Mengli Zhao

MOF-derived porous hollow Co3O4 parallelepipeds for building high-performance Li-ion batteries

Porous hollow Co3O4 parallelepipeds have been synthesized via a facile one-step calcination of a novel cobalt-based metal-organic framework template. As an anode material for lithium-ion batteries, the hollow Co3O4 parallelepipeds display enhanced reversible capacity, excellent cyclic stability (1115 mA h g−1 at 100 mA g−1 after 50 cycles) and good rate capability.

NH2+ implantations induced superior hemocompatibility of carbon nanotubes

NH2+ implantation was performed on multiwalled carbon nanotubes (MWCNTs) prepared by chemical vapor deposition. The hemocompatibility of MWCNTs and NH2+-implanted MWCNTs was evaluated based on in vitro hemolysis, platelet adhesion, and kinetic-clotting tests. Compared with MWCNTs, NH2+-implanted MWCNTs displayed more perfect platelets and red blood cells in morphology, lower platelet adhesion rate, lower hemolytic rate, and longer kinetic blood-clotting time. NH2+-implanted MWCNTs with higher fluency of 1 × 1016 ions/cm2 led to the best thromboresistance, hence desired hemocompatibility. Fourier transfer infrared and X-ray photoelectron spectroscopy analyses showed that NH2+ implantation caused the cleavage of some pendants and the formation of some new N-containing functional groups. These results were responsible for the enhanced hemocompatibility of NH2+-implanted MWCNTs.

Effect of nitrogen atomic percentage on N + -bombarded MWCNTs in cytocompatibility and hemocompatibility

N+-bombarded multi-walled carbon nanotubes (N+-bombarded MWCNTs), with different nitrogen atomic percentages, were achieved by different N ion beam currents using ion beam-assisted deposition (IBAD) on MWCNTs synthesized by chemical vapor deposition (CVD). Characterizations of N+-bombarded MWCNTs were evaluated by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), Raman spectroscopy, and contact angle. For comparison, the in vitro cytocompatibility of the N+-bombarded MWCNTs with different N atomic percentages was assessed by cellular adhesion investigation using human endothelial cells (EAHY926) and mouse fibroblast cells (L929), respectively. The results showed that the presence of nitrogen in MWCNTs accelerated cell growth and proliferation of cell culture. The higher nitrogen content of N+-bombarded MWCNTs, the better cytocompatibility. In addition, N+-bombarded MWCNTs with higher N atomic percentage displayed lower platelet adhesion rate. No hemolysis can be observed on the surfaces. These results proved that higher N atomic percentage led N+-bombarded MWCNTs to better hemocompatibility.

DIFFERENCES IN CYTOCOMPATIBILITY BETWEEN MWCNTs AND CARBOXYLIC FUNCTIONALIZED MWCNTs

Influence of carboxylic functionalization on the cytocompatibility of multiwalled carbon nanotubes (MWCNTs) was investigated in this work. Water contact angle assay showed that the surface of MWCNTs-containing carboxyl (MWCNTs-COOH) became much more hydrophilic compared with pure MWCNTs. In cell-adhesion assays, two cell lines, mouse fibroblast cells (L929) and human umbilical vein endothelial cells (EAHY926) were used to assess the cytocompatibility of materials. The MWCNTs-COOH displayed the improved cell proliferation, viability and adhesion due to the enhanced wettability, indicating their superior cytocompatibility over MWCNTs. The existence of carboxyl groups should be benefit to the adhesion and growth of both cells, which implied that MWCNTs-COOH were helpful for seeding both cells and could be used as the functional surface for the adhesion and growth of cells.

Influence of polar functional groups introduced by COOH+ implantation on cell growth and anticoagulation of MWCNTs

Though multiwalled carbon nanotubes (MWCNTs) have shown great promise in biomedical applications, our understanding about their biocompatibility is limited. Here, COOH+ implantation was performed for MWCNTs in order to gain insight into how COOH+ implantation affected the cell growth and blood adsorption of MWCNTs. The extensive measurements demonstrated that carboxyl groups were successfully introduced onto the surface of MWCNTs, inducing more hydrophilicity compared with pristine MWCNTs. Two kinds of cells, mouse fibroblast cells (L929) and human endothelial cells (EAhy926), were used to assess the cell growth of MWCNTs before and after COOH+ implantation. COOH+ implantation led to a significant improvement in cell proliferation and adhesion, indicating superior cell adhesion over pristine MWCNTs. As the ion dose increased, the platelet adhesion assays of COOH+ implantation-MWCNTs (COOH/MWCNTs) displayed a significant enhancement, which implied COOH/MWCNTs could be used as anticoagulant and nonhemolytic material. The results were helpful to design modified surfaces of nanomaterials for improving their biocompatibility.

In vitro comparison of the hemocompatibility of diamond-like carbon and carbon nitride coatings with different atomic percentages of N.

Carbon nitride (CNx) and diamond-like carbon (DLC) coatings were prepared by dc magnetron sputtering at room temperature. Different partial pressures of N2 were used to synthesize CNx to evaluate the relationship between the atomic percentage of nitrogen and hemocompatibility. Auger electron spectroscopy and atomic force microscopy indicated atomic percentages of N of 0.12 and 0.22 and that the CNx coatings were smooth. An in vitro study of the hemocompatibility of the coatings revealed that both CNx coatings had better anticoagulant properties and lower platelet adhesion than DLC. Compared with CN0.12, the CN0.22 coating showed longer dynamic clotting time (about 42 min), static clotting time (23.6 min) and recalcification time (45.6 s), as well as lower platelet adhesion (102 cells μm−2), aggregation, and activation. The presence of nitrogen in the CNx coatings induced their enhanced hemocompatibility compared with DLC.

Shape-Control of Three-Dimensional Self-Assembly Graphene by Hydrothermal Reaction Time and Its Biological Application

In this paper, three-dimensional self-assembly graphene (3D-G) was prepared by the hydrothermal synthesis method, and 3D-G was designed as a suitable biological scaffold for cell growth and adhesion. The shape of 3D-G was tuned by adjusting the hydrothermal reaction time (6 h, 12 h, 18 h and 24 h). Then the scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) analyses were used to characterize the microstructure and component of 3D-G, which showed that the length, diameter, pore size and defects of 3D-G were all decreased as the reaction-time increased. In vitro cell culture experiment, the cytocompatibility of 3D-G prepared under different hydrothermal reaction time was assessed using mouse fibroblast cells (L929) via 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT). Meanwhile, the cell adhesion, growth and proliferation were also observed by SEM. These results showed that the 3D-G with the reaction time of 24 h (3D-G/24 h) had the best cytocompatibility, which could be used as tissue scaffolds for cell growth.

Enhanced cell growth on 3D graphene scaffolds implanted with nitrogen ions

One of the key challenges in engineering tissues for cell-based therapies is developing biocompatible scaffold materials to direct cell behavior. In this paper, the cytocompatibilities of a flexible three-dimensional graphene scaffold (3D-G) and the same scaffold implanted with nitrogen ions (N+/3D-G) are compared using an in vitro assay based on 3(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. The N+/3D-G samples were prepared from low-temperature hydrothermally synthesized flexible 3D-G by ion implantation and were found to display improved adhesion and proliferation of rat osteoblast and mouse fibroblast cells. In particular, the N+/3D-G sample with a nitrogen content of ∼10% showed the highest levels of cell viability and proliferation. The flexible N+/3D-G has potential applications as a biocompatible scaffold material that provides improved surface area and hydrophilic groups for cell growth and proliferation.

Enhancement of interaction of L-929 cells with functionalized graphene via COOH + ion implantation vs. chemical method

Low hydrophilicity of graphene is one of the major obstacles for biomaterials application. To create some hydrophilic groups on graphene is addressed this issue. Herein, COOH+ ion implantation modified graphene (COOH+/graphene) and COOH functionalized graphene were designed by physical ion implantation and chemical methods, respectively. The structure and surface properties of COOH+/graphene and COOH functionalized graphene were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and contact angle measurement. Compared with graphene, COOH+/graphene and COOH functionalized graphene revealed improvement of cytocompatibility, including in vitro cell viability and morphology. More importantly, COOH+/graphene exhibited better improvement effects than functionalized graphene. For instance, COOH+/graphene with 1 × 1018 ions/cm2 showed the best cell-viability, proliferation and stretching. This study demonstrated that ion implantation can better improve the cytocompatibility of the graphene.