Loc Thai Nguyen

Electrochemical Immunosensor Based on Fe3O4/PANI/AuNP Detecting Interface for Carcinoembryonic Antigen Biomarker

A low-cost screen-printed carbon electrode (SPCE) modified with Fe3O4, gold nanoparticles (AuNPs), and polyaniline (PANI) has been developed for rapid measurement of carcinoembryonic antigen (CEA) biomarker. The electrode surface was covered with Fe3O4 nanoparticles by drop coating then with PANI via electropolymerization. The resulting surface was further modified by AuNPs via electrodeposition. Key factors affecting the electrochemical behavior and sensing performance of the electrode were investigated. The results demonstrated that Fe3O4 mass loading of 2xa0mg/cm2 and 15 cycles of PANI polymerization were optimal for electrochemical measurement of CEA biomarker. In addition, compared with bare SPCE, coating the electrode surface with PANI, Fe3O4/PANI, and Fe3O4/PANI/AuNP significantly enhanced the peak oxidation current by approximately 16%, 52%, and 93%, respectively. The sensors exhibited linear trends with CEA concentration from 0xa0ng/mL to 10xa0ng/mL. The limit of detection and sensitivity of the electrode were estimated to be 0.25xa0ng/mL and 0.3827 μA/ngxa0mL−1, respectively. Such sensors could be easily integrated into microfluidic platforms and could serve as a low-cost, rapid, point-of-care measurement method for CEA cancer biomarker.Graphical Abstract

Programmable electrochemical flow system for high throughput determination of total antioxidant capacity

The aim of this work was to develop a programmable flow system for rapid assessment of total antioxidant capacity (TAC). Novel features of the prototype include a single pressure-driven source, versatile manipulation of fluid flows, ability to adapt to different TAC assays, and compatibility with microfluidic design. Antioxidant activity was determined by electrochemical measurement of residual 2,2-diphenyl-2-picrylhydrayl hydrate (DPPH•) free radicals in the solution. The overall performance of the device was validated by the spectrophotometric method. The results indicated that dosing of reagents and samples could be controlled by pressure (R2 = 0.992) and time (R2 = 0.999) with high accuracy, and the mixing uniformity of the device was equivalent to that of the batch mixing (R2 = 0.994). TAC assays of a standard antioxidant, ascorbic acid, as well as selected samples such as orange and pomegranate juices, white wine, and green tea by the device were comparable to traditional measurement techniques. Due to the short incubation time, the approach may be more suitable for fast, rather than slow reacting antioxidant compounds. The developed system could be used for rapid TAC screening of food and biological samples.

Development of a portable electrochemical loop mediated isothermal amplification (LAMP) device for detection of hepatitis B virus

The objective of this study was to develop a simple, inexpensive prototype device for rapid detection of hepatitis B virus (HBV). The device was able to simultaneously amplify, detect and quantify the target HBV DNA. The system was fabricated from a custom-made electrochemical set-up of which the temperature was thermostatically controlled by a water bath. Real-time monitoring of HBV DNA was accomplished by measuring the response of redox indicator in the reaction mixture. Concentration of HBV DNA in the samples was determined from the peak high ratio (PHR) and threshold time relationship. The signal was processed by sigmoidal model fitting to enhance the accuracy of the results. Key parameters including concentrations of redox indicator and reaction temperatures were optimized. Sensitivity and specificity of the method toward HBV DNA were evaluated. The prototype was capable of real-time amplification and detection of HBV DNA with concentration as low as 6.18 fg μl−1. The test showed high specificity against HBV DNA. The system was also able to detect HBV positive serum directly with simple thermal pretreatment instead of tedious DNA extraction. The electrochemical set-up was compatible with microfluidic platforms and can be readily adapted for efficient and high throughput point-of-care (POC) diagnosis of HBV.

Enzymatic Hydrolysis of Catfish (Pangasius hypophthalmus) By-Product: Kinetic Analysis of Key Process Parameters and Characteristics of the Hydrolysates Obtained

ABSTRACT In this study, kinetic evaluation of enzymatic hydrolysis of catfish (Pangasius hypophthalmus) by-product meat was conducted. The effects of key factors such as type of proteases (neutrase, papain, and bromelain), enzyme to substrate ratio (E/S), substrate concentration, and extent of hydrolysis on process efficiency, properties and functionalities of hydrolysates were evaluated. The results demonstrated that, for catfish shredded meat, bromelain and papain had higher affinity than neutrase. Kinetics parameters Vm and Km of neutrase, papain, and bromelain were 4.486, 9.060, and 18.249 μM/min and 35.433, 6.582, and 7.034 g/l, respectively. Optimal E/S ratios of neutrase, papain, and bromelain were estimated to be 0.92, 2.76, and 3.31 mg/g. At optimal E/S, the highest possible substrate concentrations were found to be 108.4 g/l for neutrase, 36.2 g/l for papain, and 135.8 g/l for bromelain. Both kinetics study and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed that bromelain and papain had higher proteolytic activity toward catfish protein than neutrase. A significant increase in antioxidant activity of hydrolysates was observed with neutrase and papain hydrolysate, but not with bromelain. The results could be helpful for industrial processors to develop an efficient process for catfish by-product valorization.