Core-Shell Nanocables Decorated with Carbon Spherical Shells and Silver Nanoparticles for Sensing Ethinylestradiol Hormone in Water Sources and Pills.

The selective, rapid detection of low levels of hormones in drinking water and foodstuffs requires materials suitable for inexpensive sensing platforms. We report on core-shell Ag@C nanocables (NCs) decorated with carbon spherical shells (CSSs) and silver nanoparticles (AgNPs) by using a hydrothermal green approach. Sensors were fabricated with homogeneous, porous films on screen-printed electrodes, which comprised a 115 nm silver core covered by a 122 nm thick carbon layer and CSSs with 168 nm in diameter. NCs and CSSs were also decorated with 10-25 nm AgNPs. The NC/CSS/AgNP sensor was used to detect ethinylestradiol using square wave voltammetry in 0.1 M phosphate buffer (pH 7.0) over the 1.0-10.0 µM linear range with a detection limit of 0.76 µM. The sensor was then applied to detect ethinylestradiol in tap water samples and a contraceptive pill with recovery percentages between 93 and 101%. The high performance in terms of sensitivity and selectivity for hormones is attributed to the synergy between the carbon nanomaterials and AgNPs, which not only increased the sensor surface area and provided sites for electron exchange but also imparted an increased surface area.

Sustainable plant-wearable sensors for on-site, rapid decentralized detection of pesticides toward precision agriculture and food safety.

The synergy between eco-friendly biopolymeric films and printed devices leads to the production of plant-wearable sensors for decentralized analysis of pesticides in precision agriculture and food safety. Herein, a simple method for fabrication of flexible, and sustainable sensors printed on cellulose acetate (CA) substrates has been demonstrated to detect carbendazim and paraquat in agricultural, water and food samples. The biodegradable CA substrates were made by casting method while the full electrochemical system of three electrodes was deposited by screen-printing technique (SPE) to produce plant-wearable sensors. Analytical performance was assessed by differential pulse (DPV) and square wave voltammetry (SWV) in a linear concentration range between 0.1 and 1.0 µM with detection limits of 54.9 and 19.8 nM for carbendazim and paraquat, respectively. The flexible and sustainable non-enzymatic plant-wearable sensor can detect carbendazim and paraquat on lettuce and tomato skins, and also water samples with no interference from other pesticides. The plant-wearable sensors had reproducible response being robust and stable against multiple flexions. Due to high sensitivity and selectivity, easy operation and rapid agrochemical detection, the plant-wearable sensors can be used to detect biomarkers in human biofluids and be used in on-site analysis of other hazardous chemical substances.

Biosensors for Monitoring of Biologically Relevant Molecules.

Since the creation of the glucose enzyme sensor in the early 1960s by Clark and Lyons [...].

On-Site Therapeutic Drug Monitoring of Paracetamol Analgesic in Non-Invasively Collected Saliva for Personalized Medicine.

Paracetamol or acetaminophen is the main non-opioid analgesic recommended for mild pain by the World Health Organization (WHO) analgesic ladder. However, the high levels used of paracetamol are associated with the hepatotoxicity and nephrotoxicity caused by accumulation of toxic metabolites. The sensor is produced on a polyester substrate containing a full electrochemical device with working, auxiliary, and reference electrodes in which, guiding personalized medicine solutions are not reported. Temporal paracetamol profiles in human saliva are performed with the subject taking different amounts of commercial analgesic pills. The variation of saliva paracetamol levels is demonstrated to be interference free from electroactive interfering species and human saliva constituents. In addition, the sensor displays to be useful as a disposable device for the fast detection of paracetamol in untreated raw saliva following pill intake. The maximum concentration (Cmax ) and half-life time (t1/2 ) for paracetamol are 143.27 µm and 110 min. The results demonstrate the potential of a simple strategy with electrochemical devices for noninvasive personalized therapy toward guiding drug interventions through tracking of active substance, detecting, and correcting insufficiency of absorption to meet individual needs avoiding overdoses, side effects, and intoxication.

Wearable potentiometric biosensor for analysis of urea in sweat.

Herein, we introduce wearable potentiometric biosensors on screen-printed carbon electrodes (SPCEs) for on-body and on-site monitoring of urea in sweat. The biosensor architecture was judiciously designed to detect urea at different pHs and incorporate a pH sensor, thus containing polyaniline ink, urease bioink and a polyvinylchloride membrane. Urea detection could be performed in the wide range from 5 to 200 mM at pH 7.0, encompassing urea levels in human sweat. The biosensor response was fast (incubation time 5 min), with no interference from other substances in sweat. Reliable urea detection could be done in undiluted human sweat with a skin-worn flexible device using the pH correction strategy afforded by the pH sensor. The performance of the epidermal biosensor was not affected by severe bending strains. The feasibility of mass production was demonstrated by fabricating epidermal flexible biosensors using slot-die coating with a roll-to-roll technique.

Development and Application of an SPR Nanobiosensor Based on AuNPs for the Detection of SARS-CoV-2 on Food Surfaces.

A new transmission route of SARS-CoV-2 through food was recently considered by the World Health Organization (WHO), and, given the pandemic scenario, the search for fast, sensitive, and low-cost methods is necessary. Biosensors have become a viable alternative for large-scale testing because they overcome the limitations of standard techniques. Herein, we investigated the ability of gold spherical nanoparticles (AuNPs) functionalized with oligonucleotides to detect SARS-CoV-2 and demonstrated their potential to be used as plasmonic nanobiosensors. The loop-mediated isothermal amplification (LAMP) technique was used to amplify the viral genetic material from the raw virus-containing solution without any preparation. The detection of virus presence or absence was performed by ultraviolet-visible (UV-Vis) absorption spectroscopy, by monitoring the absorption band of the surface plasmonic resonance (SPR) of the AuNPs. The displacement of the peak by 525 nm from the functionalized AuNPs indicated the absence of the virus (particular region of gold). On the other hand, the region ~300 nm indicated the presence of the virus when RNA bound to the functionalized AuNPs. The nanobiosensor system was designed to detect a region of the N gene in a dynamic concentration range from 0.1 to 50 × 103 ng·mL-1 with a limit of detection (LOD) of 1 ng·mL-1 (2.7 × 103 copy per µL), indicating excellent sensitivity. The nanobiosensor was applied to detect the SARS-CoV-2 virus on the surfaces of vegetables and showed 100% accuracy compared to the standard quantitative reverse transcription polymerase chain reaction (RT-qPCR) technique. Therefore, the nanobiosensor is sensitive, selective, and simple, providing a viable alternative for the rapid detection of SARS-CoV-2 in ready-to-eat vegetables.

Low-cost bacterial nanocellulose-based interdigitated biosensor to detect the p53 cancer biomarker.

Low-cost sensors to detect cancer biomarkers with high sensitivity and selectivity are essential for early diagnosis. Herein, an immunosensor was developed to detect the cancer biomarker p53 antigen in MCF7 lysates using electrical impedance spectroscopy. Interdigitated electrodes were screen printed on bacterial nanocellulose substrates, then coated with a matrix of layer-by-layer films of chitosan and chondroitin sulfate onto which a layer of anti-p53 antibodies was adsorbed. The immunosensing performance was optimized with a 3-bilayer matrix, with detection of p53 in MCF7 cell lysates at concentrations between 0.01 and 1000 Ucell. mL-1, and detection limit of 0.16 Ucell mL-1. The effective buildup of the immunosensor on bacterial nanocellulose was confirmed with polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) and surface energy analysis. In spite of the high sensitivity, full selectivity with distinction of the p53-containing cell lysates and possible interferents required treating the data with a supervised machine learning approach based on decision trees. This allowed the creation of a multidimensional calibration space with 11 dimensions (frequencies used to generate decision tree rules), with which the classification of the p53-containing samples can be explained.

Updating the use of nano-biosensors as promising devices for the diagnosis of coronavirus family members: A systematic review.

Coronavidae viruses, such as SARS-CoV, SARS-CoV-2, and MERS-CoV, cause severe lower respiratory tract infection, acute respiratory distress syndrome and extrapulmonary manifestations, such as diarrhea and fever, eventually leading to death. Fast, accurate, reproductible, and cost-effective SARS-CoV-2 identification can be achieved employing nano-biosensors, reinforcing conventional methodologies to avoid the spread of COVID-19 within and across communities. Nano-biosensors built using gold, silver, graphene, In2O3 nanowire and iron oxide nanoparticles, Quantum Dots and carbon nanofibers have been successfully employed to detect specific virus antigens - nucleic acid sequences and/or proteins -or host antibodies produced in response to viral infection. Biorecognition counterpart molecules have been immobilized on the surface of these nanomaterials, leading to selective virus detection by optical or electrochemical transducer systems. This systematic review assessed studies on described and tested immunonsensors and genosensors designed from distinct nanomaterials available at the Pubmed, Scopus, and Science Direct databases. Twenty-three nano biosensors were found suitable for unequivocal coronavirus detection in clinical samples. Nano-biosensors coupled to RT-LAMP/RT-PCR assays can optimize RNA extraction, reduce analysis times and/or eliminate sophisticated instrumentation. Although promising for the diagnosis of Coronavidae family members, further trials in large populations must be adequately and rigorously conducted to address nano-biosensor applicability in the clinical practice for early coronavirus infection detection.

Electrochemical immunosensors using electrodeposited gold nanostructures for detecting the S proteins from SARS-CoV and SARS-CoV-2.

This paper reports the development of a low-cost (< US$ 0.03 per device) immunosensor based on gold-modified screen-printed carbon electrodes (SPCEs). As a proof of concept, the immunosensor was tested for a fast and sensitive determination of S proteins from both SARS-CoV and SARS-CoV-2, by a single disposable device. Gold nanoparticles were electrochemically deposited via direct reduction of gold ions on the electrode using amperometry. Capture antibodies from spike (S) protein were covalently immobilized on carboxylic groups of self-assembled monolayers (SAM) of mercaptoacetic acid (MAA) attached to the gold nanoparticles. Label-free detection of S proteins from both SARS-CoV and SARS-CoV-2 was performed with electrochemical impedance spectroscopy (EIS). The immunosensor fabricated with 9 s gold deposition had a high performance in terms of selectivity, sensitivity, and low limit of detection (LOD) (3.16 pmol L-1), thus permitting the direct determination of the target proteins in spiked saliva samples. The complete analysis can be carried out within 35 min using a simple one-step assay protocol with small sample volumes (10 µL). With such features, the immunoplatform presented here can be deployed for mass testing in point-of-care settings.

Wearable sensors made with solution-blow spinning poly(lactic acid) for non-enzymatic pesticide detection in agriculture and food safety.

On-site monitoring the presence of pesticides on crops and food samples is essential for precision and post-harvest agriculture, which demands nondestructive analytical methods for rapid, low-cost detection that is not achievable with gold standard methods. The synergy between eco-friendly substrates and printed devices may lead to wearable sensors for decentralized analysis of pesticides in precision agriculture. In this paper we report on a wearable non-enzymatic electrochemical sensor capable of detecting carbamate and bipyridinium pesticides on the surface of agricultural and food samples. The low-cost devices (

Flexible and integrated dual carbon sensor for multiplexed detection of nonylphenol and paroxetine in tap water samples.

Multiplex detection of emerging pollutants is essential to improve quality control of water treatment plants, which requires portable systems capable of real-time monitoring. In this paper we describe a flexible, dual electrochemical sensing device that detects nonylphenol and paroxetine in tap water samples. The platform contains two voltammetric sensors, with different working electrodes that were either pretreated or functionalized. Each working electrode was judiciously tailored to cover the concentration range of interest for nonylphenol and paroxetine, and square wave voltammetry was used for detection. An electrochemical pretreatment with sulfuric acid on the printed electrode enabled a selective detection of nonylphenol in 1.0-10 × 10-6 mol L-1 range with a limit of detection of 8.0 × 10-7 mol L-1. Paroxetine was detected in the same range with a limit of detection of 6.7 × 10-7 mol L-1 using the printed electrode coated with a layer of carbon spherical shells. Simultaneous detection of the two analytes was achieved in tap water samples within 1 min, with no fouling and no interference effects. The long-term monitoring capability of the dual sensor was demonstrated in phosphate buffer for 45 days. This performance is statistically equivalent to that of high-performance liquid chromatography (HPLC) for water analysis. The dual-sensor platform is generic and may be extended to other water pollutants and clinical biomarkers in real-time monitoring of the environment and health conditions. Silver pseudo-reference electrodes for paroxetine (REP) and nonylphenol (REN), working electrodes for paroxetine (WP) and nonylphenol (WN), and auxiliary electrode (AE). USP refers to the University of Sao Paulo. "Red" is reduced form and "Oxi" is oxidized form of analytes.

Biomimetic electrochemical sensors: New horizons and challenges in biosensing applications.

The urge to meet the ever-growing needs of sensing technology has spurred research to look for new alternatives to traditional analytical methods. In this scenario, the glucometer is the flagship of commercial electrochemical sensing platforms, combining selectivity, reliability and portability. However, other types of enzyme-based biosensors seldom achieve the market, in spite of the large and increasing number of publications. The reasons behind their commercial limitations concern enzyme denaturation, and the high costs associated with procedures for their extraction and purification. In this sense, biomimetic materials that seek to imitate the desired properties of natural enzymes and biological systems have come out as an appealing path for robust and sensitive electrochemical biosensors. We herein portray the historical background of these biomimicking materials, covering from their beginnings until the most impactful applications in the field of electrochemical sensing platforms. Throughout the discussion, we present and critically appraise the major benefits and the most significant drawbacks offered by the bioinspired systems categorized as Nanozymes, Synzymes, Molecularly Imprinted Polymers (MIPs), Nanochannels, and Metal Complexes. Innovative strategies of fabrication and challenging applications are further reviewed and evaluated. In the end, we ponder over the prospects of this emerging field, assessing the most critical issues that shall be faced in the coming decade.

Polyphenol oxidase-based electrochemical biosensors: A review.

The detection of phenolic compounds is relevant not only for their possible benefits to human health but also for their role as chemical pollutants, including as endocrine disruptors. The required monitoring of such compounds on-site or in field analysis can be performed with electrochemical biosensors made with polyphenol oxidases (PPO). In this review, we describe biosensors containing the oxidases tyrosinase and laccase, in addition to crude extracts and tissues from plants as enzyme sources. From the survey in the literature, we found that significant advances to obtain sensitive, robust biosensors arise from the synergy reached with a diversity of nanomaterials employed in the matrix. These nanomaterials are mostly metallic nanoparticles and carbon nanostructures, which offer a suitable environment to preserve the activity of the enzymes and enhance electron transport. Besides presenting a summary of contributions to electrochemical biosensors containing PPOs in the last five years, we discuss the trends and challenges to take these biosensors to the market, especially for biomedical applications.

Pen sensor made with silver nanoparticles decorating graphite-polyurethane electrodes to detect bisphenol-A in tap and river water samples.

Rapid, on-site detection of emerging pollutants is critical for monitoring health threats and the environment, especially if performed through autonomous systems. In this paper, we report on a new design of a complete electrochemical system whose working (WE), auxiliary (AE) and reference (RE) electrodes were obtained on a pen (PEN Sensor) made with graphite:polyurethane (GPUE). Working electrodes were decorated with spherical, ca. 200 nm silver nanoparticles (AgNPs) reduced on graphite using the polyol method. Differential pulse voltammetry (DPV) was used to detect bisphenol-A (BPA) in a linear range from 2.5 to 15 µmol L-1 with detection limit of 0.24 µmol L-1. The PEN Sensor could also detect bisphenol-A in tap and river water samples, with satisfactory reproducibility and repeatability, while common interferents did not affect electrooxidation of bisphenol-A. The high sensitivity and rapid detection are suitable for real-time analysis and in loco monitoring of emerging pollutants. With their robustness and versatility, PEN Sensors such as those fabricated here may be integrated into futuristic smart robotic systems.

Microbial nanocellulose adherent to human skin used in electrochemical sensors to detect metal ions and biomarkers in sweat.

The pursuit of biocompatible, breathable and skin-conformable wearable sensors has predominantly focused on synthetic stretchable hydrophobic polymers. Microbial nanocellulose (MNC) is an exceptional skin-substitute natural polymer routinely used for wound dressing and offers unprecedented potential as substrate for wearable sensors. A versatile strategy for engineering wearable sensing platforms is reported, with sensing units made of screen-printed carbon electrodes (SPCEs) on MNC. As-prepared SPCEs were used to detect the toxic metals cadmium (Cd2+) and lead (Pb2+) with limits of detection of 1.01 and 0.43 µM, respectively, which are sufficient to detect these metal ions in human sweat and urine. SPCEs functionalized through anodic pre-treatments were used for detecting uric acid and 17ß-estradiol in artificial sweat, with detection limits of 1.8 µM and 0.58 µM, respectively. The electrochemical treatment created oxygen groups on the carbon surfaces, thus improving wettability and hydrophilicity. MNC was herein exploited as an adhesive-free, yet highly skin-adherent platform for wearable sensing devices that also benefit from the semi-permeable, non-allergenic, and renewable features that make MNC unique within the pool of materials that have been used for such a purpose. Our findings have clear implications for the developments on greener and more biocompatible but still efficient substrates and may pave the route for combining immunosensing devices with drug delivery therapies.

Genosensor made with a self-assembled monolayer matrix to detect MGMT gene methylation in head and neck cancer cell lines.

DNA methylation is involved in the oncogenesis of head and neck squamous cell carcinoma and could be used for early detection of cancer to increase the chances of cure, but unfortunately diagnosis is usually made at late stages of the disease. In this work we developed genosensors to detect DNA methylation of the MGMT gene in head and neck cancer cell lines. The probe for MGMT promoter methylation was immobilized on gold electrodes modified with 11-mercaptoundecanoic acid (11-MUA) self-assembled monolayers (SAM). Detection was performed with electrochemical impedance spectroscopy, with clear distinction between methylated and non-methylated DNA from head and neck cell lines. The genosensor is sensitive with a low detection limit of 0.24 × 10-12 mol L-1. In addition, the cell lines FaDu, JHU28 and SCC25 for the MGMT gene, could be distinguished from the HN13 cell line which has a high degree of MGMT methylation (97%), thus confirming the selectivity. Samples with different percentages of MGMT DNA methylation could be separated in multidimensional projections using the visualization technique interactive document mapping (IDMAP). The genosensor matrix and the immobilization procedures are generic, and can be extended to other DNA methylation biomarkers.

Enzymatic biofuel cells based on protective hydrophobic carbon paste electrodes: towards epidermal bioenergy harvesting in the acidic sweat environment.

The operation of wearable epidermal biofuel cells is prone to rapid irreversible deactivation effects under dynamic sweat pH changes from neutral to acidic. We demonstrate that the encapsulation of lactate-oxidase (LOx) within a hydrophobic protective carbon-paste anode imparts unusually high stability during dynamically changing pH fluctuations and allows the BFC to continue harvesting the lactate bioenergy even after long exposures to acidic conditions. The unique power-recovery ability of the carbon-paste BFC after its failure in harsh pH is attributed to the protective action of the non-polar paste environment.

Use of zein microspheres to anchor carbon black and hemoglobin in electrochemical biosensors to detect hydrogen peroxide in cosmetic products, food and biological fluids.

Hemoglobin-containing electrochemical biosensors are useful for detecting hydrogen peroxide through oxidation of the iron ion, but high efficiency can only be reached with appropriate immobilization strategies for hemoglobin. In this work, we combined zein from corn seed with carbon black to immobilize hemoglobin, as proof of concept, and form an electroactive film that could determine hydrogen peroxide within the concentration range from 4.9 × 10-6 to 3.9 × 10-4 mo L-1, and limit of detection of 4.0 × 10-6 mol L-1, using differential pulse voltammetry. The biosensor could also detect hydrogen peroxide in commercial samples of oxygenated water, synthetic serum (physiological and glycoside) and milk. The high performance is ascribed to the large surface area and conductive nature of the porous film that had carbon black and hemoglobin anchored on zein microspheres, according to scanning and transmission electron microscopies. It is significant that a protein from renewable sources (zein) combined with a low-cost carbon material (carbon black) serves as matrix for immobilization of biomolecules.

Electrochemical biosensor made with tyrosinase immobilized in a matrix of nanodiamonds and potato starch for detecting phenolic compounds.

The envisaged ubiquitous sensing and biosensing for varied applications has motivated materials development toward low cost, biocompatible platforms. In this paper, we demonstrate that carbon nanodiamonds (NDs) can be combined with potato starch (PS) and be deposited on a glassy carbon electrode (GCE) in the form of a homogeneous, rough film, with electroanalytical performance tuned by varying the relative ND-PS concentration. As a proof of concept, the ND/PS film served as matrix to immobilize tyrosinase (Tyr) and the resulting Tyr-ND-PS/GCE biosensor was suitable to detect catechol using differential pulse voltammetry with detection limit of 3.9 × 10-7 mol L-1 in the range between 5.0 × 10-6 and 7.4 × 10-4 mol L-1. Catechol could also be detected in river and tap water samples. This high sensitivity, competitive with biosensors made with more sophisticated procedures and materials in the literature, is attributed to the large surface area and conductivity imparted by the small NDs (<5 nm). In addition, the ND-PS matrix may have its use extended to immobilize other enzymes and biomolecules, thus representing a potential biocompatible platform for ubiquitous biosensing.

Sensitive detection of estriol hormone in creek water using a sensor platform based on carbon black and silver nanoparticles.

We report the electrochemical detection of estriol using carbon black nanoballs (CNB) decorated with silver nanoparticles (AgNP) as electrode material. Homogeneous, porous films on glassy carbon electrodes (GCE) were obtained, with diameters of 20 - 25nm for CNB and 5 - 6nm for AgNP. CNB/AgNP electrodes had increased conductivity and electroactive area in comparison with bare GCE and GCE/CNB, according to cyclic voltammetry and electrochemical impedance spectroscopy. The oxidation potential peak was also down shifted by 93mV, compared to the bare GC electrode. Differential pulse voltammetry data were obtained in 0.1molL-1 PBS (pH 7.0) to detect estriol without the purification step, in the linear range between 0.2 and 3.0µmolL-1 with detection and quantification limits of 0.16 and 0.5µmolL-1 (0.04 and 0.16mgL-1), respectively. The sensor was used to detect estriol in a creek water sample with the same performance as in the official methodology based on high performance liquid chromatography.