferation as well as osteogenic differentiation. Compared to the pure MAA hydrogel, these hydrogels demonstrated higher mechanical moduli, lower swelling ratios and denser network structures. Moreover, the properties could be fine-tuned by altering the ratio of collagen and alginate. MC3T3-E1 cells in IPN hydrogels exhibited a rapid proliferation and spread gradually with prolonged culture time, and their osteogenic differentiation was greatly facilitated. While for the MAA hydrogel, the cells remained in a rounded morphology with bad osteogenic differentiation. These results should provide collagen–MAA IPN hydrogels as potential three-dimensional scaffolds for bone tissue engineering.

Modulation of immunological properties of allogeneic mesenchymal stem cells by collagen scaffolds in cartilage tissue engineering.

Influence of the structures of some collagen scaffolds on immunological properties of the seeded allogeneic mesenchymal stem cells (MSCs) was studied in this article. Hydrogels, sponge, and membrane were prepared from type-I collagen. These scaffolds were seeded with neonatal rabbit MSCs and cultured for different periods. Changes of the immunological properties associated with different scaffolds were analyzed and compared. It was found that the expression of major histocompatibility complex (MHC) class I and II molecules on MSCs increased gradually in all scaffolds, but the least increment was recorded in hydrogels. Mixed lymphocyte reactions (MLR) showed that the MSC-hydrogel constructs invoked considerably low allogeneic lymphocytes proliferation. Even in presence of interferon-γ (IFN-γ), the hydrogels with higher concentration gave comparatively lower increment of MHC-II expression and allogeneic lymphocytes proliferation. These results suggest that different scaffold structures may provide different microenvironments and extents of isolation from the host immune system for the seed cells, thereby affecting their immunological properties. Therefore, scaffold structures may modulate the immunological properties of tissue-engineered cartilage with allogeneic cells. Hydrogels, especially which were prepared from higher collagen concentrations, were found to be a promising scaffold structure, from the perspective of avoiding severe immune rejection.

Ultrasonication and Genipin Cross-Linking to Prepare Novel Silk Fibroin–Gelatin Composite Hydrogel

Hydrogels are highly desirable tissue engineering scaffolds due to their high water content and structural similarity to a natural extra cellular matrix. However, the extensive use of hydrogels is limited by their low strength and facile degradation. By combining mechanical integrity and slow degradation of silk fibroin with excellent bioactivity of gelatin, a novel biocompatible protein-based composite hydrogel of silk fibroin and gelatin was developed. The gelation of silk fibroin aqueous solution was accelerated by ultrasonication, and gelatin derived from porcine skin was immobilized into the hydrogel network by the silk fibroin β-sheets. After that, genipin was used to post-cross-link the hydrogel to form a compact and stable hydrogel network. This hydrogel composite was a mechanically robust biomaterial with predictable long-term degradation characteristics. MG63 cells readily attached, spread, and proliferated on the surface of the hydrogels as demonstrated by fluorescein diacetate/propidium iodide staining and mitochondrial activity (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay. Furthermore, the physicochemical and biological properties of hydrogel were fine-tunable by altering the ratio of silk fibroin and gelatin. The silk fibroin/gelatin composite hydrogels are anticipated to have the potential as cartilage or non-load-bearing bone tissue engineering and regeneration.

Ectopic Bone Formation in Adipose-derived Stromal Cell-seeded Osteoinductive Calcium Phosphate Scaffolds

The phenomenon of osteoinduction by biomaterials has been proven and used in animals. However, whether the ability of a biomaterial to initiate bone formation in ectopic implantation sites improves the performance of such osteoinductive biomaterial as a scaffold for tissue-engineered (TE) bone remains unclear. In this study, we compared ectopic bone formation by combining autologous adipose-derived stromal cells (ADSCs) with an osteoinductive and a nonosteoinductive biphasic calcium phosphate (BCP) ceramic to create a tissue engineering construct in the muscle of dogs. Two groups of BCP scaffolds (BCP1 and BCP2) were prepared. In each group, ADSCs were seeded, and the scaffolds without seeded cells served as controls. All implants were implanted in the back muscle of 10 adult dogs for 8 weeks and 12 weeks. Microcomputed tomography (Micro-CT) analysis and histomorphometry were performed to evaluate and quantify ectopic bone formation. The results indicated that the osteoinductive BCP1 performed significantly better compared to the nonosteoinductive BCP2 in cell-based TE bone formation ectopically. The ADSCs had a significantly positive effect on the ectopic bone formation. In addition, the usefulness of Micro-CT for the efficient and nondestructive analysis of mineralized bone and calcium phosphate scaffold was confirmed.

A novel technique to reconstruct a boxlike bone defect in the mandible and support dental implants with In vivo tissue-engineered bone.

The purpose of this study was to investigate the feasibility of using in vivo tissue-engineered (TE) bone to repair boxlike mandibular defect and support dental implant, and then provide experimental evidence for the future application of the novel technique in the clinical setting. The TE bone graft was constructed in vivo by implanting osteoinductive calcium phosphate (Ca-P) ceramics in the femoral muscles of dog for 8 weeks, then was transplanted to repair the autogeneic boxlike bone defect site created in one side of the mandible and simultaneously support a dental implant, while in the opposite side of the mandibular defect, the same ceramic was used directly as control. 8 weeks after transplantation, samples were harvested for analysis. The results demonstrated that the technique of in vivo tissue engineering improved the mechanical and biologic properties of ceramics significantly. After transplantation, the in vivo TE ceramic-bone grafts were involved in bone metabolism of the host and fused well with the host bone. The dental implants were stable and had been integrated with both TE bone grafts and autologous bone. Therefore, it is feasible to construct a live bone graft with osteoinductive Ca-P ceramics in vivo, then repair a mandibular bone defect, and support a dental implant. In conclusion, in vivo TE bone is a promising technique for bone repair.

Effect of adipic dihydrazide modification on the performance of collagen/hyaluronic acid scaffold.

Collagen and hydrazide-functionalized hyaluronic acid derivatives were hybridized by gelating and genipin crosslinking to form composite hydrogel. The study contributed to the understanding of the effects of adipic dihydrazide modification on the physicochemical and biological properties of the collagen/hyaluronic acid scaffold. The investigation included morphology observation, mechanical measurement, swelling evaluation, and collagenase degradation. The results revealed that the stability of composites was increased through adipic dihydrazide modification and genipin crosslinking. The improved biocompatibility and retention of hyaluronic acid made the composite material more favorable to chondrocytes growing, suggesting the prepared scaffold might be high potential for chondrogenesis.

Study of in vivo bone tissue engineering

In vivo bone tissue engineering is an emerging field of regenerative medicine for bone defects, which differs from classical tissue engineering. In vivo bone tissue engineering uses the body as a “bioreactor” to construct bone graft with intrinsic osteoinductive biomaterials in the non-osseous or osseous sites. This technique relies on the body’s own capacity to regenerate itself, and it does not rely on the delivery of exogenous growth factors or cells. This study has focused on the exploration of osteoinductive biomaterials, the construction of tissue engineering bone with osteoinductive biomaterials, and investigating possible applications in repairing mandibular bone defects in animals in order to develop a feasible technique for bone restoring. The results demonstrated that biomaterials without any exogenous growth factors or cells can induce bone formation in non-osseous sites, and in vivo tissue engineering bone formed with osteoinductive calcium phosphate (Ca-P) ceramics has similar histological characteristics with natural bone. It is possible to construct large bone graft with good blood supply and certain mechanical strength in vivo by using osteoinductive biomaterials. In vivo tissue engineering bone has been provided with a hope of being used to repair segmental bone defects of mandible and support dental implant.