Fast impedimetric immunosensing of IgGs associated with peanut and hazelnut allergens

Food allergies trigger a variety of clinical adverse symptoms and clinical evidence suggests that the presence of food allergy-related IgG can be helpful in the diagnosis when analyzed at the peptide-epitope level. To validate and select the peptides based on their specificity toward hazelnut or peanut epitopes, the authors of this study developed a silicon-based microchip coupled with click-chemistry bound peptides identified by the Fraunhofer Institute for Cell Therapy and Immunology. Peptides related to hazelnut and peanut allergies were identified and used to develop a silicon-based microchip. Peptides were coupled with click-chemistry to the sensor surface. The immunosensor was developed by electrografting diazotized amino phenylacetic acid and subsequently, dibenzocyclooctyne-amine (DBCO-NH2) was used as click-chemistry to allow coupling of the peptides with a C-terminal linker and azide structure. Energy-dispersive X-ray spectroscopy, electrochemical impedance spectroscopy (EIS), and fluorescence microscopy techniques have been used to analyze the bio-functionalization of the developed electrode. The peptide-epitope recognition was studied for seven allergen-derived peptides. The electrochemical responses were studied with sera from rabbits immunized with hazelnut and peanut powder. The microchips functionalized with the chosen peptides (peanut peptides T12 and EO13 and hazelnut peptides S4 and EO14 with an RSD of 4%, 3%, 9%, and 1% respectively) demonstrated their ability to specifically detect prevalent anti-nut related IgGs in rabbit sera in a range of dilutions from 1:500000 (0.0002%) until 1:50000 (0.002%). In addition, the other peptides showed promising differentiation abilities which can be further studied to perform multivariable detection fingerprint of anti-allergens in blood sera.

Exploring the Versatility of Microemulsions in Cutaneous Drug Delivery: Opportunities and Challenges

Microemulsions are novel drug delivery systems that have garnered significant attention in the pharmaceutical research field. These systems possess several desirable characteristics, such as transparency and thermodynamic stability, which make them suitable for delivering both hydrophilic and hydrophobic drugs. In this comprehensive review, we aim to explore different aspects related to the formulation, characterization, and applications of microemulsions, with a particular emphasis on their potential for cutaneous drug delivery. Microemulsions have shown great promise in overcoming bioavailability concerns and enabling sustained drug delivery. Thus, it is crucial to have a thorough understanding of their formulation and characterization in order to optimize their effectiveness and safety. This review will delve into the different types of microemulsions, their composition, and the factors that affect their stability. Furthermore, the potential of microemulsions as drug delivery systems for skin applications will be discussed. Overall, this review will provide valuable insights into the advantages of microemulsions as drug delivery systems and their potential for improving cutaneous drug delivery.

Immuno field-effect transistor (ImmunoFET) for detection of salivary cortisol using potentiometric and impedance spectroscopy for monitoring heart failure

Cortisol, a steroid hormone mostly known as "the stress hormone," plays many essential functions in humans due its involvement in several metabolic pathways. It is well-known that cortisol dysregulation is implied in evolution and progression of several chronic pathologies, including cardiac diseases such as heart failure (HF). However, although several sensors have been proposed to date for the determination of cortisol, none of them has been designed for its determination in saliva in order to monitor HF progression. In this work, a silicon nitride based Immuno field-effect transistor (ImmunoFET) has been proposed to quantify salivary cortisol for HF monitoring. Sensitive biological element was represented by anti-cortisol antibody bound onto the ISFET gate via 11-triethoxysilyl undecanal (TESUD) by vapor-phase method. Potentiometric and electrochemical impedance spectroscopy (EIS) measurements were carried out for preliminary investigations on device responsiveness. Subsequently, a more sensitive detection was obtained using electrochemical EIS. The proposed device has proven to have a linear response (R² always >0.99), to be sensitive (with a limit of detection, LoD, of 0.005 ± 0.002 ng/mL), selective in case of other HF biomarkers (e.g. N-terminal pro B-type natriuretic peptide (NT-proBNP), tumor necrosis factor-alpha (TNF-α), and interleukin 10 (IL-10)), and accurate in cortisol quantification in saliva sample by performing the standard addition method.

One-step impedimetric NT-proBNP aptasensor targeting cardiac insufficiency in artificial saliva

Currently, sensitive and accurate approaches for diagnosis, rapid assessment, and cardiac biomarker monitoring in patients with heart failure are needed. In this context, the advantages of aptamers over traditional antibodies have been employed to fabricate a single-step impedimetric N-terminal pro b-type natriuretic peptide (NT-proBNP)-modified gold microelectrode array. The development of an electrochemical aptasensing platform was based on the coimmobilization of alkanethiol self-assembled monolayers and amine-terminated aptamer that specifically recognized cardiac NT-proBNP protein resulting in charge electron transfer. Electroimpedimetric signals of the sensor were observed to be linear to the NT-proBNP concentrations in the range of 5.0 × 10^-3 to 1.0 pg mL^-1 (R² = 0.9624), while achieving a low detection limit of 5.0 × 10^-3 pg mL^-1. Clinically relevant detection levels for NT-proBNP were achieved in a simple, rapid, and label-free measurement using artificial saliva, which was highlighted to be specific, regenerative, and selective over potential interferers occurring during the processes of cardiac insufficiency, Therefore, the novel NT-proBNP aptasensor is a promising point-of-care tool exhibiting safe, non-invasive, affordable, and non-prescription home use accessible to overcome the limitations associated with conventional ELISA and previous aptasensing.

Core-shell micro/nanocapsules: from encapsulation to applications

Encapsulation is the way to wrap or coat one substance as a core inside another tiny substance known as a shell at micro and nano scale for protecting the active ingredients from the exterior environment. A lot of active substances, such as flavours, enzymes, drugs, pesticides, vitamins, in addition to catalysts being effectively encapsulated within capsules consisting of different natural as well as synthetic polymers comprising poly(methacrylate), poly(ethylene glycol), cellulose, poly(lactide), poly(styrene), gelatine, poly(lactide-co-glycolide)s, and acacia. The developed capsules release the enclosed substance conveniently and in time through numerous mechanisms, reliant on the ultimate use of final products. Such technology is important for several fields counting food, pharmaceutical, cosmetics, agriculture, and textile industries. The present review focuses on the most important and high-efficiency methods for manufacturing micro/nanocapsules and their several applications in our life.

Non-covalent π-π functionalized Gii-senseⓇ graphene foam for interleukin 10 impedimetric detection

Monitoring Interleukin 10 (IL-10) is essential for understanding the vast responses of T-cells in cancer, autoimmunity, and internal homeostasis after physical stress. However, current diagnostic methods are complex and more focused on medical screening rather than point-of-care monitoring. Biosensors based on graphene's conductivity and flexibility are attractive to offer simple single-use and reduced handling. However, oxidation of its carbon lattice to develop functional moieties for biomolecule immobilization cuts down its electronic conductivity potential. In this work, the authors present a microfluidic lab-on-chip device for simple impedimetric monitoring of IL-10 based on graphene foam (GF) flexible electrodes. Graphene's structure was maintained by employing π-π non-covalent functionalization with pyrene carboxylic acid (PCA). Impedimetric measurements could be performed in low ionic strength phosphate-buffered saline (LI-PBS). The PCA-antibody modification showed to endure the incubation, measurement, and washing processes performed in the microfluidic device. Electrode modification and measurements were characterized by, electrochemical impedance spectroscopy (EIS), contact angle, and scanning electron microscopy. From the contact angle results, we found that the wettability of the graphene surface increased gradually after each modification step. Detection measurements performed in the 3D-printed microfluidic device showed a linear response between 10 fg/mL to 100 fg/mL with a limit of detection (LOD) of 7.89 fg/mL in artificial saliva. With these features, the device was used to quantify IL-10 samples by the standard addition method for 10 fg and 50 fg with recoveries between 82% and 99%. Specificity was evaluated towards interleukin 6, TNF-⍺ and bovine serum albumin.

Nanocarriers based novel and effective drug delivery system

Nanotechnology has ultimately come into the domain of drug delivery. Nanosystems for delivery of drugs are promptly emerging science utilizing different nanoparticles as carriers. Biocompatible and stable nanocarriers are novel diagnosis tools or therapy agents for explicitly targeting locates with controllable way. Nanocarriers propose numerous advantages to treat diseases via site-specific as well as targeted delivery of particular therapeutics. In recent times, there are number of outstanding nanocarriers use to deliver bio-, chemo-, or immuno- therapeutic agents to obtain effectual therapeutic reactions and to minimalize unwanted adverse-effects. Nanoparticles possess remarkable potential for active drug delivery. Moreover, conjugation of drugs with nanocarriers protects drugs from metabolic or chemical modifications, through their way to targeted cells and hence increased their bioavailability. In this review, various systems integrated with different types of nanocarriers (inorganic. organic, quantum dots, and carbon nanotubes) having different compositions, physical and chemical properties have been discussed for drug delivery applications.

Magnetic nanoparticles: multifunctional tool for cancer therapy

INTRODUCTION

Cancer has one of the highest mortality rates globally. The traditional therapies used to treat cancer have harmful adverse effects. Considering these facts, researchers have explored new therapeutic possibilities with enhanced benefits. Nanoparticle development for cancer detection, in addition to therapy, has shown substantial progress over the past few years.

AREA COVERED

Herein, the latest research regarding cancer treatment employing magnetic nanoparticles (MNPs) in chemo-, immuno-, gene-, and radiotherapy along with hyperthermia is summarized, in addition to their physio-chemical features, advantages, and limitations for clinical translation have also been discussed.

EXPERT OPINION

MNPs are being extensively investigated and developed into effective modules for cancer therapy. They are highly functional tools aimed at cancer therapy owing to their excellent superparamagnetic, chemical, biocompatible, physical, and biodegradable properties.

Selective Antibody-Free Sensing Membranes for Picogram Tetracycline Detection

As an antibody-free sensing membrane for the detection of the antibiotic tetracycline (TC), a liquid PVC membrane doped with the ion-pair tetracycline/θ-shaped anion [3,3'-Co(1,2-C₂B₉H₁₁)₂]^- ([o-COSAN]^-) was formulated and deposited on a SWCNT modified gold microelectrode. The chosen transduction technique was electrochemical impedance spectroscopy (EIS). The PVC membrane was composed of: the tetracycline/[o-COSAN]^- ion-pair, a plasticizer. A detection limit of 0.3 pg/L was obtained with this membrane, using bis(2-ethylhexyl) sebacate as a plasticizer. The sensitivity of detection of tetracycline was five times higher than that of oxytetracycline and of terramycin, and 22 times higher than that of demeclocycline. A shelf-life of the prepared sensor was more than six months and was used for detection in spiked honey samples. These results open the way to having continuous monitoring sensors with a high detection capacity, are easy to clean, avoid the use of antibodies, and produce a direct measurement.

A Novel Cortisol Immunosensor Based on a Hafnium Oxide/Silicon Structure for Heart Failure Diagnosis

Assessing cortisol levels in human bodies has become essential to diagnose heart failure (HF). In this work, we propose a salivary cortisol detection strategy as part of an easily integrable lab-on-a-chip for detection of HF biomarkers. Our developed capacitive immunosensor based on hafnium oxide (HfO2)/silicon structure showed good linearity between increasing cortisol concentration and the charge-transfer resistance/capacitance. Moreover, the developed biosensor was demonstrated to be highly selective toward cortisol compared to other HF biomarkers such as tumor necrosis factor (TNF-α) and N-terminal pro-brain natriuretic peptide (NT-proBNP). The precision of our developed biosensor was evaluated, and the difference between the determined cortisol concentration in saliva and its expected one is <18%.

Biodegradable porous micro/nanoparticles with thermoresponsive gatekeepers for effective loading and precise delivery of active compounds at the body temperature

Stimuli-responsive controlled delivery systems are of interest for preventing premature leakages and ensuring precise releases of active compounds at target sites. In this study, porous biodegradable micro/nanoparticles embedded with thermoresponsive gatekeepers are designed and developed based on Eudragit RS100 (PNIPAM@RS100) and poly(N-isopropylacrylamide) via a double emulsion solvent evaporation technique. The effect of initiator types on the polymerization of NIPAM monomer/methylene-bis-acrylamide (MBA) crosslinker was investigated at 60 °C for thermal initiators and ambient temperature for redox initiators. The crosslinked PNIPAM plays a key role as thermal-triggered gatekeepers with high loading efficiency and precise release of a model active compound, Nile Blue A (NB). Below the volume phase transition temperature (T_VPT), the gatekeepers possess a swollen conformation to block the pores and store NB within the cavities. Above its T_VPT, the chains rearrange, allowing gate opening and a rapid and constant release rate of the compound until completion. A precise “on–off” switchable release efficiency of PNIPAM@RS100 was demonstrated by changing the temperatures to 4 and 40 °C. The materials are a promising candidate for controlled drug delivery systems with a precise and easy triggering mechanism at the body temperature for effective treatments.

Contribution of magnetic particles in molecular diagnosis of human viruses

Viral diseases are the primary source of death, making a worldwide influence on healthcare, social, and economic development. Thus, diagnosis is the vital approach to the main aim of virus control and elimination. On the other hand, the prompt advancement of nanotechnology in the field of medicine possesses the probability of being beneficial to diagnose infections normally in labs as well as specifically. Nanoparticles are efficiently in use to make novel strategies because of permitting analysis at cellular in addition to the molecular scale. Henceforth, they assist towards pronounced progress concerning molecular analysis at the nanoscale. In recent times, magnetic nanoparticles conjugated through covalent bonds to bioanalytes for instance peptides, antibodies, nucleic acids, plus proteins are established like nanoprobes aimed at molecular recognition. These modified magnetic nanoparticles could offer a simple fast approach for extraction, purification, enrichment/concentration, besides viruses' recognition precisely also specifically. In consideration of the above, herein insight and outlook into the limitations of conventional methods and numerous roles played by magnetic nanoparticles to extract, purify, concentrate, and additionally in developing a diagnostic regime for viral outbreaks to combat viruses especially the ongoing novel coronavirus (COVID-19).

Advancement in Nanoparticle-Based Biosensors for Point-of-Care In Vitro Diagnostics

Abstract:

Recently, there has been great progress in the field of extremely sensitive and precise detection of bioanalytes. The importance of the utilization of nanoparticles in biosensors has been recognized due to their unique properties. Specifically, nanoparticles of gold, silver, and magnetic plus graphene, quantum dots, and nanotubes of carbon are being keenly considered for utilizations within biosensors to detect nucleic acids, glucose, or pathogens (bacteria as well as a virus). Taking advantage of nanoparticles, faster and sensitive biosensors can be developed. Here we review the nanoparticles' contribution to the biosensors field and their potential applications.

Mathematical Modelling of Glyphosate Molecularly Imprinted Polymer-Based Microsensor with Multiple Phenomena

The massive and careless use of glyphosate (GLY) in agricultural production raises many questions regarding environmental pollution and health risks, it is then important to develop simple methods to detect it. Electrochemical impedance spectroscopy (EIS) is an effective analytical tool for characterizing properties at the electrode/electrolyte interface. It is useful as an analytical procedure, but it can also help in the interpretation of the involved fundamental electrochemical and electronic processes. In this study, the impedance data obtained experimentally for a microsensor based on molecularly imprinted chitosan graft on 4-aminophenylacetic acid for the detection of glyphosate was analyzed using an exact mathematical model based on physical theories. The procedure for modeling experimental responses is well explained. The analysis of the observed impedance response leads to estimations of the microscopic parameters linked to the faradic and capacitive current. The interaction of glyphosate molecules with the imprinted sites of the CS-MIPs film is observed in the high frequency range. The relative variation of the charge transfer resistance is proportional to the log of the concentration of glyphosate. The capacitance decreases as the concentration of glyphosate increases, which is explained by the discharging of the charged imprinted sites when the glyphosate molecule interacts with the imprinted sites through electrostatic interactions. The phenomenon of adsorption of the ions in the CMA film is observed in the low frequency range, this phenomenon being balanced by the electrostatic interaction of glyphosate with the imprinted sites in the CS-MIPs film.

Microfluidic based nanoparticle synthesis and their potential applications

A lot of substantial innovation in advancement of microfluidic field in recent years to produce nanoparticle reveals a number of distinctive characteristics for instance compactness, controllability, fineness in process, and stability along with minimal reaction amount. Recently, a prompt development, as well as realization in production of nanoparticles in microfluidic environs having dimension of micro to nanometers and constituents extending from metals, semiconductors to polymers, has been made. Microfluidics technology integrates fluid mechanics for production of nanoparticles having exclusive with homogenous sizes, shapes, and morphology, which are utilized in several bioapplications such as biosciences, drug delivery, healthcare, including food engineering. Nanoparticles are usually well-known for having fine and rough morphology because of their small dimensions including exceptional physical, biological, chemical, and optical properties. Though the orthodox procedures need huge instruments, costly autoclaves, use extra power, extraordinary heat loss, as well as take surplus time for synthesis. Additionally, this is fascinating in order to systematize, assimilate, in addition, to reduce traditional tools onto one platform to produce micro and nanoparticles. The synthesis of nanoparticles by microfluidics permits fast handling besides better efficacy of method utilizing the smallest components for process. Herein, we will focus on synthesis of nanoparticles by means of microfluidic devices intended for different bioapplications. This article is protected by copyright. All rights reserved.

A silicon nitride ISFET based immunosensor for tumor necrosis factor-alpha detection in saliva. A promising tool for heart failure monitoring

According to the European statistics, approximately 26 million patients worldwide suffer from heart failure (HF), and this number seems to be steadily increasing. Inflammation plays a central role in the development of HF, and the pro-inflammatory cytokine Tumor necrosis factor-α (TNF-α) represents inflammation gold-standard biomarker. Early detection plays a crucial role for the prognosis and treatment of HF. An Ion Sensitive Field Effect Transistor (ISFET) based on silicon nitride transducer and biofunctionalized with anti-TNF-α antibody for label-free detection of salivary TNF-α is proposed. Electrochemical impedance spectroscopy (EIS) was used for TNF-α detection. Our ImmunoFET offered a detection limit of 1 pg mL^-1, with an analytical reproducibility expressed by a coefficient of variance (CV) resulted < 10% for the analysis of saliva samples, and an analyte recovery of 94 ± 6%. In addition, it demonstrated high selectivity when compared to other HF biomarkers such as Inteleukin-10, N-terminal pro B-type natriuretic peptide, and Cortisol. Finally, ImmunoFET accuracy in determining the unknown concentration of TNF-α was successfully tested in saliva samples by performing standard addition method. The proposed ImmunoFET showed great promise as a complementary tool for biomedical application for HF monitoring by a non-invasive, rapid and accurate assessment of TNF-α.

Electrochemical Impedance Spectroscopy Microsensor Based on Molecularly Imprinted Chitosan Film Grafted on a 4-Aminophenylacetic Acid (CMA) Modified Gold Electrode, for the Sensitive Detection of Glyphosate

A novel electrochemical impedance spectroscopy (EIS) microsensor was implemented for the dosage of traces of glyphosate, in real and synthetic water samples. Molecularly imprinted chitosan was covalently immobilized on the surface of the microelectrode previously modified with 4-aminophenylacetic acid (CMA). The characterization of the resulting microelectrodes was carried out by using cyclic voltammetry measurement (CV), scanning electron microscopy (SEM), and electrochemical impedance spectrometry (EIS). EIS responses of the CS-MIPs/CMA/Au microsensor toward GLY was well-proportional to the concentration in the range from 0.31 × 10^-9 to 50 × 10^-6 mg/mL indicating a good correlation. The detection limit of GLY was 1 fg/mL (S/N = 3). Moreover, this microsensor showed good reproducibility and repeatability, high selectivity, and can be used for the detection of GLY in river water.

Innovative electrochemical sensor for the precise determination of the new antiviral COVID-19 treatment Favipiravir in the presence of coadministered drugs

Due the current pandemic of COVID-19, an urgent need is required for serious medical treatments of a huge number of patients. The world health organization (WHO) approved Favipiravir (FAV) as a medication for patients infected with corona virus. In the current study, we report the first simple electrochemical, greatly sensitive sensor using MnO₂-rGO nanocomposite for the accurate determination of Favipiravir (FAV). The developed sensor showed a high improvement in the electrochemical oxidation of FAV comparing to the unmodified screen-printed electrode (SPE). The suggested platform constituents and the electrochemical measurements parameters were studied. Under optimal experimental parameters, a current response to the concentration change of FAV was found to be in the linear range of 1.0 × 10^-8-5.5 × 10^-5 M at pH 7.0 with a limit of detection 0.11 µM and a quantification limit of 0.33 µM. The developed platform was confirmed by the precise analysis of FAV in real samples including dosage form and plasma. The developed platform can be applied in different fields of industry quality control and clinical analysis laboratories for the FAV determination.

Sensor Based on a Poly[2-(Dimethylamino)ethyl Methacrylate-Co-Styrene], Gold Nanoparticles, and Methylene Blue-Modified Glassy Carbon Electrode for Melamine Detection

Melamine has been used as a non-protein nitrogenous additive in food products to artificially increase the apparent “false” protein content. Melamine is known as a dangerous and poisonous substance for human health and it causes diverse diseases. An electrochemical sensor for melamine detection has been developed by modification of a glassy carbon electrode using copolymer poly[DMAEMA-co-styrene], gold nanoparticles, and methylene blue. The characterization of the modified electrode was conducted using several analysis techniques including cyclic voltammetry (CV), differential pulse voltammetry (DPV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). The electrochemical detection of melamine was performed by impedance spectroscopy. Obtained results revealed that the developed sensor has a large detection range from 5.0 × 10⁻¹³ to 3.8 × 10⁻⁸ M with a low detection limit of 1.8 × 10⁻¹² M (at S/N = 3). Various interfering species such as phenol, hydroquinone, and bisphenol A have been used and their behavior on modified electrode has been studied.

Recent Advances in Electrochemical Monitoring of Chromium

The extensive use of chromium by several industries conducts to the discharge of an immense quantity of its various forms in the environment which affects drastically the ecological and biological lives especially in the case of hexavalent chromium. Electrochemical sensors and biosensors are useful devices for chromium determination. In the last five years, several sensors based on the modification of electrode surface by different nanomaterials (fluorine tin oxide, titanium dioxide, carbon nanomaterials, metallic nanoparticles and nanocomposite) and biosensors with different biorecognition elements (microbial fuel cell, bacteria, enzyme, DNA) were employed for chromium monitoring. Herein, recent advances related to the use of electrochemical approaches for measurement of trivalent and hexavalent chromium from 2015 to 2020 are reported. A discussion of both chromium species detections and speciation studies is provided.

Magnetic Nanoparticles Fishing for Biomarkers in Artificial Saliva

Magnetic nanoparticles (MNPs) were synthesized using the colloidal co-precipitation method and further coated with silica using the Stöber process. These were functionalized with carboxylic and amine functionalities for further covalent immobilization of antibodies on these MNPs. The procedure for covalent immobilization of antibodies on MNPs was developed using 1-ethyl-3-(dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS). The evaluation of the efficiency of the coupling reaction was carried out by UV-vis spectrophotometry. The developed antibodies coupled to MNPs were tested for the pre-concentration of two biomarkers tumor necrosis factor alpha (TNF-α) and Interleukin-10 (IL-10). Both biomarkers were assessed in the matrix based on phosphate-buffered saline solution (PBS) and artificial saliva (AS) to carry out the demonstration of the format assay. Supernatants were used to determine the number of free biomarkers for both studies. Reduction of the nonspecific saliva protein adsorption on the surface of the complex antibodies-MNPs to levels low enough to allow the detection of biomarkers in complex media has been achieved.

The Advent of Salivary Breast Cancer Biomarker Detection Using Affinity Sensors

Breast Cancer is one of the world's most notorious diseases affecting two million women in 2018 worldwide. It is a highly heterogeneous disease, making it difficult to treat. However, its linear progression makes it a candidate for early screening programs, and the earlier its detection the higher the chance of recovery. However, one key hurdle for breast cancer screening is the fact that most screening techniques are expensive, time-consuming, and cumbersome, making them impractical for use in several parts of the world. One current trend in breast cancer detection has pointed to a possible solution, the use of salivary breast cancer biomarkers. Saliva is an attractive medium for diagnosis because it is readily available in large quantities, easy to obtain at low cost, and contains all the biomarkers present in blood, albeit in lower quantities. Affinity sensors are devices that detect molecules through their interactions with biological recognition molecules. Their low cost, high sensitivity, and selectivity, as well as rapid detection time make them an attractive alternative to traditional means of detection. In this review article, we discuss the current status of breast cancer diagnosis, its salivary biomarkers, as well as the current trends in the development of affinity sensors for their detection.

A fully integrated passive microfluidic Lab-on-a-Chip for real-time electrochemical detection of ammonium: Sewage applications

The present work reports on the development of a new generation of Lab-on-a-chip (LOC) to perform in-situ and real-time potentiometric measurements in flowing water. The device consisted of two differentiated parts: a poly (dimethylsiloxane) (PDMS) microfluidic structure obtained by soft lithography and a fully integrated chemical sensing platform including four working microelectrodes, two reference microelectrodes and one counter microelectrode for detecting ammonium in a continuous mode. The performance of the device was evaluated following its potentiometric response when analyzing ammonium containing samples. As a key parameter, its time of response was compared to that of a commercially available electrical conductivity sensor used as reference sensor during tests in laboratory using flowing tap water and technical scale using flowing wastewater. As a result, the LOC showed a slope of 55 mV/decade, a limit of detection of 4·10^-5 M and a time of full response between 10 and 12 s. It was demonstrated that the device can provide fast and reliable data at real time when immersed in a laminar flow of water. Moreover, the test of robustness showed that it was still functional after immersion in sewage for at least 15 min. Besides, the LOC reported here can be helpful for a wide variety of flowing-water applications such as aqua culture outlets control, in-situ and continuous analysis of rivers effluents and sea waters monitoring among others.

Ultrasensitive Immunosensor Array for TNF-α Detection in Artificial Saliva using Polymer-Coated Magnetic Microparticles onto Screen-Printed Gold Electrode

Tumor necrosis factor-α (TNF-α) is a biomarker of inflammation that occurs in patients suffering from heart failure (HF). Saliva can be sampled in a non-invasive way, and it is currently gaining importance as matrix alternative to blood in diagnostic and therapy monitoring. This work presents the development of an immunosensor array based on eight screen-printed gold electrodes to detect TNF-α in saliva samples. Two different functionalization strategies of electrodes were compared. In the first, anti-TNF-α antibodies were chemically bonded onto the electrode by functionalization with 4-carboxymethylaniline. The other functionalization procedure involved the binding of antibodies onto polymer-coated magnetic microparticles, which were then deposited onto the electrode by pulsed chronoamperometry. Finally, the chronoamperometry technique was applied to characterize the modified SPEAu. The use of a secondary antibody anti-TNF-α (Ab-TNF-α-HRP) labelled with horseradish peroxidase (HRP, 2 µg·mL⁻¹) was investigated using tetramethylbenzidine (TMB, pH = 3.75) as electrochemical substrate containing 0.2 mM of H₂O₂. A sandwich-type detection strategy with a secondary antibody anti-TNF-α provided chronoamperometric analyses in 10 s for each sample. Linearity, precision, limit of detection, and selectivity of devices were investigated. Interferences were evaluated by analyzing solutions containing other cytokine produced during the acute stage of inflammation. The immunosensor showed good performance within the clinically relevant concentration range, with a precision of 8%, and a limit of detection of 0.3 pg/mL. Therefore, it may represent a promising tool for monitoring HF in a non-invasive way.

A low-cost and miniaturized potentiostat for sensing of biomolecular species such as TNF-α by electrochemical impedance spectroscopy

Miniaturizing potentiostats, keeping their cost low and yet preserving full measurement characteristics (e.g. bandwidth, determination of capacitive/inductive contribution to sensor's impedance and parallel screening) is still an unresolved challenge in bioelectronics. In this work, the combination of simple analogue circuitry together with powerful microcontrollers and a digital filter implementation is presented as an alternative to complex and incomplete architectures reported in the literature. A low-cost acquisition electronic system fully integrated with a biosensors platform containing eight gold working microelectrodes and integrated reference and counter electrodes was developed and validated. The manufacturing cost of the prototype was kept below 300 USD. The performance of the proposed device was benchmarked against a commercial impedance analyzer through the electrochemical analysis of a highly sensitive biosensor for the detection of tumor necrosis factor α (TNF-α) within the randomly chosen range of 266pg/mL to 666ng/mL in physiological medium (PBS). A strong correlation between the outputs of both devices was found in a critical range of frequencies (1-10Hz), and several TNF-α cytokine concentrations were properly discriminated. These results are very promising for the development of low-cost, portable and miniaturized electrochemical systems for point-of-care and environmental diagnosis.

A fully integrated electrochemical biosensor platform fabrication process for cytokines detection

Interleukin-1b (IL-1b) and interleukin-10 (IL-10) biomarkers are one of many antigens that are secreted in acute stages of inflammation after left ventricle assisted device (LVAD) implantation for patients suffering from heart failure (HF). In the present study, we have developed a fully integrated electrochemical biosensor platform for cytokine detection at minute concentrations. Using eight gold working microelectrodes (WEs) the design will increase the sensitivity of detection, decrease the time of measurements, and allow a simultaneous detection of varying cytokine biomarkers. The biosensor platform was fabricated onto silicon substrates using silicon technology. Monoclonal antibodies (mAb) of anti-human IL-1b and anti-human IL-10 were electroaddressed onto the gold WEs through functionalization with 4-carboxymethyl aryl diazonium (CMA). Cyclic voltammetry (CV) was applied during the WE functionalization process to characterize the gold WE surface properties. Finally, electrochemical impedance spectroscopy (EIS) characterized the modified gold WE. The biosensor platform was highly sensitive to the corresponding cytokines and no interference with other cytokines was observed. Both cytokines: IL-10 and IL-1b were detected within the range of 1pgmL^-1 to 15pgmL^-1. The present electrochemical biosensor platform is very promising for multi-detection of biomolecules which can dramatically decrease the time of analysis. This can provide data to clinicians and doctors concerning cytokines secretion at minute concentrations and the prediction of the first signs of inflammation after LVAD implantation.