Search

As one of the most popular beverages in the world, coffee is a rich source of non-enzymatic bioactive compounds with antioxidant capacity. In this study, twelve commercial coffee beverages found in local Portuguese markets were assessed to determine their total phenolic and flavonoid contents, as well as their antioxidant capacity, by conventional optical procedures, namely, ferric reducing antioxidant power and DPPH-radical scavenging assay, and non-conventional procedures such as a homemade DNA-based biosensor against two reactive radicals: HO• and H2O2. The innovative DNA-based biosensor comprised an adenine-rich oligonucleotide adsorbed onto a carbon paste electrode. This method detects the different peak intensities generated by square-wave voltammetry based on the partial damage to the adenine layer adsorbed on the electrode surface by the free radicals in the presence/absence of antioxidants. The DNA-based biosensor against H2O2 presented a higher DNA layer protection compared with HO• in the presence of the reference gallic acid. Additionally, the phenolic profiles of the twelve coffee samples were assessed by HPLC-DAD, and the main contributors to the exhibited antioxidant capacity properties were caffeine, and chlorogenic, protocatechuic, neochlorogenic and gallic acids. The DNA-based sensor used provides reliable and fast measurements of antioxidant capacity, and is also cheap and easy to construct. [ABSTRACT FROM AUTHOR]

Major depressive disorder is a widespread condition with antidepressants as the main pharmacological treatment. However, some patients experience concerning adverse reactions or have an inadequate response to treatment. Analytical chromatographic techniques, among other techniques, are valuable tools for investigating medication complications, including those associated with antidepressants. Nevertheless, there is a growing need to address the limitations associated with these techniques. In recent years, electrochemical (bio)sensors have garnered significant attention due to their lower cost, portability, and precision. Electrochemical (bio)sensors can be used for various applications related to depression, such as monitoring the levels of antidepressants in biological and in environmental samples. They can provide accurate and rapid results, which could facilitate personalized treatment and improve patient outcomes. This state-of-the-art literature review aims to explore the latest advancements in the electrochemical detection of antidepressants. The review focuses on two types of electrochemical sensors: Chemically modified sensors and enzyme-based biosensors. The referred papers are carefully categorized according to their respective sensor type. The review examines the differences between the two sensing methods, highlights their unique features and limitations, and provides an in-depth analysis of each sensor. [ABSTRACT FROM AUTHOR]

• Enzymatic bioelectrode characterized for energy generation and biosensing purposes. • Bilirubin oxidase immobilized on carbon paper using PBSE as bifunctional crosslinker. • Biobattery successfully applied in powering a digital watch for over 2 h. • Biosensor revealed high sensitivity (606 μA mM−1 cm−2) and low LOD (1.3 μM) for O 2. • Response maintained (88%) for 34 days through constant bioelectrode reutilization. Biological systems can be envisaged as energy-sustainable solutions for both microenergy production to power small electronics and sensing purposes. In the present work, an enzymatic bioelectrode was characterized as biocathode in the fabrication of a biobattery and as biosensor for dioxygen detection. Carbon fibre paper was selected as transducer given its unique tailoring and electrocatalytic characteristics, being modified with carbon nanotubes for subsequent attachment of bilirubin oxidase enzyme. The immobilization process was based on a simple but effective method using the crosslinker 1-pyrenebutanoic acid N-hydroxysuccinimide ester, which creates stable bonds by maintaining a good response (88%) for over 34 days. The biobattery, that consisted of a zinc anode coupled with the developed biocathode, produced an open circuit potential of 1.69 V and maximum power of 40 μW, being capable of powering a digital watch for over 2 h. When applied as a dioxygen biosensor, the biocathode revealed high sensitivity of 606 ± 22 μA mM−1 cm−2 and low limit of detection of 1.3 ± 0.2 μM in chronoamperometric measurements at +0.4 V. The application of bilirubin oxidase in the fabrication of biobatteries is scarcely studied even given its advantages over other dioxygen reduction enzymes. Likewise, the use of the remarkable features of CP in dioxygen biosensing is yet to be explored. Therefore, this work stands as an interesting opportunity in the development of relatively simple and affordable bioelectrodes viably intended for energy and biosensing applications. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • A self-powered biosensor is proposed based on a PQQGDH bioanode and BOx biocathode. • Graphite pencils modified with carbon nanotubes are used as transducers. • Efficient and simple enzymes immobilization using the bifunctional crosslinker PBSE. • A sensitivity of 8.08 μW cm−2 mM−1 and a LOD of 0.084 mM were achieved for glucose. • The biofuel cell has high stability by retaining 94% of response after 12 days. Biofuel cells are an interesting way of microenergy production that can be advantageously channeled for biosensing applications. In this study, a biofuel cell was developed and applied as a self-powered biosensor for glucose detection. Glucose oxidase was initially tested for the bioanode and, since no evidence of direct electron transfer was observed in the absence of the co-substrate, it was not further considered. The enzymes Pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQGDH) and Bilirubin oxidase (BOx) were immobilized on Pencil graphite electrodes (PGE), previously nanostructured with MWCNT, serving as bioanode and biocathode, respectively. The bifunctional crosslinker 1-pyrenebutanoic acid succinimidyl ester (PBSE) was used as a simple but efficient tethering agent, enabling the establishment of direct electron transfer events. Cyclic and linear sweep voltammetry, and amperometry were employed for individual characterization of bioanode and biocathode as biosensors for the respective enzymatic substrates. A mean sensitivity of 77.7 ± 5.9 μA cm−2 mM−1 was obtained for glucose with a Limit of detection (LOD) of 4.0 ± 2.2 μM, whereas in the detection of O 2 , the sensitivity and LOD achieved were 336 ± 22 μA cm−2 mM−1 and 3.2 ± 1.0 μM, respectively. Finally, the PQQGDH bioanode and BOx biocathode were conjugated into a biofuel cell and further characterized as a self-powered biosensor for glucose, exhibiting a linear range up to 1 mM, an excellent sensitivity of 8.08 μW cm−2 mM−1, a low LOD of 0.084 mM and long stability (94% of the original response after 12 days). Therefore, PGE transducers and PBSE are valuable strategies for the design of simple and efficient self-powered biosensors. [ABSTRACT FROM AUTHOR]

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]

[Display omitted] • A biosensor based on laccase from Trametes versicolor was developed for BPA detection. • A bioconjugate made by BMIMBF4-laccase-chitosan was optimized. • Laccase electrocatalytic activity and stability was maintained for more than 1 month. • Low LOD (8.4 ± 0.3 nM) and high sensitivity were attained. • The biosensor has high potential applicability for on-site analysis. Bisphenol A (BPA) is an endocrine disruptor compound that has been detected in aquatic ecosystems. In this work, the development of an electrochemical biosensor for BPA determination based on laccase from Trametes versicolor is reported. A bioconjugate was optimized to maximize the biosensor electrocatalytic activity and stability, which for the first time involved the synergistic effect of this specific enzyme (6.8 UmL−1), chitosan (5 mgmL−1) and the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate in an optimum 5:5:2 (v/v/v) proportion. This bioconjugate was deposited onto a screen-printed carbon electrode previously modified with multi-walled carbon nanotubes (MWCNTs). Nanostructuration with MWCNTs enlarged the electrocatalytic activity and surface area, thus improving the biosensor performance. The BPA electrochemical reaction follows an EC mechanism at the optimum pH value of 5.0. Linearity up to 12 µM, a sensitivity of (6.59 ± 0.04) × 10-2 μAμM−1 and a detection limit of 8.4 ± 0.3 nM were obtained coupled with high reproducibility (relative standard deviations lower than 6%) and stability (87% of the initial response after one month). The developed biosensor was employed to the analysis of BPA in river water displaying appropriate accuracy (94.6–97.9%) and repeatability (3.1 to 6% relative standard deviations) proving its high potential applicability for in situ environmental analysis. [ABSTRACT FROM AUTHOR]