Junchao Wei

Highly sensitive nonenzymatic glucose and H2O2 sensor based on Ni(OH)2/electroreduced graphene oxide−Multiwalled carbon nanotube film modified glass carbon electrode

In this article, a nonenzymatic sensor based on Ni(OH)2/electroreduced graphene oxide (ERGO)-multiwalled carbon nanotube (MWNT) nanocomposites is fabricated via convenient electrodeposition of Ni(OH)2 nanoparticles on ERGO-MWNT film modified glass carbon electrode (GCE). Graphene oxide (GO) sheets can serve as surfactants to stabilize the dispersion of pristine MWNTs in aqueous solution, rendering a fine coverage of ERGO-MWNT film on GCE during the fabrication process. MWNTs perform as conducting bridges between ERGO sheets to enhance the electron transfer rate in the substrate. By combining the advantages of ERGO and MWNTs, together with electrocatalytic effect of Ni(OH)2 nanoparticles, the well-designed nanocomposites exhibit excellent sensing behavior towards glucose and hydrogen peroxide (H2O2). The linear detection ranges for glucose and H2O2 are 10-1500 µM and 10 µM-9050 µM while the detection limits are 2.7 µM and 4.0 µM, respectively. Furthermore, a very high sensitivity is achieved with 2042 µAm M(-1) cm(-2) estimated for glucose and 711 µAm M(-1) cm(-2) for H2O2. These results suggest that Ni(OH)2/ERGO-MWNT nanocomposites thus easily prepared through a green electrochemical method are promising electrode materials for biosensing. Additionally, good recoveries of analytes in real samples like urine and milk confirm the reliability of the prepared sensor in practical applications.

A Facile approach to NiCoO2 intimately standing on nitrogen doped graphene sheets by one-step hydrothermal synthesis for supercapacitors

Novel composites based on cubic binary nickel cobaltite oxide intimately standing on nitrogen doped reduced graphene sheets (NRGO–NiCoO2) were prepared by a simple one step hydrothermal synthesis. The results showed that the highly crystalline NiCoO2 nanoparticles with a uniform size were homogeneously distributed on nitrogen-doped reduced graphene sheets (NRGO). The homogeneous composites combined NiCoO2, which has high specific capacitance, and NRGO, which has efficient electronic conductivity, to consequently yield low resistance conduction between metal oxides and graphene due to a barrier-free contact. The synergistic effect of NRGO substrates and NiCoO2 nanoparticles promoted the electrochemical performance of the composites. The electrochemical properties of NRGO–NiCoO2 can be easily tuned by altering the amount of nitrogen-composed reducer. The NRGO–NiCoO2 composites exhibited a remarkable specific capacitance of 508 F g−1 at 0.5 A g−1, an excellent rate performance in cyclic voltammetry test (from 5 to 90 mV s−1) and good galvanostatic charge–discharge measurements (from 0.5 to 20 A g−1). The capacitance was maintained at 93% of the original value even after 2000 cycles. The flexible devices were assembled, which possessed a specific capacitance of 58 F g−1 at 0.5 A g−1. This facile one-step strategy is an effective method for developing excellent supercapacitor electrodes.

Preparation and characterization of electrospun PLGA/gelatin nanofibers as a drug delivery system by emulsion electrospinning

Novel biocompatible poly(lactide-co-glycolide) (PLGA) nanofiber mats with favorable biocompatibility and good mechanical strength were prepared, which could serve as an innovative type of tissue engineering scaffold or an ideal controllable drug delivery system. Both hydrophobic and hydrophilic drugs, Cefradine and 5-fluorouracil were successfully loaded into PLGA nanofiber mats by emulsion electrospinning. The natural bioactive protein gelatin (GE) was incorporated into the nanofiber mats to improve the surface properties of the materials for cell adhesion. Nanofibrous scaffolds were characterized by scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, contact angle and tensile measurements. Emulsion electrospun fibers with GE had perfect hydrophilic and good mechanical property. The in vitro release test showed thedrugs released from emulsion electrospun fibers, which achieved lower burst release. The cells cytotoxicity experiment indicated that emulsion electrospun fibers were less toxic and tended to promote fibroblasts cells attachment and proliferation, which implied that the electrospun fibers had promising potential application in tissue engineering or drug delivery.

Electrospinning of Poly(L-lactide) Nanofibers Encapsulated with Water-Soluble Fullerenes for Bioimaging Application

Photoluminescent fullerene nanoparticles/nanofibers have potential applications in bioimaging. A novel fluorescent nanofibrous material, consisting of fullerene nanoparticles and poly(L-lactide) (PLLA), was fabricated via a simple electrospinning method, and the composite nanofibers were characterized by various techniques such as scanning electron microscopy (SEM), laser scanning confocal microscopy (LSCM), and transmission electron microscopy (TEM). The nanofibers were uniform, and their surfaces were reasonably smooth, with the average diameters of fibers ranging from 300 to 600 nm. The fullerene nanoparticles were encapsulated within the composite nanofibers, forming a core-shell structure. The nanofiber scaffolds showed excellent hydrophilic surface due to the addition of water-soluble fullerene nanoparticles. The composite nanofibers used as substrates for bioimaging in vitro were evaluated with human liver carcinoma HepG2 cells, the fullerene nanoparticles signal almost displayed in every cell, implying the potential of fluorescent fullerene nanoparticles/PLLA nanofibers to be used as scaffolds for bioimaging application.

A novel thermal and pH responsive drug delivery system based on ZnO@PNIPAM hybrid nanoparticles

A smart ZnO@PNIPAM hybrid was prepared by grafting thermal responsive poly(N-isopropylacrylamide) (PNIPAM) on zinc oxide (ZnO) nanoparticles via surface-initiated atom transfer radical polymerization (ATRP). The thermal gravimetric analysis (TGA) shows that the grafting amount of PNIPAM was about 38%, and the SEM images show that the PNIPAM chains can prevent the aggregation of ZnO nanoparticles. The responsive properties of ZnO@PNIPAM were measured by photoluminescence spectra, and the results demonstrate that the PNIPAM chains grafted on ZnO surfaces can realize reversible thermal responsive and photoluminescence properties. An anticancer drug, doxorubicin (Dox), was used as a model drug and loaded into the hybrid nanoparticles, and an in vitro drug release test implied that ZnO@PNIPAM could work as a thermal responsive drug delivery system. Furthermore, pH sensitive drug releases were carried out in acetate buffer at pH 5.0 and pH 6.0 and in water at pH7.0, and the results showed evident pH dependency, showing its pH responsive properties.

Surface Modifications of Halloysite Nanotubes with Superparamagnetic Fe 3 O 4 Nanoparticles and Carbonaceous Layers for Efficient Adsorption of Dyes in Water Treatment

Surface modification of halloysite nanotube(HNT) with in situ grown Fe3O4 nanoparticles and carbonaceous layers introduced by a hydrothermal carbonization process of glucose has been achieved. Structure and morphology investigations demonstrate that iron oxide nanoparticles are uniformly anchored on the halloysite and prevent the aggregations of halloysite and carbon, forming a protective layer that stabilizes and improves the property of HNT/Fe3O4/C nanocomposite. Magnetism characterization proves the superparamagnetic behavior of HNT/Fe3O4/C hybrid at room temperature, which makes it easily separated from dye solution under an external magnetic field. Exploration of adsorption ability demonstrates that the maximum adsorption capacity of the as-prepared HNT/Fe3O4/C nanocomposite for methylene blue(MB) is about twice and 1.5 times those of HNT/Fe3O4 and HNT according to Langmuir equation, respectively. The adsorption behavior investigations indicate that HNT/Fe3O4/C hybrid has a heterogeneous structure and shows a non-ideal monolayer adsorption that fits the Redlich-Peterson isotherm, and the adsorption process follows a pseudo-second-order kinetic model. Therefore, the as-prepared HNT/Fe3O4/C hybrid is a fast, separatable and superparamagnetic adsorbent with a good adsorption ability, demonstrating great potential in the application of water treatment.

Multiple drug-loaded electrospun PLGA/gelatin composite nanofibers encapsulated with mesoporous ZnO nanospheres for potential postsurgical cancer treatment

Multiple drugs-loaded electrospun composite nanofibrous scaffolds have attracted much interest as drug delivery vehicles for the treatment of tissue defect after tumor resection. In this study, a novel mesoporous ZnO/poly(lactic-co-glycolic acid)/gelatin (mZnO/PLGA/GE) electrospun composite fiber encapsulated with both hydrophilic drug (doxorubicin hydrochloride, DOX) and hydrophobic drug (camptothecin, CPT) is fabricated. mZnO is firstly used to encapsulate DOX. Then, the DOX-loaded mZnO (DOX@mZnO) and CPT were mixed with PLGA/GE solution to fabricate electrospun hybrid nanofibers. The in vitro release results demonstrated that the CPT in the composite fibers presented a fast release, while DOX showed a sustained release behavior. The cell cytotoxicity test indicated that the composite nanofiber with two drugs showed strong antitumor efficacy against HepG-2 cells. Moreover, the addition of GE increased the hydrophilicity of the composite fibers. More importantly, the incorporated of mZnO within the PLGA/GE nanofibers cannot only significantly reduce the burst release of DOX, but also improve the mechanical durability of the composite nanofibers. Thus, the composite nanofibers could be a versatile drug delivery system encapsulated with both hydrophilic and hydrophobic anticancer drugs as implantable scaffolds for potential postsurgical cancer treatment.

Electrospun poly(L-lactide) nanofibers loaded with paclitaxel and water-soluble fullerenes for drug delivery and bioimaging

Multifunctional electrospun composite nanofibrous scaffolds have attracted much interest as drug delivery vehicles and in bioimaging application for real-time tracing the whole process of postoperative therapy. Novel poly(L-lactide) (PLLA) composite nanofibers loaded with water-soluble fullerene C70 nanoparticles and paclitaxel were successfully fabricated. The nanofibers with the average diameter of fibers ranging from 350 to 750 nm were uniform and their surfaces were reasonably smooth. The nanofibers showed an excellent hydrophilic surface and good mechanical properties. The in vitro release results demonstrated that the release rate of paclitaxel could be controlled by the content of C70 nanoparticles. With the increase of the content of C70 nanoparticles, the drug release rate became faster with increased total release amount. The composite nanofibers used as substrates for cytotoxicity and bioimaging in vitro were evaluated with human liver carcinoma HepG-2 cells. Paclitaxel was released from the composite nanofibers without losing cytotoxicity, the drug-loaded composite nanofibers inhibited the proliferation of HepG-2 cells effectively. Meanwhile, the fluorescent signal of C70 nanoparticles could be detected in HepG-2 cells, which reflected the growth state of cells clearly. These results strongly suggested that these PLLA composite nanofibers could be used in the fields of tissue engineering, drug delivery and bioimaging.

Safe and flexible ion gel based composite electrolyte for lithium batteries

A new family of three-arm polymer ionic liquids (PILs) with X counter anions [3P(MPBIm-X), X− = Br−, CF3SO3− (Tf−) and (CF3SO3)2N− (TFSI−)] were successfully synthesized. The effects of anion type on the chemical, thermal and ionic conductivity of PILs have been investigated. Results showed that 3P(MPBIm-X) with TFSI− counter anion (3P(MPBIm-TFSI)) possessed better thermal property and ionic conductivity. Furthermore, to obtain safe and flexible electrolytes with superior performance, solid-like composite electrolyte (SLCE) was fabricated by filling ion gel, the mixture of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM-TFSI) incorporated into 3P(MPBIm-TFSI), in the micropores of PVDF-HFP electrospun membranes. It was found to be thermally stable up to 370 °C and electrochemically stable above 4.8 V. SLCE was nonflammable and showed negligible leakage property when subjected to load. At 50 °C, ionic conductivity of SLCE could reach 1 mS cm−1 (1.2 × 10−3 S cm−1), which is approximately two orders of magnitude higher than that of 3P(MPBIm-TFSI). Moreover, Li/SLCE/LiFePO4 solid-like state cells exhibited excellent reversible charge/discharge reactions and considerable capacity retention up to medium rates. Coulombic efficiency can remain 100% even after 100 cycles. Potential application of SLCE as an electrolyte for flexible lithium batteries was explored by scrutinizing the electrochemical performance of cells. Consequently, pouch cell exhibited stable cycling performance even in wrinkled configurations, without suffering from internal short-circuit failures between electrodes.

Osteogenic Properties of PBLG-g-HA/PLLA Nanocomposites

New development of biomaterial scaffolds remains a prominent issue for the regeneration of lost or fractured bone. Of these scaffolds, a number of bioactive polymers have been synthesized and fabricated for diverse biological roles. Although recent evidence has demonstrated that composite scaffolds such as HA/PLLA have improved properties when compared to either HA or PLLA alone, recent investigations have demonstrated that the phase compatibility between HA and PLLA layers is weak preventing optimal enhancement of the mechanical properties and making the composites prone to breakdown. In the present study, poly (γ-benzyl-L-glutamate) modified hydroxyapatite/(poly (L-lactic acid)) (PBLG-g-HA/PLLA) composite scaffolds were fabricated with improved phase compatibility and tested for their osteogenic properties in 18 Wistar female rats by analyzing new bone formation in 3 mm bilateral femur defects in vivo. At time points, 2, 4 and 8 weeks post surgery, bone formation was evaluated by µ-CT and histological analysis by comparing 4 treatment groups; 1) blank defect, 2) PLLA, 3) HA/PLLA and 4) PBLG-g-HA/PLLA scaffolds. The in vivo analysis demonstrated that new bone formation was much more prominent in HA/PLLA and PBLG-g-HA/PLLA groups as depicted by µ-CT, H&E staining and immunohistochemistry for collagen I. TRAP staining was also utilized to determine the influence of osteoclast cell number and staining intensity to the various scaffolds. No significant differences in either staining intensity or osteoclast numbers between all treatment modalities was observed, however blank defects did contain a higher number of osteoclast-like cells. The results from the present study illustrate the potential of PBLG-g-HA/PLLA scaffolds for bone tissue engineering applications by demonstrating favorable osteogenic properties.