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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.

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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.

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Wearable sensors such as those made with paper are needed for non-destructive routine analysis of pesticides on plants, fruits, and vegetables. Herein we report on electrochemical sensors made with screen-printed carbon electrodes on kraft and parchment papers to detect the fungicide carbendazim. A systematic optimization was performed to find that electrochemical sensors on kraft paper treated in an acidic medium led to the highest performance, with a detection limit of 0.06 µM for carbendazim. The enhanced sensitivity for this sensor was attributed to the porous nature of kraft paper, which allowed for a large electrode surface area, and to the carboxylic groups formed during electrochemical activation. As a proof-of-concept, the electrochemical sensor attached to the skin of apple and cabbage was used to detect carbendazim with the same performance as the gold standard method, thus demonstrating that the sensor can be used in the farm and on supermarket shelves.

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Flexible, fully printed immunosensors can meet the requirements of precision nutrition, but this demands optimized molecular architectures to reach the necessary sensitivity. Herein, we report on flexible and label-free immunosensor chips made with tree-like gold dendrites (AuDdrites) electrochemically formed by selective desorption of l-cysteine (L-cys) on (111) gold planes. Electrodeposition was used because it is scalable and cost-effective for a rapid, direct growth of Au hyperbranched dendritic structures. The 25-hydroxyvitamin D3 (25(OH)D3) metabolite was detected within 15 min with a limit of detection (LOD) of 0.03 ng mL-1. This high performance was possible due to the careful optimization of the electroactive layer and working conditions for square wave voltammetry (SWV). Electrocrystallization was manipulated by controlling the deposition potential and the molar ratio between HAuCl4 and L-cys. Metabolite detection was performed on human serum and saliva samples with adequate recovery between 97% and 100%. The immunosensors were stable and reproducible, unresponsive to interference from other molecules in human serum and saliva. They can be extended for use as wearable sensors with their mechanical flexibility and possible customization.

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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.

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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 (

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A sensitive detection of carbohydrate antigen 15-3 (CA15-3) levels may allow for early diagnosis and monitoring the treatment of breast cancer, but this can only be made in routine clinical practice if low-cost immunosensors are available. In this work, we developed a sandwich-type electrochemical immunosensor capable of rapid detection of CA15-3 with an ultra-low limit of detection (LOD) of 0.08 fg mL-1 within a wide linear concentration range from 0.1 fg mL-1 to 1 µg mL-1. The immunosensor had a matrix of a layer-by-layer film of Au nanoparticles and reduced graphene oxide (Au-rGO) co-electrodeposited on screen-printed carbon electrodes (SPCE). The high sensitivity was achieved by using secondary antibodies (Ab2) labeled with horseradish peroxidase (HRP) in the presence of hydrogen peroxide (H2O2) as signal amplifiers, and hydroquinone (HQ) was used as an electron mediator. The immunosensor was selective for CA15-3 in human serum and artificial saliva samples, robust, and stable to permit storage at 4 °C for more than 30 days. With its high performance, the immunosensor may be incorporated into future point-of-care (POC) devices to determine CA15-3 in distinct biological fluids, including in blood and saliva samples.

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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.

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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.

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BACKGROUND: Prostate cancer is the most common visceral neoplasia in men and frequently presents chemotherapy resistance. In this context, lemongrass (Cymbopogon citratus (D.C.) Stapf) has been studied since it presents many important biological activities, such as anticancer. OBJECTIVE: We investigated the antitumor effect of lemongrass and in chemotherapy activity using prostate cancer cells line (DU-145). METHODS: DU-145 cells were exposed to different concentrations of aqueous extract of lemongrass (30; 100; 300; 500 and 1000 µg/mL), isolated and in combination with docetaxel, during 24 and 72 hours. After, cell viability and proliferation, oxidative metabolism, colony formation and cell cycle analyses were performed. Also, we exposed the African green monkey kidney cell line (VERO) to the same lemongrass concentrations to investigate a possible toxicity of this extract. RESULTS: Our findings suggested that lemongrass presented an antitumor effect and improved docetaxel chemotherapy activity by decreasing cell viability and proliferation as well as colony formation. Moreover, we found an oxidative stress increased and cell cycle arresting in G0 /G1 phase. In addition, this extract presented selectivity action for cancer cells, since it did not cause cytotoxicity in normal cells, ensuring non-toxic therapeutic concentrations. CONCLUSION: Lemongrass is a promising medicinal plant that could be used during chemotherapeutic treatment, in order to potentiate the antitumor response and decrease the resistance of prostate cancer.

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