A new sensing platform based on a ternary nanocomposite of graphitic carbon nitride-silver sulfide-nickel molybdate for quercetin determination.

In this study, we have shown how to prepare a ternary nanocomposite (Ag2S-NiMoO4-g-C3N4) consisting of graphitic carbon nitride (g-C3N4) nanosheets, silver sulfide (Ag2S) nanocrystals, and nickel molybdate (NiMoO4) nanorods and its sensing ability to detect quercetin, a flavonoid found in many fruits and vegetables. An Ag2S-NiMoO4-g-C3N4 nanocomposite-modified screen-printed electrode (SPE) exhibited remarkable sensing performance in a quercetin (Que) concentration range of 0.005 µM-20 µM with a low detection limit of 2.7 nM. Moreover, we have aimed at improving the selectivity and sensitivity of a sensor for detecting Que by optimizing the composition of Ag2S-NiMoO4-g-C3N4, the film thickness, and the electrolyte pH. The sensor's selectivity for Que was tested in the presence of potential interferents such as ascorbic acid, citric acid, fructose, glucose, lactose, maltose, mannose, sucrose, and tyrosine. The performance of the sensor was tested on a variety of food samples, including green apple, green tea, honey, and red onion skin.

An electrochemical sensor based on a Co3O4-ERGO nanocomposite modified screen-printed electrode for detection of uric acid in artificial saliva.

In this study, we report the fabrication of a nanocomposite consisting of Co3O4 nanoparticles (Co3O4 NPs) and electrochemically reduced graphene oxide (ERGO) on a screen-printed electrode (SPE) and its sensing performance in the electrochemical detection of uric acid (UA). The surface modification of the electrode was confirmed by using a variety of characterization techniques (FE-SEM, XRD, AFM, EDX, WCA, FTIR, and Raman spectroscopy). In addition, the surface modification was electrochemically characterized step by step through CV, EIS and DPV techniques, and the results showed that the Co3O4-ERGO nanocomposite exhibited highly sensitive and selective sensing performance towards the oxidation of UA in 0.1 M (pH 7.0) phosphate buffer solution (PBS). The sensor (Co3O4-ERGO/SPE) signals were observed to be linear to the UA concentration in the range of 5 µM to 500 µM (R2 = 0.9985). After revealing its other performance characteristics, such as repeatability, reproducibility, stability, sensitivity, and selectivity, the sensor was successfully applied to the analysis of UA in artificial saliva samples.

Boosting visible light response and charge separation by plasmonic Ag and TiO2 modification of Ag3VO4 for degradation of pollutants.

The formation of heterojunction structures of semiconductors is one of the most important techniques to increase the photocatalytic efficiency of a photocatalyst. In this paper, Ag/Ag3VO4/TiO2 as a visible light response photocatalyst was prepared easily by a three step process including hydrothermal, precipitation and photoreduction. The Ag/Ag3VO4/TiO2 nanocomposites demonstrated clearly increased visible light absorption and photocatalytic efficiency in degradation of Rhodamine B. The degradation yield of Rhodamine B was detected 97.3% in 45 min under visible light. Compared with Ag3VO4, TiO2 and Ag3VO4/TiO2, Ag/Ag3VO4/TiO2 exhibited the highest efficiency owing to synergetic effect between Ag3VO4 and TiO2 and surface plasmon resonance effect of Ag nanoparticles. So, the Ag/Ag3VO4/TiO2 can be effectively used as an active photocatalyst under visible light and it depicts an ideal potential in elimination organic pollutants.

Preparation of pillar[5]arene immobilized trypsin and its application in microwave-assisted digestion of Cytochrome c.

This work presents the immobilization of trypsin on the synthesized pillar[5]arene derivative (P5) containing ten iodo-terminals. The characterization has been carried out by Thermogravimetric Analysis (TGA), Fourier Transform Infrared (FTIR) and Raman spectra, Scanning Electron Microscopy (SEM) and Zeta Potential. Furthermore, Cytochrome c (Cyt c) was chosen as a model protein for evaluation of the performance of the pillar[5]arene-immobilized trypsin (P5-T), and its microwave-assisted digestion conditions were investigated by using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) for 15 second. The peptide numbers of 10 and sequence coverage of 93% for 15 second microwave-assisted digestion were obtained for P5-T. The results can be further applied in future proteomics studies due to high efficiency, good reproducibility and stability of the pillar[5]arene-immobilized trypsin.

Investigation of antibacterial properties of novel papain immobilized on tannic acid modified Ag/CuFe2O4 magnetic nanoparticles.

The non-toxic CuFe2O4 magnetic nanoparticles have been solvothermally synthesized, characterized and used as an efficient magnetic precursor for papain immobilization and then investigated antibacterial properties of them. For increasing the antibacterial activity, the silver nanoparticles were doped on CuFe2O4 magnetic nanoparticles. All prepared samples exhibited stronger antibacterial properties against Gram-positive bacteria (Staphyloccocus aureus) than Gram-negative bacteria (Escherichia coli). However, it was determined that the Ag/CuFe2O4 had a more vigorous antibacterial property against the Staphyloccocus aureus bacteria by calculating the inhibition diameter of 25 ±â€¯0.1 mm in the synthesized samples. Also, the antibacterial activity increased by immobilization of papain.

Efficient protein digestion using immobilized trypsin onto tannin modified Fe3O4 magnetic nanoparticles.

Fe3O4 magnetic nanoparticles (MNPs) were prepared via solvothermal method. A commercially available trypsin was covalently immobilized onto MNPs modified with tannin (T) via a novel binding process. The morphology, structure, surface and magnetic properties of the obtained nanostructures were characterized comprehensively. The Fe3O4 MNPs had a saturation magnetization value of 60.18emu/g at room temperature, while the tannin modified Fe3O4 MNPs, and the trypsin immobilized on tannin modified-Fe3O4 MNPs possessed a saturation magnetization value of 57.82emu/g and 55.16emu/g, respectively, which indicated the decent tannin coating and trypsin immobilization. The general applicability of the immobilized trypsin for proteomic studies was confirmed by enzymatic digestion of widely used bovine serum albumin (BSA). The immobilized trypsin was investigated by conducting the tryptic digestion of BSA within 1min, 5min and 15min. Also, microwave-assisted digestion was carried out for 15s. The digested protein fragments were identified by matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS), and a satisfactory peptide numbers of 39, and a superior sequence coverage of 84% for 1min digestion were obtained. The sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis confirmed the satisfactory digestion of BSA and egg white proteins by immobilized trypsin.

Covalent immobilization of trypsin onto modified magnetite nanoparticles and its application for casein digestion.

The immobilization method consists of the production magnetite nanoparticles (Fe3O4) by solvothermal treatment of FeCl3 and sodium acetate (NaAc) in the presence of ethylene glycol. Subsequently, the surface of magnetite nanoparticles was modified with a well-known polyphenol tannic acid. Trypsin was covalently immobilized on the tannic acid modified magnetite nanoparticles after exposing the modified nanoparticles to pH 9.4. Then, tryptic digestion of casein by free and immobilized trypsin was carried out for 13h and 1h, respectively. TGA curves, FTIR spectra, and magnetization curves demonstrated the decent amount of trypsin immobilization without compromising the enzyme activity. Digestion efficiency of casein was investigated using liquid chromatography-mass spectrometry (LC-MS/MS) technique. LC-MS chromatograms confirmed the efficient digestion of casein by immobilized trypsin compared to free trypsin owing to prevention of autohydrolysis. Also, the sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis confirmed the satisfactory digestion of casein by immobilized trypsin.

Improvement of the stability and activity of immobilized trypsin on modified Fe3O4 magnetic nanoparticles for hydrolysis of bovine serum albumin and its application in the bovine milk.

Trypsin (EC 3.4.21.4) was successfully immobilized on the surface of Fe3O4 magnetic nanoparticles that had been pre-treated with gallic acid (GA). Measurements of protein load by using Bradford assay and the trypsin-catalyzed hydrolysis of Nα-Benzoyl-dl-arginine 4-nitroanilide hydrochloride (BApNA) were made for the immobilized enzyme. By using magnetic nanoparticles, which provides easy separation and decent support material for enzyme immobilization with high surface area to volume ratio, and by employing biocompatible material gallic acid, immobilized enzyme system was synthesized along with improving trypsin activity and stability. Immobilized trypsin (TR) was more stable than the free one and demonstrated higher enzymatic activity at elevated temperatures (45-55°C) and in the alkaline pH region (6-10.5). Fe3O4 NPs-GA-TR retained 92% of its initial activity after 120days of storage at 4°C in sodium phosphate buffer (0.1M, pH 7.5), whereas the free trypsin maintained about 64% of its initial activity during the same storage period. In addition, activity of the immobilized trypsin was preserved 54.5% of its initial activity after eight times successive reuse. The Michaelis-Menten kinetic constant (Km) and maximum reaction velocity (Vmax) for free trypsin were 5.1mM and 23mM/min, respectively, whereas Km and Vmax values of immobilized trypsin were 7.88mM and 18.3mM/min, respectively. The performance of the immobilized trypsin was demonstrated by carrying out the hydrolysis of bovine serum albumin (BSA) within 1h, and the assay was performed by using liquid chromatography-mass spectrometry (LC-MS/MS) technique. The hydrolysis of bovine milk as a real food was investigated by immobilized trypsin using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE).

Characterization and immobilization of trypsin on tannic acid modified Fe3O4 nanoparticles.

Fe3O4 nanoparticles (NPs) were synthesized by co-precipitating Fe2+ and Fe3+ in an ammonia solution. Fe3O4 NPs functionalized with tannic acid were prepared. After functionalization process, trypsin enzyme was immobilized on these Fe3O4 NPs. The influence of pH, temperature, thermal stability, storage time stability and reusability on non-covalent immobilization was studied. The properties of Fe3O4 and its modified forms were examined by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), UV-vis spectrometer (UV) and X-ray diffraction (XRD), magnetization and zeta potential measurements. The immobilized enzyme was slightly more stable than the free enzyme at 45°C. According to the results, the activity of immobilized trypsin was preserved 55% at 45°C after 2 h and 90% after 120 days storage. In addition, the activity of the immobilized trypsin was preserved 40% of its initial activity after eight times of successive reuse.