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Cardiovascular diseases are among the major causes of mortality and morbidity. Warfarin is often prescribed for these disorders, an anticoagulant with inter and intra-dosage variability dose required to achieve the target international normalized ratio. Warfarin presents a narrow therapeutic index, and due to its variability, it can often be associated with the risk of hemorrhage, or in other patients, thromboembolism. Single-nucleotide polymorphisms are included in the causes that contribute to this variability. The Cytochrome P450 (CYP) 2C9*3 genetic polymorphism modifies its enzymatic activity, and hence warfarin's plasmatic concentration. Thus, the need for a selective, rapid, low-cost, and real-time detection device is crucial before prescribing warfarin. In this work, a disposable electrochemical DNA-based biosensor capable of detecting CYP2C9*3 polymorphism was developed. By analyzing genomic databases, two specific 78 base pairs DNA probes; one with the wild-type adenine (Target-A) and another with the cytosine (Target-C) single-nucleotide genetic variation were designed. The biosensor implied the immobilization on screen-printed gold electrodes of a self-assembled monolayer composed by mercaptohexanol and a linear CYP2C9*3 DNA-capture probe. To improve the selectivity and avoid secondary structures a sandwich format of the CYP2C9*3 allele was designed using complementary fluorescein isothiocyanate-labeled signaling DNA probe and enzymatic amplification of the electrochemical signal. Chronoamperometric measurements were performed at a range of 0.015–1.00 nM for both DNA targets achieving limit of detection of 42 p.m. The developed DNA-based biosensor was able to discriminate between the two synthetic target DNA targets, as well as the targeted denatured genomic DNA, extracted from volunteers genotyped as non-variant homozygous (A/A) and heterozygous (A/C) of the CYP2C9*3 polymorphism. [Display omitted] • A disposable genosensor able of distinguishing CYP2C9*3 polymorphisms was developed. • The developed sensor was able to discriminate between the two SNP probes. • Genomic DNA samples from fully genotyped volunteers were analyzed. • The developed analytical device is a promising alternative to genotyping methodologies. [ABSTRACT FROM AUTHOR]

Abstract: A glutathione-S-transferase (GST) based biosensor was developed to quantify the thiocarbamate herbicide molinate in environmental water. The biosensor construction was based on GST immobilization onto a glassy carbon electrode via aminosilane–glutaraldehyde covalent attachment. The principle supporting the use of this biosensor consists of the GST inhibition process promoted by molinate. Differential pulse voltammetry was used to obtain a calibration curve for molinate concentration, ranging from 0.19 to 7.9mgL−1 and presenting a detection limit of 0.064mgL−1. The developed biosensor is stable, and reusable during 15 days. The GST-based biosensor was successfully applied to quantify molinate in rice paddy field floodwater samples. The results achieved with the developed biosensor were in accordance with those obtained by high performance liquid chromatography. The proposed device is suitable for screening environmental water analysis and, since no sample preparation is required, it can be used in situ and in real-time measurements. [Copyright &y& Elsevier]

This study focused on the development of a sensitive enzymatic biosensor for the determination of pirimicarb pesticide based on the immobilization of laccase on composite carbon paste electrodes. Multi-walled carbon nanotubes (MWCNTs) paste electrode modified by dispersion of laccase (3%, w/w) within the optimum composite matrix (60:40%, w/w, MWCNTs and paraffin binder) showed the best performance, with excellent electron transfer kinetic and catalytic effects related to the redox process of the substrate 4-aminophenol. No metal or anti-interference membrane was added. Based on the inhibition of laccase activity, pirimicarb can be determined in the range 9.90×10−7 to 1.15×10−5 molL−1 using 4-aminophenol as substrate at the optimum pH of 5.0, with acceptable repeatability and reproducibility (relative standard deviations lower than 5%). The limit of detection obtained was 1.8×10−7 molL−1 (0.04mgkg−1 on a fresh weight vegetable basis). The high activity and catalytic properties of the laccase-based biosensor are retained during ca. one month. The optimized electroanalytical protocol coupled to the QuEChERS methodology were applied to tomato and lettuce samples spiked at three levels; recoveries ranging from 91.0±0.1% to 101.0±0.3% were attained. No significant effects in the pirimicarb electroanalysis were observed by the presence of pro-vitamin A, vitamins B1 and C, and glucose in the vegetable extracts. The proposed biosensor-based pesticide residue methodology fulfills all requisites to be used in implementation of food safety programs. [ABSTRACT FROM AUTHOR]