Rapid SARS-CoV-2 sensing through oxygen reduction reaction catalysed by Au@Pt/Au core@shell nanoparticles.

The development of rapid, accurate, sensitive, and low-cost diagnostic methods for COVID-19 detection in real-time is the unique way to control infection sources and monitor illness progression. In this work, we propose an electrochemical biosensor for the rapid and accuracy diagnosis of COVID-19, through the determination of ORF specific sequence. The biosensor is based on the immobilization of a thiolated sequence partially complementary (domain 1) to ORF on gold screen-printed electrodes and the use of bifunctional Au@Pt/Au core@shell nanoparticles modified with a second thiolated sequence partially complementary to ORF (domain 2) as electrochemical indicator of the hybridization of DNA sequences.

Controlled silver electrodeposition on gold nanoparticle antibody tags for ultrasensitive prostate specific antigen sensing using electrochemical and optical smartphone detection.

One of the current challenges in medicine is to achieve a rapid and unequivocal detection and quantification of extremely low levels of disease biomarkers in complex biological samples. Here, we present the development and analytical evaluation of a low-cost smartphone-based system designed for ultrasensitive detection of the prostate-specific antigen (PSA) using two detection alternatives: electrochemical or optical, by coupling the smartphone with a portable potentiostat or magnifying lenses. An antibody tagged with gold nanoparticles (AuNPs), and indium tin oxide coated polyethylene terephthalate platform (ITO-PET) have been used to develop a sandwich-type immunoassay.

Electrochemical monitoring of enzymatic cleavage in nanochannels with nanoparticle-based enhancement: determination of MMP-9 biomarker.

For the first time the use of nanoparticles as carriers of an enzymatic substrate immobilized inside nanoporous alumina membranes is proposed with the aim of amplifying the nanochannel blocking produced and, consequently, improving the efficiency of an enzyme determination through enzymatic cleavage. Streptavidin-modified polystyrene nanoparticles (PSNPs) are proposed as carrier agents, contributing to the steric and the electrostatic blockage due to the charge they present at different pH values. Electrostatic blockage is the predominant effect that governs the blockage in the interior of the nanochannel and is dependent not just in the charge inside the channel, but also in the polarity of the redox indicator used.

Bifunctional Au@Pt/Au nanoparticles as electrochemiluminescence signaling probes for SARS-CoV-2 detection.

A novel immunosensor based on electrochemiluminescence resonance energy transfer (ECL-RET) for the sensitive determination of N protein of the SARS-CoV-2 coronavirus is described. For this purpose, bifunctional core@shell nanoparticles composed of a Pt-coated Au core and finally decorated with small Au inlays (Au@Pt/Au NPs) have been synthesized to act as ECL acceptor, using [Ru (bpy)] as ECL donor. These nanoparticles are efficient signaling probes in the immunosensor developed.

Advances in the screening of antimicrobial compounds using electrochemical biosensors: is there room for nanomaterials?

The abusive use of antimicrobial compounds and the associated appearance of antimicrobial resistant strains are a major threat to human health. An improved antimicrobial administration involves a faster diagnosis and detection of resistances. Antimicrobial susceptibility testing (AST) are the reference techniques for this purpose, relying mainly in the use of culture techniques.

Electrochemical biosensors based on nanomaterials for aflatoxins detection: A review (2015-2021).

Due to their immunotoxicity, aflatoxins are considered as very important natural contaminants of a wide variety of agricultural products. Although conventional techniques such as high-performance liquid chromatography (HPLC) and gas chromatography (GC) combined with mass spectrometry (MS) have traditionally been used to detect such food contaminants, they are relatively expensive, laborious, and time consuming which limits their use for in field analysis at the so-called point-of-care (POC). Electrochemical biosensors are emerging devices that meet these expectations since they rely in reliable, simple, inexpensive, portable, selective, and easy-to-use analytical procedures and instruments that can be used by unskilled personnel outside the laboratory.

Electrical monitoring of infection biomarkers in chronic wounds using nanochannels.

Chronic wounds represent an important healthcare challenge in developed countries, being wound infection a serious complication with significant impact on patients' life conditions. However, there is a lack of methods allowing an early diagnosis of infection and a right decision making for a correct treatment. In this context, we propose a novel methodology for the electrical monitoring of infection biomarkers in chronic wound exudates, using nanoporous alumina membranes.

Advances in quantum dots as diagnostic tools.

Quantum dots (QDs) are crystalline inorganic semiconductor nanoparticles a few nanometers in size that possess unique optical electronic properties vs those of larger materials. For example, QDs usually exhibit a strong and long-lived photoluminescence emission, a feature dependent on size, shape and composition. These special optoelectronic properties make them a promising alternative to conventional luminescent dyes as optical labels in biomedical applications including biomarker quantification, biomolecule targeting and molecular imaging.

Enhancing the electrocatalytic activity of palladium nanocluster tags by selective introduction of gold atoms: Application for a wound infection biomarker detection.

In this work, an unprecedented study exploring the role that slight changes into the Pd/Au proportion have in the electrocatalytic activity of bimetallic Pd-AuNPs toward the oxygen reduction reaction (ORR) is conducted. In particular, a careful control of the amount of Au atoms introduced in the cluster and the evaluation of the optimum Pd:Au ratio for getting the maximum catalytic activity is performed for the first time. First, PdNPs are synthesized by alcohol reduction in the presence of polyvinylpyrrolidone, and gold atoms are selectively introduced on vertex or corner positions of the cluster in different amounts following a galvanic substitution procedure.

Unfolded p53 as a Marker of Oxidative Stress in Mild Cognitive Impairment, Alzheimer's and Parkinson's Disease.

Aims: There are several candidate biomarkers for AD and PD which differ in sensitivity, specificity, cost-effectiveness, invasiveness, logistical and technical demands. This study is aimed to test whether plasma concentration of unfolded p53 may help to discriminate among the neurodegenerative processes occurring in Mild Cognitive Impairment, Alzheimer's disease and Parkinson's disease.

Methods: An electrochemical immunosensor was used to measure unfolded p53 in plasma samples of 20 Mild Cognitive Impairment (13 males/7 females; mean age 74.

Strip modification and alternative architectures for signal amplification in nanoparticle-based lateral flow assays.

Nanoparticle (NP)-based lateral flow assay (LFA) technology has outstanding characteristics that make it ideal for point-of-care bioanalytical applications. However, LFAs still have important limitations, especially related to sensitivity, which is in general worse than that of other well-established bioassays such as ELISA or PCR. Many efforts have been made for enhancing the sensitivity of LFAs, mainly actuating on the nanoparticle labels and on alternative optical detection modes.

Electrochemical Biosensors Based on Nanomaterials for Early Detection of Alzheimer's Disease.

Alzheimer's disease (AD) is an untreatable neurodegenerative disease that initially manifests as difficulty to remember recent events and gradually progresses to cognitive impairment. The incidence of AD is growing yearly as life expectancy increases, thus early detection is essential to ensure a better quality of life for diagnosed patients. To reach that purpose, electrochemical biosensing has emerged as a cost-effective alternative to traditional diagnostic techniques, due to its high sensitivity and selectivity.

Folding-Based Electrochemical Aptasensor for the Determination of β-Lactoglobulin on Poly-L-Lysine Modified Graphite Electrodes.

Nowadays, food allergy is a very important health issue, causing adverse reactions of the immune system when exposed to different allergens present in food. Because of this, the development of point-of-use devices using miniaturized, user-friendly, and low-cost instrumentation has become of outstanding importance. According to this, electrochemical aptasensors have been demonstrated as useful tools to quantify a broad variety of targets.

Bifunctional Au@Pt/Au core@shell Nanoparticles As Novel Electrocatalytic Tags in Immunosensing: Application for Alzheimer's Disease Biomarker Detection.

In this work, bifunctional core@shell Au@Pt/Au NPs are presented as novel tags for electrochemical immunosensing. Au@Pt/Au NPs were synthesized following a chemical route based on successive metal depositions and galvanic replacement reactions from the starting AuNPs. Au protuberances growth on the surface of Au@Pt NPs allowed their easy bioconjugation with antibodies, while the high catalytic Pt surface area was approached for their sensitive detection through the electrocatalyzed water oxidation reaction (WOR) at neutral pH.

Electrochemical (Bio)Sensors for Pesticides Detection Using Screen-Printed Electrodes.

Pesticides are among the most important contaminants in food, leading to important global health problems. While conventional techniques such as high-performance liquid chromatography (HPLC) and mass spectrometry (MS) have traditionally been utilized for the detection of such food contaminants, they are relatively expensive, time-consuming and labor intensive, limiting their use for point-of-care (POC) applications. Electrochemical (bio)sensors are emerging devices meeting such expectations, since they represent reliable, simple, cheap, portable, selective and easy to use analytical tools that can be used outside the laboratories by non-specialized personnel.

Quantum Dot Bioconjugates for Diagnostic Applications.

Quantum dots (QDs) are a special type of engineered nanomaterials with outstanding optoelectronic properties that make them as a very promising alternative to conventional luminescent dyes in biomedical applications, including biomolecule (BM) targeting, luminescence imaging and drug delivery. A key parameter to ensure successful biomedical applications of QDs is the appropriate surface modification, i.e.

Electrochemical quantification of AgS quantum dots: evaluation of different surface coating ligands for bacteria determination.

In this work, novel silver sulphide quantum dots (AgS QD) are electrochemically quantified for the first time. The method is based on the electrochemical reduction of Ag to Ag at -0.3 V on screen-printed carbon electrodes (SPCEs), followed by anodic stripping voltammetric oxidation that gives a peak of currents at +0.

Direct competitive immunosensor for Imidacloprid pesticide detection on gold nanoparticle-modified electrodes.

A direct competitive immunosensor for the electrochemical determination of Imidacloprid (IMD) pesticide on gold nanoparticle-modified screen-printed carbon electrodes (AuNP-SPCE) is here reported for the first time. Self-obtained specific monoclonal antibodies are immobilized on the AuNP-SPCE taking advantage of the AuNPs biofunctionalization abilities. In our biosensor design, free IMD in the sample competes with IMD conjugated with horseradish peroxidase (IMD-HRP) for the recognition by the antibodies.

Nanoparticles as Emerging Labels in Electrochemical Immunosensors.

This review shows recent trends in the use of nanoparticles as labels for electrochemical immunosensing applications. Some general considerations on the principles of both the direct detection based on redox properties and indirect detection through electrocatalytic properties, before focusing on the applications for mainly proteins detection, are given. Emerging use as blocking tags in nanochannels-based immunosensing systems is also covered in this review.

Signal enhancement on gold nanoparticle-based lateral flow tests using cellulose nanofibers.

Lateral flow paper-based biosensors merge as powerful tools in point-of-care diagnostics since they are cheap, portable, robust, selective, fast and easy to use. However, the sensitivity of this type of biosensors is not always as high as required, often not permitting a clear quantification. To improve the colorimetric response of standard lateral flow strips (LFs), we have applied a new enhancement strategy that increases the sensitivity of LFs based on the use of cellulose nanofibers (CNF).

Simple and rapid electrochemical quantification of water-stabilized HgSe nanoparticles of great concern in environmental studies.

The sensitive monitoring of mercury (II) selenide nanoparticles (HgSe NPs) is of great potential relevance in environmental studies, since such NPs are believed to be the ultimate metabolic product of the lifesaving mechanism pathway of Hg detoxification in biological systems. In this context, we take advantage of using gold-nanostructured screen-printed carbon electrodes (SPCE-Au) for the rapid, simple and sensitive electrochemical quantification of engineered water-stable HgSe NPs, as an advantageous alternative to conventional elemental analysis techniques. HgSe NPs are first treated in an optimized oxidative/acidic medium for Hg release, followed by sensitive electrochemical detection by anodic stripping voltammetry (ASV).

A monoclonal antibody-based immunosensor for the electrochemical detection of imidacloprid pesticide.

Imidacloprid (IMD) is one of the most used pesticides worldwide as a systemic insecticide as well as for pest control and seed treatment. The toxic and potential carcinogenic character of IMD makes its monitoring of great relevance in the field of agriculture and environment, so sensitive methodologies for in field analysis are strongly required. In this context, we have developed a competitive immunoassay for the determination of IMD using specific monoclonal antibodies followed by electrochemical detection on screen-printed carbon electrodes (SPCE).

Electrical Evaluation of Bacterial Virulence Factors Using Nanopores.

In this work, we propose a novel methodology for electrical monitoring using nanoporous alumina membranes of virulence factors secreted by bacterial pathogens. Bacterial hyaluronidase (HYAL), which is produced by a number of invasive Gram-positive bacteria, is selected as a model compound to prove the concept. Our electrochemical setup takes advantage of the flat surface of indium tin oxide/poly(ethylene terephthalate) (ITO/PET) electrodes for their assembly with the nanoporous membrane.

Iridium oxide (IV) nanoparticle-based lateral flow immunoassay.

Lateral flow biosensors are paper-based devices that allow the detection of different types of analytes with quickness, robustness and selectivity, without leaving behind paper sensors benefits as low-cost, recyclability and sustainability. Nanomaterials have been widely reported in lateral flow biosensors, offering new sensing strategies based on optical or electrical detection techniques. Looking for other advantageous nanomaterials, we propose for the first time the use of iridium oxide (IV) nanoparticles in lateral flow assays for the detection of human immunoglobulin as a model protein.

In Situ Plant Virus Nucleic Acid Isothermal Amplification Detection on Gold Nanoparticle-Modified Electrodes.

Solid-phase isothermal recombinase polymerase amplification (RPA) offers many benefits over the standard RPA in homogeneous phase in terms of sensitivity, portability, and versatility. However, RPA devices reported to date are limited by the need for heating sources to reach sensitive detection. With the aim of overcoming such limitation, we propose here a label-free highly integrated in situ RPA amplification/detection approach at room temperature that takes advantage of the high sensitivity offered by gold nanoparticle (AuNP)-modified sensing substrates and electrochemical impedance spectroscopic (EIS) detection.