Towards voltammetric point of care detection of leucovorin.

Current healthcare trends have seen an increased emphasis on the move towards personalised precision medicine to tailor treatments to the individual and their response to diseases and disease therapies. This highlighting a transition from traditional "one size fits all" to a more nuanced approach. Despite advancements in fundamental knowledge to facilitate personalised prevision approaches, lack of resources to implement such plans remains one of the largest hurdles to overcome. Monitoring of drug therapies is one key aspect that could aid in the evolution of precision medicine alongside the development of drugs and targeted treatment systems. This contribution illustrates the potential of square wave voltammetry (SWV) as a proof-of-concept for monitoring of circulating blood concentrations of treatment therapies within artificial urine, using leucovorin calcium (LV) as a model cancer therapy drug. A low cost, easy-to-use and portable sensor has been developed and successfully employed for the detection of LV over the linear range 0.5-30 µM which represents the therapeutically relevant concentrations for LV within artificial urine without any prior sample preparation required with a limit of detection of 2.63 µM and initial investigations into saliva and serum as biological matrices. The developed sensor describe herein exhibits a proof-of-concept for the engagement of such electrochemical sensors as point-of-care devices, where the sensors ease of use and removal of time-consuming and complex sample preparation methods will ultimately increase its usability by physicians, widening the avenues where electrochemical sensors could be employed.

Datura quids at Pinwheel Cave, California, provide unambiguous confirmation of the ingestion of hallucinogens at a rock art site.

While debates have raged over the relationship between trance and rock art, unambiguous evidence of the consumption of hallucinogens has not been reported from any rock art site in the world. A painting possibly representing the flowers of Datura on the ceiling of a Californian rock art site called Pinwheel Cave was discovered alongside fibrous quids in the same ceiling. Even though Native Californians are historically documented to have used Datura to enter trance states, little evidence exists to associate it with rock art. A multianalytical approach to the rock art, the quids, and the archaeological context of this site was undertaken. Liquid chromatography-mass spectrometry (LC-MS) results found hallucinogenic alkaloids scopolamine and atropine in the quids, while scanning electron microscope analysis confirms most to be Datura wrightii Three-dimensional (3D) analyses of the quids indicate the quids were likely masticated and thus consumed in the cave under the paintings. Archaeological evidence and chronological dating shows the site was well utilized as a temporary residence for a range of activities from Late Prehistory through Colonial Periods. This indicates that Datura was ingested in the cave and that the rock painting represents the plant itself, serving to codify communal rituals involving this powerful entheogen. These results confirm the use of hallucinogens at a rock art site while calling into question previous assumptions concerning trance and rock art imagery.

Electrochemiluminescent screening for methamphetamine metabolites.

The abuse of methamphetamine (MA) is to date detected and subsequently verified through the monitoring of MA and its metabolites within biological specimens. Current approaches require complex sample purification strategies alongside significant analysis time. Given the high prevalence of MA within the global drug market, there remains a need for rapid, portable and alternative screening approaches appropriate for direct detection within biological matrices for employment across the forensic and clinical environments. This contribution illustrates the use of an electrochemiluminescence (ECL) strategy for the screening of MA, amphetamine (AMP) and para hydroxy-methamphetamine (pOH-MA) for such applications. The sensing system showed ideal analytical performance with linear ranges at forensically relevant concentrations of 0.1 µM to 0.5 mM for MA, 10 µM to 1 mM AMP and 10 µM to 5 mM for pOH-MA, and superb detection limits of 74.6 nM, 6 µM and 82. µM for MA, AMP and pOH-MA respectively. Furthermore, the sensor was successful in the detection of MA, AMP and pOH-AMP within human pooled serum, artificial urine and saliva, without any prior purification strategies. Here a portable ECL sensor is detailed for the successful employment of the direct screening of these amphetamine type substances and their corresponding metabolites at clinically and forensically relevant concentrations within a range of biological matrices. This approach successfully represents a strong proof-of-concept, for a novel, simple and rapid screening method with significant potential for high-throughput screening of biological samples for drug metabolites, widening the avenues where ECL sensors could be employed.

Tale of Two Alkaloids: pH-Controlled Electrochemiluminescence for Differentiation of Structurally Similar Compounds.

Electrochemiluminescence (ECL) has increased in popularity as a result of its inherent advantages, including but not limited to portability, simplicity of use, and low reagent consumption. However, its significant advantages are often over shadowed as a result of its limited specificity. ECL emissions are intrinsically broad and lack the definition of other available analytical techniques. Furthermore, species with similar functional groups have almost identical electrochemical behavior and thus typically emit within approximately the same potential region. Within this contribution we have demonstrate the use of pH controlled ECL to prove the presence of two individual species within a mixed sample. Analysis at a single pH would not provide this information. We have illustrated the potential of this methodology to quantify scopolamine alongside sister tropane alkaloid atropine, a known ECL interferent. Previously the two alkaloids could not be distinguished from one another using a single technique which did not involve a separation strategy. pH controlled ECL is a simple approach to improve the specificity of a basic [Ru(bpy)3]2+ film based sensor. By exploiting molecular characteristics, such as pKa, we have been able to fine-tune our methodology to facilitate identification of analytes previously exhibiting indistinguishable ECL emission. Thus, by improving specificity, while maintaining operational simplicity and inexpensive design, we have been able to highlight the potential power of ECL for identification of structurally similar compounds. Further improvements of specificity, such as demonstrated within this contribution, will only further future applications of ECL sensors across a range of different fields.

Electrochemiluminescent sensors as a screening strategy for psychoactive substances within biological matrices.

With the rapid growth and appearance of novel psychoactive substances (NPS) onto the global drug market, the need for alternative screening methodologies for implementation within clinical environments is substantial. The immunoassay methods currently in use are inadequate for this new drug trend with the potential for misdiagnosis and subsequent administration of incorrect patient treatment increased. This contribution illustrates a strong proof-of-concept for the use of electrochemiluminescence (ECL) as a screening methodology for NPS within biological fluids, using the hallucinogen scopolamine as a model compound. A low cost, easy-to-use and portable sensor has been developed and successfully employed for the detection of scopolamine at clinically relevant concentrations within a variety of biological matrices, including human pooled serum, urine, artificial saliva and sweat, without any prior sample preparation required. Moreover, assessment of the sensor's potential as a point-of-care wearable device was performed with sample collection from the surface of skin, demonstrating its capability for the qualitative identification of scopolamine despite collection of only minimal volumes off the skins surface. The developed sensor described herein exhibits a strong proof-of-concept for the employment of such ECL sensors as point-of-care devices, where the sensors ease of use and removal of time-consuming and complex sample preparation methods will ultimately increase its usability by physicians, widening the avenues where ECL sensors could be employed.

Utilization of an Electrochemiluminescence Sensor for Atropine Determination in Complex Matrices.

A major challenge within forensic science is the development of accurate and robust methodologies that can be utilized on-site for detection at crime scenes and can be used for analyzing multiple sample types. The recent expansion of electrochemical sensors to tackle this hurdle requires sensors that can undergo analysis without any pretreatment. Given the vast array of samples that are submitted for forensic analysis, this can pose a major challenge for all electrochemical sensors, including electrochemiluminescent (ECL)-based sensors. Within this contribution, we demonstrate the capacity for an ECL-based sensor to address this challenge and it is potential to detect and quantify atropine from a wide range of samples directly from herbal material to spiked solutions. This portable platform demonstrates satisfactory analytical parameters with linearity across a concentration range of 0.75 to 100 µM, reproducibility of 3.0%, repeatability of 9.2%, and a detection limit of ∼0.75 µM. The sensor displays good selectivity toward alkaloid species and, in particular, the hallucinogenic tropane alkaloid functionality within complex matrices. This portable sensor provides rapid detection alongside low cost and operational simplicity, thus, providing a basis for the exploitation of ECL-based sensors within the forensic arena.

Cathodic Quantum Dot Facilitated Electrochemiluminescent Detection in Blood.

The expansion of electrochemical sensors to biomedical applications at point of care requires these sensors to undergo analysis without any pretreatment or extraction. This poses a major challenge for all electrochemical sensors including electrochemiluminescent (ECL)-based sensors. ECL offers many advantages for biomedical applications; however, obtaining results from complex matrixes has proven to be a large hurdle for the application of ECL sensors within this field. This work demonstrates the potential of cathodic ECL to detect and quantify homocysteine (Hcy) with a 0.1 nM limit of detection, which is associated with hyperhomocysteinemia, in blood. This near-infrared quantum dot (NIR QD)-based ECL sensor displays good linearity allowing for rapid detection and providing a basis for exploitation of ECL-based sensors for biomedical diagnostics utilizing Hcy as a model cathodic coreactant. This work will lay the foundations for future developments in biosensing and imaging fields and stands as an initial proof of concept for the utilization of cathodic ECL technologies for biomedical applications once the limits of detection within clinically relevant levels has been achieved. This work illustrates the potential of cathodic ECL sensors, using Hcy as a model complex, for the detection of biomolecules.

A proof of principal study on the use of direct PCR of semen and spermatozoa and development of a differential isolation protocol for use in cases of alleged sexual assault.

Sexual assault samples are some of the most common samples encountered in forensic analysis. These samples can require a significant time investment due to differential extraction processes. We report on the first record of successful direct amplification of semen for STR analysis. Neat seminal fluid, dilutions ranging from 1:5 to 1:160 and GEDNAP samples were successfully amplified using a direct method. A mild differential isolation technique to enrich spermatozoa was developed and successfully implemented to separate and directly amplify a mixture of semen and female epithelial cells. Aliquots of samples subjected to the differential isolation protocol were stained with Haemotoxylin and Eosin for sperm scoring. Samples stained after PCR showed a complete lack of intact spermatozoa demonstrating that the cells are lysed during the PCR process. This paper demonstrates the potential to incorporate direct PCR in cases of sexual assault to more rapidly obtain results and achieve a higher sensitivity.

Optimising electrogenerated chemiluminescence of quantum dots via co-reactant selection.

We demonstrate that for quantum dot (QD) based electrochemiluminescence (ECL), the commonly used co-reactant does not perform as effectively as potassium persulfate. By exploiting this small change in co-reactant, ECL intensity can be enhanced dramatically in a cathodic-based ECL system. However, TPA remains the preferential co-reactant-based system for anodic ECL. This phenomenon can be rationalised through the relative energy-level profiles of the QD to the co-reactant in conjunction with the applied potential range. This work highlights the importance of understanding the co-reactant pathway for optimising the application of ECL to bioanalytical analysis, in particular for near-infrared (NIR) QDs which can be utilised for analysis in blood. Graphical Abstract Optimising ECL Production Through Careful Selection of Co-Reactions Based on Energetics Involved.

Whole Blood Electrochemiluminescent Detection of Dopamine.

Direct detection of medically relevant biomarkers in whole blood without the need for pretreatment or extraction is a great challenge for biomedical analysis and diagnosis. Electrochemical techniques, such as electrochemiluminescence (ECL), are promising tools for this area of analysis. ECL offers high sensitivities together with the ability to obtain time and spacial control over the process. This work exploits these features together with the low background signals obtained from ECL detection to clearly identify and quantify dopamine in whole blood with relative standard deviations lower than 5% (n = 5). This near-infrared quantum dot based ECL sensor displayed a linear response over the range 3.7 ≤ [dopamine] ≤ 450 µM, allowing the rapid detection of dopamine and providing a platform for future development. Significantly, the near-infrared quantum dots exhibited excellent penetrability through biological samples such as whole blood, and show the ECL detection of dopamine in whole blood for the first time. This will likely be at the forefront of development in biosensing and imaging fields in the foreseeable future.

Analytical applications of nanomaterials in electrogenerated chemiluminescence.

This critical review covers the use of carbon nanomaterials (single-wall carbon nanotubes, multi-wall carbon nanotubes, graphene, and carbon quantum dots), semiconductor quantum dots, and composite materials based on the combination of the aforementioned materials, for analytical applications using electrogenerated chemiluminescence. The recent discovery of graphene and related materials, with their optical and electrochemical properties, has made possible new uses of such materials in electrogenerated chemiluminescence for biomedical diagnostic applications. In electrogenerated chemiluminescence, also known as electrochemiluminescence (ECL), electrochemically generated intermediates undergo highly exergonic reactions, producing electronically excited states that emit light. These electron-transfer reactions are sufficiently exergonic to enable the excited states of luminophores, including metal complexes, quantum dots and carbon nanocrystals, to be generated without photoexcitation. In particular, this review focuses on some of the most advanced and recent developments (especially during the last five years, 2010-2014) related to the use of these novel materials and their composites, with particular emphasis on their use in medical diagnostics as ECL immunosensors.

Insights into electrochemiluminescent enhancement through electrode surface modification.

The electrochemiluminescent (ECL) properties of a luminescent metal centre, [Ru(bpy)(3)](2+), can be significantly modulated through its electronic interaction with neighbouring centres and the polymer backbone used to confine it on an electrode surface. From the perspective of ECL based sensing devices, an increase in the ECL efficiency of a metallopolymer film can result in enhanced sensor sensitivity and selectivity. This work probes the ECL properties of both conjugated, [Ru(bpy)(2)(PPyBBIM)(10)](2+), and non-conjugated, [Ru(bpy)(2)(PVP)(10)](2+), ruthenium based metallopolymer films based on a well documented reaction with sodium oxalate, where bpy is 2,2'-bipyridyl, PPYBBIM is poly[2-(2-pyridyl)-bibenzimidazole] and PVP is poly(4-vinylpyridine). Through a combination of ground state electrochemical studies and ECL measurements, the ECL efficiency for each film is determined. This study reveals that despite a dramatic influence in charge transfer rates between metal centres, as observed for the conducting polymer, mediated through the conducting polymer backbone, a corresponding increase in ECL efficiency is not always observed. The degree of communication between the adjacent excited state metal centres are an important consideration for ECL enhancement however self quenching, luminophore distribution and film porosity must also be considered.

Evolution of nanomaterial Electrochemiluminescence luminophores towards biocompatible materials.

Electrochemiluminescence (ECL) is a powerful electrochemical technique for the detection and quantification of molecules, both synthetic and biological in origin. Traditional ECL luminophores are based on organic or organometallic compounds, however nanoparticle-based materials offer the benefits of tuneable wavelengths and narrow emission profiles. Materials based on cadmium have been the most extensively studied for ECL nanoparticles to date. Cadmium based nanoparticles exhibit high levels of toxicity thereby impacting their suitability for mass produced sensing applications. As such, alternative materials with reduced toxicities are required. This review focuses on the innovations and applications of low toxicity semi-conductor quantum dots (SCQDs) utilised as ECL luminophores within biosensors. These materials include silver, copper, zinc, tin, silicon and germanium. This contribution presents an evaluative overview of these materials for use as ECL luminophores in terms of toxicity, tunability of emission, potential for amplification, and water dispersibility. Capacity for functionalisation and multiplexing potential are also explored.

A comprehensive chromatographic comparison of amphetamine and methylamphetamine extracted from river water using molecular imprinted polymers and without the need for sample derivatization.

This work explores the differences between two GCMS instruments for the determination of amphetamine and methylamphetamine extracted from water samples (ultra pure water and river water) without the necessity for derivatization. The instruments contained different generations of gas chromatograph and mass selective detector components and revealed significantly different results when presented with the same samples. The extraction methodology also compared two SPE systems. The extraction efficiency of commercially available molecular imprinted polymers as a sorbent in SPE was compared with commonly used hydrophilic balance sorbent. Molecular imprinted polymers provided excellent recoveries (81 ± 2% and 108 ± 3% at 30 µg L(-1), and 94 ± 2% and 94 ± 2% at 200 µg L(-1) for amphetamine and methylamphetamine, respectively). The best LOD obtained was sufficient for the determination of both drugs extracted from river water (0.029 ± 0.003 and 0.015 ± 0.004 µg L(-1) for amphetamine and methylamphetamine, respectively). These were comparable to literature values obtained through conventional extraction and analysis using LC-MS/MS but had the advantage of being achieved using an underivatized GCMS method.

Electrocatalytic enhancement of [Ru(bpy)3]2+ electrochemiluminescence for gemcitabine detection toward precision measurement via gold nanoparticle addition.

With a rise in the development and subsequent employment of precision medicine, their lies an immediate necessity for the development of technology to enable the implementation of such treatment plans into the healthcare environment. Electrochemistry stands to offer one of the most viable techniques for such technologies given its success within current medical devices. One electrochemical technique, electrochemiluminescence (ECL), warrants investigation. Previously we have determined the inability to reliably detect cancer therapy gemcitabine via traditional ruthenium based ECL. Here we demonstrate how the addition of gold nanoparticles into the ECL film can promote GMB detection via enhanced electrocatalytic oxidation, generating the required ECL radicals. Via this approach we have been able to improve the ECL signal intensity 60-fold and achieve detection down to 6.25 µM across a linear range of 6.25-50 µM. Which lies within the therapeutically relevant range. This approach has successfully addressed the prior limitations encountered for the employment of traditional ruthenium based ECL for substance identification, where species exhibit limited electro-activity and suffer from electrochemically induced side reactions.

Electrochemiluminescence within veterinary Science: A review.

Veterinary science or veterinary medicine is a diverse and significant field. Concerned not only with the diagnosis and treatment of domestic animals and livestock, but it also places focus upon zoonotic diseases, the development and effectiveness of potential vaccines and the possibility of transmission of veterinary medication or viruses into animal food products. Electrochemiluminescence (ECL) is a powerful analytical technique, which despite its significant intrinsic benefits has not seen enormous adoption into the wider analytical chemical community. In contrast, the veterinary science sector has reaped the merit of ECL as far back as the late 90's and continue to benefit from development of the technique a further three decades later. ECL offers the superb sensitivity, low running costs, rapid results and high reliability required within the veterinary science sector, as such its employment in this area shouldn't be surprising. To this end this article aims to summarise the standing of ECL within the veterinary science field, in an attempt increase the awareness of its successful employment within this area to the electro-analytical and wider analytical chemistry communities. Where it is hope veterinary science will gain recognition as possible end user targets for academic and industrial electrochemical researchers.

A multiswitchable poly(terthiophene) bearing a spiropyran functionality: understanding photo- and electrochemical control.

An electroactive nitrospiropyran-substituted polyterthiophene, poly(2-(3,3''-dimethylindoline-6'-nitrobenzospiropyranyl)ethyl 4,4''-didecyloxy-2,2':5',2''-terthiophene-3'-acetate), has been synthesized for the first time. The spiropyran, incorporated into the polymer backbone by covalent attachment to the alkoxyterthiophene monomer units, leads to multiple colored states as a result of both photochemical and electrochemical isomerization of the spiropyran moiety to merocyanine forms as well as electrochemical oxidation of the polyterthiophene backbone and the merocyanine substituents. While electrochemical polymerization of the terthiophene monomer can take place without oxidation of the spiropyran, increasing the oxidation potential leads to complex electrochemistry that clearly involves this substituent. To understand this complex behavior, the first detailed electrochemical study of the oxidation of the precursor spiropyran, 1-(2-hydroxyethyl)-3,3-dimethylindoline-6'-nitrobenzospiropyran, was undertaken, showing that, in solution, an irreversible electrochemical oxidation of the spiropyran occurs leading to reversible redox behavior of at least two merocyanine isomers. With these insights, an extensive electrochemical and spectroelectrochemical study of the nitrospiropyran-substituted polyterthiophene films reveals an initial irreversible electrochemical oxidative ring-opening of the spiropyran to oxidized merocyanine. Subsequent reduction and cyclic voltammetry of the resulting nitromerocyanine-substituted polyterthiophene film gives rise to the formation of both merocyanine π-dimers or oligomers and π-radical cation dimers, between polymer chains. Although merocyanine formation is not electrochemically reversible, the spiropyran can be photochemically regenerated, through irradiation with visible light. Subsequent electrochemical oxidation of the nitrospiropyran-substituted polymer reduces the efficiency of the spiropyran to merocyanine isomerization, providing electrochemical control over the polymer properties. SEM and AFM images support the conclusion that the bulky spiropyran substituent is electrochemically isomerized to the planar merocyanine moiety, affording a smoother polymer film. The conductivity of the freestanding polymer film was found to be 0.4 S cm(-1).

Ground and excited state communication within a ruthenium containing benzimidazole metallopolymer.

Emission spectroscopy and electrochemistry has been used to probe the electronic communication between adjacent metal centres and the conjugated backbone within a family of imidazole based metallopolymers, [Ru(bpy)(2)(PPyBBIM)(n)](2+), in the ground and excited states, bpy is 2,2'-bipyridyl, PPyBBIM is poly[2-(2-pyridyl)-bibenzimidazole] and n = 3, 10 or 20. Electronic communication in the excited state is not efficient and upon optical excitation dual emission is observed, i.e., both the polymer backbone and the metal centres emit. Coupling the ruthenium moiety to the imidazole backbone results in a red shift of approximately 50 nm in the emission spectrum. Luminescent lifetimes of up to 120 ns were also recorded. Cyclic voltammetry was also utilized to illustrate the distance dependence of the electron hopping rates between adjacent metal centres with ground state communication reduced by up to an order of magnitude compared to previously reported results when the metal to backbone ratio was not altered. D(CT) and D(e) values of up to 3.96 × 10(-10) and 5.32 × 10(-10) cm(2) S(-1) were observed with corresponding conductivity values of up to 2.34 × 10(-8) S cm(-1).

Electrochemical monitoring of alcohol in sweat.

Rapid, periodic monitoring and detection of ethanol (EtOH) after consumption via a non-invasive measurement has been an area of increased research in recent years. Current point-of-care or on-site detection strategies rely on single use sensors which are inadequate for monitoring during a longer period. A low cost, portable and novel approach is developed here for real-time monitoring over several days utilising electrochemical techniques. The sensor shows oxidation of the ethanol in phosphate buffer and artificial sweat using the amperometric response from the application of +0.9 V to the polyaniline modified screen printed electrode using 1 mM EtOH as the averaged amount of EtOH eliminated in sweat after the consumption of one alcoholic beverage. Our enzyme based electrochemical sensor exhibits a qualitative assessment of the presence of EtOH in small volumes (≤40 µL) of 0.1 M sodium bicarbonate and subsequently artificial sweat, with 50 measurements taken daily over 11 days. While quantitative information is not obtained, the sensor system exhibits excellent stability after 3 months' dried storage in this complex biological matrix in an oxygen free cabinet. This addresses one of the key challenges for enzyme based electrochemical sensors, namely, the ability for real-time monitoring in complex biological matrices. The qualitative response illustrates the potential for this sensor to be exploited by non-experts which suggests the promise for their wider application in next-generation wearable electronics necessary for alcohol monitoring.

Development of an Electrochemical CCL17/TARC Biosensor toward Rapid Triage and Monitoring of Classic Hodgkin Lymphoma.

A point-of-care blood test for the detection of an emerging biomarker, CCL17/TARC, could prove transformative for the clinical management of classic Hodgkin lymphoma (cHL). Primary care diagnosis is challenging due to nonspecific clinical presentation and lack of a diagnostic test, leading to significant diagnostic delays. Treatment monitoring encounters false-positive and negative results, leading to avoidable chemotherapy toxicity, or undertreatment, impacting patient morbidity and mortality. Here, we present an amperometric CCL17/TARC immunosensor, based on the utilization of a thiolated heterobifunctional cross-linker and sandwich antibody assay, to facilitate novel primary care triage and chemotherapy monitoring strategies for cHL. The immunosensor shows excellent analytical performance for clinical testing; linearity (R2 = 0.986), detection limit (194 pg/mL), and lower and upper limits of quantitation (387-50 000 pg/mL). The biosensor differentiated all 42 newly diagnosed cHL patients from healthy volunteers, based on serum CCL17/TARC concentration, using blood samples collected prior to treatment intervention. The immunosensor also discriminated between paired blood samples of all seven cHL patients, respectively, collected prior to treatment and during chemotherapy, attributed to the decrease in serum CCL17/TARC concentration following chemotherapy response. Overall, we have shown, for the first time, the potential of an electrochemical CCL17/TARC biosensor for primary care triage and chemotherapy monitoring for cHL, which would have positive clinical and psychosocial implications for patients, while streamlining current healthcare pathways.