A Novel Immunosensor Based on Au Nanoparticles and Polyaniline/Multiwall Carbon Nanotubes/Chitosan Nanocomposite Film Functionalized Interface

A novel multilayer film based on Au nanoparticles(AuNPs) and polyaniline/carboxylated multiwall carbon nanotubes-chitosan nanocomposite(PANI/MWCNTs/CS) was exploited to fabricate a highly sensitive immunosensor for detecting chlorpyrifos. PANI-coated MWCNTs were prepared by in situ chemical polymerization and carboxylated MWCNTs played an important role in obtaining the thin and uniform coating of PANI resulting in the improved immunosensor response. Au NPs were used as a linker to immobilize chlorpyrifos antibody. The performance of the immunosensor was characterized by means of cyclic voltammetry(CV), electrochemical impedance spectroscopy(EIS) and scanning electron microscopy(SEM), respectively. All variables involved in the preparation process and analytical performance of the immunosensor were optimized.Under optimal conditions(antibody concentration: 5 μg/mL, working buffer pH: 6.5, incubation time: 40 min,incubation temperature: 25℃), the immunosensor exhibited a wide linear range from 0.1 to 40× 10^(-6)mg/mL and from 40 × 10^(-6)mg/mL to 500 × 10^(-6)mg/mL, and with a detection limit of 0.06 × 10^(-6)mg/mL, which provided a valuable tool for the chlorpyrifos detection in real samples.

Electrochemical Aptasensor Based on Prussian Blue-Chitosan-Glutaraldehyde for the Sensitive Determination of Tetracycline

In this paper, a novel and sensitive electrochemical aptasensor for detecting tetracycline(TET)with prussian blue(PB) as the label-free signal was fabricated. A PB-chitosan-glutaraldehyde(PB-CS-GA)system acting as the signal indicator was developed to improve the sensitivity of the electrochemical aptasensor.Firstly, the PB-CS-GA was fixed onto the glass carbon electrode surface. Then, colloidal gold nanoparticles(Au NPs) were droped onto the electrode to immobilize the anti-TET aptamer for preparation of the aptasensor.The stepwise assembly process of the aptasensor was characterized by cyclic voltammetry(C-V) and scanning electron microscope(SEM). The target TET captured onto the electrode induced the current response of the electrode due to the non-conducting biomoleculars. Under the optimum operating conditions, the response of differential pulse voltammetry(DPV) was used for detecting the concentration of TET. The proposed aptasensor showed a high sensitivity and a wide linear range of 109-～ 105-M and 105-～ 102-M with the correlation coefficients of 0.994 and 0.992, respectively. The detection limit was 3.2×1010-M(RSD 4.12%). Due to its rapidity, sensitivity and low cost, the proposed aptasensor could be used as a pre-scanning method in TET determination for the analysis of livestock products.

Acetylcholinesterase Biosensor Based on Poly(diallyldimethylammonium chloride)-multi-walled Carbon Nanotubes-graphene Hybrid Film

In this paper, an amperometric acetylcholinesterase(ACh E) biosensor for quantitative determination of carbaryl was developed. Firstly, the poly(diallyldimethy-lammonium chloride)-multi-walled carbon nanotubes-graphene hybrid film was modified onto the glassy carbon electrode(GCE) surface, then ACh E was immobilized onto the modified GCE to fabricate the ACh E biosensor. The morphologies and electrochemistry properties of the prepared ACh E biosensor were investigated by using scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. All variables involved in the preparation process and analytical performance of the biosensor were optimized. Based on the inhibition of pesticides on the ACh E activity, using carbaryl as model compounds, the biosensor exhibited low detection limit, good reproducibility and high stability in a wide range. Moreover, the biosensor can also be used for direct analysis of practical samples, which would provide a new promising tool for pesticide residues analysis.

Optimization of plasma-processed air(PPA)inactivation of Escherichia coli in button mushrooms for extending the shelf life by response surface methodology

The effect of plasma-processed air(PPA)treatment with different conditions(time,power andflow rate)on the inactivation of Escherichia coli(E.coli)in button mushroom was evaluated.Response surface methodology(RSM)was applied to optimize PPA treatments on the E.coli of button mushrooms.According to the response surface analysis,the optimal treatment parameters were a treatment time of 12 min,treatment power of 90 W and flow rate of 1.2 l min-1.As with verifying tests from the optimization exercise,the number of E.coli reduced by 5.27 log CFU/g at the determined optimum conditions.The scanning electronic microscopy(SEM)micrography showed that the surface of the E.coli was significantly changed under the optimized PPA treatment.Quality parameters of button mushrooms treated at the determined optimum conditions were compared with untreated samples during the storage for 12 d at 4°C?±?1°C.The PPA treatment was found to be effective in inhibiting microbes and preserving postharvest quality in button mushrooms,and these results suggested PPA treatment may provide an alternative for the sterilization of foodborne and maintaining postharvest of fruits and vegetables.