Rapid and simultaneous detection of Campylobacter spp. and Salmonella spp. in chicken samples by duplex loop-mediated isothermal amplification coupled with a lateral flow biosensor assay

Development of a simple, rapid and specific assay for the simultaneous detection of Campylobacter spp. and Salmonella spp. based on duplex loop-mediated isothermal amplification (d-LAMP), combined with lateral-flow biosensor (LFB) is reported herein. LAMP amplicons of both pathogens were simultaneously amplified and specifically differentiated by LFB. The specificity of the d-LAMP-LFB was evaluated using a set of 68 target and 12 non-target strains, showing 100% inclusivity and exclusivity. The assay can simultaneously detect Campylobacter and Salmonella strains as low as 1 ng and 100 pg genomic DNA per reaction, respectively. The lowest inoculated detection limits for Campylobacter and Salmonella species in artificially contaminated chicken meat samples were 103 CFU and 1 CFU per 25 grams, respectively, after enrichment for 24 h. Furthermore, compared to culture-based methods using field chicken meat samples, the sensitivity, specificity and accuracy of d-LAMP- LFB were 95.6% (95% CI, 78.0%-99.8%), 71.4% (95% CI, 29.0%-96.3%) and 90.0% (95% CI, 73.4%-97.8%), respectively. The developed d-LAMP-LFB assay herein shows great potentials for the simultaneous detection of the Campylobacter and Salmonella spp. and poses a promising alternative approach for detection of both pathogens with applications in food products.

Continuous Monitoring of pH and Blood Gases Using Ion-Sensitive and Gas-Sensitive Field Effect Transistors Operating in the Amperometric Mode in Presence of Drift

Accurate and cost-effective integrated sensor systems for continuous monitoring of pH and blood gases continue to be in high demand. The capacity of ion-selective and Gas-sensitive field effect transistors (FETs) to serve as low-power sensors for accurate continuous monitoring of pH and blood gases is evaluated in the amperometric or current mode of operation. A stand-alone current-mode topology is employed in which a constant bias is applied to the gate with the drain current serving as the measuring signal. Compared with voltage-mode operation (e.g., in the feedback mode in ion-selective FETs), current-mode topologies offer the advantages of small size and low power consumption. However, the ion-selective FET (ISFET) and the Gas-sensitive FET (GasFET) exhibit a similar drift behavior, imposing a serious limitation on the accuracy of these sensors for continuous monitoring applications irrespective of the mode of operation. Given the slow temporal variation associated with the drift characteristics in both devices, a common post-processing technique that involves monitoring the variation of the drain current over short intervals of time can potentially allow extraction of the measuring signal in presence of drift in both sensor types. Furthermore, in the amperometric mode the static sensitivity of a FET-based sensor, given by the product of the FET transconductance and the sensitivity of the device threshold voltage to the measurand concentration, can be increased by adjusting the device design parameters. Increasing the sensitivity, while of interest in its own right, also enhances the accuracy of the proposed method. Rigorous analytical validation of the method is presented for GasFET operation in the amperometric mode. Moreover, the correction algorithm is verified experimentally using a Si₃N₄-gate ISFET operating in the amperometric mode to monitor pH variations ranging from 3.5 to 10.

Miniaturization of EISCAP sensor for triglyceride detection

In this paper we discuss the fabrication and characterization of miniaturized triglyceride biosensors on crystalline silicon and porous silicon (PS) substrates. The sensors are miniaturized Electrolyte Insulator Semiconductor Capacitors (mini-EISCAPs), which primarily sense the pH variation of the electrolyte used. The lipase enzyme, which catalyses the hydrolysis of triglycerides, was immobilized on the sensor surface. Triglyceride solutions introduced into the enzyme immobilized sensor produced butyric acid which causes the change in pH of the electrolyte. Miniaturized EISCAP sensors were fabricated using bulk micromachining technique and have silicon nitride as the pH sensitive dielectric layer. The sensors are cubical pits of dimensions 1,500 microm x 1,500 microm x 100 microm which can hold an electrolyte volume of 0.1 microl. The pH changes in the solution can be sensed through the EISCAP sensors by monitoring the flatband voltage shift in the Capacitance-Voltage (C-V) characteristics taken during the course of the reaction. The reaction rate is found to be quite high in the miniature cells when compared to the sensors of bigger dimensions.

A novel method for the assay of alpha-glucosidase inhibitory activity using a multi-channel oxygen sensor

The quantification of glucose by using a multi-channel dissolved oxygen (DO) meter (DOX96) with immobilized glucose oxidase (GOD) and mutarotase (MUT) was performed. An evaluation of the inhibitory activities for alpha-glucosidase (AGH) by modifying our batch-type pseudo-in vivo assay system [Oki et al.; Biol Pharm. Bull., 2000, 232, 1084] was also performed using a DOX96. When 45 U/well GOD and 18.75 U/well MUT were immobilized on the surface of a gelatin membrane on the electrodes, the response shown by the decrease percent of DO (%) obtained with 8 electrode wells in the same row was linear with the glucose concentration up to 3.3 mM and a correlation coefficient larger than 0.9. To estimate the AGH inhibitory activity, AGH-immobilized Sepharose supports in the well of a silent screen plate were used. The IC50 values of acarbose and 1-deoxynojirimycin, a medicinal inhibitor for diabetes, were 0.70 +/- 0.08 microM and 0.40 +/- 0.13 microM, respectively, and coincided well with those by a pseudo-in vivo assay.

Sensor calibration models for a non-invasive blood glucose measurement sensor

A calibration model was developed for a noninvasive blood glucose sensor, to determine how the blood glucose data measured by this sensor is related to blood glucose data measured with laboratory capillary finger sticks and to corrupting noise. The variability of calibration models for different patients was analyzed as well as the dynamics of the non-invasive blood glucose sensor according to reference blood glucose measurements and corrupting noise.

Nano Assessing Nano: Nanosensor-Enabled Detection of Cell Phenotypic Changes Identifies Nanoparticle Toxicological Effects at Ultra-Low Exposure Levels

Industrial use of nanomaterials is rapidly increasing, making the effects of these materials on the environment and human health of critical concern. Standard nanotoxicity evaluation methods rely on detecting cell death or major dysfunction and will miss early signs of toxicity. In this work, the use of rapid and sensitive nanosensors that can efficiently detect subtle phenotypic changes on the cell surface following nanomaterial exposure is reported. Importantly, the method reveals significant phenotypic changes at dosages where other conventional methods show normal cellular activity. This approach holds promise in toxicological and pharmacological evaluations to ensure safer and better use of nanomaterials.

An absolute calibration method of an ethyl alcohol biosensor based on wavelength-modulated differential photothermal radiometry

In this work, laser-based wavelength-modulated differential photothermal radiometry (WM-DPTR) is applied to develop a non-invasive in-vehicle alcohol biosensor. WM-DPTR features unprecedented ethanol-specificity and sensitivity by suppressing baseline variations through a differential measurement near the peak and baseline of the mid-infrared ethanol absorption spectrum. Biosensor signal calibration curves are obtained from WM-DPTR theory and from measurements in human blood serum and ethanol solutions diffused from skin. The results demonstrate that the WM-DPTR-based calibrated alcohol biosensor can achieve high precision and accuracy for the ethanol concentration range of 0-100 mg/dl. The high-performance alcohol biosensor can be incorporated into ignition interlocks that could be fitted as a universal accessory in vehicles in an effort to reduce incidents of drinking and driving.

A comparison of Prx- and OxyR-based H2O2 probes expressed in S. cerevisiae

Genetically encoded fluorescent H₂O₂ probes continue to advance the field of redox biology. Here, we compare the previously established peroxiredoxin-based H₂O₂ probe roGFP2-Tsa2ΔC_R with the newly described OxyR-based H₂O₂ probe HyPer7, using yeast as the model system. Although not as sensitive as roGFP2-Tsa2ΔC_R, HyPer7 is much improved relative to earlier HyPer versions, most notably by ratiometric pH stability. The most striking difference between the two probes is the dynamics of intracellular probe reduction. HyPer7 is rapidly reduced, predominantly by the thioredoxin system, whereas roGFP2-Tsa2ΔC_R is reduced more slowly, predominantly by the glutathione system. We discuss the pros and cons of each probe and suggest that future side-by-side measurements with both probes may provide information on the relative activity of the two major cellular reducing systems.

An enzyme electrode based on lipoxygenase immobilized in gelatin for selective determination of essential fatty acids

An enzyme electrode for the specific determination of omega-3 and omega-6 fatty acids from the mixture of essential fatty acids (EFAs) was developed by using lipoxygenase (LOX) (EC 1.13.11.12) from soy beans in combination with a dissolved oxygen (DO) probe. The enzyme electrode showed different sensitivities for linoleic (LA) and alpha-linolenic acids (ALA), the most common essential fatty acids. Enzyme electrode response depends linearly on LA concentration between 12.8-160.5 microM and ALA concentration between 3.8-18.9 microM in borate buffer, 0.2 M at pH 9.0. However, in phosphate buffer 0.2 M at pH 6.0 linearity is in the range of 7.5-22.5 microM of ALA concentration at 5 minutes response times. Moreover, maximum electrode response was found in borate buffer at pH 9.0 and 30 degrees C.

Hydrophilic sensor membrane based on cation-selective protic chromoionophore

The first potassium optode based on a protic chromoionophore immobilized in a hydrogel matrix is presented. The highly selective protic chromoionophore consists of a cryptohemispherand moiety and a trinitroanilino chromophore part. The acidifying power of potassium ions over sodium ions is 0.6 pH units. This correlates with the findings in solution. In contrast to several crown and aza-crown based chromophores the highly pre-organized moiety allows ion detection even in aqueous environment. The detection limit for potassium ions at pH 7.7 is 5 microM.

Continuous monitoring of arterial blood gases and pH during intraoperative rapid blood administration using a Paratrend sensor

BACKGROUND AND OBJECTIVES

The aim of this study was to determine the effects of rapid transfusion of packed red cells on the arterial blood gases and acid-base status of the recipient.

MATERIALS AND METHODS

We studied 16 patients (mean age 66.3+/-9.9 years) who received rapid transfusion of 632.8+/-287.2 g of packed red cells in CPDA-1, stored before use for a period of 15.2+/-4.4 days. During transfusion, monitoring of pH, PCO2 and PO2 was continuous using an intra-arterial multiparameter sensor (Paratrend 7, Biomedical Sensors, UK).

RESULTS

The rate of the transfusion was 73.1+/-9.6 g/min and the duration of observation was 35.8+/-12.8 min. Arterial pH decreased from 7.446+/-0.023 to 7.385+/-0.034 (p<0.001) and PCO2 increased from 32.31+/-1.35 to 36.41+/-1.86 mmHg (p<0.001). Delta pH and delta PCO2 showed significant correlation to the weight and the age of the transfused blood (p<0.001 for both dependent variables). The rate of pH change was positively but insignificantly correlated to the rate of the transfusion. Base excess was significantly decreased and end-tidal CO2 (PetCO2) was increased from 25.8+/-2.0 to 28.1+/-2.3 mmHg (p<0.05), significantly correlating to the amount and age of the administered component (p<0.05). PetCO2 was not elevated when PCO2 changes were minimal. Alterations in PO2 were not specific and our clinical impression was that they were related to unmeasured parameters.

CONCLUSION

Our findings suggest that the fall in pH and the elevation in PCO2 which occur during rapid transfusion of packed red cells may go undetected or be misinterpreted if the acid-base status of the recipient is not monitored continuously. These alterations are mainly of metabolic character and depend on the amount and age of the transfused component. Our data suggest that arterial sampling is essential during massive transfusions.

Dual-Functional Plasmonic Photothermal Biosensors for Highly Accurate Severe Acute Respiratory Syndrome Coronavirus 2 Detection

The ongoing outbreak of the novel coronavirus disease (COVID-19) has spread globally and poses a threat to public health in more than 200 countries. Reliable laboratory diagnosis of the disease has been one of the foremost priorities for promoting public health interventions. The routinely used reverse transcription polymerase chain reaction (RT-PCR) is currently the reference method for COVID-19 diagnosis. However, it also reported a number of false-positive or -negative cases, especially in the early stages of the novel virus outbreak. In this work, a dual-functional plasmonic biosensor combining the plasmonic photothermal (PPT) effect and localized surface plasmon resonance (LSPR) sensing transduction provides an alternative and promising solution for the clinical COVID-19 diagnosis. The two-dimensional gold nanoislands (AuNIs) functionalized with complementary DNA receptors can perform a sensitive detection of the selected sequences from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) through nucleic acid hybridization. For better sensing performance, the thermoplasmonic heat is generated on the same AuNIs chip when illuminated at their plasmonic resonance frequency. The localized PPT heat is capable to elevate the in situ hybridization temperature and facilitate the accurate discrimination of two similar gene sequences. Our dual-functional LSPR biosensor exhibits a high sensitivity toward the selected SARS-CoV-2 sequences with a lower detection limit down to the concentration of 0.22 pM and allows precise detection of the specific target in a multigene mixture. This study gains insight into the thermoplasmonic enhancement and its applicability in the nucleic acid tests and viral disease diagnosis.

Miniaturized Rapid Electrochemical Immunosensor Based on Screen Printed Carbon Electrodes for Mycobacterium tuberculosis Detection

In 2019, over 21% of an estimated 10 million new tuberculosis (TB) patients were either not diagnosed at all or diagnosed without being reported to public health authorities. It is therefore critical to develop newer and more rapid and effective point-of-care diagnostic tools to combat the global TB epidemic. PCR-based diagnostic methods such as Xpert MTB/RIF are quicker than conventional techniques, but their applicability is restricted by the need for specialized laboratory equipment and the substantial cost of scaling-up in low- and middle-income countries where the burden of TB is high. Meanwhile, loop-mediated isothermal amplification (LAMP) amplifies nucleic acids under isothermal conditions with a high efficiency, helps in the early detection and identification of infectious diseases, and can be performed without the need for sophisticated thermocycling equipment. In the present study, the LAMP assay was integrated with screen-printed carbon electrodes and a commercial potentiostat for real time cyclic voltammetry analysis (named as the LAMP-Electrochemical (EC) assay). The LAMP-EC assay was found to be highly specific to TB-causing bacteria and capable of detecting even a single copy of the Mycobacterium tuberculosis (Mtb) IS6110 DNA sequence. Overall, the LAMP-EC test developed and evaluated in the present study shows promise to become a cost-effective tool for rapid and effective diagnosis of TB.

[Real time observation of binding of measles virus to Vero cells and neutralization of measles virus by human immunoglobulin using optical biosensor--a new real time diagnosis system for viral infections]

An optical biosensor to monitor molecular intractions was developed. This system made possible to observe reactions with a few minutes. We tried to apply this system for rapid diagnosis of viral infections. Measles virus propagated in our laboratory and crude rabbit anti-measles antiserum were used. A commercially available human immunoglobulin was used as a representative of patient sera. A crude rabbit anti-measles antiserum was fixed on the reaction surface of aminosilane coated cuvette, and specific binding of measles virus to this antibody was monitored. Specific purified IgG antibody was known to give as high sensitivity as the conventional culture method. But the sensitivity by crude antibody was found to be 1/10 in the sensitivity. This might be caused by the masked effects on specific antibody to the contaminated high amounts of non-specific proteins. None purified polyclonal antisera for most of the viruses are commercially available, and 10-20 times highly concentrated antibody solutions could be used for this titrations. Estimated anti-measles antibody titer of the commercial available human immunoglobulin by biosensor system was found to be the same as that by the conventional culture method. It was suggested that 1 X 10(3) virus particles/ml in the test solutions could be detectable and titerable by using commercially available specific anti-viral antibody in real time, and the viral infections could be diagnosed within an hour.

Whole blood electrolyte assay using ChemPro 500. A comparison of assay performance with standard laboratory instruments

The ChemPro 500 'near-the-patient' analyser, with ChemPro 'Ion Profile' sensor cards, was evaluated for the assay of pH, Ca2+, K+ and Na+ in whole blood samples from patients in the intensive care unit or during surgery for heart or major blood vessel disease, or for liver transplantation. Imprecisions estimated from replicate whole blood measurements were much greater for all four ions than even the least stringent of the generally accepted analytical goals, and much greater than those estimated using quality assurance materials. Comparisons of assayed values with those obtained using standard laboratory instruments showed significant constant and proportional biases. The performance of the ChemPro 500 with the Ion Profile cards gave us no confidence in recommending their use to anaesthetists and intensivists.

Analysis for transaminases in serum with an amperometric glutamate electrode

We determined transaminases in human blood serum with an amperometric glutamate biosensor. The probe was a hydrogen peroxide sensor assembled with appropriate selective membranes to enhance the probe specificity and lifetime. Calibration curves of glutamate were linear in the range 1-1000 mumol/L, with a response time of < 1 min. This probe was subsequently applied to the measurement of activities of aspartate and alanine aminotransferases in human sera. Analytical recovery studies demonstrated the suitability of the glutamate sensor by measuring 91-99% of added glutamate, 92-106% of added aspartate aminotransferase, and 101-105% of added alanine aminotransferase. Transaminase activity measured in 80 sera correlated well with results obtained with a spectrophotometric procedure.

Standards for reporting optical biosensor experiments (STROBE): Improving standards in the reporting of optical biosensor-based data in the literature

The number of peer-reviewed publications that feature biosensor data increases every year. A search of PubMed using common technique terminology, including bio-layer interferometry (BLI), surface plasmon resonance (SPR) and grating-coupled interferometry (GCI) generated more than 2500 scientific papers from 2022. Compared to 2009, when David Myszka and Rebecca Rich presented their most recent review of biosensor literature (Rich and Myszka, 2011), this number has nearly doubled. With this increasing number of publications comes an increasing need for standardization of the way biosensor data is reported in journals to allow for replication of the experiments that were performed. Biosensor data is often poorly described in papers which makes it difficult, if not impossible, to replicate the experiment. Critical information typically missing includes sample preparation, method settings, and data evaluation details. We have also found published work in which the authors have failed to report the type of sensor that was used, or which biosensor instrumentation was used. To come to terms with this growing problem, we propose a standardization of the way biosensor data is reported in scientific journals. We call this standard STROBE, standards for reporting optical biosensor experiments.

Improving lactate analysis with the YSI 2300 GL: hemolyzing blood samples makes results comparable with those for deproteinized whole blood

To obviate the well-documented problem of hematocrit dependency of the Yellow Springs Instruments (YSI) whole-blood lactate analyzer, we modified the dilution buffer by including a lysing reagent. This makes the results comparable with those of methods performed with deproteinized whole-blood samples. No centrifugation step is needed, thus preserving the convenience of the YSI instrument for stat and field use. The modification works equally well on plasma samples. Lactate concentrations measured in nonhemolyzed whole blood are not comparable with results for hemolyzed whole blood or protein-precipitated whole blood. We therefore recommend to all users of YSI equipment to lyse the erythrocytes before lactate determinations.

Interoperability as a quality label for portable & wearable health monitoring systems

Advances in ICT promising universal access to high quality care, reduction of medical errors, and containment of health care costs, have renewed interest in electronic health records (EHR) standards and resulted in comprehensive EHR adoption programs in many European states. Health cards, and in particular the European health insurance card, present an opportunity for instant cross-border access to emergency health data including allergies, medication, even a reference ECG. At the same time, research and development in miniaturized medical devices and wearable medical sensors promise continuous health monitoring in a comfortable, flexible, and fashionable way. These trends call for the seamless integration of medical devices and intelligent wearables into an active EHR exploiting the vast information available to increase medical knowledge and establish personal wellness profiles. In a mobile connected world with empowered health consumers and fading barriers between health and healthcare, interoperability has a strong impact on consumer trust. As a result, current interoperability initiatives are extending the traditional standardization process to embrace implementation, validation, and conformance testing. In this paper, starting from the OpenECG initiative, which promotes the consistent implementation of interoperability standards in electrocardiography and supports a worldwide community with data sets, open source tools, specifications, and online conformance testing, we discuss EHR interoperability as a quality label for personalized health monitoring systems. Such a quality label would support big players and small enterprises in creating interoperable eHealth products, while opening the way for pervasive healthcare and the take-up of the eHealth market.

Measuring IP3 Generation in Real-Time Using a NanoBiT Luminescence Biosensor

G protein-coupled receptors that activate Gq/11 regulate a range of physiological processes including neurotransmission, energy homeostasis, blood pressure regulation, and calcium homeostasis. Activation of Gq/11-coupled receptors stimulates the generation of inositol 1,4,5-trisphosphate (IP3), which mobilizes intracellular calcium release from the endoplasmic reticulum. This chapter describes an assay that uses a NanoBiT-IP3 luminescent biosensor to detect increases in IP3 in live cells. It describes how to perform these assays to assess signaling by the ghrelin receptor and the calcium-sensing receptor in HEK293 cells.