In-situ engineered MXene-TiO2/ BiVO4 hybrid as an efficient photoelectrochemical platform for sensitive detection of soluble CD44 proteins.

Interfacial charge-carrier recombination is a bottle-neck issue restricting photoelectrochemical biosensors advancement in the wearable clinical electronics. In this study, we propose a simple approach to construct a highly efficient photoactive heterojunction capable of functioning as an active substrate in PEC biosensing of CD44 proteins. Taking the advantage of high photocatalytic activity of BiVO4, and biocompatible yet conductive 2D-Ti3C2Tx nanosheets, a workable heterojunction was constructed between in-situ formed TiO2 from the partially oxidized Ti3C2Tx and lysine functionalized BiVO4 (TiO2/MX-BiVO4). The interfacial arrangement was ideal for promoting fast charge transfer from photo-excited BiVO4 and TiO2 to Ti3C2Tx, constructing an energy level-cascade that permits minimal charge-carrier recombination besides robust photocatalytic redox activity. The PEC biosensor relies on the ligand-protein interaction, where hyaluronic acid was directly immobilized over TiO2/MX-BiVO4 based on the interactions between carboxyl of lysine and amino moieties of hyaluronic acid. The PEC biosensor response depends on the inhibition in the measured photo-oxidation current of mediator species, i.e., ascorbic acid after the addition of CD44 proteins. The superior photo-activity, and robust heterojunction arrangement, produced a sensitive signal capable of recognizing CD44 in the wide concentration window of 2.2 × 10-4 ng mL-1 to 3.2 ng mL-1 with a low-detection limit of 1.4 × 10-2 pg mL-1. The strong interaction between lysine functionalized BiVO4 and hyaluronic acid enabled biosensor to exhibit robust antifouling characteristics towards similar proteins such as PSA and NSE. The quantification of CD44 protein from real-blood serum samples further confirmed the biosensor's reliability for clinical application.

One-pot conjugated linoleic acid production from castor oil by Rhizopus oryzae lipase and resting cells of Lactobacillus plantarum.

Conjugated linoleic acid (CLA) has attracted as novel type of fatty acids having unusual health-promoting properties such as anticarcinogenic and antiobesitic effects. The present work employed castor oil as substrate for one-pot production of CLA using washed cells of Lactobacillus plantarum (L. plantarum) and lipases as catalysts. Among the screened lipases, the lipase Rhizopus oryzae (ROL) greatly assisted resting cells to produce CLA. Mass spectral analysis of the product showed that two major isomers of CLA were produced in the reaction mixture i.e. cis-9, trans-11 56.55% and trans-10, cis-12 43.45%. Optimum factors for CLA synthesis were found as substrate concentration (8 mg/mL), pH (6.5), washed cell concentration (12% w/v), and incubation time of 20 h. Hence, the combination of ROL with L. plantarum offers one pot production of CLA selectively using castor oil as a cost-effective substrate.

Highly sensitive determination of atropine using cobalt oxide nanostructures: Influence of functional groups on the signal sensitivity.

This study describes sensitive determination of atropine using glassy carbon electrodes (GCE) modified with Co3O4 nanostructures. The as-synthesised nanostructures were grown using cysteine (CYS), glutathione (GSH) and histidine (HYS) as effective templates under hydrothermal action. The obtained morphologies revealed interesting structural features, including both cavity-based and flower-shaped structures. The as-synthesised morphologies were noted to actively participate in electro-catalysis of atropine (AT) drug where GSH-assisted structures exhibited the best signal response in terms of current density and over-potential value. The study also discusses the influence of functional groups on the signal sensitivity of atropine electro-oxidation. The functionalisation was carried with the amino acids originally used as effective templates for the growth of Co3O4 nanostructures. The highest increment was obtained when GSH was used as the surface functionalising agent. The GSH-functionalised Co3O4-modified electrode was utilised for the electro-chemical sensing of AT in a concentration range of 0.01-0.46 µM. The developed sensor exhibited excellent working linearity (R2 = 0.999) and signal sensitivity up to 0.001 µM of AT. The noted high sensitivity of the sensor is associated with the synergy of superb surface architectures and favourable interaction facilitating the electron transfer kinetics for the electro-catalytic oxidation of AT. Significantly, the developed sensor demonstrated excellent working capability when used for AT detection in human urine samples with strong anti-interference potential against common co-existing species, such as glucose, fructose, cysteine, uric acid, dopamine and ascorbic acid.

Multipesticide residue levels in UHT and raw milk samples by GC-µECD after QuEChER extraction method.

In the present study, milk samples including raw and ultra-high temperature (UHT) processed milk were analyzed for pesticide residue levels, including five pesticides, viz chloripyrifos, endosulfan (α and ß), profenofos and bifenthrin by gas chromatography microelectron capture detector (GC-µECD) after extraction by QuEChERS method. Further confirmation of the pesticide residue was done by GC-MS. The pesticide residual level in raw and UHT milk samples (n = 70) was determined in the range of 0.1-30 µg L(-1). All UHT processed milk samples contain pesticide residues within permissible limit set by the World Health Organization (WHO); however, among raw milk samples, chloripyrifos (12 %), α (24 %), and ß (14 %) endosulfan were found above the maximum residue limit (MRL). The estimated daily intake (EDI) of these four pesticide residues were also calculated as 1.32, 16.16, 5.30, 10.20, and 9.93 µg kg(-1) body weight for chloripyrifos, endosulfan α, profenofos, endosulfan ß, and bifenthrin, respectively. It is concluded that the raw milk samples showed higher prevalence of pesticide residues as compared to UHT processed milk. Graphical abstract Determination of pesticide residues in dairy milk by GC-µECD after QuEChERS extraction method.

Contamination profile of aflatoxin M1 residues in milk supply chain of Sindh, Pakistan.

Aflatoxin M1 (AFM1) is a potent carcinogen, teratogen and mutagen found in the milk when lactating animals consume feed contaminated with aflatoxin B1 (AFB1). In the present study, the contamination of AFM1 was evaluated in the milk supply chain of the province of Sindh, Pakistan. For the broader profiling of targeted toxin, enzyme-linked immunosorbent assay (ELISA) was used for the determination of AFM1 in both branded and non-branded milk samples. The results showed that 96.43% of samples (81 out of 84) were contaminated with AFM1 in the range of 0.01-0.76 µg/L. The average contamination level was 0.38 µg/L. The determined values of AFM1 in the collected milk samples were above the standard limit of the European Commission while 70% of the samples exceeded levels established by United States regulations. According to these results, the estimated daily intake of AFM1 for adults was determined as 3.1 ng/kg of body weight per day.

Rapid detection of melamine adulteration in dairy milk by SB-ATR-Fourier transform infrared spectroscopy.

Melamine is a nitrogenous chemical substance used principally as a starting material for the manufacture of synthetic resins. Due to its very high proportion of nitrogen melamine has been added illegitimately to foods and feeds to increase the measured protein content, which determines the value of the product. These issues prompted private as well as governmental laboratories to develop methods for the analysis of melamine in a wide variety of food products and ingredients. Owing to this fact present study is aimed to use single bounce attenuated total reflectance (SB-ATR) Fourier transform infrared spectroscopy (FTIR) method as an effective rapid tool for the detection and quantification of melamine in milk (liquid and powder). Partial least-squares (PLS) models were established for correlating spectral data to melamine concentration with R(2)>0.99, and RMSEC 0.370. Linear calibration curves were obtained over the calibration range of 25-0.0625%. The LOD and LOQ of the method was 0.00025% (2.5 ppm) and 0.0015% (15 ppm) respectively. Proposed SB-ATR-FTIR method requires little or no sample preparation with an assay time of 1-2 min.