Electrochemical Biosensors for Point of care Applications

Biosensor refers to powerful and innovative analytical tool involving biological sensing element and transducer with broad range of applications, such as diagnosis, drug discovery, biomedicine, food safety and processing, environmental monitoring, security and defense. Recent advances in the field of biotechnology, microelectronics, and nanotechnology have improved the development of biosensors. Glucometers utilizing the electrochemical determination of oxygen or hydrogen peroxide employing immobilised glucose oxidase electrode seeded the discovery and development of biosensors. Molecular recognition based on geometry and forces of interaction play an important role in the biosensor development. The advent of nanotechnology led to highly efficient and sensitive biosensors. They also provide an effective immobilisation matrix for the various bioreceptors. Enzymatic and their mimetic (metalloporphyrin)-based biosensors for reactive oxygen, nitrogen species and cytochrome c will also be discussed. The role of antibodies and their applications in immunosensors development for cytochrome c and superoxide dismutase will be highlighted. The electrochemical biosensors are less expensive, miniaturised and used for point-of-care applications. Further, the fabrication of labVIEW based virtual biosensor instrumentation and microcontroller based portable biosensor for wide variety of applications also devices will be presented

Enabling Inkjet Printed Graphene for Ion Selective Electrodes with Postprint Thermal Annealing

Inkjet printed graphene (IPG) has recently shown tremendous promise in reducing the cost and complexity of graphene circuit fabrication. Herein we demonstrate, for the first time, the fabrication of an ion selective electrode (ISE) with IPG. A thermal annealing process in a nitrogen ambient environment converts the IPG into a highly conductive electrode (sheet resistance changes from 52.8 ± 7.4 MΩ/□ for unannealed graphene to 172.7 ± 33.3 Ω/□ for graphene annealed at 950 °C). Raman spectroscopy and field emission scanning electron microscopy (FESEM) analysis reveals that the printed graphene flakes begin to smooth at an annealing temperature of 500 °C and then become more porous and more electrically conductive when annealed at temperatures of 650 °C and above. The resultant thermally annealed, IPG electrodes are converted into potassium ISEs via functionalization with a poly(vinyl chloride) (PVC) membrane and valinomycin ionophore. The developed potassium ISE displays a wide linear sensing range (0.01–100 mM), a low detection limit (7 μM), minimal drift (8.6 × 10–6 V/s), and a negligible interference during electrochemical potassium sensing against the backdrop of interfering ions [i.e., sodium (Na), magnesium (Mg), and calcium (Ca)] and artificial eccrine perspiration. Thus, the IPG ISE shows potential for potassium detection in a wide variety of human fluids including plasma, serum, and sweat

Biosensors and bioelectronics

Biosensors and Bioelectronics presents the rapidly evolving methodologies that are relevant to biosensors and bioelectronics fabrication and characterization. The book provides a comprehensive understanding of biosensor functionality, and is an interdisciplinary reference that includes a range of interwoven contributing subjects, including electrochemistry, nanoparticles, and conducting polymers. Authored by a team of bioinstrumentation experts, this book serves as a blueprint for performing advanced fabrication and characterization of sensor systems-arming readers with an application-based r

Electrochemical cotinine sensing with a molecularly imprinted polymer on a graphene-platinum nanoparticle modified carbon electrode towards cigarette smoke exposure monitoring

Cotinine, a metabolite of nicotine, has shown promise as a biomarker for the detection of tobacco use and smoke exposure due its ability to persist in human bodily fluids for days (ca. 4-5 days) after tobacco consumption. However, current cotinine detection strategies primarily include arduous laboratory sensing methods or qualitative in-field biosensing devices. Herein, we report an electrochemical cotinine sensor based on a selective molecularly-imprinted polymer (MIP) electrodeposited on a screen-printed carbon electrode (SPCE) modified with graphene flakes and platinum nanoparticles (PtNPs). The PtNP-graphene modified SPCE exhibited a 4-fold increase in electrochemical sensitivity (10 µA to 40 µA) during ferryicyanide cyclic voltammetry. This developed biosensor functionalized with the MIP was consequently capable of selective sensing of cotinine in spiked saliva samples across a wide sensing range (1-100 nM) and low detection limit of (0.33 nM). This sensing range covers cotinine concentration levels that are typically found in saliva for non-smokers and smokers (ca. 10 – 75 nM). Moreover, the sensing is capable of acquiring a cotinine measurement within 12 minutes with minimal interference from both nicotine and myosmine–cotinine chemical analogs that are typically found in tobacco products. Hence, the developed biosensor is well-suited for use in the field such as at point-of-care facilities.This is a manuscript of an article published as Parate, Kshama, Chandran Karunakaran, and Jonathan C. Claussen. "Electrochemical cotinine sensing with a molecularly imprinted polymer on a graphene-platinum nanoparticle modified carbon electrode towards cigarette smoke exposure monitoring." Sensors and Actuators B: Chemical (2019). DOI: 10.1016/j.snb.2019.02.032. Posted with permission.</p

A Volume Miniaturized Hydrogen Peroxide Sensor Based on Peroxidase Activity of Copper(II) Chlorophyllin on Zinc Oxide and Polypyrrole Nanocomposite

Measurement of hydrogen peroxide (H2O2) is essential in human physiology and pathology as it provides valuable information with regard to signaling and prognostic of various diseases viz. oxidative stress and cardiovascular diseases. Therefore, we developed an alternate volume miniaturized electrochemical enzyme mimetic sensor having high stability, reproducibility and fast response time for the determination of H2O2. The enzyme mimetic sensor was constructed using copper (II) chlorophyllin trisodium (CuCP) functionalized on to the zinc oxide (ZnO)-polypyrrole (PPy) nanocomposite modified screen printed carbon electrode (SPCE). Scanning electron microscope (SEM) was used to characterize the surface morphology of nanocomposite PPy and ZnO-CuCP modified electrodes. The electrochemical behavior of enzyme mimetic sensor was examined by cyclic voltammetry exhibiting a characteristic quasi-reversible peak at the potential, +0.06 V versus Ag/AgCl, for the electrodeposited CuCP. It reveals that the combination of ZnO and CuCP could enhance the sensor performance in terms of sensitivity and selectivity. In addition, new reversible redox peaks at +0.15 and -0.15 V were observed accounting for the mechanism of superoxide anion radical (O2•-) formation. The enzyme mimetic sensor exhibited a linear response over the H2O2 concentration ranges from 300 nM to 1 mM with a detection limit of 100 nM and a sensitivity of 78.4 ± 1.5 nA μM-1 cm-2. Further, the sensor was successfully applied for the determination of H2O2 in biological samples such as human blood and plasma

Electrochemical Determination of Hydrogen Peroxide and Bicarbonate Using Peroxidase Activity of Copper, Zinc Superoxide Dismutase on Carbon Nanotube, Polypyrrole Nanocomposite Modified Pt Electrode

Measurement of hydrogen peroxide (H2 O2) and bicarbonate (HCO– 3) are essential in human pathology and pathophysiology as it provides valuable information with regard to signalling and prognostic of various diseases viz. oxidative stress and cardiovascular diseases. Therefore, we have developed here a novel electrochemical method for the determination of H2O2and HCO– 3 based on the peroxidase activity of copper, zinc superoxide dismutase (SOD). By immobilizing SOD onto the single walled carbon nanotubes (SWCNT)-polypyrrole (PPy) nanocomposite modified platinum electrode, the concentrations of H2O2and HCO– 3 were measured. The electrochemical behaviour of the SOD modified electrode was examined by cyclic voltammetry exhibiting characteristic quasi-reversible redox peak at the potential,+ 0.06 V versus Ag/AgCl. The peroxidase activity of SOD observed at –0.45 V was linear from 300 nM to 1 mM with a detection limit of 100 nM and sensitivity of 78.6 ± 1.7 nA μ M–1 cm–2. In the presence of HCO– 3, the peroxidase activity of SOD was enhanced linearly with HCO– 3concentration from 500 M to 50 mM. Based on this, we have measured here the HCO– 3 with a detection limit of 200 M and sensitivity of 1.23 μ A mM–1. Further, the concentrations of H2 O2 and HCO– 3 present in the human plasma samples were measured

Molecular dynamics simulation approach to explore atomistic molecular mechanism of peroxidase activity of apoptotic cytochrome c mutants

Mutations in cytochrome c (Cyt c) have been reported in tuning peroxidase activity, which in-turn cause Cyt c release from mitochondria and early apoptosis. However, the molecular tuning mechanism underlying this activity remains elusive. Herein, multiple 20 ns molecular dynamics (MD) simulations of wild type (WT), Y67F and K72W mutated Cyt c in aqueous solutions have been carried out to study how the changes in structural features alters the peroxidase activity of the protein. MD simulation results indicate that Y67F mutation caused, (i) increased distances between critical electron-transfer residues, (ii) higher fluctuations in omega loops, and (iii) weakening of intraprotein hydrogen bonds result in open conformation at heme crevice loop in Cyt c leading to an enhanced peroxidase activity. Interestingly, the aforementioned structural features are strengthened in K72W compared to WT and Y67F, which triggers K72W mutated Cyt c into a poor peroxidase. Essential dynamics results unveil that first two eigenvectors are responsible for overall motions of WT, Y67F and K72W mutated Cyt c. This study thus provides atomic level insight into molecular mechanism of peroxidase activity of Cyt c, which will help in designing novel Cyt c structures that is more desirable than natural Cyt c for biomedical and industrial processes. Keywords: Peroxidase activity, Cytochrome c, Mutations, Apoptosis, Molecular dynamic