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Multiplexed analysis in medical diagnostics is widely accepted as a more thorough and complete method compared to single-analyte detection. While analytical methods like polymerase chain reaction and enzyme-linked immunosorbent assay (ELISA) exist for multiplexed detection of biomarkers, they remain time-consuming and expensive. Lateral flow assays (LFAs) are an attractive option for point-of-care testing, and examples of multiplexed LFAs exist. However, these devices are limited by spatial resolution of test lines, large sample volume requirements, cross-reactivity, and poor sensitivity. Recent work has developed capillary-flow microfluidic ELISA platforms as a more sensitive alternative to LFAs; however, multiplexed detection on these types of devices has yet to be demonstrated. In the aftermath of the initial SARS-CoV-2 pandemic, the need for rapid, sensitive point-of-care devices has become ever clearer. Moving forward, devices that can distinguish between diseases with similar presenting symptoms would be the ideal home diagnostic. Here, the first example of a multiplexed capillary-flow immunoassay device for the simultaneous detection of multiple biomarkers is reported. From a single sample addition step, the reagents and washing steps required for two simultaneous ELISAs are delivered to spatially separated test strips. Visual results can be obtained in <15 min, and images captured with a smartphone can be analyzed for quantitative data. This device was used to distinguish between and quantify H1N1 hemagglutinin (HA) and SARS-CoV-2 nucleocapsid protein (N-protein). Using this device, analytical detection limits of 840 and 133 pg/mL were obtained for hemagglutinin and nucleocapsid protein, respectively. The presence of one target in the device did not increase the signal on the other test line, indicating no cross-reactivity between the assays. Additionally, simultaneous detection of both N-protein and HA was performed as well as simultaneous detection of N-protein and human C-reactive protein (CRP). Elevated levels of CRP in a patient infected with SARS-CoV-2 have been shown to correlate with more severe outcomes and a greater risk of death as well. To further expand on the simultaneous detection of two biomarkers, CRP and N-protein were detected simultaneously, and the presence of SARS-CoV-2 N-protein did not interfere with the detection of CRP when both targets were present in the sample.
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Hemaglutininas , Vírus da Influenza A Subtipo H1N1 , Humanos , Imunoensaio/métodos , SARS-CoV-2 , Proteína C-Reativa/análise , Biomarcadores/análise , Proteínas do NucleocapsídeoRESUMO
There have been significant advances in the formulation and stabilization of proteins in the liquid state over the past years since our previous review. Our mechanistic understanding of protein-excipient interactions has increased, allowing one to develop formulations in a more rational fashion. The field has moved towards more complex and challenging formulations, such as high concentration formulations to allow for subcutaneous administration and co-formulation. While much of the published work has focused on mAbs, the principles appear to apply to any therapeutic protein, although mAbs clearly have some distinctive features. In this review, we first discuss chemical degradation reactions. This is followed by a section on physical instability issues. Then, more specific topics are addressed: instability induced by interactions with interfaces, predictive methods for physical stability and interplay between chemical and physical instability. The final parts are devoted to discussions how all the above impacts (co-)formulation strategies, in particular for high protein concentration solutions.'
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Estabilidade de Medicamentos , Estabilidade Proteica , Proteínas , Humanos , Proteínas/química , Excipientes/química , Composição de Medicamentos/métodos , Química Farmacêutica/métodos , Animais , Anticorpos Monoclonais/químicaRESUMO
Integrating electrochemistry into capillary-flow driven immunoassay devices provides unique opportunities for quantitative point-of-care testing. Although custom electrodes can be inexpensive and are tunable, they require skilled fabrication. Here, we report the incorporation of a commercial electrode into a capillary-flow driven immunoassay (iceCaDI) device for a single end-user step sandwich electrochemical enzyme-linked immunosorbent assay (ELISA). The iceCaDI device is a pump-free portable microfluidic device with an integrated commercial screen-printed electrode and flow driven by capillary action. The iceCaDI device is composed of alternating polyester transparency film and double-sided adhesive film layers that are patterned with a laser cutter. This platform was designed to address known limitations of laminated device fabrication methods and operation. First, we developed a foldable laminated device fabrication using hinges for easy assembly and precise alignment. Second, reagent dispersing was achieved by incorporating a 1 mm wide arrow-shaped notch in the middle of the channel that trapped an air bubble and formed a baffle that facilitated reagent spreading to cover the detection area. Third, small vent holes were added to the top layer of the channels to prevent air bubbles from blocking flow. Finally, we fabricated a CRP immunosensor with a detection range of 0.625 to 10.0 µg mL-1 as a proof-of-concept to demonstrate an automatically driven sandwich electrochemical ELISA using the iceCaDI device. Three concentrations of CRP were successfully measured under flow conditions within 8 min. Our proposed device is a promising approach and a step forward in the development of point-of-care (POC) devices for techniques that traditionally require multiple user steps.
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Técnicas Biossensoriais , Imunoensaio/métodos , Ensaio de Imunoadsorção Enzimática , Microfluídica , Eletrodos , Técnicas Eletroquímicas/métodos , Dispositivos Lab-On-A-ChipRESUMO
Laser-induced graphene (LIG) electrodes have become popular for electrochemical sensor fabrication due to their simplicity for batch production without the use of reagents. The high surface area and favorable electrocatalytic properties also enable the design of small electrochemical devices while retaining the desired electrochemical performance. In this work, we systematically investigated the effect of LIG working electrode size, from 0.8 mm to 4.0 mm diameter, on their electrochemical properties, since it has been widely assumed that the electrochemistry of LIG electrodes is independent of size above the microelectrode size regime. The background and faradaic current from cyclic voltammetry (CV) of an outer-sphere redox probe [Ru(NH3)6]3+ showed that smaller LIG electrodes had a higher electrode roughness factor and electroactive surface ratio than those of the larger electrodes. Moreover, CV of the surface-sensitive redox probes [Fe(CN)6]3- and dopamine revealed that smaller electrodes exhibited better electrocatalytic properties, with enhanced electron transfer kinetics. Scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy showed that the physical and chemical surface structure were different at the electrode center versus the edges, so the electrochemical properties of the smaller electrodes were improved by having rougher surface and more density of the graphitic edge planes, and more oxide-containing groups, leading to better electrochemistry. The difference could be explained by the different photothermal reaction time from the laser scribing process that causes different stable carbon morphology to form on the polymer surface. Our results give a new insight on relationships between surface structure and electrochemistry of LIG electrodes and are useful for designing miniaturized electrochemical devices.
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Human exposure to heavy metals is a concerning global problem because of its detrimental effect on our health and ecosystem. Assessing the levels of these metals is cost- and labor-intensive and nonuser friendly because current analysis approaches typically rely on heavy instrumentations like inductively coupled plasma-mass spectrometry, which is only possible in centralized labs. Hence, simple economical detection methods are in high demand in developing countries and areas with insufficient infrastructure, professional experts, and appropriate environmental treatment. Several microfluidic paper-based analytical devices have been reported as promising alternatives to conventional testing methods for on-site heavy metal detection. Paper-based microfluidics are advantageous because of their simple fabrication, biodegradability, low cost, and ability to operate without pumps. However, typical assay times for current platforms are slow, and they typically rely on pipetting a fixed volume into the assay cards. This adds complexity in actual field scenarios. Here, we report a novel, inexpensive, and straightforward capillary-driven microfluidic device combined with paper for rapid and user-friendly detection of Ni(II), Cu(II), and Fe(III) in water. A colorimetric approach was adopted to quantify these metals. The device was able to produce a homogeneous color signal within 8 s of sample insertion. The limit of detection and limit of quantification were calculated to be 2 and 6.67 ppm for nickel, 0.3 and 1 ppm for Cu, and 1.1 and 3.67 ppm for Fe, respectively. The majority (>90%) of the collected samples showed recovery in the 80-110% range with acceptable accuracy and precision (<15% RSD) for a colorimetric device. This technique can be beneficial for rapidly assessing heavy metal exposure in drinking and surface water at drastically reduced assay time and is the first example of capillary flow-driven microfluidic devices as a transport medium for heavy metal detection.
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Metais Pesados , Microfluídica , Humanos , Água , Ecossistema , Compostos Férricos , Papel , Metais Pesados/análiseRESUMO
Rapid species radiations provide insight into the process of speciation and diversification. The radiation of Chrysoperla carnea-group lacewings seems to be driven, at least in part, by their species-specific pre-mating vibrational duets. We associated genetic markers from across the genome with courtship song period in the offspring of a laboratory cross between Chrysoperla plorabunda and Chrysoperla adamsi, two species primarily differentiated by their mating songs. Two genomic regions were strongly associated with the song period phenotype. Large regions of chromosomes one and two were associated with song phenotype, as fewer recombination events occurred on these chromosomes relative to the other autosomes. Candidate genes were identified by functional annotation of proteins from the C. carnea reference genome. The majority of genes that are associated with vibrational courtship signals in other insects were found within QTL for lacewing song phenotype. Together these findings suggest that decreased recombination may be acting to keep together loci important to reproductive isolation between these species. Using wild-caught individuals from both species, we identified signals of genomic divergence across the genome. We identified several candidate genes both in song-associated regions and near divergence outliers including nonA, fruitless, paralytic, period, and doublesex. Together these findings bring us one step closer to identifying the genomic basis of a mating song trait critical to the maintenance of species boundaries in green lacewings.
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Genômica , Insetos , Animais , Insetos/genética , ReproduçãoRESUMO
Microfluidic paper-based analytical devices (µPADs) have garnered significant interest as a promising analytical platform in the past decade. Compared with traditional microfluidics, µPADs present unique advantages, such as easy fabrication using established patterning methods, economical cost, ability to drive and manipulate flow without equipment, and capability of storing reagents for various applications. This Review aims to provide a comprehensive review of the field, highlighting fabrication methods available to date with their respective advantages and drawbacks, device designs and modifications to accommodate different assay needs, detection strategies, and the growing applications of µPADs. Finally, we discuss how the field needs to continue moving forward to realize its full potential.
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Técnicas Analíticas Microfluídicas , Microfluídica , Bioensaio , Desenho de Equipamento , Dispositivos Lab-On-A-Chip , PapelRESUMO
Thermoplastic carbon electrodes (TPEs) are an alternative form of carbon composite electrodes that have shown excellent electrochemical performance with applications in biological sensing. However, little has been done to apply TPEs to environmental sensing, specifically heavy metal analysis. The work here focuses on lead analysis and based on their electrochemical properties, TPEs are expected to outperform other carbon composite materials; however, despite testing multiple formulations, TPEs showed inferior performance. Detailed electrode characterization was conducted to examine the cause for poor lead sensing behavior. X-Ray photoelectron spectroscopy (XPS) was used to analyze the surface functional groups, indicating that acidic and alkaline functional groups impact lead electrodeposition. Further, scanning electron microscopy (SEM) and electrochemical characterization demonstrated that both the binder and graphite can influence the surface morphology, electroactive area, and electron kinetics.
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The potential reach of point-of-care (POC) diagnostics into daily routines for exposure to reactive oxygen species (ROS) and Cu in aerosolized particulate matter (PM) demands that microfluidic paper-based analytical devices (µPADs) take into consideration the simple detection of these toxic PM components. Here, we propose µPADs with a dual-detection system for simultaneous ROS and Cu(II) detection. For colorimetric ROS detection, the glutathione (GSH) assay with a folding design to delay the reaction yielded complete ROS and GSH oxidation, and improved homogeneity of color development relative to using the lateral flow pattern. For electrochemical Cu(II) determination, 1,10-phenanthroline/Nafion modified graphene screen-printed electrodes showed ability to detect Cu(II) down to pg level being low enough to be applied to PM analysis. No intra- and inter-interference affecting both systems were found. The proposed µPADs obtained LODs for 1,4-naphthoquinone (1,4-NQ), used as the ROS representative, and Cu(II) of 8.3 ng and 3.6 pg, respectively and linear working ranges of 20 to 500 ng for ROS and 1 × 10-2 to 2 × 102 ng for Cu(II). Recovery of the method was between 81.4 and 108.3% for ROS and 80.5-105.3% for Cu(II). Finally, the sensors were utilized for simultaneous ROS and Cu(II) determination in PM samples and the results statistically agreed with those using the conventional methods at 95% confidence.
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Cobre , Microfluídica , Espécies Reativas de Oxigênio , Material Particulado , Aerossóis , Estresse OxidativoRESUMO
A significant bottleneck exists for mass-production of ion-selective electrodes despite recent developments in manufacturing technologies. Here, we present a fully-automated system for large-scale production of ISEs. Three materials, including polyvinyl chloride, polyethylene terephthalate and polyimide, were used as substrates for fabricating ion-selective electrodes (ISEs) using stencil printing, screen-printing and laser engraving, respectively. We compared sensitivities of the ISEs to determine the best material for the fabrication process of the ISEs. The electrode surfaces were modified with various carbon nanomaterials including multi-walled carbon nanotubes, graphene, carbon black, and their mixed suspensions as the intermediate layer to enhance sensitivities of the electrodes. An automated 3D-printed robot was used for the drop-cast procedure during ISE fabrication to eliminate manual steps. The sensor array was optimized, and the detection limits were 10-5 M, 10-5 M and 10-4 M for detection of K+, Na+ and Ca2+ ions, respectively. The sensor array integrated with a portable wireless potentiometer was used to detect K+, Na+ and Ca2+ in real urine and simulated sweat samples and results obtained were in agreement with ICP-OES with good recoveries. The developed sensing platform offers low-cost detection of electrolytes for point-of-care applications.
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Líquidos Corporais , Nanotubos de Carbono , Eletrodos Seletivos de Íons , Smartphone , ÍonsRESUMO
Tonic immobility is a passive antipredator strategy employed late in the predation sequence that may decrease individual mortality in prey animals. Here, we investigate how energetic state and genetic predisposition influence antipredator decision-making in green lacewing larvae, Chrysoperla plorabunda (Fitch), using simulated predatory encounters. We demonstrate that tonic immobility is a plastic response influenced by energetic resource limitation. Larvae exposed to 1 or 2 days of food deprivation initiate tonic immobility more often and with less physical provocation than individuals fed ad libitum. Recently molted individuals exposed to food deprivation, the individuals most energetically challenged, engage in tonic immobility at a higher rate than any other group. We also find that variation in antipredator strategy between individuals is partly the result of within-population genetic variation. We estimate the propensity to enter tonic immobility to have a broad-sense heritability of 0.502. Taken together our results suggest that larval lacewings under energetic stress are more likely to engage in tonic immobility. Yet, energetic state does not explain all within-population variation, as individuals can have a genetic predisposition for tonic immobility.
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Holometábolos , Insetos , Animais , Larva/genética , Insetos/fisiologia , Predisposição Genética para Doença , Comportamento PredatórioRESUMO
It has been shown that short-chain fatty acids (SCFAs) produced by the gut microbiome are of importance to host tissue health; however, measuring such compounds in biological samples is often limited to using hours to days old fecal and blood plasma samples. Organ-on-a-chip models have been created to simplify the complexity but struggle to reproduce the full biology of the gut specifically. We recently reported a tissue-in-a-chip gut model that incorporates gut explanted tissue into a microfluidic device. The system maintains a biologically relevant oxygen gradient and tissue ex vivo for days at a time, but minimal characterization of biological activity was reported. Herein, we use 1H-NMR to analyze the SCFA content of tissue media effluents from gut explants cultured in the recently developed microfluidic organotypic device (MOD). 1H-NMR can identify key SCFAs in the complex samples with minimal sample preparation. Our findings show that maintaining physiologically relevant oxygen conditions, something often missing from many other culture systems, significantly impacts the SCFA profile. Additionally, we noted the changes in SCFAs with culture time and potential variability between SCFA levels in male and female mouse tissue explants cultured in the MOD system based on 1H-NMR spectral profiles.
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Microbioma Gastrointestinal , Dispositivos Lab-On-A-Chip , Animais , Ácidos Graxos Voláteis/análise , Fezes/química , Feminino , Microbioma Gastrointestinal/fisiologia , Masculino , Camundongos , Oxigênio/análise , Espectroscopia de Prótons por Ressonância MagnéticaRESUMO
Urinary tract infections (UTIs) are one of the most common infections across the world and can lead to serious complications such as sepsis if not treated in a timely manner. Uropathogenic Escherichia coli account for 75% of all UTIs. Early diagnosis is crucial to help control UTIs, but current culturing methods are expensive and time-consuming and lack sensitivity. The existing point-of-care methods fall short because they rely on indirect detection from elevated nitrates in urine rather than detecting the actual bacteria causing the infection. Magnetophoresis is a powerful method used to separate and/or isolate cells of interest from complex matrices for analysis. However, magnetophoresis typically requires complex and expensive instrumentation to control flow in microfluidic devices. Coupling magnetophoresis with microfluidic paper-based analytical devices (µPADs) enables pump-free flow control and simple and low-cost operation. Early magnetophoresis µPADs showed detection limits competitive with traditional methods but higher than targets for clinical use. Here, we demonstrate magnetophoresis using hybrid µPADs that rely on capillary action in hydrophilic polyethylene terephthalate channels combined with paper pumps. We were able to detect E. coli with a calculated limit of detection of 2.40 × 102 colony-forming units per mL.
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Infecções por Escherichia coli , Infecções Urinárias , Escherichia coli Uropatogênica , Infecções por Escherichia coli/diagnóstico , Infecções por Escherichia coli/microbiologia , Humanos , Dispositivos Lab-On-A-Chip , Sistemas Automatizados de Assistência Junto ao Leito , Infecções Urinárias/diagnóstico , Infecções Urinárias/microbiologiaRESUMO
Point-of-care (POC) methods currently available for detecting SARS-CoV-2 infections still lack accuracy. Here, we report the development of a highly sensitive electrochemical immunoassay capable of quantitatively detecting the presence of the SARS-CoV-2 virus in patient nasopharyngeal samples using stencil-printed carbon electrodes (SPCEs) functionalized with capture antibodies targeting the SARS-CoV-2 nucleocapsid protein (N protein). Samples are added to the electrode surface, followed by horseradish peroxidase (HRP)-conjugated detection antibodies also targeting the SARS-CoV-2 N protein. The concentration of the virus in samples is quantified using chronoamperometry in the presence of 3,3'5,5'-tetramethylbenzidine. Limits of detection equivalent to less than 50 plaque forming units/mL (PFU/mL) were determined with virus sample volumes of 20 µL. No cross-reactivity was detected with the influenza virus and other coronavirus N proteins. Patient nasopharyngeal samples were tested as part of a proof-of-concept clinical study where samples were also tested using the gold-standard real-time quantitative polymerase chain reaction (RT-qPCR) method. Preliminary results from a data set of 22 samples demonstrated a clinical specificity of 100% (n = 9 negative samples according to RT-qPCR) and a clinical sensitivity of 70% for samples with RT-PCR cycle threshold (Ct) values under 30 (n = 10) and 100% for samples with Ct values under 25 (n = 5), which complies with the World Health Organization (WHO) criteria for POC COVID-19 diagnostic tests. Our functionalized SPCEs were also validated against standard plaque assays, and very good agreement was found between both methods (R2 = 0.9993, n = 6), suggesting that our assay could be used to assess patient infectivity. The assay currently takes 70 min from sampling to results.
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COVID-19 , SARS-CoV-2 , COVID-19/diagnóstico , Humanos , Imunoensaio/métodos , Proteínas do Nucleocapsídeo , Sensibilidade e EspecificidadeRESUMO
Here, we developed a microfluidic paper device by combining ion-selective electrodes (ISE) and a distance-based paper device (dPAD) for simultaneous potentiometric and colorimetric detection of urine electrolytes including K+, Na+ and Cl-. The working and reference electrode zones were coated with polystyrene as a non-ionic polymer to improve hydrophobic properties on the paper surface for fabrication of K+-ISE and Na+-ISE. The layer of polymer coating was optimized to enhance the sensitivity of the ISEs. Under optimized conditions, the electrode surfaces were modified with carbon black to improve the electrochemical characteristics of the ISEs. The ISEs showed good performance with sensitivities of 54.14 ± 3.94 mV per decade and 55.08 ± 1.15 mV per decade for K+ and Na+ within the linear concentration range 0.100 mM-100 mM K+ and 5 mM-1 M Na+, respectively. The limits of detection (LOD) were 0.05 mM and 1.36 mM for K+ and Na+, respectively. The linear working range of Cl- was 0.50 to 50 mM and the LOD and limit of quantification (LOQ) were found to be 0.16 ± 0.05 mM (3SD) and 0.53 ± 0.05 mM (10SD), respectively. The dual-mode ISE-dPAD was validated in human urine and recoveries were obtained as 90-108%, 94-105%, and 90-96% for K+, Na+, and Cl-, respectively, showing successful application of the developed device in a complex matrix. The ISE-dPAD has advantages including low-cost ($ 0.33 per test), eco-friendly, portability, simple operation, the need of low sample volume (100 µL), and simultaneous analysis on a single device.
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Eletrodos Seletivos de Íons , Dispositivos Lab-On-A-Chip , Eletrodos , Humanos , Íons , Polímeros/química , Poliestirenos , Sódio , FuligemRESUMO
Exposure to natural rubber latex (NRL) can result in sensitivity to NRL protein with resulting allergic reactions. Low-cost, portable, simple, sensitive analytical tools for NRL protein measurements are needed for rapid and accurate assessments of allergenic risks at the point-of-care (POC) instead of using traditional methods that require large and expensive instruments, long-time analysis, and complex sample preparation steps. Here, an electrochemical paper-based analytical device (ePAD) is presented by combining sample preparation and electrochemical detection within a single device to offer a one-step NRL analysis. The lack of antibodies and/or enzymes against NRL makes POC analysis difficult. In this work, detection is based on electrochemical measurement of the remaining Cu after in situ protein complexation instead of more complex biological assays for the first time. Graphene screen-printed electrodes modified with 1,10-phenanthroline and Nafion were used in the ePAD to improve Cu signal 18-fold relative to unmodified carbon screen-printed electrodes. The optimum parameters including 1,10-phenanthroline concentration, reaction time between Cu and protein, and the starting Cu concentration were 5% w/v, 1 min, and 600 µg mL-1, respectively. In addition to short analysis time (4 min), the system selectivity indicated no other interfering species affecting protein detection. The proposed ePAD achieved an LOD of 3.0 mg dL-1 and a linear range of 10.0-200.0 mg dL-1. Finally, the proposed sensors were applied for NRL protein detection and the results were not significantly different from the traditional Lowry method at 95% confidence.
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Grafite , Látex , Alérgenos , Carbono , Técnicas Eletroquímicas/métodos , EletrodosRESUMO
Huanglongbing (HLB), or citrus greening disease, has significantly decreased citrus production all over the world. The disease management currently depends on the efficient application and adequate distribution of insecticides to reduce the density of the disease vector, the Asian citrus psyllid. Here, we use a novel fluorescent-based method to evaluate insecticide distribution in an HLB-infected citrus grove in Florida. Specifically, we evaluated six different locations within citrus trees, the top and bottom sides of leaves, the effect of application approach (tractor versus airplane), and different application rates. We found that despite the insecticide distribution being highly variable among the different locations within a tree, the top of the leaves received an average increase of 21 times more than the bottom of the leaves. Application by tractor also resulted in a 4- to 87-fold increase in insecticide coverage compared with aerial application, depending on the location in the tree and side of the leaf. When taken to context with the type of insecticide that is applied (systemic vs. contact), these results can be used to optimize a pest management strategy to effectively target psyllids and other pests while minimizing the time and money spent on insecticide application and reducing risk to the environment.
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Citrus , Hemípteros , Rhizobiaceae , Animais , Fluorescência , Controle de Pragas , Doenças das PlantasRESUMO
A microfluidic paper-based thermoplastic electrode (TPE) array has been developed for point-of-care detection of Na+ and K+ ions using a custom-made portable potentiometer. TPEs were fabricated using polystyrene as the binder and two different types of graphite to compare the electrode performance. The newly designed TPE array embedded in a polymethyl methacrylate chip consists of two working electrodes modified with carbon black nanomaterial and an ion-selective membrane, and an all-solid-state reference electrode modified with Ag/AgCl ink and poly(butyl methacrylate-co-methyl methacrylate) membrane via drop-casting. Ion-selective membrane compositions and conditioning steps were optimized. Under optimized conditions, ion-selective TPEs demonstrated fast response time (4 s) and good stability. The TPE array demonstrated a Nernstian behavior for K+ with a sensitivity of 59.2 ± 0.2 mV decade-1 and near-Nernstian response for Na+ with a sensitivity of 54.0 ± 1.1 mV decade-1 in the range 10-1 - 10-4 M and 1 - 10-3 M, respectively. The detection limits were 1 × 10-5 M and 1 × 10-4 M for K+ and Na+, respectively. In addition, a K+ and Na+ selective microfluidic paper-based analytical device (µPAD) was applied to artificial serum analysis and found in good agreement with average recoveries of 101.3% and 99.7%, respectively, suggesting that the developed ISE array is suitable for detection of sodium and potassium in complex matrix.
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Microfluídica , Potássio , Eletrodos Seletivos de Íons , Íons , Sistemas Automatizados de Assistência Junto ao Leito , SódioRESUMO
Biogenic amines are an important and widely studied class of molecules due to their link to the physiological processes of food-related illnesses and histamine poisoning. Electrochemiluminescent (ECL) detection offers an inexpensive and portable analytical method of detection for biogenic amines when coupled with recent advancements in low-cost carbon-based electrodes and a smartphone camera. In this work, a mobile phone camera was evaluated against a piece of conventional instrumentation, the charge-coupled device, for the detection of ECL from the reaction of biogenic amines with the luminescent compound tris(2,2'-bipyridyl)ruthenium(II). Assisted by a 3D-printed light-tight housing, the mobile phone achieved limits of detection of 127, 425 and 421 µM for spermidine, putrescine, and histamine, respectively. The mobile phone's analytical figures of merit were lesser than the CCD camera but were still within the range to detect contamination. In an exploration of real-world samples, the mobile phone was able to determine the contents of amines in skim milk on par with that of a CCD camera.
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Telefone Celular , Compostos Organometálicos , Aminas Biogênicas , Carbono , Histamina , Medições Luminescentes/métodos , Putrescina , EspermidinaRESUMO
Thermoplastic electrodes (TPEs) are carbon composite electrodes consisting of graphite and thermoplastic polymer binder. TPE production is a solvent-based method, which makes it easy to fabricate and pattern into complex geometries, contrary to classical carbon composite electrodes. Depending on the composition (carbon type, binder, and composition ratio), TPEs can give excellent electrochemical performance and high conductivity. However, these TPEs are relatively new electrode materials, and thorough electrochemical characterization is still missing to understand and predict why large differences between TPEs exist. We used scanning electrochemical microscopy (SECM) as a screening tool to characterize TPEs. SECM data treatment based on scanning probe microscopy imaging allows a fast and easy comparison of the numerous images, as well as the optimization of the preparation. Experiments suggest that TPEs behave as a network of interacting microelectrodes made by electrochemically active islands isolated between less active areas. Higher carbon content in TPEs is not always indicative of more uniform electrodes with better electrochemical performances. Using various SECM redox probes, it is possible to select a specific graphite or polymer type for the analyte of interest. For example, TPEs made with COC:3569 are the best compromise for general detection, whereas PMMA:11 µm is better suited for catechol-like polyphenol analysis.