In order to increase the lifetime of polymer electrolytemembrane(PEM) fuel cells (PEMFCs) and water electrolyzers (PEMWEs), understandinglocal degeneration processes in membrane electrode assemblies (MEAs)is crucial. By a combination of scanning electrochemical microscopy(SECM) with a flow-through diffusion cell (DiffC-DC-SECM) and ferrocyanideand protons as redox mediators, a spatially resolved analytical methodwas developed that can differentiate between different functionaland structural degeneration phenomena in the aging process of a membrane.An SECM scan at cathodic potential detects the diffusion of protonsthrough the membrane and thus its through-plane proton conductivity,while a second SECM scan at anodic potential visualizes the diffusionof the iron complex through the membrane, thus perforating structuraldamage such as cracks and holes. The method was successfully validatedfor the spatially resolved differentiation of membrane damage in pristinePEMs and catalyst-coated membranes (CCMs) with artificial holes, chemicallyaged CCMs, and MEAs in fully assembled operational PEMFCs aged byan open-circuit voltage membrane accelerated stress test. DiffC-DC-SECMthus provides a powerful technique with high local resolution formembrane integrity testing under realistic operation conditions todevelop long-term durable materials for PEMFCs and PEMWEs.

The contaminationof natural basins by agricultural orindustrialactivities, and the growing need for potable water due to climatechanges accelerate the drive to find versatile, fast, practical, andeasy-to-use methods for water analysis. A potentially versatile techniquesuitable for water analysis is Raman Spectroscopy (RS). Featured bygood resolution but low sensitivity, RS detects molecular vibrationalmodes of an analyte in water. Nitrate is an indicator of chemicaland/or biological pollution, it displays Raman active vibrationalmodes affected by the interaction with other systems in solution,allowing a wide range of applications. Concerning Nitrate analysisin water, a general introduction to the Raman effect and the basicinstrumentation were herein discussed. RS is a potential solutionto wastewater analysis. This review first reports the theoreticalbackground of the technique and its basic working principles, then,the state-of-the-art scientific contributions related to Nitrate detectionare investigated with a particular interest in the instrumental setupand the chemometric techniques employed to improve its sensitivity.In the studies hereby considered, instrumental setup (for example,laser frequency, laser power, acquisition times) and different technicalsolutions (for example, micro- versus macro-Raman instruments) toincrease the technique’s sensitivity on Nitrate detection aredescribed. Concisely, the use of deep-UV lasers, optically activeSurface-Enhanced Raman Spectroscopy (SERS) or Fiber-Enhanced Ramanspectroscopy (FERS) equipment, coupled with instrumental settings,i.e. acquisition time, variable temperature of acquisition, use ofspecial sampling apparatus (cuvettes or immersion probes), or withion exchange resins for analyte enrichment, have been reported. Remarkably,examples of large data correction of unwanted fluorescence by mathematicalprocessing or chemical quenching were reported too, suggesting solutionsfor the Raman analysis of wastewaters. Finally, a short digressionon Machine Learning (ML) applied to RS is proposed, showing the promisingresults reported in other fields. Data-driven methods could be a solutionto improve the low sensitivity of the RS for Nitrate detection. Hence,an approach of ML methods for the typical RS spectra processing (spikeremoval, baseline correction, fluorescence curve elimination, instrumentalnoise correction) was hereby mentioned, suggesting an improvementin the detection capability of Nitrate ion in water.

A surface-acoustic-wave-driven microactuator that allows separation of the piezoelectric substrate and chip has been fabricated and characterized. By simply placing the microactuator on a disposable chip, the microactuator did not contaminate the substrate with any reagent and could easily transport droplets and powders. The microactuator also allowed mixing of heterophase materials, such as powder and droplets, in a microfluidic well to increase their chemical reaction. This microactuator will enable significant cost savings and automation of plants and research facilities.

Phosphorylation and glycosylation are two important proteinpost-transitionalmodifications (PTMs). However, quantification of these PTMs is challengingdue to the lack of protein or peptide standards. In this study, weintroduced a novel approach using coulometric mass spectrometry (CMS)for absolute quantitation of phosphopeptides and glycopeptides withoutusing standards. First, phosphorylated tyrosine peptides such as TSTEPQpYQPGENLand RRLIEDAEpYAARG can be converted into electrochemically activetyrosine peptides via enzymatic phosphate removal using alkaline phosphataseprior to CMS quantitation. Accurate quantitation was obtained withsmall quantitation errors (0.3–6.6%). Alternatively, for electrochemicallyinactive phosphopeptides and glycopeptides, derivatization of theirN-termini with an NHS ester reagent, 2,5-dioxo-1-pyrrolidinyl 3,4-dihydroxybenzenepropanoate (DPDP), was conducted to introduce one electroactive catecholtag, allowing the DPDP-derivatized peptides to be quantified by CMS.This strategy was first validated using peptides RGD, GGYR, phosphopeptideRRApSVA, and glycopeptide NYIVGQPSS­(β-GlcNAc)­TGNL–OH,and successful quantification was achieved with quantification errorsless than 6%. Taking one step further, we applied this approach toquantify glycopeptides generated from tryptic digestion of the NISTmonoclonal antibody (mAb). Through hydrophilic interaction liquidchromatography column separation, five N297 glycopeptides were successfullyderivatized, separated, and quantified by CMS without the use of standards.Due to the biological significance of PTMs, this study for quantifyingpeptides carrying PTMs would have a high potential for quantitativeproteomics and biological research.

Screen-printed electrodes (SPEs) are an innovative technologyinelectrochemical sensors, offering advantages such as easy fabrication,large-scale production, low cost, and potential for miniaturization.These electrodes can be disposable and customized for various applications.Due to these advantages, SPEs are gaining attention in fields suchas medicine and pharmacy. In this study, an electrochemical sensorwas developed through screen-printing, using new conductive ink, compoundedwith carbon black, Chinese shellac, and acetone. The device was characterizedby different approaches to analyze its characteristics, includingscanning electron microscopy, Fourier transform infrared spectroscopy,X-ray diffraction, thermogravimetry, and contact angle. Also, theelectrochemical characterizations were performed by using cyclic voltammetryand impedance spectroscopy. The sensor was employed to detect melatonin,a sleep-regulating hormone, and, under optimized parameters, the analyticalcurve by differential pulse voltammetry exhibited a linear range from1.0 to 100 μmol L–1, with a limit of detectionof 0.1 μmol L–1. The device was applied tosynthetic urine samples using the addition and recovery method, yieldingrecovery values from 86.7 to 110%. The results indicate that the conductiveink is suitable for manufacturing printed electrodes, and the deviceproved promising for melatonin detection.

Tafel analysis iswidely used to characterize electrode kinetics.The technique has found use in electrochemistry, catalysis, materials,and corrosion research. Accurate Tafel analysis is especially criticalin comparison of electrocatalysts. However, classical Tafel analysis(CTA) relies on the user’s subjective selection of a linearrange in the Tafel plot; dependent on linear regression of the user-selectedrange, kinetic parameters can vary by orders of magnitude. As useof CTA in the literature grows, a need is identified for more reliable,user-independent Tafel analysis. Here, Taffit, an algorithm constructedin the widely available Microsoft Excel, is presented. Taffit generatesa Tafel plot from linear sweep voltammetric data and determines theexchange current density j0, charge transfercoefficient α, and Tafel slopes by closest statistical fit.Comparisons between Taffit and CTA are made for the hydrogen evolutionreaction (HER, 2H+ + 2e ⇌ H2) on glassy carbon (GC) and platinum electrodes. Taffit findslog j0 values of −7.2 and −3.9for GC and Pt under H2 at pH 0, as measured without resistivecompensation. This is the first report of j0 for HER on GC. Because algorithmic fitting in the low overpotentialregion uses both cathodic and anodic branches of the Tafel plot, Taffithas greater precision than CTA. Agreement is also shown between literaturevalues reported by CTA and those obtained by Taffit for HER on metalphosphide and selenide electrocatalysts. The Taffit algorithm substantiallyreduces subjectivity to improve the accuracy and precision of Tafelanalysis.

The development of enzyme-based bioelectronic devices,includingbiosensors and biomimetic systems, has significantly advanced withthe introduction of innovative materials such as hydrogels, deep eutecticsolvents (DES), and ionic liquids (ILs). These materials offer uniqueadvantages in enhancing biodevice performance, particularly in enzymestabilization, biocompatibility, and electrochemical sensitivity.Hydrogels, known for their high water content and flexibility, providean ideal matrix for enzyme immobilization in biological applicationsbut are limited by low ionic conductivity. DES, with their green chemistrycredentials and ability to stabilize enzymes under harsh conditions,show great promise, although scalability and performance in complexbiological systems remain challenges. ILs, with their superior electrontransfer capabilities, enable high sensitivity in electrochemicalbiosensors, though issues of viscosity and potential toxicity needto be addressed for broader biomedical use. This review provides acomparative analysis of the roles of these materials in enzyme-basedbiosensors and bioelectronics, including microbatteries and bioelectrosynthesis,highlighting their respective strengths, limitations, and future opportunities.The integration of these materials holds great potential for advancingbioelectronics technologies, with applications spanning medical diagnostics,environmental monitoring, and industrial processes. By addressingcurrent challenges and optimizing these materials for large-scaleuse, the future of enzyme-based devices could see significant improvementsin efficiency, sensitivity, and sustainability.

In the United States, ∼30,000 units of red bloodcells (RBCs)are transfused daily to patient recipients. These RBCs are storedin one of multiple variations of media known as additive solutions,all of which contain glucose at concentrations well above physiologicallevels. Recently, strategies for storage of the RBCs in normoglycemicversions of the additive solutions whose glucose levels are maintainedwith periodic boluses of glucose were developed, resulting in benefitsto the stored RBCs. Here, we describe a system capable of semiautonomous,Wi-Fi-enabled control of glucose delivery using a microperistalticpump for maintenance of physiological concentrations of glucose ina closed RBC storage system. The RBCs stored in these normoglycemicconditions demonstrated reduced lysis and reduced hemoglobin glycationin comparison to those of the currently used hyperglycemic additivesolutions. Furthermore, a novel single cell technique using pressure-inducedconductivity mapping showed an improved Young’s modulus forthose RBCs stored in normoglycemic solutions. These quantitative measurementsof the RBCs’ chemical and physical properties coincide withimprovements in cell functionality. Specifically, determinations ofRBC-derived ATP using a 3D-printed microfluidic device show an increasedrelease of ATP for RBCs stored in normoglycemic solutions in comparisonto hyperglycemic storage, even for cells that were 2 weeks past astorage expiration of 42 days.

The drying treatment of dissolved organic matter (DOM)eluate wasoften used to prepare DOM solutions for chemodiversity analysis usingFourier transform ion cyclotron resonance mass spectrometry. However,the effects of drying treatment on the chemodiversity of DOM havenot been thoroughly investigated. In this study, vacuum freeze-dryingand vacuum centrifuge drying resulted in approximately half and 10%loss of DOM mass loss, respectively. Although the overall values ofmolecular functional diversity indices and main DOM fractions wereinsignificantly affected by both drying treatments, the Cl-containingmolecules (Cl-OM) and saturated compounds were significantly affectedby the drying treatments, particularly for vacuum centrifuge drying.Therefore, the DOM eluate was strongly recommended for the measurementof Fourier transform ion cyclotron resonance mass spectrometry onlyafter dilution by desired folds when the minor DOM fractions, suchas Cl-OM and saturated compounds, were of interest. The findings ofthis study have provided valuable evidence of sample preparationfor the accurate elucidation of DOM chemodiversity from various sources.