PtNPs-GNPs-MWCNTs-ß-CD nanocomposite modified glassy carbon electrode for sensitive electrochemical detection of folic acid.

A novel electrochemical sensor, platinum nanoparticles/graphene nanoplatelets/multi-walled carbon nanotubes/ß-cyclodextrin composite (PtNPs-GNPs-MWCNTs-ß-CD) modified carbon glass electrode (GCE), was fabricated and used for the sensitive detection of folic acid (FA). The PtNPs-GNPs-MWCNTs-ß-CD nanocomposite was easily prepared with an ultrasound-assisted assembly method, and it was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical behavior of FA at PtNPs-GNPs-MWCNTs-ß-CD/GCE was investigated in detail. Some key experimental parameters such as pH, amount of PtNPs-GNPs-MWCNTs-ß-CD composite, and scan rate were optimized. A good linear relationship (R2 = 0.9942) between peak current of cyclic voltammetry (CV) and FA concentration in the range 0.02-0.50 mmol L-1 was observed at PtNPs-GNPs-MWCNTs-ß-CD/GCE. The detection limit was 0.48 µmol L-1 (signal-to-noise ratio = 3). A recovery of 97.55-102.96% was obtained for the determination of FA in FA pills (containing 0.4 mg FA per pill) at PtNPs-GNPs-MWCNTs-ß-CD/GCE, indicating that the modified electrode possessed relatively high sensitivity and stability for the determination of FA in real samples.

A sensitive non-enzymatic electrochemical sensor based on acicular manganese dioxide modified graphene nanosheets composite for hydrogen peroxide detection.

In this work, a novel manganese dioxide-graphene nanosheets (MnO2-GNSs) composite was synthesized by a facile one-step hydrothermal method, in which manganese dioxide (MnO2) was fabricated by hydrothermal reduction of KMnO4 with GNSs. The structure and morphology of MnO2-GNSs composite were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) analysis and X-ray photoelectron spectroscopy (XPS). A sensitive non-enzymatic electrochemical sensor based on MnO2-GNSs composite for the detection of low concentration hydrogen peroxide (H2O2) was fabricated. The electrochemical properties of MnO2-GNSs composite modified glassy carbon electrode (MnO2-GNSs/GCE) were investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and amperometry. The observations confirmed that the fabricated sensor exhibited high electrocatalytic activity for oxidation of H2O2 owing to the catalytic ability of MnO2 particles and the conductivity of GNSs. Under the optimum conditions, the calibration curve was linear for the amperometric response versus H2O2 concentration over the range 0.5-350 µM with a low detection limit of 0.19 µM (S/N = 3) and high sensitivity of 422.10 µA mM-1 cm-2. The determination and quantitative analysis of H2O2 in antiseptic solution on MnO2-GNSs/GCE exhibited percent recovery of 96.50%-101.22% with relative standard deviation (RSD) of 1.48%-4.47%. The developed MnO2-GNSs/GCE might be a promising platform for the practical detection of H2O2 due to its prominent properties including excellent reproducibility, good anti-interference and repeatability.

Preparation and characterization of glutaraldehyde cross-linked O-carboxymethylchitosan microspheres for controlled delivery of pazufloxacin mesilate.

O-carboxymethylchitosan (OCMC) microspheres containing an antibiotic drug pazufloxacin mesilate (PM) have been successfully prepared by emulsion cross-linking using glutaraldehyde (GA). Various manufacturing parameters, including amount of cross-linking agent and OCMC:PM ratios were altered to optimize process variables during the microspheres production. The structure and morphology were characterized by Fourier transform infrared (FT-IR), wide-angle X-ray diffraction (WXRD) and scanning electron microscopy (SEM). The swelling and releasing behaviors of the microspheres at pH 1.2 and 7.4 media were investigated. The results revealed that the microspheres had a spherical, rough morphology and with a narrow size distribution. The degree of swelling of microspheres at pH 7.4 media was higher than that at pH 1.2 media. The microspheres proved to be successful in prolonging drug release. The release of PM was found to depend upon the extent of matrix cross-linking and drug loading. The release profiles of PM from OCMC microspheres were found to be biphasic with a burst release followed by a gradual release phase, and followed the Higuchi matrix model.