Zhide Zhou

Immobilization of Saccharomyces cerevisiae alcohol dehydrogenase on hybrid alginate–chitosan beads

Saccharomyces cerevisiae alcohol dehydrogenase (SCAD) was effectively immobilized on hybrid alginate-chitosan beads which are hardened with glutaraldehyde. Immobilization conditions and characterization of the immobilized enzyme were investigated. Orthogonal test design and intuitive analysis method were employed to evaluate the effects of immobilization parameters such as Na-alginate concentration, glutaraldehyde concentration, CaCl(2) concentration and immobilization time. Under optimized working conditions (3.0% Na-alginate, 0.5% chitosan, 2.0% CaCl(2), 0.5% glutaraldehyde and 6h), the SCAD activity was 339.25 U/mL. For the reduction of phenylglyoxylic acid, the immobilization process changed the enzymes optimum temperature from 30 to 40 degrees C, the enzymes optimum pH from 6.8 to 6.0, and the immobilized SCAD retained 62.76% of its original activity. The maximum reaction rate (V(max)) was 358.63 nmol min(-1) and the Michaelis-Menten constant (K(m)) was 37.33 mmol L(-1). Compared to the free SCAD, the immobilization of the enzyme showed higher thermal stability and operational stability.

Formulation optimization of chelerythrine loaded O-carboxymethylchitosan microspheres using response surface methodology

The aims of this investigation were to develop a procedure to prepare chelerythrine (CHE) loaded O-carboxymethylchitosan (O-CMCS) microspheres by emulsion cross-linking method and optimize the process and formulation variables using response surface methodology (RSM) with a three-level, three-factor Box-Behnken design (BBD). The independent variables studied were O-CMCS/CHE ratio, O/W phase ratio, and O-CMCS concentration, dependent variables (responses) were drug loading content and encapsulation efficiency. Mathematical equations and response surface plots were used to relate the dependent and independent variables. The process and formulation variables were optimized to achieve maximum drug loading content and entrapment efficiency by the desirability function. The optimized microsphere formulation was characterized for particle size, shape, morphology and in vitro drug release. Results for mean particle size, drug loading content, entrapment efficiency, and in vitro drug release of CHE-loaded O-CMCS microspheres were found to be of 12.18 μm, 4.16 ± 3.36%, 57.40 ± 2.30%, and 54.5% at pH 7.4 after 70 h, respectively. The combination use of RSM, BBD and desirability function could provide a promising application for O-CMCS as controlled drug delivery carrier and help to develop procedures for a lab-scale microemulsion process.

Biosorption of palladium(II) from aqueous solution by grafting chitosan on persimmon tannin extract.

A low-cost and environmentally green biosorbent (PTCS) was prepared by grafting chitosan onto persimmon tannin extract and its potentiality for efficient adsorption of palladium ion (Pd(II)) from aqueous solution was evaluated. Various adsorption parameters such as pH, the initial Pd(II) concentration and temperature were investigated. The maximum adsorption capacity reached 330mg/g at 323K and pH 5.0 when the initial Pd(II) concentration was 100mg/L. The equilibrium adsorption data were satisfactorily fitted with Freundlich isotherm model and biosorption kinetics was found to be in good agreement with pseudo-second-order kinetics model. Thermodynamic calculations indicated that the adsorption process was endothermic and spontaneous in nature because of the negative value of free energy change (ΔG) and positive value of enthalpy change (ΔH). The positive value of entropy change (ΔS) revealed the increased randomness at the solid-liquid interface. FT-IR and XRD analysis verified that Pd(II) adsorption on PTCS was electrostatic interaction and redox reaction. Moreover, selective adsorption study revealed that the adsorbent exhibited good adsorption ability to Pd(II) in the mixture metal ions solutions. All these results indicated that the PTCS biosorbent could be used as a low-cost alternative for the adsorption of Pd(II) in waste-water treatment.

Rapamycin loaded magnetic Fe3O4/carboxymethylchitosan nanoparticles as tumor-targeted drug delivery system: Synthesis and in vitro characterization.

A novel tumor-targeted drug delivery system (Fe3O4/CMCS-Rapa NPs) was prepared using magnetic Fe3O4/carboxymethylchitosan nanoparticles (Fe3O4/CMCS NPs) as carrier and rapamycin (Rapa) as the model anti-tumor drug. The morphology, composition, and properties of the Fe3O4/CMCS-Rapa NPs were characterized by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscope (TEM), X-ray diffraction (XRD), thermal analysis (TG/DSC), vibration sample magnetometer (VSM), and drug release kinetics, cytotoxicity, cellular uptake, apoptosis studies in vitro. The results showed that the synthesized Fe3O4/CMCS-Rapa NPs were spherical in shape with an average size of 30±2 nm, the saturated magnetization reached 67.1 emu/g, and the loading efficiency of Rapa was approximately 6.32±0.34%. In addition, the in vitro drug release behavior displayed that the Fe3O4/CMCS NPs exhibited a biphasic drug release pattern with initial burst release and consequently sustained release. Furthermore, the Fe3O4/CMCS-Rapa NPs showed lower cytotoxicity to liver cell line (LO2) and comparatively higher cytotoxicity to human hepatocarcinoma cell line (HepG2) than native Rapa. Fe3O4/CMCS-Rapa NPs could enhance cellular uptake and reduce Rapa drug damage to the normal cells so as to improve the curative effect of drug to tumor cells. All these results demonstrated that the Fe3O4/CMCS-Rapa NPs may be useful as a promising candidate for targeted cancer diagnostic and therapy.

Equilibrium, kinetics and mechanism of Au3 +, Pd2 + and Ag+ ions adsorption from aqueous solutions by graphene oxide functionalized persimmon tannin

In this study, a novel bio-adsorbent (PT-GO) was prepared by functionalization persimmon tannin (PT) with graphene oxide (GO) and the effective adsorption behaviors of Au3+, Pd2+ and Ag+ ions from aqueous solution was investigated. The PT-GO was characterized by Fourier transform infrared spectrometer (FTIR), scanning electronic microscope (SEM), thermogravimetric analysis (TGA) and Zeta potential. Many influence factors such as pH value, bio-adsorbent dosage, initial concentration of metal ions and contact time were optimized. The maximum adsorption capacity for Au3+, Pd2+ and Ag+ was 1325.09mg/g, 797.66mg/g and 421.01mg/g, respectively. The equilibrium isotherm for the adsorption of Au3+ and Ag+ on PT-GO were found to obey the Langmuir model, while the Freundlich model fitted better for Pd2+. The adsorption process of Au3+, Pd2+ presented relatively fast adsorption kinetics with pseudo-second-order equation as the best fitting model, while the pseudo-first-order kinetic model was suitable for describing the adsorption of Ag+. Combination of ion exchange, electrostatic interaction and physical adsorption was the mechanism for adsorption of Au3+, Pd2+ and Ag+ onto PT-GO bio-adsorbent. Therefore, the PT-GO bio-adsorbent would be an ideal adsorbent for removal of precious metal ions and broaden the potential applications of persimmon tannin in environmental research.

Graphene and Au NPs co-mediated enzymatic silver deposition for the ultrasensitive electrochemical detection of cholesterol

Cholesterol is an essential ingredient in mammals, and serum cholesterol is a major component of atherosclerotic plaques. The level of cholesterol in human serum has become an important index for clinical diagnosis and prevention of cardiovascular disease. In this paper, a simple and ultrasensitive cholesterol biosensor based on graphene oxide (GO) and gold nanoparticles (Au NPs) co-mediated enzymatic silver deposition was designed by immobilizing cholesterol oxidase (CHOD), cholesterol esterase (CHER) and GO onto the surface of Au NPs modified screen-printed carbon electrode (SPE). Under the synergistic effect of CHER, CHOD and GO, the cholesterol was hydrolyzed to generate hydrogen peroxide, which can reduce the silver (Ag) ions in the solution to metallic Ag which deposited on the surface of Au NPs modified SPE. The ultrasensitive detection of cholesterol was achieved by anodic stripping voltammetry measurement of the enzymatically deposited Ag. Under optimal conditions, the anodic stripping peak current of Ag increased with the increasing cholesterol concentration in the range from 0.01μg/mL to 5000μg/mL with a limit of detection of 0.001μg/mL (S/N = 3). In addition, the ultrasensitive cholesterol biosensor exhibited higher specificity, acceptable reproducibility and excellent recoveries for cholesterol detection.

Novel Carboxymethyl Chitosan Microspheres for Controlled Delivery of Chelerythrine

Novel carboxymethyl chitosan (O-CMCS) microspheres containing an anti-tumor drug chelerythrine (CHE) have been successfully prepared by an emulsion crosslinking method using glutaraldehyde. The optimized microsphere formulation was characterized for particle size, shape, morphology, crystallinity and in vitro drug release. Results for mean particle size, drug loading content, entrapment efficiency and in vitro drug release of chelerythrine loaded microspheres were found to be 12.18 μm, 4.08%, 54.78% and 35.30% at pH 7.4 in 20 h, respectively. The optimized microspheres had an imperfect crystalline lattice and a spherical, rough morphology and the CHE release from O-CMCS microspheres followed the Higuchi matrix model. All these results suggested that O-CMCS microspheres are a promising carrier system for controlled drug delivery.

Label-free electrochemical aptasensor for detection of alpha-fetoprotein based on AFP-aptamer and thionin/reduced graphene oxide/gold nanoparticles

Sensitive and accurate detection of tumor markers is critical to early diagnosis, point-of-care and portable medical supervision. Alpha fetoprotein (AFP) is an important clinical tumor marker for hepatocellular carcinoma (HCC), and the concentration of AFP in human serum is related to the stage of HCC. In this paper, a label-free electrochemical aptasensor for AFP detection was fabricated using AFP-aptamer as the recognition molecule and thionin/reduced graphene oxide/gold nanoparticles (TH/RGO/Au NPs) as the sensor platform. With high electrocatalytic property and large specific surface area, RGO and Au NPs were employed on the screen-printed carbon electrode to load TH molecules. The TH not only acted as a bridging molecule to effectively capture and immobilize AFP-aptamer, but as the electron transfer mediator to provide the electrochemical signal. The AFP detection was based on the monitoring of the electrochemical current response change of TH by the differential pulse voltammetry. Under optimal conditions, the electrochemical responses were proportional to the AFP concentration in the range of 0.1-100.0 μg/mL. The limit of detection was 0.050 μg/mL at a signal-to-noise ratio of 3. The proposed method may provide a promising application of aptamer with the properties of facile procedure, low cost, high selectivity in clinic.

Preparation and characterization of a novel polyethyleneimine cation-modified persimmon tannin bioadsorbent for anionic dye adsorption

A novel and recyclable bioadsorbent (PTP) has been prepared by the cationization of persimmon tannin (PT) using polyethyleneimine (PEI) for application in the removal of the anionic dye methyl orange (MO) from aqueous solution. The physicochemical properties of the prepared PTP were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, Zeta potential measurements, Brunauer-Emmett-Teller and thermogravimetric analysis. Systematic batch adsorption experiments were carried out with pH, bioadsorbent dosage, initial MO concentration and contact time. Kinetic regression analysis indicated that the adsorption processes followed the pseudo-second order model. The equilibrium isotherm was in good fit with the Freundlich model with a maximum adsorption capacity of 225.74 mg/g. Thermodynamics data revealed that the adsorption of MO onto PTP was feasible, spontaneous and endothermic. A possible biosorption mechanism was presented where electrostatic interactions, hydrogen bonding, and π-π interactions dominated the adsorption of MO onto PTP. Moreover, the regeneration of the PTP was easily achieved and MO removal efficiency remained high (81.47%) after six cycles. The actual sewage treatment simulation was evaluated and the PTP had a good preference to adsorption MO. All these results indicated that PTP could be considered a high performance and promising candidate for the effective removal of anionic dyes from aqueous solutions.

Chitosan modification persimmon tannin bioadsorbent for highly efficient removal of Pb(II) from aqueous environment: the adsorption equilibrium, kinetics and thermodynamics

ABSTRACT Lead (Pb) pollution has triggered a great threat to ecological system as well as public health due to its highly toxic and mutagenic properties. In this study, chitosan surface modified persimmon tannin (PT-CS) biomass composite as an environmental-friendly bioadsorbent for highly efficient removal of Pb(II) from aqueous solutions was investigated. Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscope, Brunauer–Emmett–Teller, X-ray photoelectron spectroscopy and Zeta potential were used to elucidate the adsorption mechanism. Combining oxidation reaction, electrostatic interaction and chelation reaction, PT-CS exhibited fine adsorption to Pb(II). The maximum adsorption capacity was 179.3 mg/g. Equilibrium isotherm for the adsorption of Pb(II) was analyzed by the Langmuir, Freundlich and Temkin models, and the Langmuir isotherm (R2 > 0.99) was the best. The pseudo-first-order, pseudo-second-order and intraparticle diffusion equations were used to analyze the kinetic data of the adsorption process and the pseudo-second-order kinetic (Rs2 > 0.98) model was fitted well. Moreover, thermodynamic parameters including ΔG0 < 0, ΔH0 (150.57 KJ/mol) > 0 and ΔS0 (456.13 J/mol K) > 0 showed that the process of Pb(II) adsorption by PT-CS was spontaneous and endothermic. All these results illustrated that PT-CS would be a promising and low-cost alternative bioadsorbent of Pb(II) in wastewater treatment. GRAPHICAL ABSTRACT