Guangyao Xiong

One-Step In Situ Biosynthesis of Graphene Oxide–Bacterial Cellulose Nanocomposite Hydrogels

Graphene oxide-bacterial cellulose (GO/BC) nanocomposite hydrogels with well-dispersed GO in the network of BC are successfully developed using a facile one-step in situ biosynthesis by adding GO suspension into the culture medium of BC. During the biosynthesis process, the crystallinity index of BC decreases and GO is partially reduced. The experimental results indicate that GO nanosheets are uniformly dispersed and well-bound to the BC matrix and that the 3D porous structure of BC is sustained. This is responsible for efficient load transfer between the GO reinforcement and BC matrix. Compared with the pure BC, the tensile strength and Youngs modulus of the GO/BC nanocomposite hydrogel containing 0.48 wt% GO are significantly improved by about 38 and 120%, respectively. The GO/BC nanocomposite hydrogels are promising as a new material for tissue engineering scaffolds.

A general strategy of decorating 3D carbon nanofiber aerogels derived from bacterial cellulose with nano-Fe3O4 for high-performance flexible and binder-free lithium-ion battery anodes

Flexible, binder-free, and cost-effective materials have been highly sought-after in the development of next generation electrodes. Herein, we report a general, scalable, and eco-friendly synthesis of a novel flexible nano-Fe3O4-decorated three-dimensional (3D) carbon nanofiber (CNF) aerogel derived from bacterial cellulose (BC) (named Fe3O4-BC-CNFs) via a hydrothermal approach followed by carbonization. The as-prepared Fe3O4-BC-CNF electrodes with optimal Fe3O4 loading exhibit greatly improved electrochemical performance over bare BC-CNFs and Fe3O4 nanoparticles. Furthermore, compared with most of the other relevant types of electrodes, the flexible and binder-free Fe3O4-BC-CNF electrodes can deliver a higher reversible capacity of 754 mA h g−1 (after 100 cycles at 100 mA g−1). The excellent electrochemical performance is ascribed to the highly dispersed Fe3O4 nanoparticles on CNFs, the 3D porous structure, large surface area, and the interconnected CNFs, which offer a large material/electrolyte contact area, promote a high diffusion rate of Li ions, and accommodate volume changes of the active materials during cycling. The excellent flexibility and high reversible capacity of the electrodes as well as the eco-friendly and scalable process make them promising for the development of flexible energy-storage devices.

A novel three-dimensional graphene/bacterial cellulose nanocomposite prepared by in situ biosynthesis

Graphene has been widely used to reinforce various hydrogels while there is no report on the composite hydrogels of bacterial cellulose (BC) and graphene. In this work, a graphene/BC (GE/BC) nanocomposite hydrogel was prepared by in situ biosynthesis. The morphology and structure of the obtained GE/BC nanocomposite were characterized by SEM, TEM, XRD, and Raman. Results showed that the presence of graphene in the culture medium of BC changed the crystalline structure of BC while the in situ biosynthesis process had no influence on the structure of graphene. It was found that graphene nanoplates were uniformly dispersed in the three-dimensional (3D) BC matrix and tightly bound by BC nanofibers. This unique 3D structure will impart the GE/BC nanocomposite with excellent mechanical, electrical, and biological properties.

Constructing a novel three-dimensional scaffold with mesoporous TiO2 nanotubes for potential bone tissue engineering

Three-dimensional (3D) nanofibrous scaffolds for tissue engineering have been widely studied while 3D scaffolds made of nanotubes are rarely reported. Herein, we report a novel 3D porous network-structured scaffold built of mesoporous TiO2 nanotubes. The TiO2 nanotubes were synthesized using the template-assisted sol-gel method followed by calcination. Bacterial cellulose (BC) with 3D network structure was used as the template. TEM observation confirms the formation of tubular TiO2 nanotubes. The as-synthesized TiO2 nanotubes exhibit an average outer diameter of less than 100 nm and mesoporous walls consisting of aggregated TiO2 nanoparticles with a size of around 7 nm. SEM and TEM observations reveal that the TiO2 nanotube scaffold possesses 3D porous network structure and the surfaces of TiO2 nanotubes are rugged with nanotopography. Additionally, the scaffold built of mesoporous nanotubes with a mesopore size of 3.3 nm exhibits an extremely large surface area of 1629 m2 g-1. The capacity of the scaffold to support cell proliferation and osteogenic differentiation was evaluated using CCK-8 assay, alkaline phosphatase (ALP), and calcium content assay. The scaffold shows enhanced cell growth and proliferation and improved ALP activity and mineralization compared to the TCPS (tissue culture plate) control. Furthermore, the ALP activity of the scaffold is as high as a hydroxyapatite-coated nanofibrous scaffold. The enhanced proliferation and osteogenic differentiation of the TiO2 nanotube scaffold is ascribed to the outer surface roughness of TiO2 nanotubes, 3D porous network structure, mesopores, and large surface area.

Facile and scalable production of three-dimensional spherical carbonized bacterial cellulose/graphene nanocomposites with a honeycomb-like surface pattern as potential superior absorbents

Frequent contamination of water by oils and organic solvents necessitates efficient and low cost absorbents. Here, for the first time, a novel nanocomposite of sphere-like carbonized bacterial cellulose (SCBC) and graphene (GE) with a honeycomb-like surface morphology and a three-dimensional (3D) interconnected porous structure was synthesized via a facile and scalable one-pot in situ biosynthesis route under agitated culture conditions followed by carbonization. The as-prepared SCBC/GE nanocomposite was characterized by SEM, TEM, XRD, FTIR, Raman, wettability, and absorption capacity measurements. SEM images reveal that the SCBC/GE nanocomposite exhibits a honeycomb-like surface pattern consisting of ridges and large cavities with an average diameter of around 97 μm. Furthermore, the SCBC/GE nanocomposite has high porosity, large specific surface area, strong hydrophobicity, and good elasticity. Importantly, it shows superior absorption capacities for a wide range of oils and organic solvents (the maximum value reaches 457 times of its own weight), higher than any other CNF-based aerogels reported so far, thus having the potential to be used in the field of environmental protection. Additionally, the underlying absorption mechanisms for oil and organic solvents have been explored.

Mechanical properties and cytotoxicity of nanoplate-like hydroxyapatite/polylactide nanocomposites prepared by intercalation technique

Hydroxyapatite (HAp) in the forms of fiber, needle, and whisker has been employed as fillers in polymer composites. Herein, nanoplate-like HAp synthesized by template-assisted self-assembly was used to reinforce polylactide (PLA) nanocomposites via the solution intercalation method. Dynamic and static mechanical properties and cytotoxicity of the as-prepared HAp/PLA nanocomposites were assessed in addition to characterizations by XRD, FTIR, and TGA. XRD analysis confirms the formation of exfoliated structure in the HAp/PLA nanocomposites. The HAp/PLA nanocomposites exhibit better static and dynamic mechanical properties than unreinforced PLA. Furthermore, the HAp/PLA nanocomposite with an optimum HAp content of 20wt% (20HAp/PLA) demonstrates not only the best mechanical performance but also the highest thermal stability among the nanocomposite samples. Cell studies using a mouse fibroblast cell line (L929) suggest that 20HAp/PLA shows excellent biocompatibility, which makes it a promising material for biomedical applications.

Preparation of three-dimensional braided carbon fiber-reinforced PEEK composites for potential load-bearing bone fixations. Part I. Mechanical properties and cytocompatibility

In this study, we focused on fabrication and characterization of three-dimensional carbon fiber-reinforced polyetheretherketone (C3-D/PEEK) composites for orthopedic applications. We found that pre-heating of 3-D fabrics before hot-pressing could eliminate pores in the composites prepared by 3-D co-braiding and hot-pressing techniques. The manufacturing process and the processing variables were studied and optimum parameters were obtained. Moreover, the carbon fibers were surface treated by the anodic oxidization and its effect on mechanical properties of the composites was determined. Preliminary cell studies with mouse osteoblast cells were also performed to examine the cytocompatibility of the composites. Feasibility of the C3-D/PEEK composites as load-bearing bone fixation materials was evaluated. Results suggest that the C3-D/PEEK composites show good promising as load-bearing bone fixations.

Evolution of morphology of bacterial cellulose scaffolds during early culture

Morphological characteristics of a fibrous tissue engineering (TE) scaffold are key parameters affecting cell behavior. However, no study regarding the evolution of morphology of bacterial cellulose (BC) scaffolds during the culture process has been reported to date. In this work, BC scaffolds cultured for different times starting from 0.5h were characterized. The results demonstrated that the formation of an integrated scaffold and its 3D network structure, porosity, fiber diameter, light transmittance, and the morphology of hydroxyapatite (HAp)-deposited BC scaffolds changed with culture time. However, the surface and crystal structure of BC fibers did not change with culture time and no difference was found in the crystal structure of HAp deposited on BC templates regardless of BC culture time. The findings presented herein suggest that proper selection of culture time can potentially enhance the biological function of BC TE scaffold by optimizing its morphological characteristics.

The inhibition of lamellar hydroxyapatite and lamellar magnetic hydroxyapatite on the migration and adhesion of breast cancer cells

Hydroxyapatite nanoparticles have been reported to exhibit potent anti-tumor effects in some cancer cells. In our previous study, we have successfully synthesized two types of hydroxyapatite nanoparticles, laminated hydroxyapatite (L-HAp) and laminated magnetic hydroxyapatite (LM-HAp). In this study, we wanted to investigate the effects of L-HAp and LM-HAp with various concentrations on human breast cancer MDA-MB-231 cells. Cell proliferation was assessed with a MTT colorimetric assay. Scratch and adhesion assays were used to detect the effects of these two materials on migration and adhesion. The expressions of integrin β1 and Akt were measured by Western blotting. Our results showed that L-HAp and LM-HAp had little cell cytotoxicity and significantly reduced cell mobility and adhesion. LM-HAp showed greater inhibitor ability on migration and adhesion of MDA-MB-231 cells. Moreover, results from western blotting showed that L-HAp and LM-HAp impacted the phosphorylation of integrin β1, but showed no regular impact on Akt. This study suggests that L-HAp and LM-HAp may be potential anti-tumor and delivery system for breast cancer therapy.

Creation of macropores in three-dimensional bacterial cellulose scaffold for potential cancer cell culture

There is an increasing need for an effective in vitro model that can resemble the 3-D nature of tumor microenvironments. In this work, a 3-D bacterial cellulose (BC) scaffold with macropores was fabricated by a facile freeze drying method for potential culture of cancer cells. This in vitro study reported, for the first time, the role of macropores in the adjustment of cancer cell behavior when compared with previous results cultured in BC scaffolds without macropores. The scaffold was characterized by SEM and mercury intrusion porosimeter. A human breast cancer cell line (MDA-MB-231) cultured in the macroporous BC scaffold was examined via cell proliferation, histological and SEM analyses. The results demonstrated that the macroporous scaffold provided a good environment for cell viability, adhesion, proliferation, and infiltration. These findings suggested that the macroporous BC scaffold might have great potential for use in the in vitro culture of cancer cells.