Biosensors developed in yeast cells represent an attractive research area in biomedicine because they allow for the detection of molecules of various structures and biological activities, economically and simply, without the use of harmful radioactive materials. We focused our attention on the identification of androgen, glucocorticoid and estrogen receptor α/β ligands using fluorescent biosensors in yeast. Identification of compounds that modulate the activity of androgen (AR) or estrogen receptors (ER) is one of the major goals in the design of new treatments of hormone-dependent cancers. Similarly, glucocorticoid receptor (GR) ligands are used to treat autoimmune and inflammatory diseases, but due to a large number of side effects and drug resistance, great effort has been directed to finding new modulators. In this study, ligand-binding domains (LBDs) of AR, ERα, ERβ or GR fused with yellow fluorescent protein (YFP) were expressed in Saccharomyces cerevisiae. Recombinant yeast cells were treated with tested steroid hormone or bile acid derivatives, and, due to the fluorescence resonance energy transfer phenomenon following ligand binding, relative binding affinities were quantified fluorometrically. Our results show that some of the tested compounds have moderate to high binding affinity for particular steroid receptors, similar to natural ligands, while the affinities of other compounds were low or negligible. To elucidate the mechanisms of action for these compounds, additional experiments are necessary, and to better understand the molecular interactions within the ligand-binding pocket of the receptor, molecular docking analysis can be conducted. In summary, the yeast-based biosensors used in this work have proven to be very useful for in vitro screening of novel anticancer and anti-inflammatory drug candidates, as well as for the elimination of compounds that do not deserve further attention and resources due to their lack of desired bioactivities. Full article

Preliminary results on an electrosynthesized ion-imprinted polymeric (IIP) film for the development of a Co²⁺ sensor are reported herein. The sensor was prepared by CV electropolymerization of 2-aminophenol (2-AP) monomer in the presence of Co²⁺ ions, which acted as the template. The screen-printed carbon electrodes (SPCEs) were used as transducers during sensor development, whereas the cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used for the electrochemical characterization of sensors and for Co²⁺ ion sensing, respectively. The CV (potential range −0.2 and 1.2 V) and EIS measurements were performed in PBS (pH 7.8 , 0.1 M) containing 0.1 mol L⁻¹ KCl solution and 5.0 mmol L⁻¹ of Fe(CN)₆³⁻/⁴⁻ as the redox probe ; for EIS an open circuit and data were settled through a sinusoidal potential perturbation of 0.01 V amplitude and 57 as frequency values that were logarithmically distributed over a range of frequencies between 0.01 Hz and 100 kHz. A not imprinted polymer (NIP) was prepared as a control under the same protocol, but without adding the template into the polymerization mixture. In these preliminary tests, the electropolymerization patterns of IIP polymers were found to be consistent with the findings previously reported. After electropolymerization, rinsed electrodes were incubated in different Co²⁺ concentrations of ions to be tested through EIS showing a response in the range 1–8 μM. A multivariate optimization based on the design of experiment (DOE) was employed to study the effect of parameters on electrochemical performances of the sensor. Full article

Methylmalonic acid (MMA) plays a vital role in metabolism and energy production. It has been studied and reported as a sensitive early indicator for mild or serious Vitamin B12 deficiency. The normal range in health people is from 0.00 to 0.40 µM. Thus, most of MMA detection research was focused on Vitamin B12 deficiency with a small detection range. Recently, MMA has been reported to promote tumor progression due to age-induced accumulation. It was found that MMA concentration can reach as high as 80 µM in elderly people. MMA can be of great value as a promising biomarker for cancer diagnostics, as well as a therapeutic target for cancer treatment. Clinical determination of MMA concentration is by the method of gas chromatography mass spectroscopy (GCMS) or liquid chromatography mass spectroscopy (LCMS). However, these methods require extensive sample pre-treatment and large sample volume. They are also expensive and time-consuming. Hence, we proposed an attractive and effective strategy to detect MMA with a broad linear range by a low-cost molecularly imprinted polyaniline paper sensor. The polyaniline paper strip was fabricated by a one-step solution process using MMA as the template by molecular imprinting technology. The concentration of MMA was determined by the resistance change of the paper sensor. A calibration curve as a function of MMA concentration in aqueous solution was acquired with a correlation coefficient of 0.962. We demonstrated detection of the added MMA in plasma with a wide concentration range of 0 to 100 µM with a limit of detection (LoD) of 0.197 µM. This low-cost disposable paper sensor shows great potential in point-of-care MMA detection for cancer prognostics and diagnostics, especially in underserved communities. Full article

Graphene, a 2D material with high conductivity and stability in aqueous media, could complement silicon as raw material for sensing with transistor-based devices in liquids. Furthermore, the fabrication of graphene-based transistors is affordable with low-cost techniques such as inkjet printing from graphene oxide (GO)-based inks. Deposited on plastic conformable substrates, graphene-based logic gates are standing as favorable and compelling candidates in the field of biosensing, to make electrical transduction and binary operations match with aqueous media and facilitate diagnostic operations. Full article

Metallic nanoparticles are usually applied in biosensors as catalysts and/or mediators of electron transfer. We describe the development of amperometric biosensors (ABSs) based on oxidases and nanoparticles of CuCe (nCuCe). nCuCe, being an electro-active mediator and active peroxidase (PO) mimetic, was used as an H₂O₂-sensing platform in oxidase-based ABSs. ABSs for glucose, primary alcohols, methyl amine, catechol, and L-arginine, which are based on corresponding oxidases and nCuCe, were developed. These ABSs exhibited improved analytical characteristics in comparison with the appropriate bi-enzyme ABSs containing natural PO. Including electrodeposited porous gold in the chemo-sensing layer was shown to increase significantly the sensitivities of all constructed ABSs. Full article

The consumption of water contaminated with bacteria can lead to foodborne disease outbreaks. For this reason, the development of rapid and sensitive analytical methods for bacteria detection is of primary importance for public health protection. Here, a miniaturized immunosensor based on Mach–Zehnder Interferometry for the simultaneous, real-time determination of S. typhimurium and E.coli in drinking water is presented. For the assay, mixtures of bacteria solutions with anti-bacteria-specific antibodies were run over the chip, followed by biotinylated anti-species-specific antibody and streptavidin solutions. The assay was fast (10 min), accurate, sensitive (LOD: 3 × 10² cfu/mL for S. typhimurium; 2 × 10² cfu/mL for E.coli) and reproducible. The analytical characteristics achieved combined with the small chip size make the proposed biosensor suitable for on-site bacteria determination in drinking water samples. Full article

Bacterial contamination in food is real and presents a valid danger to human health. Therefore, we focused on the detection of Escherichia coli and Listeria innocua with optical and acoustic methods. In both methods, we used specific DNA aptamers as receptors. For the optical method, we modified gold nanoparticles (AuNPs) with aptamers and analyzed the interaction of AuNPs with bacteria by measurement of the changes in the absorbance spectrum. We also applied white light reflectometry to measure changes in thickness on a silicon chip modified with aminylated aptamer through silica chemistry. We also used quartz crystal microbalance (QCM) in multiharmonic mode. In this case, the thiolated aptamers were chemisorbed at the gold layer of the quartz crystal and the changes in resonant frequency were measured following the addition of bacteria. The limit of detection (LOD) of the optical method using AuNPs was estimated to be 10⁵ CFU/mL of Listeria monocytogenes. For the reflectometric method, we were able to detect E. coli at concentrations around 2 × 10⁴ CFU/mL. Using TSM, we analyzed the viscoelastic properties of the aptamer layers when they formed at the surface. Full article

Since the outbreak of the COVID-19 pandemic, great emphasis has been placed on the development of rapid virus detection devices, the principle of operation of many of which is the detection of the virus structural protein spike. Although several such devices have been developed, most are based on the visual observation of the result, without providing the possibility of its electrical processing. This paper presents a biosensor platform for the rapid detection of spike proteinboth in laboratory conditions and in swab samples from hospitalized patients. The platform consists of a microcontroller-based readout circuit, which measures the capacitance change generated in an interdigitated electrode transducer by the presence of the spike protein. The circuit efficiency is calibrated by its correlation with the capacitance measurement of an LCR meter. The test result is made available in less than 2 min through the microcontroller’s LCD screen, and at the same time, the collected data are sent wirelessly to a mobile application interface. In this way, the continuous and effective screening of SARS-CoV-2 patients is facilitated and enhanced, providing big data statistics of COVID-19 in terms of space and time. Full article

This is a continuation of our research into the development of novel biosensing technologies for early diagnostics of prostate cancer (PCa). The existing PCa diagnostics based on PSA detection (prostate cancer antigen) in blood serum often yield controversial outcomes and require improvement. At the same time, the long non-coded RNA transcript PCA3 overexpressed in PCa patients’ urine proved to be an ideal biomarker for PCa diagnosis, and recent research mainly focuses on developing biosensors for the detection of PCA3. One of the most promising directions in this research is the use of aptamers as bio-receptors for PCA3. We demonstrated the earlier great potential of electrochemical sensors exploiting aptamer labelled with redox group ferrocene. In this work, we use the RNA-based aptamer specific to 227 nt fragment of lncRNA PCA3 labelled with methylene blue redox label which offers a higher affinity to PCA3 than commonly used DNA-based aptamers. Before proceeding with biosensing experiments, the gold screen-printed electrodes were cleaned by CV scanning in a sulfuric acid solution, which removed surface contaminations and thus improved immobilization of aptamers. The quality of the gold surface was assessed by contact angle measurements. Moreover, the concentration of immobilized aptamers was optimized to achieve the best results in electrochemical measurements. Initial tests were carried out using cyclic voltammograms (CV) measurements and showed a correlation between oxidation/reductions peaks intensities and the concentration of PCA3. Such experiments proved the main concept of the proposed apta-sensing, e.g., the changes of aptamer secondary structure during binding the target (PCA3) resulting in redox labels coming closer to the electrode surface and thus increasing the charge transfer. The lowest recorded concentration of PCA3 was 0.01 nM in CV measurements, which is close to the LDL level for this method. Much more promising results were obtained with the electrochemical impedance spectroscopy (EIS) measurements, which showed remarkable features of increasing sensitivity at low concentrations of PCA3. The extrapolation of data below 0.05 nM level allowed estimating LDL of about 0.4 pM. The results obtained are very encouraging and constitute a major step towards developing a simple, reliable, and cost-effective diagnostic tool for the early detection of prostate cancer. Full article

Continuous monitoring is of upmost importance to manage emergency situations in healthcare. Therefore, we investigated the use of MAX30102, a commercial photometric biosensing module coupled to a ESP32 system-on-a-chip and its internet-of-things capabilities to continuously gather and process peripheral oxygen levels (SpO₂) and heartrates (HR) from users. Moreover, a user-friendly graphic interface was designed and implemented, and an anatomical case was 3D printed in thermoplastic polyester. Results showcased that the device functioned reliably, and according to literature describing photometric sensor functioning, thereby shedding light on the use of simple and affordable electronics for developing biosensing medical devices. Full article

A simple to realize optical fiber sensor specific for uranium(VI) detection in water is reported to demonstrate the sensing approach’s capability to determine uranyl (UO₂²⁺) in water solution in the ppb range. The proposed sensor was obtained by combining a specific receptor layer for uranium to a gold thin film at which the surface plasmon resonance (SPR) phenomenon takes place via optical fiber. In particular, an SPR D-shaped plastic optical fiber (POF) probe was used for signal transduction. The proposed optical-chemical sensing method is attractive because, in principle, it can be applied directly in the field, giving an analytical response in a fast and not overly expensive manner. Full article

Amongst label-free optical sensors, those relying on silicon photonics are especially promising for the development of small-sized devices appropriate for applications at the point-of-need. In this context, our work over the last 10 years has focused on the development of silicon photonic chips that combine all optical components, both active and passive, onto the same substrate. The approach followed for this monolithic integration, as well as the application of the different silicon photonic chip versions as immunosensors for the determination of single or panels of analytes, related to biodiagnostics or the food safety sector, will be presented. Full article

Research on cellulose and its derivatives as biosensors is developing rapidly through the innovation and improvement of materials, chemical synthesis, and methods of preparation and formulation. This study presents the state of the art by introducing what has been innovated and patented concerning cellulose-based biosensors between 2010 and 2020. More specifically, this form of patent analysis encapsulates information that could be used as a reference by researchers in the fields of biosensors and cellulose-based biosensing platforms, as well as those interested especially in cellulose and its derivatives. As a result of this study, a total of 241 patent documents related to cellulose-based biosensors were found. The United States leads the patent race in this sector. Based on patent classifications, most patents and inventions are intended for chemical analysis of biological materials and testing involving biospecific ligand binding methods, as well as measuring or testing apparatus with condition measuring or sensing means. Research and development are based on the investigating or analyzing of materials by the use of electric or electrochemical means, as well as nanotechnology for interacting, sensing, or actuating, which are concentrated in most patents. Full article

Illicit drug consumption remains a problem to public safety and health, with abuse of illicit drugs having increased significantly over the last years. A concern related to this abuse is driving under the influence of drugs (DUID). Currently, police and law enforcement agencies rely on the use of lateral flow immunoassays (LFAs), which suffer from a lack of specificity. In this report, we present a rapid, sensitive, and affordable electrochemical method for the detection of cocaine in oral fluid (OF) by square-wave adsorptive stripping voltammetry on screen-printed electrodes (SPE). For the first time, the effects of the OF matrix on the electrochemical sensing of cocaine are deeply explored. The interference of endogenous compounds in OF, cutting agents and adulterants is studied. Interestingly, the electrochemical signal for cocaine is shown to be partially suppressed by the biofouling properties of albumin and most probably other proteins present in the OF matrix. Thus, strategies to mitigate these biofouling properties are explored. Subsequently, two sampling methods for OF, expectoration and the use of a commercial OF collection device (i.e., the Intercept i2), are investigated. The developed method shows promising potential in point-of-care testing for recent illicit drug use. Full article

Ochratoxins are a group of mycotoxins produced as secondary metabolites by several fungi of Aspergillus and Penicillium species. Ochratoxin A (OTA) is the most toxic member of the group and can be found in a large variety of widely consumed foods, such as coffee, cocoa, wine, and flour. Reliable determination of OTA levels in food samples is therefore indispensable to ensure compliance with MRLs set by national/European regulations and minimize health risks for consumers. In the current study, a label-free biosensor based on white light reflectance spectroscopy (WLRS) for the rapid and accurate determination of OTA in cereal flour samples is demonstrated. A Si chip with a 1-μm-thick thermal SiO₂ on top plays the role of transducer after the immobilization of an OTA–protein conjugate on its surface. For the assay, a mixture of an in-house-developed anti-OTA antibody with the calibrators or the samples is injected over the chip surface, followed by reaction with a secondary biotinylated antibody and streptavidin for signal amplification. The label-free, real-time monitoring of immunoreactions occurring on the SiO₂/Si chip surface is achieved by recording the shift in the reflected interference spectrum caused by the immunoreactions. This shift is converted through appropriate mathematical processing to an effective biomolecular adlayer thickness. After optimization, the sensor is capable of detecting OTA in wheat flour samples at concentrations as low as 60 pg/mL within 25 min. The assay is repeatable, with intra- and inter-assay CVs ≤5.9% and ≤9.0%, respectively. The assay’s excellent analytical characteristics and short analysis time, in combination with the small size of the device, render the proposed WLRS system ideal for the quantitative determination of minute OTA levels at the point-of-need. Full article

A critical characteristic for continuous monitoring using DNA biosensors is the design of the microfluidics system used for sample manipulation, effective and rapid reaction and an ultra-low detection limit of the analyte. The selection of the appropriate geometrical design and control of microfluidic parameters are highly important for the optimum performance. In the present study, a number of different shapes of microchambers are designed and computationally assessed using a Multiphysics software. Flow parameters such as pressure drop, and shear rates are compared. Three-dimensional printing was used to construct the designs and an experimental investigation is underway for the validation of the computational results. Full article

Wearable biosensors for the detection of analytes in sweat are an emerging and promising technology with important applications in monitoring a person’s physiological state. Sweat, being an easily accessible biofluid, shows great potential as a biological fluid for wearable devices, but also a number of challenges that must be addressed before a sensor can be commercialized. As an example, sensor fabrication on flexible substrates can greatly affect the performance of the device. Herein, the development of an enzymatic electrochemical sensor on a flexible substrate for glucose detection is presented. The sensor’s three-electrode systems were made entirely with carbon-based ink on polyimide substrates and decorated with carbon black. The developed and optimized sensor design exhibited a stable and reproducible performance and was able to detect glucose in concentrations relevant to the ones present in sweat. Full article