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  • Open access
  • 50 Reads
Development of Electrochemical Sensors Based on Electrosynthesized Ion Imprinted Polymers for Cobalt (Co2+) Ions Determination in Water

Preliminary results on an electrosynthesized ion imprinted polymeric (IIP) film for Co2+ ions determination in sensor development are here reported. The sensor was prepared by electropolymerization of poly-2-aminophenol (2-AP) monomer in presence of Co2+ ions, which acts as the template. The screen-printed carbon electrodes (SPCE) were used as transducer during sensor development, whereas the cyclic voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS) was used for the electrochemical characterization of sensor and for Co2+ ions sensing, respectively. The measurements consisted of 5.0 mmol FeCN-KCl solution prepared in PBS at pH 7.8 (0.1 M) for CV assay within a potential range between −0.2 and 1.2 V and EIS essays an open circuit and data was 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 multivariate optimization based on design of experiment (DOE) was employed to study the effect of parameters on electrochemical performances of the sensor. After electropolymerization and rinsed electrodes was incubated in different Co2+ concentrations ions to be tested through EIS. A non-imprinted polymer (NIP) was prepared as a control under the same protocol, but without adding the template into the polymerization mixture. The results showed in the first experiment an adequate response for the characterization and testing of IIP and NIP. For these preliminary tests, the electropolymerization patterns of IIP polymers were found to be consistent with the ones previously reported. The first electropolymerization CV cycle of the IIP showed a unique peak at +0.3 V during polymerization process and the EIS essays during the IIP showed a consistent behavior for the lowest concentrations that were tested (1-8 μM).

  • Open access
  • 46 Reads
Use of fluorescent yeast-based biosensors for evaluation of the binding affinities of new steroid hormone and bile acid derivatives for select steroid receptors

Biosensors developed in yeast cells represent attractive research area in biomedicine because they allow for detection of molecules of various structures and biological activities, economically and simply, without use of harmful radioactive materials. We have focused our attention on 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 made to find 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 fluorescence resonance energy transfer phenomenon following ligand-binding, relative binding affinities were quantified fluorimetrically. Our results show that some of the tested compounds have moderate to high binding affinity for particular steroid receptors, similar to natural ligands, while affinities of other compounds were low or negligible. To elucidate 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 anti-cancer and anti-inflamatory drug candidates, as well as for elimination of compounds that do not deserve further attention and resources due to their lack of desired bioactivities.

  • Open access
  • 44 Reads
Monolithically integrated optical immunosensors

Optical biosensors are one of the most widely used category of sensing tools due to their high detection sensitivity, immunity to parasitic electronic noise, multi-analyte capabilities and in many cases ability for label-free detection of biomolecular interactions. Amongst label-free optical sensors, those relying on silicon photonics are especially promising for developing small size devises appropriate for applications at the point-of-need, once the hybrid integration of light sources and detectors is realized in a cost and labor effective way. In this context, our work the last 10 years focuses on the development of silicon photonic chips that combine all optical components, both active and passive, onto the same substrate. The approach followed for the monolithic integration of arrays of thin silicon nitride optical waveguides, light emitting diodes and photodetectors on a single silicon chip as well as the different silicon photonic sensors realized over the years, including the one currently developed, will be presented. In addition, the application of the different silicon photonic chip versions as immunosensors for the determination of single or panels of analytes related to biodiagnostics or food safety sector will be discussed.

  • Open access
  • 78 Reads
Electrochemical detection of cocaine in authentic oral fluid
Published: 15 February 2022 by MDPI in The 2nd International Electronic Conference on Biosensors session Biosensors in POCT

Illicit drug consumption remains a problem to public safety and health, with abuse of illicit
drugs having increased significantly over the last years.[1]
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),[2]
which suffer from a lack of specificity.[3]
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 and 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. 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.

(1) United Nations Office on Drugs and Crime (UNODC). World Drug Report 2021; 2021.
(2) Ahmed, S. R.; Chand, R.; Kumar, S.; Mittal, N.; Srinivasan, S.; Rajabzadeh, A. R. Recent
Biosensing Advances in the Rapid Detection of Illicit Drugs.
TrAC - Trends Anal. Chem. 2020,
131, 116006.
(3) Posthuma-Trumpie, G. A.; Korf, J.; Van Amerongen, A. Lateral Flow (Immuno)Assay: Its
Strengths, Weaknesses, Opportunities and Threats. A Literature Survey.
Anal. Bioanal. Chem.
2009, 393 (2), 569–582.

  • Open access
  • 58 Reads
An optical fiber sensor system for uranium detection in water

The by-product of the uranium enrichment process, the depleted uranium, has been applied as armour-piercing ammunition in several international military conflicts. Depleted uranium is used because of its high density, hardness, and pyrophoric properties. The testing and use of such ammunitions have led to the release of depleted uranium into the environment at several locations worldwide. So, the issue of the possible presence of depleted uranium in the environment has recently attracted considerable public interest. The use of depleted uranium in non-fission nuclear weapons results in the addition of toxic 238U to the natural uranium in the environment, producing environmental damage even if this isotope is not radioactive.

In this work, optical fiber sensors specific for uranium detection in water are presented to demonstrate the capability of the sensing approach for the determination of uranyl in water solution in the ppb range. In particular, the optical fiber sensor has been obtained by combining the surface at which the plasmonic resonance (SPR) takes place with a specific receptor layer for uranium. The resonant surface employed in the sensor here proposed is a multilayer one, with a characteristic D-shaped profile obtained simply by erasing a multimode POF.

The proposed sensing method is attractive because, in principle, it can be applied directly in the field, giving an analytical response in a fast and not too expensive way.

Moreover, it is a marker-free sensing device, and, as such, it can be applied to different metal ions, even not electroactive as in the case of electrochemical transduction, provided that a proper receptor is fixed at the SPR interface.

  • Open access
  • 154 Reads
Towards the development of cellulose-based and low-cost implantable biosensors using open source and accessible fabrication equipment for pH biosensing and IoT applications

The determination of optimal growth conditions for crops is crucial to avoid losses in agricultural production due to preventable factors. Although multiple devices have been developed to determine the chemistry of soil, and correlate them with plant health, these sensors cannot provide individualised information in real-time. As such, new devices for the in vivo quantification of plant biomarkers are necessary to allow an early response by the farmers. In particular, the design of implantable sensors represents a promising technology to enable the in-situ evaluation of key environmental conditions such as soil pH, pollution, or dryness. However, current developments in the field require expensive equipment, either for the fabrication of sensors, or measurement processes, limiting their applications within real-world environments. This work presents for the first time a low-cost and accessible approach for the fabrication of miniaturised pH biosensors, that can be fabricated using open-source and low-cost equipment. This device was developed by electrodepositing Ruthenium oxide nanoparticles onto thin copper films using a microcontroller-based potentiostat (>£50). A cellulose-based coating was then incorporated by an aerosol-based method, developed using off-the-shelf devices. The combination of these two low-cost deposition methods allowed the fabrication of nanometrically thick pH biosensors. The results were proven to be similar to the ones achieved by standardised laboratory equipment. The final setup combined the pH sensing layer of ruthenium oxide and cellulose, with a microcontroller that could send the collected data wirelessly to online servers for IoT applications. A proof-of-concept device was implanted inside a tomato plant, including multiple environmental sensors, and the changes in pH inside the stem, a well-known health biomarker, could be measured continuously. These results represent a step forward towards the practical application of implantable sensors in crop production, offering a plethora of applications in smart farming and plant research within low-resource settings.

  • Open access
  • 87 Reads
Surface acoustic wave resonators for milk analysis

The analysis of milk samples includes both identification and quantification of specific components and the analysis of liquid properties. The former covers both the normal ingredients of milk and unwanted components, such as veterinary drug residues and pathogenic microorganisms, while the latter includes conductivity and viscosity measurements. Taken together, the parameters allow a comprehensive statement about the quality of the milk tested. Acoustic sensors, such as quartz crystal microbalances and surface acoustic wave (SAW) sensors, can in principle be used for both types of analysis, whereby the actual application depends on the surface coating and functionalization. The viscosity of milk is typically used as indicator of quality and freshness, since it is influenced, among others, by protein aggregation. However, the addition of some drugs, such as ampicillin (a penicillin antibiotic), may also influence the viscosity of milk, since ampicillin is known to form polymers and conjugates with proteins. Measurements with SAW resonators were applied to distinguish between milk samples with and without ampicillin. The sensors were coated with a hydrogel layer to reduce interfering effects from non-specific mass adsorption, similar to the use of shielding layers in biosensor applications.

  • Open access
  • 73 Reads
Platform set-up by multifunctional PEG microgels for bead-based assay in immunoglobulin detection

In this work, we want to apply the microgels-based platform to design innovative immunoassay biosensors for antibodies and antigens detection, afterwards miniaturized into lab-on-chip devices. The immunoassay is based on the non-competitive sandwich format for immunoglobulin IgG detection. The detection of the target occurs due to the interaction between two particles: microgels and magnetic particles. Microgels are used as the carrier of both anti-Fab antibodies and horseradish peroxide HRP enzyme. Magnetic particles functionalized with anti-Fc antibodies are involved acting as capture particles. The target is recognized by antibodies to produce the “sandwich structure”. After magnetic separation, the HRP enzyme on microgels produces an optical signal to show the target presence. The HRP enzymes confined to the small volume of the microgels results in signal amplification.

Microgels are multifunctional particles with chemical flexibility and a highly tunable nature. Recently, we had synthesized microgels with a core−shell molecular architecture with two different fluorescent dyes as an optical barcode. They were endowed with a fluorescent probe for miRNA detection chosen as cancer biomarkers. Oligonucleotide assay with microgels-based platform had high sensitivity due to the confinement of probes onto the surface of nanometric particles producing an enhancement of fluorescent signal. This represents a modular platform that can be generalized for any direct detection applied to a wide spectrum of biomedical applications.

For the immunoassay biosensors presented here, microgels composed of PEGDMA copolymerized with a fluorescent dye were synthesized by suspension polymerization. The polyacrylic acid was introduced during the synthesis to create pendant groups for post-modifications. Microgels were characterized to determine their physical, chemical, and optical properties. The functionalization of microgels with fluorescent test anti-IgG and HRP enzyme was performed. The capture magnetic particles were functionalized with test IgG. As a proof of concept, interactions between capture and carrier particles were carried out.

The synthesized microgels showed a sub-micrometric size and the optical barcode recovered by fluorescence emission. The bioconjugation reactions on microgels of fluorescent test anti-IgG antibodies and enzyme had shown a modulable functionalization degree by changing the number of particles involved in the reaction. Such a parameter is fundamental to improving the sensitivity and the limit of detection of the assay. The signal produced by biomolecules onto microgels was amplified due to their confinement on the particles small volume. Even magnetic particles had shown a good functionalization degree with test antibodies IgG. To prove the feasibility of interactions, carrier and capture particles were mixed. The binding was shown by recovering the microgel optical barcode at the confocal laser scanning microscope. After the immunoassay optimization, its miniaturization into lab-on-chip will give the possibility to improve its sensitivity to reach the best performance of the assay. The on-chip biosensor allows improving microgels abilities linked to the assay sensitivity and the limit of the detection. Moreover, the microfluidic biosensors offer faster analysis times and advantages in portability and ease of use.

  • Open access
  • 119 Reads
Aptamer functionalisation of back-gated graphene field effect transistors for Pb2+ sensing
, , , , , ,

We discuss the development of aptamer functionalised, back-gated, graphene field effect transistor (GFET) biosensors for the targeted detection of Lead (Pb2+) ions. The widespread existence of the heavy metal Pb2+ in the environment is a severe threat to the health of humans. It is a neurotoxin that accumulates over time in the body restricting the cognitive, behavioural and psychological development of children along with causing irreversible harm to the human foetus. New biosensors which allow for the rapid, sensitive and low-cost detection of Pb2+ are required to monitor this toxicant in water sources worldwide. The GFET devices were fabricated using a scalable photolithographic patterning process with evaporated Cr and sputtered Au contacts over monolayer graphene on Si/SiO2. The single stranded Thrombin Binding Aptamer (TBA) was immobilised onto the graphene channel either directly with a pyrene terminated 5’ end or indirectly using the 1-pyrenebutanoic acid succinimidyl ester (PBASE) molecule to facilitate DNA crosslinking with an amine modified 5’ end. Herein provides an evaluation of these two immobilisation strategies for the detection of Pb2+. Functionalised states were verified using Raman spectroscopy and electrically characterised using 4-probe electrical measurements to determine transfer curves allowing the calculation of field effect mobility and Dirac Point characteristics.

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