Jiabing Ran

Preparation and evaluation of collagen-silk fibroin/hydroxyapatite nanocomposites for bone tissue engineering.

A new in situ precipitation technique was developed to synthesize collagen-silk fibroin/hydroxyapatite nanocomposites. The componential properties and morphological of nanocomposites were investigated. It was revealed that the inorganic phase in the nanocomposite was carbonate-substituted hydroxyapatite with low crystallinity. Morphology studies showed that hydroxyapatite particles with size ranging from 30 to 100 nm were distributed uniformly in the polymer matrix. According to the TEM micrographs, inorganic particles were composed of more fine sub-particles whose diameters were between 2 and 5 nm in size without regular crystallographic orientation. The mechanical properties of the composites were evaluated by measuring their elastic modulus. The data indicated that the elastic modulus of nanocomposites was improved by the addition of silk fibroin. Finally, the cell biocompatibility of the composites was tested in vitro, which showed that they have good biocompatibility. These results suggest that the collagen-silk fibroin/hydroxyapatite nanocomposites are promising biomaterials for bone tissue engineering.

Incorporation of homogeneous Co3O4 into a nitrogen-doped carbon aerogel via a facile in situ synthesis method: implications for high performance asymmetric supercapacitors

A novel high-performance electrode material, nitrogen-doped carbon aerogel/cobalt oxide (NCA/Co3O4) material, was prepared by a facile, one step and in situ coating method, followed by a freeze-drying process. The effects of different amounts of Co3O4 on the structural properties, specific surface areas, elemental compositions and electrochemical performance of the composite electrodes were investigated. Consequently, the electrode with 75% mass content of Co3O4 exhibited excellent electrochemical performance, in particular, a high specific capacitance of 616 F g−1 at a current density of 1 A g−1, excellent rate capability (445 F g−1 at 20 A g−1) and outstanding cycle performance. In addition, the asymmetric supercapacitor assembled with NCA/Co3O4-3 and NCA electrodes could be cycled in a high voltage range of 1.5 V and deliver a maximum energy density of 33.43 W h kg−1 at a power density of 375 W kg−1. The enhanced electrochemical performance is attributed to the complementary contributions of the 3D interconnected porous structure and the efficient pseudocapacitance of the uniformly dispersed Co3O4 nanoparticles. The preparation method offers a new fabrication strategy to in situ fabricate carbon-supported metal oxide electrodes for high-performance energy storage applications.

A novel nanocomposite for bone tissue engineering based on chitosan–silk sericin/hydroxyapatite: biomimetic synthesis and its cytocompatibility

A simple and effective approach was developed to synthesize chitosan–silk sericin/hydroxyapatite nanocomposites by in situ precipitation and two methods of alkali diffusion were carried out in this study. The objective of this paper was to investigate the different properties of the nanocomposites. SEM showed that the rod-like hydroxyapatite particles with a diameter of 20–50 nm were distributed homogeneously within the chitosan–silk sericin matrix, and the formation mechanism was also investigated. The results of FTIR and XRD indicated that the inorganic phase in the nanocomposite was carbonate-substituted hydroxyapatite with low crystallinity. In terms of mechanical properties, chitosan–silk sericin/hydroxyapatite nanocomposites exhibited a higher elastic modulus and compressive strength than that of the chitosan/hydroxyapatite nanocomposites. In vitro cytocompatibility of the nanocomposite was evaluated by CCK-8 assay and SEM through MG63 osteoblast cells cultured on the samples, which demonstrated that they are non-toxic and support cell growth. These results suggest that the chitosan–silk sericin/hydroxyapatite nanocomposites are promising biomaterials for bone tissue engineering.

A detailed study of homogeneous agarose/hydroxyapatite nanocomposites for load-bearing bone tissue.

Agarose/hydroxyapatite (agar/HA) nanocomposites for load-bearing bone substitutes were successfully fabricated via a novel in situ precipitation method. Observation via SEM and TEM revealed that the spherical inorganic nanoparticles of approximately 50 nm were well dispersed in the organic matrix, and the crystallographic area combined closely with the amorphous area. The uniform dispersion of HA nanoparticles had prominent effect on improving the mechanical properties of the agar/HA nanocomposites (the highest elastic modulus: 1104.42 MPa; the highest compressive strength: 400.039 MPa), which proved to be potential load-bearing bone substitutes. The thermal stability of agarose and nanocomposites was also studied. The MG63 osteoblast-like cells on the composite disks displayed fusiform and polygonal morphology in the presence of HA, suggesting that the cell maturation was promoted. The results of cell proliferation and cell differentiation indicated that the cells cultured on the agar/HA composite disks significantly increased the alkaline phosphatase activity and calcium deposition. The structural role of agarose in the composite system was investigated to better understand the effect of biopolymer on structure and properties of the composites. The optimal properties were the result of a comprehensive synergy of the components.

Rational design of uniformly embedded metal oxide nanoparticles into nitrogen-doped carbon aerogel for high-performance asymmetric supercapacitors with a high operating voltage window

We report the design of a high-performance asymmetric supercapacitor (ASC) based on manganese monoxide/carbon aerogel (MnO/NCA) composites as the positive electrode and iron oxide/carbon aerogel (Fe2O3/NCA) composites as the negative electrode. The prepared MnO/NCA hybrid composites display a highly interconnected network structure with ultrathin MnO nanoparticles uniformly embedded into the 3D nitrogen-doped carbon matrix. Because of the synergistic effects of the highly conductive carbon aerogel and highly pseudocapacitive metal oxides, the hybrid MnO/NCA electrode exhibits highly effective surface area, greatly enhanced ion transportation, and excellent electrochemical performance, in comparison with other MnOx-based electrode materials. Matching it with the Fe2O3/NCA cathode, the novel ASC devices can achieve a high voltage window of 2.0 V, delivering a remarkable energy density of 48.67 W h kg−1 at a power density of 1000 W kg−1 and still retains 27.39 W h kg−1 at a high power density of 10 kW kg−1, consequently giving rise to stable cycling performance. These encouraging results will provide a fresh route for the design and fabrication of metal oxide@carbon aerogel materials for application in next-generation storage systems.

Biomineralization-inspired synthesis of chitosan/hydroxyapatite biocomposites based on a novel bilayer rate-controlling model

In order to prepare sophisticated biomaterials using a biomimetic approach, a deeper understanding of biomineralization is needed. Of particular importance is the control and regulation of the mineralization process. In this study, a novel bilayer rate-controlling model was designed to investigate the factors potentially influencing mineralization. In the absence of a rate-controlling layer, nano-scale hydroxyapatite (HA) crystallites exhibited a spherical morphology, whereas, in the presence of a rate-controlling layer, HA crystallites were homogeneously dispersed and spindle-like in structure. The mineralization rate had a significant effect on controlling the morphology of crystals. Furthermore, in vitro tests demonstrated that the reaction layer containing spindle-like HA crystallites possessed superior biological properties. These results suggest that a slow mineralization rate is required for controlling the morphology of inorganic crystallites, and consumption by the rate-controlling layer ensured that the ammonia concentration remained low. This study demonstrates that a biomimetic approach can be used to prepare novel biomaterials containing HA crystallites that have different morphologies and biological properties.

Constructing multi-component organic/inorganic composite bacterial cellulose-gelatin/hydroxyapatite double-network scaffold platform for stem cell-mediated bone tissue engineering

Bacterial cellulose/hydroxyapatite (BC/HAp) composite had good bioaffinity but its poor mechanical strength limited its widespread applications in bone tissue engineering (BTE). Bacterial cellulose/gelatin (BC/GEL) double-network (DN) composite had excellent mechanical properties but was seldom used in biomedical fields. In this regard, a multi-component organic/inorganic composite BC-GEL/HAp DN composite was synthesized, which combined the advantages of BC/HAp and BC/GEL. Compared with BC/GEL, the BC-GEL/HAp exhibited rougher surface topography and higher thermal stability. Compression and tensile testing indicated that the mechanical strength of the BC-GEL/HAp was greatly reinforced compared with BC/HAp and was even higher than that of BC/GEL. In vitro cell culture demonstrated that the rat bone marrow-derived mesenchymal stem cells (rBMSCs) cultured on the BC-GEL/HAp showed better adhesion and higher proliferation and differentiation potential than the cells cultured on BC/GEL. We hope the BC-GEL/HAp composite could be used as ideal bone scaffold platform or biomedical membrane in the future.

A novel chitosan-tussah silk fibroin/nano-hydroxyapatite composite bone scaffold platform with tunable mechanical strength in a wide range

Currently, great efforts have been made to enhance the mechanical strength of bone tissue engineering (BTE) scaffolds, which are composed of biopolymeric matrices and inorganic nano-fillers. But the tunability of mechanical strength in a wide range for BTE scaffolds has seldom been investigated in spite of the great importance of this performance. In this work, a chitosan-tussah silk fibroin/hydroxyapatite (CS-TSF/HAp) hydrogel was synthesized by using a novel in situ precipitation method. Through in situ inducing the conformation transition of TSF in the CS-TSF/HAp hydrogel, which could be monitored by XRD, FT-IR, TGA, and DTA, the elastic modulus and fracture strength of the final CS-TSF/HAp composite could be tailored in a wide range without changing its composition, morphology, roughness, and crystal structures. The elastic modulus of the CS-TSF/HAp composite ranged from ∼250 to ∼400MPa while its fracture strength ranged from ∼45 to ∼100MPa. In order to clarify the rationale behind this process, a speculative explanation was provided. In vitro cell culture indicated that MC3T3-E1 cells cultured on the CS-TSF/HAp composite had positive adhesion, proliferation, and differentiation potential. We believed that the CS-TSF/HAp composite could be used as an ideal scaffold platform for cell culture and implantation of bone reconstruction.

Carboxylated Agarose (CA)-Silk Fibroin (SF) Dual Confluent Matrices Containing Oriented Hydroxyapatite (HA) Crystals: Biomimetic Organic/Inorganic Composites for Tibia Repair.

By in situ combining the dual cross-linking matrices of the carboxylated agarose (CA) and the silk fibroin (SF) with the hydroxyapatite (HA) crystals, the CA-SF/HA composites with optimal physicochemical and biological properties were obtained, which were designed to meet the clinical needs of load-bearing bone repair. With the synergistic modulation of the dual organic matrices, the HA nanoparticles presented sheet and rod morphologies due to the preferred orientation, which successfully simulated the biomineralization in nature. The chemical reactivity of the native agarose (NA) was significantly enhanced via carboxylation, and the CA exhibited higher thermal stability than the NA. In the presence of SF, the composites showed optimal mechanical properties that could meet the standard of bone repair. The degradation of the composites in the presence of CA and SF was significantly delayed such that the degradation rate of the implant could satisfy the growth rate of the newly formed bone tissue. The in vitro tests confirmed that the CA-SF/HA composite scaffolds enabled the MG63 cells to proliferate and differentiate well, and the CA/HA composite presented greater capability of promoting the cell behaviors than the NA/HA composite. After 24 days of implantation, newly formed bone was observed at the tibia defect site and around the implant. Extensive osteogenesis was presented in the rats treated with the CA-SF/HA composites. In general, the CA-SF/HA composites prepared in this work had the great potential to be applied for repairing large bone defects.

Comparisons among Mg, Zn, Sr, and Si doped nano-hydroxyapatite/chitosan composites for load-bearing bone tissue engineering applications

In load-bearing bone tissue engineering (BTE), ionic doping is a promising strategy to make up for the inherent defects of hydroxyapatite (HAp). However, the influence of doped elements on the structures and properties of in vitro mineralized HAp has not been investigated in detail so far. In addition, no systematic investigations have been found comparing the properties of different kinds of element doped HAp-based organic/inorganic composites. In this work, the hydroxyapatite/chitosan composite (CS/HAp) and Mg, Zn, Sr, and Si doped hydroxyapatite/chitosan composites (Mg-CS/HAp, Zn-CS/HAp, Sr-CS/HAp, and Si-CS/HAp) were synthesized by using a facile in situ precipitation method. The impacts of different kinds of doped elements on the crystallinity, crystal morphology, and crystal structure of the mineralized HAp were carefully studied. In addition, we also investigated and compared the surface morphology, surface roughness, thermal stability, mechanical strength, and in vitro cytocompatibility of the five samples in detail. We anticipate that our work could shed new light on the influence of ionic doping on the mineralization of HAp and inspire researchers to prepare an HAp-based organic/inorganic composite load-bearing bone substitute in the future.