Yongkun Liu

Electrospun carbon nanofibers coated with urchin-like ZnCo2O4 nanosheets as a flexible electrode material

Electrospun carbon nanofiber composites (ZnCo2O4/Ag–GO–CNFs) coated with 3D urchin-like ZnCo2O4 nanosheets to form a shish-kebab structure have been prepared using a combination of electrospinning, carbonization and hydrothermal treatments. The composition and microstructure of ZnCo2O4/Ag–GO–CNFs were investigated using field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Brunauer–Emmett–Teller (BET) analysis. Interestingly, ZnCo2O4/Ag–GO–CNFs provided a new style of electrode materials and exhibited an excellent specific capacity of 459.48 mA h g−1 at 20 mV s−1. Notably, the specific capacity of ZnCo2O4/Ag–GO–CNFs also exhibited a remarkable cycling stability (96.0% retention after 9000 cycles), which holds great promise for practical applications in energy storage devices as a carbon-based electrode material.

Preparation of chitosan-based multifunctional nanocarriers overcoming multiple barriers for oral delivery of insulin.

To overcome multiple barriers for oral delivery of insulin, the chitosan-based multifunctional nanocarriers modified by L-valine (LV, used as a target ligand to facilitate the absorption of the small intestine) and phenylboronic acid (PBA, used as a glucose-responsive unit) have been designed and evaluated in this study. The resultant nanocarriers exhibited low cytotoxicity against HT-29 cells and excellent stability against protein solution. The insulin release behaviors were evaluated triggered by pH and glucose in vitro. The chemical stability of loaded insulin against digestive enzyme were established in presence of simulated gastric fluid (SGF) containing pepsin and simulated intestinal fluid (SIF) containing pancreatin, respectively. The uptake behavior of HT-29 cells was evaluated by confocal laser scanning microscope. After oral administration to the diabetic rats, an effective hypoglycemic effect was obtained compared with subcutaneous injection of insulin. This work suggests that L-valine modified chitosan-based multifunctional nanocarriers may be a promising drug delivery carrier for oral administration of insulin.

Preparation of novel carbon nanofibers with BiOBr and AgBr decoration for the photocatalytic degradation of rhodamine B

Novel carbon nanofibers with BiOBr and AgBr decoration have been prepared by a combination of electrospinning, carbonization and solvothermal treatments. BiOBr/AgBr hybrids interweaved together and covered the carbon nanofibers to form a three-dimensional (3D) open porous structure. The resultant composite carbon nanofibers exhibited a high efficiency for the photocatalytic degradation of RhB in aqueous solution and were convenient to separate from water.

A composite hydrogel system containing glucose-responsive nanocarriers for oral delivery of insulin.

Development of an oral delivery strategy for insulin therapeutics has drawn much attention in recent years. In this study, a glucose-responsive nanocarriers for loading of insulin has been prepared firstly. The resultant nanocarriers exhibited relative low cytotoxicity against Caco-2 cells and excellent stability against protein solution. The insulin release behaviors were evaluated triggered by pH and glucose in vitro. In order to enhance the oral bioavailability of insulin, the insulin-loaded glucose-responsive nanocarriers were further encapsulated into a three-dimensional (3D) hyaluronic acid (HA) hydrogel environment for overcoming multiple barriers and providing multi-protection for insulin during the transport process. The hypoglycemic effect for oral delivery of insulin was studied in vivo. After oral administration to the diabetic rats, the released insulin from hydrogel systems containing insulin-loaded glucose-responsive nanocarriers exhibited an effective hypoglycemic effect for longer time compared with insulin-loaded nanocarriers.

Fabrication of biodegradable composite microneedles based on calcium sulfate and gelatin for transdermal delivery of insulin

To reduce the inconvenience and pain of subcutaneous needle injection, the calcium sulfate and gelatin biodegradable composite microneedle patches with high aspect-ratio microneedles (MNs) and a flexible substrate have been developed. The microneedles with an aspect-ratio approximate 6:1 exhibit excellent mechanical property which can achieve 0.4N for each needle. The cross-section views show the inside of microneedles that have abundant pores and channels which offer potential for different drug-release profiles. The preparation procedures, degradable property for the biodegradable composite microneedle patches are described in the paper. Insulin, the drug to control blood glucose levels in diabetic patients, has been embedded into the biodegradable composite MNs. The hypoglycemic effect for transdermal delivery of insulin is studied using diabetic Sprague-Dawley (SD) rats as models in vivo. After transdermal administration to the diabetic rats, the released insulin from biodegradable composite MNs exhibit an obvious and effective hypoglycemic effect for longer time compared with that of subcutaneous injection route. This work suggests that biodegradable composite MNs containing of insulin have a potential application in diabetes treatment via transdermal ingestion.

Photo-induced synthesis glucose-responsive carriers for controlled release of insulin in vitro

The glucose-responsive amphiphilic poly(PEGMA-co-AAPBA) copolymer micelles as drug carriers have been developed using 3-phenylpyruvic acid (3-PPA) as photoinitiator. Under the light irradiation, 3-PPA could be self-polymerized into the trimer structure to execute the emulsifier and initiator functions that confirmed by gas chromatography-mass spectrum (GC-MS) analysis. The structure and morphology of resultant poly(PEGMA-co-AAPBA) micelles were characterized by 1H NMR and TEM. Insulin, as the model drug of diabetes, was loaded into micelles during the photopolymerization process. The as-prepared polymeric micelles exhibited the excellent glucose sensitivity. The loaded insulin could be released from micelles triggered by regulation of temperature and glucose concentration in the environment. The new drug carriers provided a potential application for the therapy of diabetes based on glucose-sensitive controlled drug delivery systems.

Controlled growth of hexagonal Zn2GeO4 nanorods on carbon fibers for photocatalytic oxidation of p-toluidine

In this paper, hexagonal Zn2GeO4 nanorods grown on the surface of carbon fibers (CFs) that were pre-activated by sodium hypochlorite were prepared by a facile solvothermal method. The possible growth mechanism has been investigated by theoretical calculations and a simulation experiment by growth of Zn2GeO4 on a 2D flat surface of graphene. The (113) crystal facet of Zn2GeO4 nanorods attached to the CFs surface was the most stable structure. Due to the synergistic effect between the photocatalytic activity of Zn2GeO4 and excellent adsorption capacity of CFs, the resultant Zn2GeO4/CFs composites exhibited excellent photocatalytic activity for oxidation of p-toluidine.

Preparation of glucose-responsive and fluorescent micelles via a combination of RAFT polymerization and chemoenzymatic transesterification for controlled release of insulin

A glucose-responsive and fluorescent copolymer was prepared via a one-pot method that combines RAFT polymerization and enzymatic transesterification. The as-prepared copolymer tended to self-assemble into spherical micelles that were confirmed using 1H NMR, FT-IR and GPC, and transmission electron microscopy (TEM) and dynamic light scattering (DLS) analysis. Due to the attachment of fluorescent side groups, the optical properties of the micelles were analyzed using a UV-Vis spectrometer, fluorescence spectrophotometer and confocal laser scanning microscopy (CLSM). Owing to the amphiphilic and glucose-responsive properties, the micelles could be used as carriers for loaded insulin. The insulin release behaviour was evaluated when triggered by glucose in vitro. In addition, the resultant micelles exhibited relatively lower cytotoxicity and excellent stability against a protein solution. The insulin retained its structure stability after release, investigated through circular dichroism (CD) spectra analysis. These results showed that the obtained glucose-responsive and fluorescent polymer micelles with a good biological imaging performance and biocompatibility could be one of the effective candidate carriers for controllable release of insulin.

Preparation of Au/PAN nanofibrous membranes for catalytic reduction of 4-nitrophenol

Due to their high surface energy, naked gold nanoparticles (AuNPs) tend to form agglomerates, which could lead to the decrease of active sites and catalytic activity of AuNPs. Herein, the gold nanoparticles/polyacrylonitrile (AuNPs/PAN) nanofibrous membranes have been prepared via an environmentally friendly and efficient route combining electrospinning, amination, and electroless plating technique. The abundant amine and imine groups can be introduced onto the surface of PAN nanofibrous membranes via amination treatment which could be used as “anchoring sites” to immobilize AuNPs. The resultant composite membranes were applied as the new catalytic materials for reduction of 4-nitrophenol to 4-aminophenol under room temperature. The new catalytic membranes exhibited the significant advantages, such as low dosage, high catalytic activity, easy recycling, and excellent stability.

Preparation of poly(lactic-co-glycolic acid) and chitosan composite nanocarriers via electrostatic self assembly for oral delivery of insulin

To improve insulin bioavailability and overcome multiple barriers for oral delivery of insulin, the composite nanocarriers (PLGA/FA-CS) prepared from poly(lactide-co-glycoside) (PLGA) and folic acid modified chitosan (FA-CS) were fabricated via electrostatic self-assembly method. The resultant composite nanocarriers exhibited low cytotoxicity against HT-29 cells and excellent stability against protein solution. The chemical stability of loaded insulin against digestive enzyme were established in presence of simulated gastric fluid (SGF) containing pepsin and simulated intestinal fluid (SIF) containing pancreatin, respectively. The uptake behavior of HT-29 cells was evaluated by confocal laser scanning microscope. After oral administration to the diabetic rats, an effective hypoglycemic effect was obtained compared with subcutaneous injection of insulin. This work suggests that the as-prepared composite nanocarriers may be a promising drug delivery system for oral administration of insulin and other biomacromolecules.