Abstract: Cable bacteria are filamentous, multicellular microorganisms that display an exceptional form of biological electron transport across centimeter-scale distances. Currents are guided through a network of nickel-containing protein fibers within the cell envelope. Still, the mechanism of long-range conduction remains unresolved. Here, we characterize the conductance of the fiber network under dry and wet, physiologically relevant, conditions. Our data reveal that the fiber conductivity is high (median value: 27 S cm−1; range: 2 to 564 S cm−1), does not show any redox signature, has a low thermal activation energy (Ea = 69 ± 23 meV), and is not affected by humidity or the presence of ions. These features set the nickel-based conduction mechanism in cable bacteria apart from other known forms of biological electron transport. As such, conduction resembles that of an organic semi-metal with a high charge carrier density. Our observation that biochemistry can synthesize an organo-metal-like structure opens the way for novel bio-based electronic technologies.

Abstract: Photoelectrochemical detection of nucleic acid-based cancer biomarkers offers opportunities for highly sensitive, selective, and fast quantitative detection using low-cost measurement instruments. In order to establish itself as a standard method for identifying and quantifying nucleic acids, we have developed a multiplexing strategy using LED technology for photoelectrochemical detection in 96 samples simultaneously. A dedicated setup based on the 96-well plate configuration with a custom-made 96-well LED array was developed. Subsequently, a proof-of-concept study was performed for three miRNAs that are associated with prostate cancer, i.e., miRNA-141, miRNA-145, and miRNA-375. First, measurements with photosensitizer chlorin e6 and redox reporter hydroquinone free in solution proved the proper functioning of the multiplexed detection. Second, the photoelectrochemical detection of the three miRNAs at 24 nM levels was successfully demonstrated. Thereafter, linear calibration curves (R2 > 0.9 for all analytes) were made with plasma spiked with 8–500 pM miRNA. This work presents the first system for multiplexed high-throughput photoelectrochemical detection, allowing it potentially to become a cost-effective and faster alternative to RT-qPCR and gene sequencing techniques in the future.

Abstract: The growing non-medical use of benzodiazepines (BZs) has led to the emergence of counterfeit BZ pills and new psycho-active substances (NPS) in the BZ class on the illicit market. Comprehensive analytical methods for BZ identification are required to allow law enforcement, first aid responders and drug-checking services to analyze a variety of sample types and contents to make timely decisions on the spot. In this work, the electrochemical behavior of diazepam (DZ), clonazepam (CZ) and alprazolam (AP) is studied on graphite screen-printed electrodes, both with and without dissolved oxygen in the solution, to link their redox signals to their chemical structure. After elucidation of their reduction mechanisms using liquid chromatography coupled to highresolution mass spectrometry, three structural classes (Class 1, Class 2 and Class 3) were defined, each with different redox centers and electrochemical behavior. Subsequently, 22 confiscated pills containing 14 different BZs were correctly assigned to these three structural classes, with the deoxygenated conditions displaying the highest class selectivity. Finally, the three classes were successfully detected after being spiked into five alcoholic beverages in the context of drug-facilitated sexual assault. For analysis in red wine, which complicated the analysis by interfering with Class 1, a dual test strategy in pH 2 and pH 7 was proposed for accurate detection. Its rapid measurements, broad scope and lack of interference from diluents or colors makes this method a promising approach for aiding various services in combating problematic BZ use.

Abstract: Carbon-based screen-printed electrodes (SPEs) are extensively employed in electrochemistry due to their reproducibility, low-cost production, disposability and versatility. It is commonly accepted that batch to batch variations may occur due to variations in the ink formulation or the use of a different ink to print the electrodes. In this paper, three different commercial carbon-based inks (DuPont, Loctite and SunChemical) were used to manufacture SPEs, referred to respectively as Dup-SPE, Loc-SPE and Sun-SPE, using a semi-automated screen-printing technology. This study focuses on evaluating the quality, characteristics and electrochemical performance of the fabricated SPEs. Furthermore, the study aimed to investigate potential correlations between the ink composition and the nature of different target molecules, as well as their electroanalytical responses. Specifically, phenolic compounds and cocaine cutting agents are tested in alkaline conditions, while benzodiazepines and cephalosporine antibiotics are investigated in acidic media using square wave voltammetry (SWV). This aims to extract insights for the proper selection of inks and SPEs in both conditions. Additionally, a scan rate study of cephalosporine antibiotics using linear sweep voltammetry (LSV) is performed confirming the ion-exchange polymer layer on the electrode surface of Loc-SPE, which impact surface and electrochemical properties, leading to drawbacks in alkaline SWV sensing, but strategic benefits in reductive sensing resulting in an enhanced selective detection of specific targets. The insights on ink-specific influences on the surface and electrochemical properties of the SPEs obtained, may be useful for facilitating the electrode selection in diverse electrochemical applications, emphasizing the critical role of ink composition in achieving desired sensing capabilities.

Abstract: The pyroantimonate pigments Naples yellow and lead tin antimonate yellow are recognized as some of the most stable synthetic yellow pigments in the history of art. However, this exceptional lightfastness is in contrast with experimental evidence suggesting that this class of mixed oxides is of semiconducting nature. In this study the electronic structure and light-induced behavior of the lead pyroantimonate pigments were determined by means of a combined multifaceted analytical and computational approach (photoelectrochemical measurements, UV-vis diffuse reflectance spectroscopy, STEM-EDS, STEM-HAADF, and density functional theory calculations). The results demonstrate both the semiconducting nature and the lightfastness of these pigments. Poor optical absorption and minority carrier mobility are the main properties responsible for the observed stability. In addition, novel fundamental insights into the role played by Na atoms in the stabilization of the otherwise intrinsically unstable Pb2Sb2O7 pyrochlore were obtained.

Abstract: This work reports on a local induced near-surface pH effect (pHS), due to the presence of one analyte, leading to an influence or even suppression of redox signals of a second analyte present in solution. This concept and its impact on voltammetric sensing is illustrated by focusing on the detection of cocaine in the presence of the common adulterant benzocaine. An in-depth study on the occurring interference mechanism and why it occurs for benzocaine specifically and not for other adulterants was performed through the use of multiple electrochemical strategies. It was concluded that the potential shift and loss of intensity of the squarewave voltammetric cocaine signal in the presence of benzocaine was caused by a local pHS effect. A cathodic pretreatment strategy was developed to nonetheless allow accurate cocaine detection. The gathered insights are useful to explain unidentified phenomena involving compounds with properties similar to benzocaine in voltammetric electroanalysis.

Abstract: Wearable electrochemical sensors capable of noninvasive monitoring of chemical markers represent a rapidly emerging digital-health technology. Recent advances toward wearable continuous glucose monitoring (CGM) systems have ignited tremendous interest in expanding such sensor technology to other important fields. This article reviews for the first time wearable electrochemical sensors for monitoring therapeutic drugs and drugs of abuse. This rapidly emerging class of drug-sensing wearable devices addresses the growing demand for personalized medicine, toward improved therapeutic outcomes while minimizing the side effects of drugs and the related medical expenses. Continuous, noninvasive monitoring of therapeutic drugs within bodily fluids empowers clinicians and patients to correlate the pharmacokinetic properties with optimal outcomes by realizing patient-specific dose regulation and tracking dynamic changes in pharmacokinetics behavior while assuring the medication adherence of patients. Furthermore, wearable electrochemical drug monitoring devices can also serve as powerful screening tools in the hands of law enforcement agents to combat drug trafficking and support on-site forensic investigations. The review covers various wearable form factors developed for noninvasive monitoring of therapeutic drugs in different body fluids and toward on-site screening of drugs of abuse. The future prospects of such wearable drug monitoring devices are presented with the ultimate goals of introducing accurate real-time drug monitoring protocols and autonomous closed-loop platforms toward precise dose regulation and optimal therapeutic outcomes. Finally, current unmet challenges and existing gaps are discussed for motivating future technological innovations regarding personalized therapy. The current pace of developments and the tremendous market opportunities for such wearable drug monitoring platforms are expected to drive intense future research and
commercialization efforts.

Abstract: The illicit consumption of heroin is an increasing concern in our society. For this reason, rapid analytical methods to seize heroin samples in the field are of paramount importance to hinder drug trafficking, and thus prevent the availability of heroin in the drug market. The present work reports on the enriched electrochemical fingerprint of heroin, allowing its selective detection in street samples, based on the use of electrochemical pretreated screen printed electrodes (p-SPE). The voltammetric identification is built on two oxidation peaks of both heroin and its degradation product 6-monoacetylmorphine (6-MAM), generated in alkaline conditions. Interestingly, an anodic pretreatment of the screen printed electrodes (SPE) shifts the peak potential of paracetamol (the most encountered cutting agent in heroin seizures), allowing the detection of 6-MAM peak, overlapping with the paracetamol signal in the case of untreated SPE. Subsequently, the characterization of the p-SPE with scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy, Raman and Fourier transform infrared (FTIR) spectroscopy is provided to demonstrate local changes on the surface of the electrode. From an analytical perspective, p-SPE provide higher sensitivity (0.019 μA μM-1), excellent reproducibility (6-MAM, RSD = 2.85%, and heroin RSD = 0.91%, n = 5) and lower limits of detection (LOD) (5.2 μM) in comparison to untreated SPE. The proposed protocol which integrates a tailor-made script is interrogated against common cutting agents, and finally, validated with the screening of 14 street samples, also analyzed by standard methods. Besides, a comparison with portable spectroscopic techniques on the confiscated samples shows the better performance of the electrochemical strategy. Overall, this sensing approach offers promising results for the rapid on-site profiling of suspicious heroin samples, also in the presence of paracetamol.

Abstract: Recent studies are concisely reviewed, in which X-ray beams of (sub)micrometre to millimetre dimensions have been used for non-destructive analysis and characterization of pigments, minute paint samples, and/or entire paintings from the seventeenth to the early twentieth century painters. The overview presented encompasses the use of laboratory and synchrotron radiation-based instrumentation and deals with the use of several variants of X-ray fluorescence (XRF) as a method of elemental analysis and imaging, as well as with the combined use of X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). Microscopic XRF is a variant of the method that is well suited to visualize the elemental distribution of key elements, mostly metals, present in paint multi-layers, on the length scale from 1 to 100 μm inside micro-samples taken from paintings. In the context of the characterization of artists pigments subjected to natural degradation, the use of methods limited to elemental analysis or imaging usually is not sufficient to elucidate the chemical transformations that have taken place. However, at synchrotron facilities, combinations of μ-XRF with related methods such as μ-XAS and μ-XRD have proven themselves to be very suitable for such studies. Their use is often combined with microscopic Fourier transform infra-red spectroscopy and/or Raman microscopy since these methods deliver complementary information of high molecular specificity at more or less the same length scale as the X-ray microprobe techniques. Since microscopic investigation of a relatively limited number of minute paint samples, taken from a given work of art, may not yield representative information about the entire artefact, several methods for macroscopic, non-invasive imaging have recently been developed. Those based on XRF scanning and full-field hyperspectral imaging appear very promising; some recent published results are discussed.