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Laser irradiation to induce networks of graphene‐based structures toward cost‐effective, flexible device fabrication is a highly pursued area, with applications in various polymeric substrates. This work reports the application of this approach toward commonly available, eco‐friendly, low‐cost substrates, namely, chromatographic and office papers. Through an appropriate chemical treatment with sodium tetraborate as a fire‐retardant agent, photothermal conversion to porous laser‐induced graphene (LIG) on paper is achieved. Raman peaks are identified, with I2D/IG and ID/IG peak ratios of 0.616 ± 0.095 and 1.281 ± 0.173, showing the formation of multilayered graphenic material, exhibiting sheet resistances as low as 56.0 Ω sq–1. Coplanar, LIG‐based, three‐electrode systems (working, counter and reference electrodes) are produced and characterized, showing high current Faradaic oxidation and reduction peaks, translating in high electrochemical active area, doubling the geometric area. Good electron transfer kinetics performed exclusively with on‐chip measurements are reached, with k0 values as high as 7.15 × 10–4 cm s–1. Proof‐of‐concept, amperometric, enzymatic glucose biosensors are developed, exhibiting good analytical performance in physiologically relevant glucose levels, with results pointing to the applicability of paper‐based LIG toward efficient, disposable electrochemical sensor development, increasing their sustainability and accessibility, while simplifying their production and reducing their cost.

This work describes a novel use for the polymeric film, poly(o-aminophenol) (PAP) that was made respon-sive to a specific protein. This was achieved through templated electropolymerization of aminophenol (AP) in the presence of protein. The procedure involved adsorbing prot ein on the electrode surface and thereafter electroploymerizing the aminophenol. Proteins embedded at the outer surface of the polymeric film were digested by proteinase K and then washed away thereby creating vacant sites. The capacity of the template film to specifically rebind protein was tested with myoglobin (Myo), a cardiac biomarker for ischemia. The films acted as biomimetic artificial antibodies and were produced on a gold (Au) screen printed electrode (SPE), as a step towards disposable sensors to enable point-of-care applications.Raman spectroscopy was used to follow the surface modification of the Au-SPE. The ability of the mate-rial to rebind Myo was measured by electrochemical techniques, namely electrochemical impedance spectroscopy (EIS) and square wave voltammetry (SWV). The d evices displayed linear responses to Myo in EIS and SWV assays down to 4.0 and 3.5 µg/mL, respectively, with detection limits of 1.5 and 0.8 µg/mL. Good selectivity was observed in the presence of troponin T (TnT) and creatine kinase (CKMB) in SWV assays, and accurate results were obtained in applications to spiked serum. The sensor described in this work is a potential tool for screening Myo in point-of-care due to the simplicity of fabrication, disposability, short time response, low cost, good sensitivit y and selectivity.

This work, describes for the first time, a simple biosensing design to yield an ultrasensitive electrochemical biosensor for a cancer biomarker detection, miRNA-155, with linear response down to the attomolar range. MiRNA-155 was selected for being overexpressed in breast cancer. The biosensor was assembled in two stages: (1) the immobilization of the anti-miRNA-155 that was thiol modified on an Au-screen printed electrode (Au-SPE), followed by (2) blocking the areas of non-specific binding with mercaptosuccinic acid. Atomic force microscopy (AFM) and electrochemical techniques including cyclic voltammetry (CV), impedance spectroscopy (EIS) and square wave voltammetry (SWV) confirmed the surface modification of these devices and their ability to hybridize successfully and stably with miRNA-155. The final biosensor provided a sensitive detection of miRNA-155 from 10 aM to 1.0 nM with a low detection limit (LOD) of 5.7 aM in real human serum samples. Good results were obtained in terms of selectivity towards breast cancer antigen CA-15.3 and bovine serum albumin (BSA). Raw fluid extracts from cell-lines of melanoma did not affect the biosensor response (no significant change of the blank), while raw extracts from breast cancer yielded a positive signal against miRNA-155. This simple and sensitive strategy is a promising alternative for simultaneous quantitative analysis of multiple miRNA in physiological fluids for biomedical research and point-of-care (POC) diagnosis.

A B S T R A C TThe purpose of the present work is to determine the antioxidant capacity (AC) of 27 commercial beers. The AC indicates the degree of protection of a certain organism against oxidative damage provoked by reactive oxygen and nitrogen species.Assays were carried out by the following methods: (i) total radical trapping antioxidant parameter (TRAP); (ii) trolox equivalent antioxidant capacity (TEAC); (iii) trolox equivalent antioxidant capacity (DPPH); (iv) ferric-ion reducing antioxidant parameter (FRAP); (v) cupric reducing antioxidant capacity (CUPRAC); (vi) oxygen radical absorbance capacity (ORAC). Ascorbic acid (AA), gallic acid (GA) and trolox (TR) were used as standards.All beers showed antioxidant power, but a wide range of ACs was observed. The effect of several factors upon these differences was studied. Statistical differences were found between ACs of beers of different colours. ORAC method provided always higher experimental ACs, of significant statistical differences to other assays.

No abstract

We report an optical sensor based on localized surface plasmon resonance (LSPR) to study small-molecule protein interaction combining high sensitivity refractive index sensing for quantitative binding information and subsequent conformation-sensitive plasmonactivated circular dichroism spectroscopy. The interaction of R-amylase and a small-size molecule (PGG, pentagalloyl glucose) was log concentration-dependent from 0.5 to 154 μM. In situ tests were additionally successfully applied to the analysis of real wine samples.These studies demonstrate that LSPR sensors to monitor small moleculeÀprotein interactions in real time and in situ, which is a great advance within technological platforms for drug discovery.

Expanding the single molecule detection, enabled by laserinduced graphene (LIG) technology, for portable and on-site analysis, a dual molecule system with a two-working-electrode architecture was developed for ascorbic acid (AA) and amoxicillin (AMOX) detection, which are currently used in aquaculture and persist as water contaminants. The biorecognition element of each target compound was a suitable molecularly imprinted polymer (MIP). The AMOX MIP was developed herein for the first time and assembled by electropolymerization of eriochrome black T (EBT). It showed a wide linear response from 50 nM to 100 μM, with a sensitivity of −13.32 μA/decade. Calibration curves revealed good squared correlation coefficients (R 2 > 0.99) with a limit of detection (LOD) of 11.98 nM. AA MIP was assembled according to a previous work reported in the literature, displaying a linear response from 1.5 to 4 mM and a sensitivity of 1.356 μA/decade. The developed dual-LIG device was further tested in real samples and successfully applied to the analysis of binary mixtures prepared in environmental water samples from a well. Overall, the proposed device allows in situ analysis of two different molecules and holds an exceptionally low-cost design when compared to competing architectures in the literature, and the fabrication method here employed offers the possibility of easily adjusting the desired architecture on demand.