Zhenling Wang

Fabrication, mechanical properties, and biocompatibility of reduced graphene oxide-reinforced nanofiber mats

Fibrous functional scaffolds that could mimic the natural growth environment of cells and govern cell-specific behaviors are crucial for meeting the requirements of tissue engineering. Graphene-based materials, which is an important one of them have captured tremendous interests of researchers. However, few research about graphene nanofibers with excellent electrical and mechanical properties have been fabricated and found to have real applications. In this study, we reported a novel PAN-reduced graphene oxide reinforced composite nanofiber mats (rGO–NFMs), which were fabricated by the electrospinning process combined with chemical reduction. SEM, FTIR and XRD revealed that rGO–NFMs were successfully produced. These rGO–NFMs displayed superior mechanical properties (tensile strain and tensile stress are 18.5% and 1.38 MPa, respectively). The cell proliferation and morphology of adipose-derived stem cells (ADSCs as model cells) cultured on the rGO–NFMs were tested with a 7 days culture period. Cellular test results showed that rGO–NFMs exhibited excellent biocompatibility, cells on the nanofibers formed stable cell–fiber constructs, and the rate of cell proliferation was similar to that of tissue culture plates (TCPs) and PAN nanofibers mats (PAN–NFMs). This study demonstrated that rGO–NFMs may be a good choice for application in tissue engineering, particularly cell culture scaffolds for electrical stimulation.

Fabrication, Characterization, and Biocompatibility of Polymer Cored Reduced Graphene Oxide Nanofibers

Graphene nanofibers have shown a promising potential across a wide spectrum of areas, including biology, energy, and the environment. However, fabrication of graphene nanofibers remains a challenging issue due to the broad size distribution and extremely poor solubility of graphene. Herein, we report a facile yet efficient approach for fabricating a novel class of polymer core-reduced graphene oxide shell nanofiber mat (RGO-CSNFM) by direct heat-driven self-assembly of graphene oxide sheets onto the surface of electrospun polymeric nanofibers without any requirement of surface treatment. Thus-prepared RGO-CSNFM demonstrated excellent mechanical, electrical, and biocompatible properties. RGO-CSNFM also promoted a higher cell anchorage and proliferation of human bone marrow mesenchymal stem cells (hMSCs) compared to the free-standing RGO film without the nanoscale fibrous structure. Further, cell viability of hMSCs was comparable to that on the tissue culture plates (TCPs) with a distinctive healthy morphology, indicating that the nanoscale fibrous architecture plays a critically constructive role in supporting cellular activities. In addition, the RGO-CSNFM exhibited excellent electrical conductivity, making them an ideal candidate for conductive cell culture, biosensing, and tissue engineering applications. These findings could provide a new benchmark for preparing well-defined graphene-based nanomaterial configurations and interfaces for biomedical applications.

Biocompatible, Free-Standing Film Composed of Bacterial Cellulose Nanofibers–Graphene Composite

In recent years, graphene films have been used in a series of wide applications in the biomedical area, because of several advantageous characteristics. Currently, these films are derived from graphene oxide (GO) via chemical or physical reduction methods, which results in a significant decrease in surface hydrophilicity, although the electrical property could be greatly improved, because of the reduction process. Hence, the comprehensive performance of the graphene films showed practical limitations in the biomedical field, because of incompatibility of highly hydrophobic surfaces to support cell adhesion and growth. In this work, we present a novel fabrication of bacterial cellulose nanofibers/reduced graphene oxide (BC-RGO) film, using a bacterial reduction method. Thus-prepared BC-RGO films maintained excellent hydrophilicity, while electrical properties were improved by bacterial reduction of GO films in culture. Human marrow mesenchymal stem cells (hMSCs) cultured on these surfaces showed improved cellular response with higher cell proliferation on the BC-RGO film, compared to free-standing reduced graphene oxide film without the nanoscale fibrous structure. Furthermore, the cellular adhesion and proliferation were even comparable to that on the tissue culture plate, indicating that the bacterial cellulose nanofibers play a critically contructive role in supporting cellular activities. The novel fabrication method greatly enhanced the biochemical activity of the cells on the surface, which could aid in realizing several potential applications of graphene film in biomedical area, such as tissue engineering, bacterial devices, etc.

Synergistic effects of a novel free-standing reduced graphene oxide film and surface coating fibronectin on morphology, adhesion and proliferation of mesenchymal stem cells

Graphene films have broad use in engineering, energy and biomedical applications. The cost-effective, eco-friendly and easy to scale-up fabrication methods of graphene films are always highly desired. In this work, we develop a novel fabrication method of free-standing reduced graphene oxide (RGO) films by vacuum filtration of graphene oxide aqueous solution through a nanofiber membrane in combination with chemical reduction. Instead of the smooth surface, the generated RGO films have nanoscale patterns transferred from the nanofiber membrane and controlled in a large range by varying the parameters of the electrospinning process. The cellular culture results of the human marrow mesenchymal stem cells (hMSCs) show that the fibronectin modified RGO films could exhibit excellent biocompatibility, which could be attributed to the synergistic effects of the RGO films including both surface morphology and fibronectin modification. The novel fabrication method greatly enhances the fabrication capability and the potential of graphene films for application in cell culture, tissue engineering as well as in other engineering and biomedical applications.

Facile synthesis of carbon dots with superior sensing ability

Carbon dots (CDs) have various applications in biomedical and environmental field, such as bio-imaging, bio-sensing and heavy metal detection. In this study, a novel class of CDs were synthesized using a one-step hydrothermal method. The fabricated CDs displayed stable photoluminescence, good water solubility, and photo stability. Moreover, the functional groups (carboxylic acid moieties and hydroxyls) on the surface of the obtained CDs enable it with superior sensing ability (e.g., very low detectable concentration for Pb2+: 5xa0nmol/L). With superior detection sensitivity, excellent fluorescent properties and facile fabrication method, the as-obtained CDs can find practical applications as cost-effective and sensitive chemo-sensors in water and food safety field.

Fabrication and Characterization of Three-Dimensional (3D) Core–Shell Structure Nanofibers Designed for 3D Dynamic Cell Culture

Three-dimensional elastic nanofibers (3D eNFs) can offer a suitable 3D dynamic microenvironment and sufficient flexibility to regulate cellular behavior and functional protein expression. In this study, we report a novel approach to prepare 3D nanofibers with excellent mechanical properties by solution-assisted electrospinning technology and in situ polymerization. The obtained 3D eNFs demonstrated excellent biocompatible properties to meet cell culture requirements under a dynamic environment in vitro. Moreover, these 3D eNFs also promoted human bone marrow mesenchymal stem cells (hMSCs) adhesion and collagen expression under biomechanical stimulation. The results demonstrated that this dynamic cell culture system could positively impact cellular collagen but has no significant effect on the proliferation of hMSCs grown in the 3D eNFs. This work may give rise to a new approach for constructing a 3D cell culture for tissue engineering.

Synergistic Effects of Electrical Stimulation and Aligned Nanofibrous Microenvironment on Growth Behavior of Mesenchymal Stem Cells

Incontrollable cellular growth behavior is a significant issue, which severely affects the functional tissue formation and cellular protein expression. Development of natural extracellular matrix (ECM) like biomaterials to present microenvironment cues for regulation of cell responses can effectively overcome this problem. The external simulation and topological characteristics as typical guiding cues are capable of providing diverse influences on cellular growth. Herein, we fabricated two-dimensional aligned conductive nanofibers (2D-ACNFs) by an electrospinning process and surface polymerization, and the obtained 2D-ACNFs provided the effects of both alignment and electrical stimulation (ES) on cellular response of human mesenchymal cells (hMSCs). The results of cellular responses implied that the obtained 2D-ACNFs could offer a synergistic effect of both ES and aligned nanopattern on hMSC growth behavior. The effects could not only promote hMSCs to contact each other and maintain cellular activity but also provide positive promotion to regulate cellular proliferation. Thus, we believe that the obtained 2D-ACNFs will have a broad application in the biomedical field, such as cell culture with ES, directional induction for cell growth, and damaged tissue repair, etc.

Three-dimensional nanofibrous microenvironment designed for the regulation of mesenchymal stem cells

The three-dimensional functional nanofibrous microenvironment plays a key role in the regulation of cellular growth, because it can mimic the natural extracellular matrix structure. As an important nanofibrous scaffold, 3D functional nanofibers display broad application prospects in biomedical areas, such as tissue engineering, drug release, and biosensors. Recently, these functional nanofibrous scaffolds based on biocompatible natural materials with excellent flexibility and biochemical characteristics show great potential in tissue engineering applications. Herein, we prepared 3D chondroitin sulfate surface-modified silk nanofibers (3D CS-SNFs) using a combination of electrospinning and chemical grafting methods. The as-prepared 3D CS-SNFs exhibited excellent biocompatible properties. Moreover, there are numerous deeply interconnected pores (larger than 20xa0µm) for enhanced cellular entry into CS-SNFs and for 3D cell culture in vitro. The 3D CS-SNFs are beneficial to cell adhesion, nutrient delivery, and excretion of excrement, which provides healthy growth environment and living conditions for those cells that penetrate into the interior of the scaffold. Our results indicate that the 3D CS-SNFs show much higher degrees of promotion of bone marrow mesenchymal stem cells adhesion and osteogenic differentiation, as compared with the 3D raw silk nanofibers. These results demonstrate that the as-prepared 3D CS-SNFs could provide a suitable 3D microenvironment for cellular growth, adhesion, and excellent osteogenic differentiation. This work paves a new way for 3D cell culture construction for damaged bone repair and regeneration.