Cell apoptosis causes release of cytochrome c (cyt c) in programmed cell death. It can be used as biomarker to evaluate chemotherapy efficacy. However, detection and study of cyt c interaction with lipid membranes proves to be a challenging task. Recent studies suggest innovative development in cyt c detection by binding it to specific DNA aptamers. To achieve this goal, it is necessary to provide surface with bound cyt c. Our research was focused on preparation of supported lipid membranes on the gold surface of the quartz crystal. Lipid membranes were prepared by liposome fusion at the surface of 1-dodecanethiol chemisorbed at gold surface of the crystal. The liposomes were composed of a mixture of L-α-Phosphatidylcholine (lecithin) and Dimyristoyl phosphatidylglycerol (DMPG), which were used in different ratios. Subsequent formation of the lipid membrane was monitored by multiharmonic quartz crystal microbalance (QCM). Cyt c was applied on lipid layer and we observed changes in fundamental and several higher harmonic frequencies. Energy dissipation changes were recorded as well. The data on frequency and dissipation changes were used for the analysis of the viscoelastic properties of adsorbed layers.

This work has been supported by Science Grant Agency VEGA (project No. 1/0419/20).

Graphene transistors are becoming a promising building block in the large field of Chemical Logic but also for application as biosensors, requiring highly stable materials in aqueous and biological media.
The low-cost fabrication process of reduced Graphene Oxide Electrolyte-Gated Transistors (rGO-EGFET) from homemade formulation of Graphene Oxide (GO) ink¹ is paving the way to the development of cheap and competitive graphene-based logic gates, operating at low-voltage thanks to the thin double layer capacitance forming at the electrolyte/conductive layer interfaces.

In this work, we investigate the conception of a complementary-like inverter from two rGO-EGFET, with different doping states induced either by changing the reduction charge amount or the nature of the electrolyte itself (which could be a biological medium).₂ In both cases, the system can be simply modelled by two resistors in series, and the switch occurs when the value of one resistor becomes significantly lower than the other one, while changing the applied gate voltage.³
The proof of concept of our transduction method has been obtained with connecting two rGO-EGFET with different aqueous electrolytes; we noticed therefore a switch operating around 1V from the High state to the Low state of the logic gate.

On the other side, measuring electrolyte losses from sweat is of interest, in particular for monitoring sports activities and prevent e.g., dehydration. In such application, an alert when a given electrolyte (eg., K+) reaches a threshold value is more valuable than continuous quantification.
A compelling application of our rGO-based logic gate consists in building a proper ion-sensor through the functionalization of the gates with ionophore-based membrane: A sufficient change of the Gate/Electrolyte capacitance, induced by the presence of a targeted molecule, could lead to a change of the input voltage and thus to the switch of the logic state. As an application here, in order to monitor the K+ concentration in human or artificial sweat, the valinomycin ionophore is added into a membrane functionalizing the gate contacts. The switch between the two logic states is then depending on a threshold concentration of K+ ions, that can be considered as the analogic input signal of our ion-sensitive logic gate, which could then trigger another action.

References:

1. Vasilijević, S., Mattana, G., Anquetin, G., Battaglini, N. & Piro, B. Electrochemical tuning of reduced graphene oxide in printed electrolyte-gated transistors. Impact on charge transport properties. Electrochimica Acta 371, 137819 (2021).
2. Son, M. et al. Low-Power Complementary Logic Circuit Using Polymer-Electrolyte-Gated Graphene Switching Devices. ACS Appl. Mater. Interfaces 11, 47247–47252 (2019).
3. Traversi, F., Russo, V. & Sordan, R. Integrated complementary graphene inverter. Appl. Phys. Lett. 94, 223312 (2009).

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. Herein, we present an epidermal patch type device, with an enzymatic electrochemical sensor for glucose monitoring and a microfluidic network for continuous sweat sampling. Detection of glucose in sweat removes the painful invasive blood sampling step of commercial devices, while paving the way for continuous monitoring of glucose levels. The microfluidic network was designed according to data acquired from microfluidic simulations using the COMSOL Multiphysics software package. A 3D-printed scaffold was used to transfer the network design to a PDMS layer, so that the patch could be attached to the user’s skin. The sensor’s electrodes were hand-drawn on a polyimide layer using conductive carbon ink. A dispersion of carbon black in a chitosan aqueous solution was subsequently drop-casted on the working electrode, followed by enzyme immobilization (glucose oxidase). The sensor was characterized in artificial sweat, taking into account the possible fluctuations of sweat pH, and was able to detect glucose in the range of 0.01 – 1 mM. The ability of the sensor to detect glucose was also tested using real samples of sweat.

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 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 protein both in laboratory conditions and in swab samples from hospitalized patients that have been correlated with qRT-PCR method. 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 minutes through the microcontroller’s LCD screen and at the same time the collected data is 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.

The photochemical techniques applied to the sensing of bioactive molecules have become one of the fastest-growing scientific fields. Surface-enhanced Raman scattering (SERS) measurement is highly sensitive for detecting low-concentration, single molecules or oligomers, including DNA, microRNA, and proteins. In the field of SERS biosensor design, the use of carbon-based nanomaterials as substrate materials is rapidly developing, and we intend to investigate mechanisms of the dynamic interaction of oligomers with the environment of the SERS sensor to specify the fingerprints of such interactions in the spectra to enhance resolution. We study the vibrational spectra of the nucleotides in the dynamic interaction with the Au nanoparticles (NP) relaxed at (grown on) graphene nanopore that combines (1) translocation localization by graphene nanopore and (2) nucleotide interaction enhancement by Au NP. The spectral map of the cytosine nucleotide was tested by molecular dynamics (MD) simulation with LJ interaction between components. The spectra of various bonds were compared in reaction coordinates for DNA nucleotides and Cartesian ones for Au NP. Spectra at the interaction with the Au NP were used to select a transient COM velocity of nucleotide passing along the cluster. At the edge of the graphene pore, the velocity has been set at 0.025 m/s that compared with the experimental range. We test the sensor’s system to evaluate the influence of the interaction with Au NP and graphene on the transient spectra calculated by MD. The frequencies and modes that can serve as markers of the corresponding Au – nucleotide and graphene - nucleotide interactions are estimated. The MD simulation creates spectral libraries for oligomer’s vibrations to specify the interaction’s type and strength in SERS sensors that can be further utilized as training data for the machine learning application in spectral recognition.

Ovarian cancer (OC), the most lethal gynecological cancer, is often referred to as the “silent” killer since early-stage symptoms are not radically different from normal conditions. Worldwide there are 150,000 deaths, annually; notably, the survival rate when OC is detected in stage I is over 90%. However, the only current diagnostic test for OC is notorious for providing both false positive and negative results. The common imaging modalities can not be used in the early stage and large scale for the disease. Accordingly, there is an urgent need for a low-cost screening test that is rapid, sensitive and selective, and can be applied to the general population. We have developed a simple, precise, and low-cost screening test using electrochemical techniques to fabricate a point-of-care testing (POCT) device for early detection of OC. The device detects Lysophosphatidic acid (LPA), a highly promising biomarker, which was found to be elevated in 90% of stage I OC patients and gradually increases as the disease progresses to later stages. Electrochemical techniques are highly sensitive and fast, and can be easily miniaturized, which will reduce the cost of the fabrication. The main challenge in developing such a tool is overcoming a ubiquitous, problematic phenomenon known as non-specific adsorption (NSA), which is due to the fouling of non-target molecules in the blood on the recognition surface of the device. To overcome the NSA, we have followed a unique and novel strategy using silane-based interfacial chemistry to modify medical-grade stainless steel electrodes. The biorecognition surface was developed using the affinity-based gelsolin-actin system, which was previously invented by our group to detect LPA using fluorescence spectroscopy.

This project provides a proof-of-concept for a diagnostic tool that could be conducted on a small sample of blood, in a similar manner to the blood glucose monitoring devices. The development of this POCT device would significantly improve the survival of ovarian cancer patients and would save millions of dollars for the healthcare system. Furthermore, this project will open new frontiers in POCT by advancing the current knowledge in anti-fouling strategies.

Ara h1 is one of the major peanut allergens. It is considered one of the most severe, life-threatening food sensitivities since it triggers the highest frequency of severe and fatal reactions, even in trace amounts. Thus, it is extremely important to develop fast, accurate and easy-to-use analytical methods to determine Ara h1 allergen from food products that might contain traces of peanuts [1].

Electrochemical aptasensors have high specificity thanks to the affinity reaction between the DNA receptor and the analyte and have the ability to bind the target, even from complex matrices. The most critical steps in their development are represented by the immobilisation of the DNA strands and the signal generation [2].

This poster presents the preliminary results in the development of an electrochemical aptasensor for Ara h1 allergen detection. Although high porosity is beneficial for sensing, it brings specific challenges, since the properties of nanostructured materials often differ significantly from their bulk counterparts. Therefore, two approaches to manage the sensitivity and selectivity of the proposed aptasensor were examined. Both platforms used gold and platinum nanoparticles in order to increase the electrocatalytic effect of a screen-printed carbon electrode. For the first platform, chemical receptors based on single-walled carbon nanotubes and poly-anthranilic acid were synthesized. As for the second platform, graphene oxides modified with carboxylic groups were used as carboxyl groups donors with a polymer used to decrease the reactivity of the gold and platinum nanoparticles. These findings were used to investigate the immobilization of a 5’ amino and 3’ Ferrocene modified aptamer. For investigation of the aptamer selectivity, the newly developed aptasensor was tested in the presence of Ara h1. The process was monitored by DPV and analyzed the redox activity of the label to establish in-situ information on the binding process.

Acknowledgments

The authors acknowledge the financial support of the Romanian Ministry of Education and Research, CNCS-UEFISCDI, project number PN-III-P1-1.1-PD-2019-0631, within PNCDI III and the Italian Government in the framework of PRIN 2017, Prot. 2017YER72K_005

Bibliography

1. Tran, D.T. et al. Biosensors and Bioelectronics 2013, 43, 245–251,
2. Piro, B. et al. Biosensors 2016, 6.

Exhaled human breath contains thousands of different volatile organic compounds (VOCs) derived from the body's metabolic processes. It is well known that the diabetes patients produce excess amounts of ketones such as acetone. Hence rapid and easy detection of the presence of acetone vapors in the breath of such patients, especially done in a non-invasive way, is of great importance for the early discovery and control of diabetes. The existing non-invasive methods for detecting acetone in the breath of diabetes patients use analytical techniques such as gas chromatography and mass spectrometry, as well as many other highly sensitive methods including electrochemical sensors and devices of the “electronic nose” type. However, their disadvantage is the complexity of the methods and complications of using them for daily monitoring.

In this work we propose a simple method of optical detection of acetone vapors based on color/reflectance change. Acetone-sensitive thin films of poly(vinyl alcohol)-graft-poly(methyl acrylate) with two different copolymer compositions were deposited on a silica substrates by spin-coating of aqueous dispersions. Comprehensive optical characterization of the films has been made and films thickness, refractive index and extinction coefficient were calculated. Sensing properties of the films toward acetone vapors were studied by measuring reflectance spectra before and after exposure to the analyte at room temperature. Maximum reflectance change ∆R_max was calculated from measured spectra in order to evaluate the reaction of the films. The possibility of using this copolymer as a sensitive element in the design of optical sensors has been demonstrated and discussed.

Acknowledgments: Research equipment of Distributed Research Infrastructure INFRAMAT, part of Bulgarian National Roadmap for Research Infrastructures, supported by Bulgarian Ministry of Education and Science was used in this investigation.

Methamphetamine (MA) is a synthetic psychoactive drug with medical applicability, being prescribed for Attention-Deficit and Hyperactivity Disorder and short-term treatment of obesity. Most frequently though, it is abused for various effects such as euphoria, the stimulation of the reward centers, and hallucinations. This behavior is illustrated by the increased spread and abuse of MA, which had the largest increase in quantities seized in the last decade¹. Therefore, analytical tools for the screening of suspected cargos by law enforcement agencies play an important role in the disruption of the illegal distribution of MA. Hence, the present study took advantage of the highly sensitive and accurate detection provided by the electrochemical techniques^2,3, aiming for the detection of MA in confiscated samples using a portable device. In this regard, the electrochemical behavior of MA was investigated by means of square wave voltammetry on disposable graphite screen-printed electrodes. Firstly, the analytical characterization of the method was performed, exhibiting a LOD of 66.4 µM. Interestingly, two potential zones were identified for MA detection, depending on its concentration level. Thereafter, the selectivity of the method towards MA in mixtures with other drugs of abuse as well as common adulterants/cutting agents was evaluated. Finally, the described method was employed for the screening of confiscated samples with 100% true positive results, displaying its potential as a fast and easy to use method for on-site analysis.

Acknowledgements: This project was supported by a PhD Research Project no. PCD 1033/21/January 13, 2021, offered by “Iuliu Hatieganu” University of Medicine and Pharmacy, Cluj–Napoca, Romania.

References:

1. European Drug Report 2021: Trends and Developments (DOI: 10.2810/18539).
2. Dragan A-M, et al. Front Chem (DOI: 10.3389/fchem.2021.641147).
3. Parrilla M, et al. Sens Actuators B Chem (DOI: 10.1016/j.snb.2021.129819).

The prevalence of recreational substance abuse amongst young adults has markedly increased over the past two decades and it remains one of the major problems facing our society today worldwide. Amphetamine (AMP) is one of the most common substances abused and one of the most potent sympathomimetic amines with respect to stimulatory effects on the central nervous system (1).

The direct electrochemical detection of AMP is a challenge because the molecule is non-electroactive at the potential window of conventional graphite SPEs. In this regard, a molecularly imprinted polymer (MIP) for AMP detection was synthesized The MIPs nanoparticles (nanoMIPs) were synthesized in the presence of a template molecule. After polymerization and removal of the template, MIPs are embossed with complementary cavities and functionalities (2). The technology presented herein could potentially help to rapidly determine AMP from confiscated street samples. The voltammetric sensor for AMP detection uses electroactive nanoMIPs, produced by introducing ferrocene monomer into the polymeric structures, which serves as an efficient transducer of electrochemical response. For the immobilization of nanoMIPs onto the surface of graphite SPEs different approaches were tried, and the best results in terms of stability, sensitivity, and specificity were obtained after the direct deposition of a suspension that contains chitosan, nanoMIPs, and graphene oxide (GPHOx).

Acknowledgments: This project was supported by a PhD Research Project PCD no. : 1033/68/13 January 2021, offered by UMF, Cluj-Napoca, Romania.

1.Parrilla, M. et. al., Derivatization of amphetamine to allow its electrochemical detection in illicit drug seizures, 129819 (2021).

2.Alanazi, K. et al. Disposable paracetamol sensor based on electroactive MIPs for plasma monitoring, 129128 (2021).