Electroactive Molecularly Imprinted Polymer Nanoparticles (eMIPs) for Label-free Detection of Glucose: Toward Wearable Monitoring.

The diagnosis of diabetes mellitus (DM) affecting 537 million adults worldwide relies on invasive and costly enzymatic methods that have limited stability. Electroactive polypyrrole (PPy)-based molecularly imprinted polymer nanoparticles (eMIPs) have been developed that rival the affinity of enzymes whilst being low-cost, highly robust, and facile to produce. By drop-casting eMIPs onto low-cost disposable screen-printed electrodes (SPEs), sensors have been manufactured that can electrochemically detect glucose in a wide dynamic range (1 µm-10 mm) with a limit of detection (LOD) of 26 nm. The eMIPs sensors exhibit no cross reactivity to similar compounds and negligible glucose binding to non-imprinted polymeric nanoparticles (eNIPs). Measurements of serum samples of diabetic patients demonstrate excellent correlation (>0.93) between these eMIPs sensor and the current gold standard Roche blood analyzer test. Finally, the eMIPs sensors are highly durable and reproducible (storage >12 months), showcasing excellent robustness and thermal and chemical stability. Proof-of-application is provided via measuring glucose using these eMIPs sensor in a two-electrode configuration in spiked artificial interstitial fluid (AISF), highlighting its potential for non-invasive wearable monitoring. Due to the versatility of the eMIPs that can be adapted to virtually any target, this platform technology holds high promise for sustainable healthcare applications via providing rapid detection, low-cost, and inherent robustness.

Multiplex antibiotic susceptibility testing of urinary tract infections using an electrochemical lab-on-a-chip.

Urinary tract infections (UTIs) represent the most prevalent type of outpatient infection, with significant adverse health and economic burdens. Current culture-based antibiotic susceptibility testing can take up to 72 h resulting in ineffective prescription of broad-spectrum antibiotics, poor clinical outcomes and development of further antibiotic resistance. We report an electrochemical lab-on-a-chip (LOC) for testing samples against seven clinically-relevant antibiotics. The LOC contained eight chambers, each housing an antibiotic-loaded hydrogel (cephalexin, ceftriaxone, colistin, gentamicin, piperacillin, trimethoprim, vancomycin) or antibiotic-free control, alongside a resazurin bulk-modified screen-printed electrode for electrochemical detection of metabolically active bacteria using differential pulse voltammetry. Antibiotic susceptibility in simulated UTI samples or donated human urine with either Escherichia coli or Klebsiella pneumoniae could be established within 85 min. Incorporating electrochemical detection onto a LOC provides an inexpensive, simple method for the sensitive determination of antibiotic susceptibility that is significantly faster than using a culture-based approach.

Optimised graphite/carbon black loading of recycled PLA for the production of low-cost conductive filament and its application to the detection of ß-estradiol in environmental samples.

The production, optimisation, physicochemical, and electroanalytical characterisation of a low-cost electrically conductive additive manufacturing filament made with recycled poly(lactic acid) (rPLA), castor oil, carbon black, and graphite (CB-G/PLA) is reported. Through optimising the carbon black and graphite loading, the best ratio for conductivity, low material cost, and printability was found to be 60% carbon black to 40% graphite. The maximum composition within the rPLA with 10 wt% castor oil was found to be an overall nanocarbon loading of 35 wt% which produced a price of less than £0.01 per electrode whilst still offering excellent low-temperature flexibility and reproducible printing. The additive manufactured electrodes produced from this filament offered excellent electrochemical performance, with a heterogeneous electron (charge) transfer rate constant, k0 calculated to be (2.6 ± 0.1) × 10-3 cm s-1 compared to (0.46 ± 0.03) × 10-3 cm s-1 for the commercial PLA benchmark. The additive manufactured electrodes were applied to the determination of ß-estradiol, achieving a sensitivity of 400 nA µM-1, a limit of quantification of 70 nM, and a limit of detection of 21 nM, which compared excellently to other reports in the literature. The system was then applied to the detection of ß-estradiol within four real water samples, including tap, bottled, river, and lake water, where recoveries between 95 and 109% were obtained. Due to the ability to create high-performance filament at a low material cost (£0.06 per gram) and through the use of more sustainable materials such as recycled polymers, bio-based plasticisers, and naturally occurring graphite, additive manufacturing will have a permanent place within the electroanalysis arsenal in the future.

Multi-walled carbon nanotubes/carbon black/rPLA for high-performance conductive additive manufacturing filament and the simultaneous detection of acetaminophen and phenylephrine.

The combination of multi-walled carbon nanotubes (MWCNT) and carbon black (CB) is presented to produce a high-performance electrically conductive recycled additive manufacturing filament. The filament and subsequent additively manufactured electrodes were characterised by TGA, XPS, Raman, and SEM and showed excellent low-temperature flexibility. The MWCNT/CB filament exhibited an improved electrochemical performance compared to an identical in-house produced bespoke filament using only CB. A heterogeneous electrochemical rate constant, [Formula: see text] of 1.71 (± 0.19) × 10-3 cm s-1 was obtained, showing an almost six times improvement over the commonly used commercial conductive CB/PLA. The filament was successfully tested for the simultaneous determination of acetaminophen and phenylephrine, producing linear ranges of 5-60 and 5-200 µM, sensitivities of 0.05 µA µM-1 and 0.14 µA µM-1, and limits of detection of 0.04 µM and 0.38 µM, respectively. A print-at-home device is presented where a removable lid comprised of rPLA can be placed onto a drinking vessel and the working, counter, and reference components made from our bespoke MWCNT/CB filament. The print-at-home device was successfully used to determine both compounds within real pharmaceutical products, with recoveries between 87 and 120% over a range of three real samples. This work paves the way for fabricating new highly conductive filaments using a combination of carbon materials with different morphologies and physicochemical properties and their application to produce additively manufactured electrodes with greatly improved electrochemical performance.

Confined Element Distribution with Structure-Driven Energy Coupling for Enhanced Prussian Blue Analogue Cathode.

The structural failure of Na2Mn[Fe(CN)6] could not be alleviated with traditional modification strategies through the adjustable composition property of Prussian blue analogues (PBAs), considering that the accumulation and release of stress derived from the MnN6 octahedrons are unilaterally restrained. Herein, a novel application of adjustable composition property, through constructing a coordination competition relationship between chelators and [Fe(CN)6]4- to directionally tune the enrichment of elements, is proposed to restrain structural degradation and induce unconventional energy coupling phenomenon. The non-uniform distribution of elements at the M1 site of PBAs (NFM-PB) is manipulated by the sequentially precipitated Ni, Fe, and Mn according to the Irving-William order. Electrochemically active Fe is operated to accompany Mn, and zero-strain Ni is modulated to enrich at the surface, synergistically mitigating with the enrichment and release of stress and then significantly improving the structural stability. Furthermore, unconventional energy coupling effect, a fusion of the electrochemical behavior between FeLS and MnHS, is triggered by the confined element distribution, leading to the enhanced electrochemical stability and anti-polarization ability. Consequently, the NFM-PB demonstrates superior rate performance and cycling stability. These findings further exploit potentialities of the adjustable composition property and provide new insights into the component design engineering for advanced PBAs.

Mixed Graphite/Carbon Black Recycled PLA Conductive Additive Manufacturing Filament for the Electrochemical Detection of Oxalate.

Mixing of graphite and carbon black (CB) alongside recycled poly(lactic acid) and castor oil to create an electrically conductive additive manufacturing filament without the use of solvents is reported herein. The additively manufactured electrodes (AMEs) were electrochemically benchmarked against a commercial conductive filament and a bespoke filament utilizing only CB. The graphite/CB produced a heterogeneous rate constant, k0, of 1.26 (±0.23) × 10-3 cm s-1 and resistance of only 155 ± 15 Ω, compared to 0.30 (±0.03) × 10-3 cm s-1 and 768 ± 96 Ω for the commercial AME. Including graphite within the filament reduced the cost of printing each AME from £0.09, with the CB-only filament, to £0.05. The additive manufacturing filament was successfully used to create an electroanalytical sensing platform for the detection of oxalate within a linear range of 10-500 µM, achieving a sensitivity of 0.0196 µA/µM, LOD of 5.7 µM and LOQ of 18.8 µM was obtained. Additionally, the cell was tested toward the detection of oxalate within a spiked synthetic urine sample, obtaining recoveries of 104%. This work highlights how, using mixed material composites, excellent electrochemical performance can be obtained at a reduced material cost, while also greatly improving the sustainability of the system.

Electrochemical and thermal detection of allergenic substance lysozyme with molecularly imprinted nanoparticles.

Lysozyme (LYZ) is a small cationic protein which is widely used for medical treatment and in the food industry to act as an anti-bacterial agent; however, it can trigger allergic reactions. In this study, high-affinity molecularly imprinted nanoparticles (nanoMIPs) were synthesized for LYZ using a solid-phase approach. The produced nanoMIPs were electrografted to screen-printed electrodes (SPEs), disposable electrodes with high commercial potential, to enable electrochemical and thermal sensing. Electrochemical impedance spectroscopy (EIS) facilitated fast measurement (5-10 min) and is able to determine trace levels of LYZ (pM) and can discriminate between LYZ and structurally similar proteins (bovine serum albumin, troponin-I). In tandem, thermal analysis was conducted with the heat transfer method (HTM), which is based on monitoring the heat transfer resistance at the solid-liquid interface of the functionalized SPE. HTM as detection technique guaranteed trace-level (fM) detection of LYZ but needed longer analysis time compared to EIS measurement (30 min vs 5-10 min). Considering the versatility of the nanoMIPs which can be adapted to virtually any target of interest, these low-cost point-of-care sensors hold great potential to improve food safety.

Toward the rapid diagnosis of sepsis: dendritic copper nanostructure functionalized diazonium salt modified screen-printed graphene electrode for IL-6 detection.

Sepsis, an infectious disease affecting millions of people's health worldwide each year, calls for urgent attention to an improvement of analytical devices. Chemiluminescence immunoassay is a typical diagnostic method utilized to assess the risk development of sepsis. However, due to its high-cost, delayed, and complicated procedure, the practical utilization is therefore undoubtedly limited, especially for point-of-care test. Herein, we fabricated for the first time an immunosensor based on dendritic copper nanostructures (CuNSs) combined with 4-aminobenzoic acid (4-AB, the diazonium salt) as antibody linker modified on a screen-printed graphene electrode for the early detection of the sepsis biomarker interleukin-6 (IL-6). The electrode fabrication is made by electrodeposition, thus eliminating the multistep of nanomaterial synthesis and time wasting. The resulting dendritic CuNSs significantly increase the effective surface area (1.2 times) and the sensor's performance. The morphology of this combination was characterized using CV, EIS, SEM, EDX, and FTIR techniques. In the detection process, the appearance of IL-6 suppresses the current response of the redox probe indicator measured by differential pulse voltammetry due to the antibody-antigen complex. The subtraction of signal (ΔI) was interpreted as IL-6 concentration. This sensor exhibited a linear range from 0.05 to 500 pg mL-1 with low detection limit of 0.02 pg mL-1, proving a possibility for early sepsis screening. In addition, the established immunosensor can successfully quantify IL-6 in human serum sample, in which the results agreed well with those achieved using the standard approach, further showing high practical applicability of this developed immunosensor.

Exploring the Role of the Connection Length of Screen-Printed Electrodes towards the Hydrogen and Oxygen Evolution Reactions.

Zero-emission hydrogen and oxygen production are critical for the UK to reach net-zero greenhouse gasses by 2050. Electrochemical techniques such as water splitting (electrolysis) coupled with renewables energy can provide a unique approach to achieving zero emissions. Many studies exploring electrocatalysts need to "electrically wire" to their material to measure their performance, which usually involves immobilization upon a solid electrode. We demonstrate that significant differences in the calculated onset potential for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) can be observed when using screen-printed electrodes (SPEs) of differing connection lengths which are immobilized with a range of electrocatalysts. This can lead to false improvements in the reported performance of different electrocatalysts and poor comparisons between the literature. Through the use of electrochemical impedance spectroscopy, uncompensated ohmic resistance can be overcome providing more accurate Tafel analysis.

Additively Manufactured Rotating Disk Electrodes and Experimental Setup.

This manuscript details the first report of a complete additively manufactured rotating disk electrode setup, highlighting how high-performing equipment can be designed and produced rapidly using additive manufacturing without compromising on performance. The additively manufactured rotating disk electrode system was printed using a predominantly acrylonitrile butadiene styrene (ABS) based filament and used widely available, low-cost electronics, and simplified machined parts to create. The additively manufactured rotating disk electrode system costs less than 2% of a comparable commercial solution (£84.47 ($102.26) total). The rotating disk electrode is also additively manufactured using a carbon black/polylactic acid (CB/PLA) equivalent, developing a completely additively manufactured rotating disk electrode system. The electrochemical characterization of the additively manufactured rotating disk electrode setup was performed using hexaamineruthenium(III) chloride and compared favorably with a commercial glassy carbon electrode. Finally, this work shows how the additively manufactured rotating disk electrode experimental system and additive manufactured electrodes can be utilized for the electroanalytical determination of levodopa, a drug used in the treatment of Parkinson's disease, producing a limit of detection of 0.23 ± 0.03 µM. This work represents a step-change in how additive manufacturing can be used in research, allowing the production of high-end equipment for hugely reduced costs, without compromising on performance. Utilizing additive manufacturing in this way could greatly enhance the research possibilities for less well-funded research groups.

Exploration of defined 2-dimensional working electrode shapes through additive manufacturing.

In this work, the electrochemical response of different morphologies (shapes) and dimensions of additively manufactured (3D-printing) carbon black (CB)/poly-lactic acid (PLA) electrodes are reported. The working electrodes (WE) are printed using standard non-conductive PLA based filament for the housing and commercial Protopasta (carbon black/PLA) filament for the electrode and connection parts. Discs, squares, equilateral triangles and six-point stars with varying working electrode (WE) widths from 2 to 10 mm are evaluated herein towards the well-known near-ideal outer sphere redox probe hexaamineruthenium(III) chloride (RuHex). The results obtained show that triangular and squared electrodes exhibit a faster heterogeneous electron transfer (HET) rate constant (k°) than those of discs and stars, the latter being the slowest one. The results reported here also show a trend between the WE dimension and the reversibility of the electrochemical reaction, which decreases as the WE size increases. It is also observed that the ratio of the geometrical and electroactive area (%realarea) decreases as the overall WE size increases. On the other hand, these four WE shapes were applied toward the well-known and benchmarking detection of ascorbic acid (AA), uric acid (UA), ß-nicotinamide adenine dinucleotide (NADH) and dopamine (DA). Moreover, electroanalytical detection of real acetaminophen (ACOP) samples is also showcased. The different designs for the working electrode proposed in this manuscript are easily changed to any other desired shapes thanks to the additive manufacturing methodology, these four shapes being just an example of what additive manufacturing can offer to experimentalists and to electrochemists in particular. Additive manufacturing is shown here as a versatile and rapid prototyping tool for the production of novel electrochemical sensing platforms, with scope for this work to be able to impact a wide variety of electroanalytical applications.

Electroanalytical point-of-care detection of gold standard and emerging cardiac biomarkers for stratification and monitoring in intensive care medicine - a review.

Determination of specific cardiac biomarkers (CBs) during the diagnosis and management of adverse cardiovascular events such as acute myocardial infarction (AMI) has become commonplace in emergency department (ED), cardiology and many other ward settings. Cardiac troponins (cTnT and cTnI) and natriuretic peptides (BNP and NT-pro-BNP) are the preferred biomarkers in clinical practice for the diagnostic workup of AMI, acute coronary syndrome (ACS) and other types of myocardial ischaemia and heart failure (HF), while the roles and possible clinical applications of several other potential biomarkers continue to be evaluated and are the subject of several comprehensive reviews. The requirement for rapid, repeated testing of a small number of CBs in ED and cardiology patients has led to the development of point-of-care (PoC) technology to circumvent the need for remote and lengthy testing procedures in the hospital pathology laboratories. Electroanalytical sensing platforms have the potential to meet these requirements. This review aims firstly to reflect on the potential benefits of rapid CB testing in critically ill patients, a very distinct cohort of patients with deranged baseline levels of CBs. We summarise their source and clinical relevance and are the first to report the required analytical ranges for such technology to be of value in this patient cohort. Secondly, we review the current electrochemical approaches, including its sub-variants such as photoelectrochemical and electrochemiluminescence, for the determination  of important CBs highlighting the various strategies used, namely the use of micro- and nanomaterials, to maximise the sensitivities and selectivities of such approaches. Finally, we consider the challenges that must be overcome to allow for the commercialisation of this technology and transition into intensive care medicine.

Influence of design and material characteristics on 3D printed flow-cells for heat transfer-based analytical devices.

Redesigning 3D-printed flow cells is reported used for heat transfer based detection of biomolecules from a flow-through system to an addition-type measurement cell. The aim of this study is to assess the performance of this new measurement design and critically analyse the influence of material properties and 3D printing approach on thermal analysis. Particular attention is paid to reduce the time to stabilisation, the sample volume in order to make the technique suitable for clinical applications, and improving the sensitivity of the platform by decreasing the noise and interference of air bubbles. The three different approaches that were studied included a filament polylactic acid cell using only fused filament fabrication (FFF), a resin cell printed using stereolitography (SLA), and finally a design made of copper, which was manufactured by combining metal injection moulding (MIM) with fused filament fabrication (FFF). Computational fluid dynamic (CFD) modelling was undertaken using ANSYS Fluent V18.1 to provide insight into the flow of heat within the measurement cell, facilitating optimisation of the system and theoretical response speed.It was shown that the measurement cells using SLA had the lowest noise (~ 0.6%) and shortest measurement time (15 min), whereas measurement cells produced using other approaches had lower specificity or suffered from voiding issues. Finally, we assessed the potential of these new designs for detection of biomolecules and amoxicillin, a commonly used beta lactam antibiotic, to demonstrate the proof of concept. It can be concluded that the resin addition-type measurement cells produced with SLA are an interesting affordable alternative, which were able to detect amoxicillin with high sensitivity and have great promise for clinical applications due to the disposable nature of the measurement cells in addition to small sample volumes.

Adjusting the Connection Length of Additively Manufactured Electrodes Changes the Electrochemical and Electroanalytical Performance.

Changing the connection length of an additively manufactured electrode (AME) has a significant impact on the electrochemical and electroanalytical response of the system. In the literature, many electrochemical platforms have been produced using additive manufacturing with great variations in how the AME itself is described. It is seen that when measuring the near-ideal outer-sphere redox probe hexaamineruthenium (III) chloride (RuHex), decreasing the AME connection length enhances the heterogeneous electrochemical transfer (HET) rate constant (k0) for the system. At slow scan rates, there is a clear change in the peak-to-peak separation (ΔEp) observed in the RuHex voltammograms, with the ΔEp shifting from 118 ± 5 mV to 291 ± 27 mV for the 10 and 100 mm electrodes, respectively. For the electroanalytical determination of dopamine, no significant difference is noticed at low concentrations between 10- and 100-mm connection length AMEs. However, at concentrations of 1 mM dopamine, the peak oxidation is shifted to significantly higher potentials as the AME connection length is increased, with a shift of 150 mV measured. It is recommended that in future work, all AME dimensions, not just the working electrode head size, is reported along with the resistance measured through electrochemical impedance spectroscopy to allow for appropriate comparisons with other reports in the literature. To produce the best additively manufactured electrochemical systems in the future, researchers should endeavor to use the shortest AME connection lengths that are viable for their designs.

2D-Hexagonal Boron Nitride Screen-Printed Bulk-Modified Electrochemical Platforms Explored towards Oxygen Reduction Reactions.

A low-cost, scalable and reproducible approach for the mass production of screen-printed electrode (SPE) platforms that have varying percentage mass incorporations of 2D hexagonal boron nitride (2D-hBN) (2D-hBN/SPEs) is demonstrated herein. These novel 2D-hBN/SPEs are explored as a potential metal-free electrocatalysts towards oxygen reduction reactions (ORRs) within acidic media where their performance is evaluated. A 5% mass incorporation of 2D-hBN into the SPEs resulted in the most beneficial ORR catalysis, reducing the ORR onset potential by ca. 200 mV in comparison to bare/unmodified SPEs. Furthermore, an increase in the achievable current of 83% is also exhibited upon the utilisation of a 2D-hBN/SPE in comparison to its unmodified equivalent. The screen-printed fabrication approach replaces the less-reproducible and time-consuming drop-casting technique of 2D-hBN and provides an alternative approach for the large-scale manufacture of novel electrode platforms that can be utilised in a variety of applications.

Toward the Rapid Diagnosis of Sepsis: Detecting Interleukin-6 in Blood Plasma Using Functionalized Screen-Printed Electrodes with a Thermal Detection Methodology.

This paper reports the detection of the inflammatory and sepsis-related biomarker, interleukin-6 (IL-6), in human blood plasma using functionalized screen-printed electrodes (SPEs) in conjunction with a thermal detection methodology, termed heat-transfer method (HTM). SPEs are functionalized with antibodies specific for IL-6 through electrodeposition of a diazonium linking group and N'-ethylcarbodiimide hydrochloride (EDC) coupling, which was tracked through the use of cyclic voltammetry and Raman spectroscopy. The functionalized SPEs are mounted inside an additively manufactured flow cell and connected to the HTM device. We demonstrate the ability to detect IL-6 at clinically relevant concentrations in PBS buffer (pH = 7.4) with no significant interference from the similarly sized sepsis-related biomarker procalcitonin (PCT). The limit of detection (3σ) of the system is calculated to correspond to 3.4 ± 0.2 pg mL-1 with a working range spanning the physiologically relevant concentration levels in both healthy individuals and patients with sepsis, indicating the sensitivity of the sensor is suitable for the application. Further experiments helped provide a proof-of-application through the detection of IL-6 in blood plasma with no significant interference observed from PCT or the constituents of the medium. Due to the selectivity, sensitivity, straightforward operation, and low cost of production, this sensor platform has the potential for use as a traffic light sensor for the multidetection of inflammatory biomarkers for the diagnosis of sepsis and other conditions in which the rapid testing of blood biomarkers has vital clinical application.

Electrospun Nylon Fibers with Integrated Polypyrrole Molecularly Imprinted Polymers for the Detection of Glucose.

Electrospun nylon 6,6 fibers incorporating polypyrrole (PPy) molecular-imprinted polymers (MIPs) were produced for the selective detection of d-glucose using a thermal detection methodology. PPy MIPs were produced using a facile bulk synthesis approach and electrospun into intricate fibrous scaffolds giving a highly mass-producible sensing interface. The maximum incorporation of MIPs and greatest sensing performance was found to be 12.1 wt % in conjunction with the heat-transfer method (HTM), a low-cost and simple thermal detection method that measures changes in the thermal resistance at the solid-liquid interface. It is demonstrated that a 12.1% incorporation of MIPs into electrospun fibers produces the widest working linear range with a limit of detection of 0.10 ± 0.01 mM. There were no observed changes in the measured thermal resistance response to incubation with a series of structurally similar compounds, providing evidence toward the selectivity of the platform. Additionally, the sensing platform exhibited a linear working response to glucose samples in artificial sweat solutions in the biologically relevant range. This is the first report of the incorporation of MIPs into nylon 6,6 fibers for the detection of glucose and points toward the possibility of developing mass-producible electrospun fibers embedded with low-cost recognition elements of improved thermal and chemical stability for the application of wearable sensor technology.

Electrochemical Improvements Can Be Realized via Shortening the Length of Screen-Printed Electrochemical Platforms.

Screen-printed electrodes (SPEs) are ubiquitous within the field of electrochemistry and are commonplace within the arsenal of electrochemists. Their popularity stems from their reproducibility, versatility, and extremely low-cost production, allowing their utilization as single-shot electrodes and thus removing the need for tedious electrode pretreatments. Many SPE studies have explored changing the working electrode composition and/or size to benefit the researcher's specific applications. In this paper, we explore a critical parameter of SPEs that is often overlooked; namely, we explore changing the length of the SPE connections. We provide evidence of resistance changes through altering the connection length to the working electrode through theoretical calculations, multimeter measurements, and electrochemical impedance spectroscopy (EIS). We demonstrate that changing the physical length of SPE connections gives rise to more accurate heterogeneous electrode kinetics, which cannot be overcome simply through IR compensation. Significant improvements are observed when utilized as the basis of electrochemical sensing platforms for sodium nitrite, ß-nicotinamide adenine dinucleotide (NADH), and lead (II). This work has a significant impact upon the field of SPEs and highlights the need for researchers to characterize and define their specific electrode performance. Without such fundamental characterization as the length and resistance of the SPE used, direct comparisons between two different systems for similar applications are obsolete. We therefore suggest that, when using SPEs in the future, experimentalists report the length of the working electrode connection alongside the measured resistance (multimeter or EIS) to facilitate this standardization across the field.

Electroanalytical overview: the pungency of chile and chilli products determined via the sensing of capsaicinoids.

When you bite into a chile pepper or eat food containing chile (chilli), one might feel heat, or other associated feelings, some good such as the release of endorphins, and some bad. The heat, or pungency, and related feelings from eating chile peppers are the result of their chemical composition, i.e. the concentrations of capsaicinoids. The major components are capsaicin and dihydrocapsaicin, which occur in chiles in the ratio of 6 : 4. Other capsaicinoids occur in smaller concentrations and are known as the "minor" capsaicinoids. Wilbur L. Scoville in 1912 created an organoleptic test, now known as the Scoville scale, which asked a panel of tasters to state when an increasingly dilute solution of the chile pepper in alcohol no longer burned the mouth. Following the Scoville scale, a plethora of analytical techniques later followed. In this overview, we explore the endeavours directed to the development of electrochemical-based sensors for the determination of capsaicin and related compounds, starting from their use in hyphenated laboratory set-ups to their modern use as stand-alone electroanalytical sensors. The latter have the advantage of providing a rapid and sensitive methodology that has the potential to be translated in the field; future trends and issues to be overcome are consequently suggested.

Rapid antibiotic susceptibility testing using resazurin bulk modified screen-printed electrochemical sensing platforms.

Urinary tract infections (UTIs) are one of the most common types of bacterial infection. UTIs can be associated with multidrug resistant bacteria and current methods of determining an effective antibiotic for UTIs can take up to 48 hours, which increases the chances of a negative prognosis for the patient. In this paper we report for the first time, the fabrication of resazurin bulk modified screen-printed macroelectrodes (R-SPEs) demonstrating them to be effective platforms for the electrochemical detection of antibiotic susceptibility in complicated UTIs. Using differential pulse voltammetry (DPV), resazurin was able to be detected down to 15.6 µM. R-SPEs were utilised to conduct antibiotic susceptibility testing (AST) of E. coli (ATCC® 25922) to the antibiotic gentamicin sulphate using DPV to detect the relative concentrations of resazurin between antibiotic treated bacteria, and bacteria without antibiotic treatment. Using R-SPEs, antibiotic susceptibility was determined after a total elapsed time of 90 minutes including the inoculation of the artificial urine, preincubation and testing time. The use of electrochemistry as a phenotypic means of identifying an effective antibiotic to treat a complicated UTI offers a rapid and accurate alternative to culture based methods for AST with R-SPEs offering an inexpensive and simpler alternative to other AST methods utilising electrochemical based approaches.