Impedimetric Biosensor Research Articles

An Impedimetric Biosensing Strategy Based on BicyclicPeptides as Bioreceptors for Monitoring h-uPA Cancer Biomarkers

In the era of liquid biopsies, the reliable and cost-effective detection and screening of cancer biomarkers has become of fundamental importance, thus paving the way for the advancement of research in the field of point-of-care testing and the development of new methodologies and technologies. Indeed, the latter ones can help designing advanced diagnostic tools that can offer portability, ease of use with affordable production and operating costs. In this respect, impedance-based biosensing platforms might represent an attractive alternative. In this work, we describe a proof-of-concept study aimed at designing portable impedimetric biosensors for the monitoring of human urokinase-type plasminogen activator (h-uPA) cancer biomarker by employing small synthetic receptors. Aberrant levels of h-uPA were correlated with different types of cancers. Herein, we report the use of two bicyclic peptides (P2 and P3) which have been engineered to bind h-uPA with high affinity and exquisite specificity. The synthetic receptors were immobilized via biotin-streptavidin chemistry on the surface of commercial screen-printed electrodes. The impedimetric changes in the electrode/solution interface upon incubation of spiked h-uPA samples in the presence of a redox probe were followed via electrochemical impedance spectroscopy. The P3-based impedimetric assay showed the best outcomes in terms of dynamic range and linearity (0.01–1 μg mL−1) and sensitivity (LOD = 9 ng mL−1). To fully assess the performances of P3 over P2, and to compare the label-free architecture vs. labelled architecture, a voltammetric assay was also developed.

ZnO-Based Electrochemical Immunosensor to Assess Vaccine-Induced Antibody-Mediated Immunity against Wild-Type and Gamma SARS-CoV-2 Strains

The evaluation of serological responses to COVID-19 is crucial for population-level surveillance, developing new vaccines, and evaluating the efficacy of different immunization programs. Research and development of point-of-care test technologies remain essential to improving immunity assessment, especially for SARS-CoV-2 variants that partially evade vaccine-induced immune responses. In this work, an impedimetric biosensor based on the immobilization of the recombinant trimeric wild-type spike protein (S protein) on zinc oxide nanorods (ZnONRs) was employed for serological evaluation. We successfully assessed its applicability using serum samples from spike-based COVID-19 vaccines: ChAdOx1-S (Oxford-AstraZeneca) and BNT162b2 (Pfizer-BioNTech). Overall, the ZnONRs/ spike-modified electrode displayed accurate results for both vaccines, showing excellent potential as a tool for assessing and monitoring seroprevalence in the population. A refined outcome of this technology was achieved when the ZnO immunosensor was functionalized with the S protein from the P.1 linage (Gamma variant). Serological responses against samples from vaccinated individuals were acquired with excellent performance. Following studies based on traditional serological tests, the ZnONRs/spike immunosensor data reveal that ChAdOx1-S vaccinated individuals present significantly less antibody-mediated immunity against the Gamma variant than the BNT162b2 vaccine, highlighting the great potential of this point-of-care technology for evaluating vaccine-induced humoral immunity against different SARS-CoV-2 strains.

An Impedimetric Biosensor for Detection of Volatile Organic Compounds in Food.

The demand for a wide choice of food that is safe and palatable increases every day. Consumers do not accept off-flavors that have atypical odors resulting from internal deterioration or contamination by substances alien to the food. Odor response depends on the volatile organic compounds (VOCs), and their detection can provide information about food quality. Gas chromatography/mass spectrometry is the most powerful method available for the detection of VOC. However, it is laborious, costly, and requires the presence of a trained operator. To develop a faster analytic tool, we designed a non-Faradaic impedimetric biosensor for monitoring the presence of VOCs involved in food spoilage. The biosensor is based on the use of the pig odorant-binding protein (pOBP) as the molecular recognition element. We evaluated the affinity of pOBP for three different volatile organic compounds (1-octen-3-ol, trans-2-hexen-1-ol, and hexanal) related to food spoilage. We developed an electrochemical biosensor conducting impedimetric measurements in liquid and air samples. The impedance changes allowed us to detect each VOC sample at a minimum concentration of 0.1 μM.

Bacteriophage-based nano-biosensors for the fast impedimetric determination of pathogens in food samples

The early and rapid detection of pathogenic microorganisms is of critical importance in addressing serious public health issues. Here, a new bacteriophage-based nano-biosensor was constructed and the electrochemical impedimetric method was fully optimized and applied for the quantitative detection of Escherichia coli O157:H7 in food samples. The impact of using a nanocomposite consisting of gold nanoparticles (AuNPs), multi-walled carbon nanotubes (MWCNTs), and tungsten oxide nanostructures (WO3) on the electrochemical performance of disposable screen printed electrodes was identified using the cyclic voltammetry and electrochemical impedance spectroscopy. The use nanomaterials enabled high capturing sensitivity against the targeting bacterial host cells with the limit of detection of 3.0 CFU/ml. Moreover, selectivity of the covalently immobilized active phage was tested against several non-targeting bacterial strains, where a high specificity was achieved. Thus, the targeting foodborne pathogen was successfully detected in food samples with high specificity, and the sensor provided an excellent recovery rate ranging from 90.0 to 108%. Accordingly, the newly developed phage-biosensor is recommended as a disposable label-free impedimetric biosensor for the quick and real-time monitoring of food quality.

Electrochemical biosensors based on in situ grown carbon nanotubes on gold microelectrode array fabricated on glass substrate for glucose determination

A highly sensitive electrochemical sensor is reported for glucose detection using carbon nanotubes grown in situ at low temperatures on photolithographically defined gold microelectrode arrays printed on a glass substrate (CNTs/Au MEA). One of the main advantages of the present design is its potential to monitor 64 samples individually for the detection of glucose. The selectivity of the fabricated MEA towards glucose detection is achieved via modification of CNTs/Au MEA by immobilizing glucose oxidase (GOx) enzyme in the matrix of poly (paraphenylenediamine) (GOx/poly (p-PDA)/CNTs/Au MEA). The electrocatalytic and electrochemical responses of the proposed sensing platform towards glucose determination were examined via cyclic voltammetry and electrochemical impedance spectroscopy. The developed impedimetric biosensor exhibits a good linear response towards glucose detection, i.e., 0.2–27.5 µM concentration range with sensitivity and detection limits of 168.03 kΩ−1 M−1 and 0.2 ± 0.0014 μM, respectively. The proposed glucose biosensor shows excellent reproducibility, good anti-interference property, and was successfully tested in blood serum samples. Further, the applicability of the proposed sensor was successfully validated through HPLC. These results supported the viability of using such devices for the simultaneous detection of multiple electroactive biomolecules of physiological relevance.Graphical

Impedimetric Biosensor Coated with Zinc Oxide Nanorods Synthesized by a Modification of the Hydrothermal Method for Antibody Detection

Impedimetric biosensors are used for detecting a wide range of analytes. The detection principle is a perspective for the development of new types of analytical devices for biomolecular diagnosis of diseases. Of particular interest are biosensors with very high sensitivities, capable of detecting trace amounts of biomarkers or drugs in biological fluids. Impedimetric biosensors possess a potential for increased sensitivity, since their electrodes can be modified with nanostructured materials, in particular zinc oxide. In this work, a miniature biosensor with an array of zinc oxide nanorods synthesized by the hydrothermal method has been created. Protein A was immobilized on the resulting structure, which was previously tested for binding to omalizumab by capillary electrophoresis. Using impedance spectroscopy, it was possible to detect the binding of omalizumab at concentrations down to 5 pg/mL. The resulting structures are suitable for creating reusable biosensor systems, since ZnO-coated electrodes are easily cleaned by photocatalytic decomposition of the bound molecules. The biosensor is promising for use in Point-of-Care systems designed for fast, multimodal detection of molecular markers of a wide range of diseases.

Silver nanoparticle doped graphene-based impedimetric biosensor towards sensitive detection of procalcitonin

In the early detection of sepsis, procalcitonin (PCT) appears to be a highly sensitive biomarker for severe inflammation and infection. A significant interaction between the electrode material to be used in the design of the biosensor and the material to be attached to the surface is of great importance. Here, we demonstrated a silver nanoparticle (AgNp) doped graphene-based sensitive PCT biosensor with low-cost, environmentally friendly materials. Cyclic voltammetry curves showing the reusability of the electrodes obtained were obtained and showed antibody-protein adhesion on the AgNp/SLG@ITO surface. The anodic and cathodic peak currents values after 20 cycles show that these values are suitable even after 20 measurements. Electrochemical impedance spectroscopy (EIS) studies confirmed the effects of PCT on binding events due to increasing concentration at a constant PCT-antibody concentration. The limit of detection (LOD) value of the fabricated PCT/Ab/AgNp/SLG@ITO impedimetric biosensor was determined as 0.55 ngmL−1. The low LOD value can be attributed to the uniform and large surface area of single-layer graphene (SLG) and noble AgNp. The LOD value based on the EIS studies has revealed that the PCT/Ab/AgNp/SLG@ITO impedimetric biosensor can be employed in real samples.

Chitosan-Based Biosensors-A Comprehensive Review

Chitosan is a copolymer that is linearly linked to 2-amino-2-deoxy-Dglucopyronos and is synthesized by diacylation of chitin. A biosensor is an integrated and compact device that makes use of a biological component as a sensing element and is coupled to a transducer for the purpose of signal detection. This review article discusses the chitosan-based biosensors that are currently in high demand due to their advanced applications, excellent range, and detection limits in fields such as soil monitoring, water sample detection, disease detection, food quality management, and many others. These biosensors are described in this article. In this overview, we have discussed biosensors from two different points of view: the transducing and the bioluminescent perspectives. The method of transducing encompasses electrochemical, optical, and physical biosensors respectively. Additionally, a variety of electrochemical biosensors, including amperometric, voltammetric, potentimetric, and impedimetric biosensors, are discussed in detail. Other types of bioluminescent biosensors can be broken down further into categories such as those that detect enzymes, DNA/RNA, herbicides, and pesticides.

Magnetite azolla impedimetric nanobiosensor for phthalic acid esters quantification.

Phthalic acid esters (PAEs) are a group of organic compounds that show vulnerability effects in different stages of human development. In this work, two sensitive and efficient impedimetric biosensors (IBs) were introduced and their interactions with four PAEs, namely dibutyl phthalate (DBP), dimethyl phthalate (DMP), di(2-ethylhexyl) phthalate (DEHP), and dicyclohexyl phthalate (DCHP), in aqueous solutions with these biosensors were separately investigated via electrochemical impedance spectroscopy (EIS). The surface of a copper electrode was modified by azolla fern dried powder (AZ) and magnetite-modified azolla nanocomposites (MAZ NCs) to form an azolla-based impedimetric biosensor (AZIB) and magnetite azolla nanocomposite-based impedimetric nanobiosensor (MAZIB), respectively. Determinations of PAEs with the designed biosensors were conducted based on their blocking effect on the biosensor surface to ferrous ions oxidation. After each impedimetric measurement, the electrode surface was covered again with the modifier. Nyquist plots were obtained and indicated that the charge-transfer resistance (RCT) values of the bare electrode, AZIB, and MAZIB without injection of PAEs were 468.8, 438.7, and 285.1 kΩ, respectively. After the separate injection of DBP, DMP, DEHP, and DCHP (3 μg L-1) on the surface of AZIB and MAZIB, RCT values were obtained as 563.9, 588.5, 548.7, and 570.1 kΩ for AZIB and 878.2, 1219.2, 754.3, and 814.7 kΩ for MAZIB, respectively. It was observed that the PAE blockers with a smaller structure provided better point-by-point coverage of the surface, which led to a bigger shift in RCT. The linear relationship between the EIS responses and each PAE concentration was investigated in the range of 0.1-1000 μg L-1. The limit of detection (LOD) and limit of quantification (LOQ) values were obtained in the ranges of 0.003-0.005 μg L-1 and 0.010-0.016 μg L-1 for AZIB and 0.008-0.009 μg L-1 and 0.027-0.031 μg L-1 for MAZIB, respectively. The results showed that these biosensors can be used to determine PAEs in real aqueous samples with good relative recoveries ranging from 93.0-97.7% (RSD < 2.58%) for AZIB and 93.3-99.3% (RSD < 2.45%) for MAZIB. The results confirmed that these impedimetric biosensors offer high sensitivity and performance for the determination of trace PAEs in aqueous samples.

A Low-Cost Handheld Reconfigurable Impedimetric Readout System for Diagnostics of Viral Infections

This paper presents a portable impedimetric biosensor for detecting infectious diseases such as SARS-CoV-2 Infections. A bio-ready sensing electrode functionalized with SARS-CoV-2 nucleocapsid antibody was employed to quantitatively convert the concentration of nucleocapsid protein (N-protein) into impedance changes. In this paper, we proposed a readout system with a dynamic input range of 200 Ω to 1 MΩ magnitude and 0 to 180° phase. The resolution of this device is 1% and 6.5° for measuring the magnitude and phase, respectively. Herein we demonstrate and discuss the proposed system’s functionality, sensitivity, and selectivity using the clinical swab samples. As per these results, this readout system is suitable for the detection of N-protein ranging up to 10,000 pg/mL with a resolution of 56 fg/mL. The proposed impedimetric sensing system can be adopted for the detection of infectious diseases in the future. This low-cost (<$80) device using off-the-shelf is a unique candidate for batch production purposes during urgent pandemic situations.

Recent Developments in Electrochemical-Impedimetric Biosensors for Virus Detection.

Viruses, including influenza viruses, MERS-CoV (Middle East respiratory syndrome coronavirus), SARS-CoV (severe acute respiratory syndrome coronavirus), HAV (Hepatitis A virus), HBV (Hepatitis B virus), HCV (Hepatitis C virus), HIV (human immunodeficiency virus), EBOV (Ebola virus), ZIKV (Zika virus), and most recently SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2), are responsible for many diseases that result in hundreds of thousands of deaths yearly. The ongoing outbreak of the COVID-19 disease has raised a global concern and intensified research on the detection of viruses and virus-related diseases. Novel methods for the sensitive, rapid, and on-site detection of pathogens, such as the recent SARS-CoV-2, are critical for diagnosing and treating infectious diseases before they spread and affect human health worldwide. In this sense, electrochemical impedimetric biosensors could be applied for virus detection on a large scale. This review focuses on the recent developments in electrochemical-impedimetric biosensors for the detection of viruses.

Recent advances in development of electrochemical biosensors for the detection of biogenic amines.

Biogenic amines (BAs) are widely found in food as a consequence of diverse factors including free amino acid availability, microbial production of decarboxylases, and variations in processing and storage conditions. Hence, BAs are considered as an important marker for determining the freshness and quality of food. Owing to the documentation of BAs in different dietary products, their numerous negative impacts on human health have reported to be a serious concern in past few decades. Therefore, the quantification of these chemical species in food becomes crucial as it can immensely contributes toward control of new episodes on food intoxication in humans. In this line, various chromatographic and colorimetric methods have been developed to detect BAs. However, these methods are in use from a longer time, still are limited by high cost, lengthy procedures, huge infrastructure and skilled personnel requirements that hinder their on-field application. In pursuit of a reliable method offering accurate detection of BAs, this review presents the state-of-the-art of electrochemical strategies for BAs sensing in food. The core of the review discusses about the widely employed electrochemical transducers, such as amperometric, potentiometric, impedimetric and conductometric-based BAs biosensors with significant findings of research work conducted previously. The application of electrochemical sensors to analyze BAs in different fields including food systems (fermented and non-fermented types) and smart packaging systems has been reviewed. Moreover, existing challenges and further available prospects for the development of rapid, facile, and sensitive electrochemical strategies for on-site determination of BAs have also been discussed.

A Simple and Low-Cost Electrochemical Immunosensor for Ultrasensitive Determination of Calreticulin Biomarker in Human Serum.

An early on time detection of breast cancer significantly affects the treatment process and outcome. Herein, a new label-free impedimetric biosensor is developed to determine the lowest change in the level of calreticulin (CALR), which is a new biomarker of breast carcinoma. The proposed immunosensor is fabricated by using reduced graphene oxide/amino substituted polypyrrole polymer (rGO-PPyNH2 ) nanocomposite modified disposable electrode. The anti-CALR antibodies are first attached on the rGO-PPyNH2 nanocomposite coated electrode through glutaraldehyde crosslinking; the CALR antigens are then immobilized with the addition of CALR antigens to form an immunocomplex on the sensing surface. This immunocomplex induces considerably larger interfacial electron transport resistance (Rct ). The variation in the Rct has a linear relationship with CALR level in the detection range of 0.025 to 75pg mL-1 , with a detection limit of 10.4 fg mL-1 . The suggested biosensor shows high selectivity to CALR, good storage stability (at least 5 weeks) and suitable reproducibility results as shown in quality control chart. The designed immunosensor is utilized to analyze CALR levels in human sera with satisfying results. This immunosensor provides a novel way for the clinical determination of CALR and other cancer biological markers.

Cu2+@NMOFs-to-bimetallic CuFe PBA transformation: An instant catalyst with oxidase-mimicking activity for highly sensitive impedimetric biosensor

In this work, a facile impedance biosensor was constructed for sensitive assaying of miRNA-10b based on the Cu2+ modified NH2-metal organic frameworks (NMOF@Cu2+) coupling with a three-dimensional (3D) DNA walker signal amplification strategy. Specifically, abundant Cu2+ can adhere to the MOF via the coordination reaction between NH2 and Cu2+, which can be applied as a skeleton to produce CuFe Prussian blue analogue@NMOF (CuFe PBA@NMOF) just in time. Meanwhile, the carboxyl group, which is rich in the organic ligands of the NMOF, can be used to assemble DNA strands (complementary strand, CS) (CS-NMOF@Cu2+) for biorecognition reaction. With the introduction of the target, a 3D DNA walker was triggered to shear out large amounts of assistant strands (AS), which were then anchored on the surface of GCE. Afterward, CS-NMOF@Cu2+ can be assembled on the GCE by hybridization with AS. Eventually, abundant CuFe PBA@NMOF were generated in situ on the electrode with the help of K₃[Fe(CN)6], which can catalyze the 4-chloro-1-naphthol (4-CN) precipitation without H2O2, thereby increasing the resistance of the platform. Under the optimal conditions, the EIS biosensor presents reliable analytical performance in a wide linear range from 0.8 pM to 250 pM with a low detection limit of 0.5 pM.

Development of Folate-Group Impedimetric Biosensor Based on Polypyrrole Nanotubes Decorated with Gold Nanoparticles.

In this study, polypyrrole nanotubes (PPy-NT) and gold nanoparticles (AuNPs) were electrochemically synthesized to form a hybrid material and used as an electroactive layer for the attachment of proteins for the construction of a high-performance biosensor. Besides the enhancement of intrinsic conductivity of the PPy-NT, the AuNPs act as an anchor group for the formation of self-assembly monolayers (SAMs) from the gold-sulfur covalent interaction between gold and Mercaptopropionic acid (MPA). This material was used to evaluate the viability and performance of the platform developed for biosensing, and three different biological approaches were tested: first, the Avidin-HRP/Biotin couple and characterizations were made by using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), wherein we detected Biotin in a linear range of 100-900 fmol L-1. The studies continued with folate group biomolecules, using the folate receptor α (FR-α) as a bioreceptor. Tests with anti-FR antibody detection were performed, and the results obtained indicate a linear range of detection from 0.001 to 6.70 pmol L-1. The same FR-α receptor was used for Folic Acid detection, and the results showed a limit of detection of 0.030 nmol L-1 and a limit of quantification of 90 pmol L-1. The results indicate that the proposed biosensor is sensitive and capable of operating in a range of clinical interests.

Probing the Influence of Crosslinking Layer Incubation Time on the Performance of Non-Faradaic Impedimetric Biosensors

Non-faradaic impedimetric biosensors have received a wide interest due to their direct detection approach. The crosslinking layer in these biosensors has to be dense to avoid permeation of ions into the electrode to allow direct detection of diseases. In this work, we investigate, for the first time, the effect of incubation time of cysteamine crosslinking layer on non-faradaic impedimetric biosensors performances. Two sets of interdigitated gold electrodes were functionalized with cysteamine for 1 h and 24 h. Then, UL83-antibodies were immobilized on the surface via glutaraldehyde for the detection of human cytomegalovirus. The sensitivity of biosensors functionalized with cysteamine for 24 h were superior to those functionalized with cysteamine for 1 h (i.e. 0.046 nF/ln(ng ml−1) compared to 0.0224 nF/ln(ng ml−1)). Probing the cysteamine layer with faradaic-EIS and X-ray photoelectron spectroscopy suggests that the better biosensing performance of biosensors incubated in cysteamine for 24 h is related to the better coverage of cysteamine at the biosensor surface. Atomic force microscopy analysis also revealed an increase in surface roughness with increasing cysteamine incubation time which resulted in better biosensing performances due to the enlarged surface area.

A SARS-CoV-2 impedimetric biosensor based on the immobilization of ACE-2 receptor-containing entire cell membranes as the biorecognition element

A SARS-CoV-2 biosensor based on the biorecognition of the spike protein to the angiotensin-converting enzyme 2 (ACE-2) transmembrane receptor was developed using entire cell membranes as the biorecognition layer. In this new SARS-CoV-2 detection platform, cellular membranes from VeroCCL81 (mVero) and Calu-3 (mCalu) cells (which overexpress the ACE-2 transmembrane receptors) were extracted and immobilized as vesicles on an indium tin oxide electrode (ITO). Electrochemical impedance spectroscopy was used to optimize the performance of the developed devices for SARS-CoV-2 detection. This novel biosensor comprises a low-cost system (less than one US$ dollar) that uses the unique properties of cell membranes combined with the catalytic properties of electrochemical platforms to allow spike proteins recognition. A linear response from 10 to 100 ng/mL was obtained from the optimized biosensors, a limit of detection of 10.0 pg/mL and 7.25 pg/mL and limit of quantification of 30.4 pg/mL and 21.9 pg/mL were achieved with satisfactory accuracy for ITO-APTES-mVero and ITO-APTES-mCalu, respectively. Selectivity studies revealed that this platform was able to differentiate the target spike proteins from NS1 proteins from dengue and Zika viruses. In addition, sensors comprising cell membranes devoid of the ACE-2 transmembrane receptor exhibited no biorecognition signal. The developed devices are suitable for SARS-CoV-2 detection based on spike protein recognition, and capable of providing a low-cost, accurate, and accessible tool for use in a pandemic and post-pandemic scenario.

Modeling of an Impedimetric Biosensor with Ultrasonic-Assisted Cell Alignment for the Detection of Yeast

Yeast is an integral part of our environment. The detection of yeast is of great significance in many fields. The impedance-based sensor with interdigital microelectrodes is a promising method to establish a simple and portable detection system. However, the positions of yeast cells greatly influence the impedance variation and eventually the sensitivity of detection. In this study, an impedimetric biosensor with ultrasonic-assisted cell alignment for yeast detection was proposed. In order to verify the feasibility of this biosensor, finite element modeling was conducted using the software COMSOL. The acoustic pressure field and the acoustic radiation force exerted on yeast cells were investigated. Cell positions in the microfluidic channel were determined using the fluid particle tracking module. After that, the impedance between the microelectrodes was calculated. Yeast suspensions with different cell concentrations were used as the tested samples for the simulation. The proposed sensor showed a higher sensitivity than the conventional impedimetric biosensor on which the cells were randomly located. It can be used for the detection of microorganisms. This finite element modeling provided an effective approach for the design of biosensors.

Split aptamers immobilized array microelectrodes for detection of chlorpyrifos pesticide using electrochemical impedance spectroscopy

Pesticide contamination in foods and its high persistence in environments are major serious issues globally. Chlorpyrifos (CPS), a broad-spectrum organophosphate insecticide, is commonly used as an active ingredient for pest control in agricultures and industries, and eventually it is found in high prevalence of contamination in food chains. Unfortunately, CPS exerts several adverse effects, especially as a neurotoxic agent, that cause severe health implications on humans and animals. To prevent the overexposure of pesticide residues in contaminated foods and environments, a label-free impedimetric aptamer-based biosensor for CPS determination was developed. The split aptamers for CPS were designed from its parent sequence to encounter nonspecific binding, and were immobilized onto the array microelectrodes consisting of four gold (Au) working microelectrodes, a platinum (Pt) counter microelectrode, and two Ag/AgCl reference microelectrodes. The aptasensor showed a good linear EIS response with CPS concentration ranging from 0.01 to 1 μg/mL with a detection limit (LOD) of 0.01 μg/mL. Moreover, the aptamer-immobilized Au multi-microelectrodes provided excellent selectivity to CPS over high level of other interferences, yet it also revealed good reproducibility. The sensitivity of CPS was successfully determined with acceptable recoveries in the range of 75–128% in spiked coriander, orange juice, and tap water. Therefore, the split aptamer-functionalized microchip could be a potential biosensor for monitoring CPS contamination in fruits, vegetables, and environments to improve human health and well-being.

Electrochemical Immunosensors Based on Zinc Oxide Nanorods for Detection of Antibodies Against SARS-CoV-2 Spike Protein in Convalescent and Vaccinated Individuals.

Even after over 2 years of the COVID-19 pandemic, research on rapid, inexpensive, and accurate tests remains essential for controlling and avoiding the global spread of SARS-CoV-2 across the planet during a potential reappearance in future global waves or regional outbreaks. Assessment of serological responses for COVID-19 can be beneficial for population-level surveillance purposes, supporting the development of novel vaccines and evaluating the efficacy of different immunization programs. This can be especially relevant for broadly used inactivated whole virus vaccines, such as CoronaVac, which produced lower titers of neutralizing antibodies. and showed lower efficacy for specific groups such as the elderly and immunocompromised. We developed an impedimetric biosensor based on the immobilization of SARS-CoV-2 recombinant trimeric spike protein (S protein) on zinc oxide nanorod (ZnONR)-modified fluorine-doped tin oxide substrates for COVID-19 serology testing. Due to electrostatic interactions, the negatively charged S protein was immobilized via physical adsorption. The electrochemical response of the immunosensor was measured at each modification step and characterized by scanning electron microscopy and electrochemical techniques. We successfully evaluated the applicability of the modified ZnONR electrodes using serum samples from COVID-19 convalescent individuals, CoronaVac-vaccinated with or without positive results for SARS-CoV-2 infection, and pre-pandemic samples from healthy volunteers as controls. ELISA for IgG anti-SARS-CoV-2 spike protein was performed for comparison, and ELISA for IgG anti-RBDs of seasonal coronavirus (HCoVs) was used to test the specificity of immunosensor detection. No cross-reactivity with HCoVs was detected using the ZnONR immunosensor, and more interestingly, the sensor presented higher sensitivity when compared to negative ELISA results. The results demonstrate that the ZnONRs/spike-modified electrode displayed sensitive results for convalescents and vaccinated samples and shows excellent potential as a tool for the population’s assessment and monitoring of seroconversion and seroprevalence.