Showing papers in "Sensing and bio-sensing research in 2017"

Recent advances in wearable sensors for animal health management

Abstract: Biosensors, as an application for animal health management, are an emerging market that is quickly gaining recognition in the global market. Globally, a number of sensors being produced for animal health management are at various stages of commercialization. Some technologies for producing an accurate health status and disease diagnosis are applicable only for humans, with few modifications or testing in animal models. Now, these innovative technologies are being considered for their future use in livestock development and welfare. Precision livestock farming techniques, which include a wide span of technologies, are being applied, along with advanced technologies like microfluidics, sound analyzers, image-detection techniques, sweat and salivary sensing, serodiagnosis, and others. However, there is a need to integrate all the available sensors and create an efficient online monitoring system so that animal health status can be monitored in real time, without delay. This review paper discusses the scope of different wearable technologies for animals, nano biosensors and advanced molecular biology diagnostic techniques for the detection of various infectious diseases of cattle, along with the efforts to enlist and compare these technologies with respect to their drawbacks and advantages in the domain of animal health management. The paper considers all recent developments in the field of biosensors and their applications for animal health to provide insight regarding the appropriate approach to be used in the future of enhanced animal welfare.

The strategies of DNA immobilization and hybridization detection mechanism in the construction of electrochemical DNA sensor: A review

Abstract: In recent years, electrochemical deoxyribonucleic acid (DNA) sensor has recently emerged as promising alternative clinical diagnostic devices especially for infectious disease by exploiting DNA recognition events and converting them into an electrochemical signal This is because the existing DNA diagnostic method possesses certain drawbacks such as time-consuming, expensive, laborious, low selectivity and sensitivity DNA immobilization strategies and mechanism of electrochemical detection are two the most important aspects that should be considered before developing highly selective and sensitive electrochemical DNA sensor Here, we focus on some recent strategies for DNA probes immobilization on the surface of electrochemical transducer such as adsorption, covalent bonding and Avidin/Streptavidin-Biotin interaction on the electrode surface for specific interaction with its complementary DNA target A numerous approach for DNA hybridization detection based electrochemical technique that frequently used including direct DNA electrochemical detection and label based electrochemical (redox-active indicator, enzyme label and nanoparticles were also discussed in aiming to provide general guide for the design of electrochemical DNA sensor We also discussed the challenges and suggestions to improve the application of electrochemical DNA sensor at point-care setting

Multifunctional nanoparticle developments in cancer diagnosis and treatment

Abstract: Nanotechnology, although still in the early stages, has the potential to revolutionize the early diagnosis, treatment, and monitoring of disease progression. Technological application of nanometer molecules in medicine with the aim of fighting and curing ailments is the globally definition of nanomedicine. The success of nanotechnology in the healthcare part is driven by the possibility to work at the same scale of several biological processes, cellular mechanisms, and organic molecules. With the growing understanding of methods to functionalize nanoparticles and the continued efforts of creative scientists to advance this technology, it is likely that functionalized nanoparticles will become an important tool in the above mentioned areas. This paper describes the role of multifunctional nanoparticle in diagnosis and treatment of cancer. Therefore, the aim of this review is to provide basic information on nanoparticles, describe previously developed methods to functionalize nanoparticles and discuss their potential applications in biomedical sciences and finally mention the therapeutic nanoparticle commercialization challenges.

Folded cladding porous shaped photonic crystal fiber with high sensitivity in optical sensing applications: Design and analysis

Abstract: A micro structure folded cladding porous shaped with circular air hole photonic crystal fiber (FP-PCF) is proposed and numerically investigated in a broader wavelength range from 1.4 µm to 1.64 µm (E+S+C+L+U) for chemical sensing purposes. Employing finite element method (FEM) with anisotropic perfectly matched layer (PML) various properties of the proposed FP-PCF are numerically inquired. Filling the hole of core with aqueous analyte ethanol (n = 1.354) and tuning different geometric parameters of the fiber, the sensitivity order of 64.19% and the confinement loss of 2.07 × 10- 5 dB/m are attained at 1.48 µm wavelength in S band. The investigated numerical simulation result strongly focuses on sensing purposes; because this fiber attained higher sensitivity with lower confinement loss over the operating wavelength. Measuring time of sensitivity, simultaneously confinement loss also inquired. It reflects that confinement loss is highly dependable on PML depth but not for sensitivity. Beside above properties numerical aperture (NA), nonlinearity, and effective area are also computed. This FP-PCF also performed as sensor for other alcohol series (methanol, propanol, butanol, pentanol). Optimized FP-PCF shows higher sensitivity and low confinement loss carrying high impact in the area of chemical as well as gas sensing purposes. Surely it is clear that install such type of sensor will flourish technology massively.

Rapid, low cost prototyping of transdermal devices for personal healthcare monitoring

Abstract: The next generation of devices for personal healthcare monitoring will comprise molecular sensors to monitor analytes of interest in the skin compartment. Transdermal devices based on microneedles offer an excellent opportunity to explore the dynamics of molecular markers in the interstitial fluid, however good acceptability of these next generation devices will require several technical problems associated with current commercially available wearable sensors to be overcome. These particularly include reliability, comfort and cost. An essential pre-requisite for transdermal molecular sensing devices is that they can be fabricated using scalable technologies which are cost effective. We present here a minimally invasive microneedle array as a continuous monitoring platform technology. Method for scalable fabrication of these structures is presented. The microneedle arrays were characterised mechanically and were shown to penetrate human skin under moderate thumb pressure. They were then functionalised and evaluated as glucose, lactate and theophylline biosensors. The results suggest that this technology can be employed in the measurement of metabolites, therapeutic drugs and biomarkers and could have an important role to play in the management of chronic diseases.

Electrochemical determination of serotonin in urine samples based on metal oxide nanoparticles/MWCNT on modified glassy carbon electrode

Abstract: The electrochemical response of serotonin on the modified electrode based on multiwalled-carbon-nanotube (MWCNT) doped respectively with nickel, zinc and iron oxide nanoparticles coating on glassy carbon electrode (GCE) at physiological pH 7 was determined using cyclic voltammetry (CV) and square wave voltammetry (SWV). The modified GCE/MWCNT-metal oxide electrodes exhibited excellent electrocatalytic activity towards the detection of serotonin at large peak current and lower oxidation potentials compared to other electrodes investigated. The dynamic range for the serotonin determination was between 5.98 × 10− 3 μM to 62.8 μM with detection limits 118, 129 and 166 nM for GCE/MWCNT-NiO, GCE/MWCNT-ZnO and GCE/MWCNT-Fe3O4 sensors respectively. GCE-MWCNT-NiO was the best electrode in terms of serotonin current response, electrode stability, resistance to fouling and limit of detection towards the analyte. The developed sensors were found to be electrochemically stable, reusable, economically effective due to their extremely low operational cost, and have demonstrated good limit of detection, sensitivity and selectivity towards serotonin determination in urine samples.

Nano molar detection of acyclovir, an antiviral drug at nanoclay modified carbon paste electrode

Abstract: A nano level voltammetric sensing method has been developed for determination of acyclovir (ACV) at nano clay modified carbon paste sensor by employing cyclic voltammetry (CV) and square wave voltammetry (SWV) techniques in pH 5.0. The electro-oxidation current of ACV was enhanced two times greater by the modification of the sensor. The modifier nano clay was characterized by utilizing X-ray diffraction (XRD) and scanning electronic microscope (SEM). The influence of parameters like scan rate, pH, accumulation time, amount of the modifier and concentration on the peak current of the drug were studied. The effect of ACV concentration variation was studied using SWV technique and got lowest detection limit compared to the earlier reported techniques. The fabricated sensor was employed for the determination of acyclovir in pharmaceutical and biological samples.

A new structure of photonic crystal fiber with high sensitivity, high nonlinearity, high birefringence and low confinement loss for liquid analyte sensing applications

Abstract: This paper proposes the design and optimization of microstructure optical fiber for liquid sensing applications. A number of propagation characteristics have been compared between two formations of hexagonal cladding of our proposed PCF structure. The core of the proposed PCF structure is designed with two rows of supplementary elliptical air holes. We investigate the performance of the designed PCFs for Ethanol as a liquid sample to be sensed. Numerical analysis is carried out by employing the full vectorial Finite Element Method (FEM) to examine the modal birefringence, confinement loss, relative sensitivity and nonlinear coefficient of the proposed PCF structure.

Design of single mode spiral photonic crystal fiber for gas sensing applications

Abstract: In this paper, a spiral shape photonic crystal fiber (S-PCF) has been suggested as a gas sensor for detecting toxic or colorless gases as well as monitoring the air pollution by metering gas condensate elements in production facilities. Our reported S-PCF is micro-structured where two layers porous core is encircled by a spiral shape cladding. The geometrical parameters have altered to optimize the parameters of the proposed structure. The numerical analysis of the proposed S-PCF is performed by utilizing finite element method (FEM). The relative sensitivity and birefringence of the proposed S-PCF are 55.10% and 7.23 × 10− 3 respectively at the 1.33 μm wavelength that lies in the absorption line of toxic gases (methane and hydrogen fluoride). Besides, effective area, nonlinear coefficient and V parameters are also described briefly.

Electroanalysis of estriol hormone using electrochemical sensor

Abstract: At present, there is the whole area of research community occupied with developing of new materials and fabrication of new biosensors. With the intention to propose an effective, quick and inexpensive method for determination of biomolecules. Here in, we report the electrocatalytic oxidation of Estriol (ET) was analysed by poly (glycine) modified carbon paste electrode (PGMCPE) using cyclic voltammetry and differential voltammetry. Compared to bare carbon paste electrode (BCPE), the PGMCPE indicates good electrocatalytic activity towards the oxidation of ET in phosphate buffer solution (PBS) pH 6. PGMCPE shows a linear response between concentrations of ET. The prepared modified electrode showed high voltammetric responses with sensitivity for ET, results showed it very suitable for the detection of ET at trace levels. Under the optimized conditions, the peak current was linear to ET concentration over the concentration range of 2 × 10− 6 to 1 × 10− 4 M using cyclic voltammetry (CV). The detection limit and limit of quantification were 8.7 × 10− 7 M and 2.6 × 10− 6 M. The proposed method was successfully applied for the determination of ET in the real samples.

Simultaneous determination of caffeine and theophylline using square wave voltammetry at poly(l-aspartic acid)/functionalized multi-walled carbon nanotubes composite modified electrode

Abstract: A simple and reproducible poly( l -aspartic acid)/functionalized multi-walled carbon nanotubes composite modified glassy carbon electrode, P(L Asp)/f-MWCNTs/GCE, was constructed for simultaneous determination of caffeine and theophylline using square wave voltammetry. The electrode preserves and combines the properties of the individual modifiers synergistically. The electrochemical response of P(L Asp)/f-MWCNTs/GCE was characterized by cyclic voltammetry. A significant enhancement in the peak current response of CF and TP were observed accompanied with a negative shift in peak potential at the composite modified electrode compared to the bare electrode. The prepared P(L Asp)/f-MWCNTs/GCE exhibited excellent SWV response towards the simultaneous detection of CF and TP in the range of 1–150 and 0.1–50 μM with limit of detection of 0.28 and 0.02 μM (S/N = 3), respectively. Real sample analysis has been successfully carried out in green tea, blood serum and pharmaceutical formulation of Panadol extra samples, which revealed good recovery results, 92.0–106%. The proposed sensor also displayed good selectivity, repeatability and reproducibility with appreciable long-term stability, indicating the feasibility and reliability.

Nanostructured ZnO-based biosensor: DNA immobilization and hybridization

Abstract: An electrochemical DNA biosensor was successfully fabricated by using (3-aminopropyl) triethoxysilane (APTES) with zinc oxide (ZnO) nanorods synthesized using microwave-assisted chemical bath deposition method on thermally oxidized SiO2 thin films. The structural quality and morphology of the ZnO nanorods were determined by employing scanning electron microscopy (SEM) and X-ray diffraction (XRD), which show a hexagonal wurtzite structure with a preferred orientation along the (101) direction. The surface of the SiO2 thin films was chemically modified with ZnO. Label-free detection DNA immobilization and hybridization were performed using potassium hexacyanoferrate with cyclic voltammetry (CV) measurements. The capacitance, permittivity, and conductivity profiles of the fabricated sensor clearly indicate DNA immobilization and hybridization. Results show that the capacitance values of bare, ZnO- modified surface immobilization, and target DNA hybridization were 46 × 10− 12 F, 47 × 10− 8 F, 27 μF, and 17 μF, respectively, at 1 Hz. The permittivity measurement increased from 3.94 × 103 to 251 × 103 and 165 × 103 at the frequency range of approximately 200 to 1 Hz for bare and DNA immobilization and hybridization, respectively. The measured conductivity values for the bare, ZnO, immobilized, and hybridization device were 2.4 × 10− 9, 10 × 10− 8, 1.6 × 10− 7, and 1.3 × 10− 7 S cm− 1, respectively.

Synthesis of silver nanoparticles using Matricaria recutita (Babunah) plant extract and its study as mercury ions sensor

Abstract: Silver (Ag) nanoparticles comprise a highly selective approach for development of nanosensors for the detection of Hg2 + ions. When Ag nanoparticles mixes with Hg2 + ions, loses its UV–Vis absorption intensity. Here, green synthesis of Ag nanoparticles was done using plant extract of Matricaria recutita (Babunah) under ambient conditions. Biosynthesized Ag nanoparticles are well-dispersed having quasi-spherical shape and average particle size of 11 nm. XRD, SAED and HRTEM analysis showed that nanoparticles are well crystalline in nature and having cubic phase of geometry. We report here highly selective colorimetric detection of mercury ions (Hg2 +) using biosynthesized Ag nanoparticles.

Synthesis of Ag nanoparticles using diatom cells for ammonia sensing

Abstract: Growth of silver nanoparticles through photo induced bioreduction mechanism on the surface of diatom cells, which is a kind of photosensitive fresh water organism containing hydrated amorphous silica structure, has been found to be a cost-effective, rapid, non-toxic, eco-friendly, photo-induced bottom-up process. This material shows broad absorbance in the visible light spectra. Light sensitive fucoxanthin pigment of diatoms that contain hydroxyl (− OH) groups, play a vital role in the formation of silver cluster on the surface of diatom cells and its growth process. Involvement of the compounds and proteins of the diatoms which are responsible for reduction of metal ions and stabilization of the grown nanoparticles on diatom cells, are confirmed by FTIR analysis. Investigations are done to see if the synthesized samples acted as sensing material in the fabrication of a room temperature sensor of dissolved ammonia. With increase in ammonia concentration the visible light absorption peaks tend to higher intensity with blue shift due to the formation of [Ag(NH3)2]+ complexes causing repulsion between the Ag nanoparticles and consequently lead to the formation of smaller Ag nanoparticles. The intensity of absorption of the as-synthesized material is linearly correlated with the concentration of dissolved ammonia as observed from 0 to 100 ppm. The use of naturally occurring diatoms for Ag nanoparticles synthesis has the benefits of amenability for large-scale easy production. Also the experimental findings indicate that the as-synthesized material can act as fast and reliable sensing material.

Effect of biomolecule position and fill in factor on sensitivity of a Dielectric Modulated Double Gate Junctionless MOSFET biosensor

Abstract: In this work, the performance of Junctionless Double Gate MOSFET for the label-free electrical detection of biomolecules like enzyme, cell, DNA, etc. has been investigated with the help of an analytical model. The impact of neutral biomolecules on the electrical characteristics of n-type Si Junctionless Double Gate MOSFET has been analyzed under dry environment situation. The change in the threshold voltage has been used as the sensing metric to detect the sensitivity of the mentioned device architecture for biomolecule detection. Biomolecule position and their fill in factor of the sensing site have been investigated to find out their effect on sensitivity. Moreover, the effect of drain bias on sensitivity has been found to be a crucial factor for the optimization of biosensor's detection capability.

Sensitivity analysis of graphene coated surface plasmon resonance biosensors for biosensing applications

Abstract: This paper describes the effect of adding graphene layers in prism and planar waveguide based surface plasmon resonance biosensors using angular interrogation mode. The proposed sensors are designed based on graphene material as biomolecular recognition elements (BRE) and the sharp SPR curve of gold (Au)·Our calculations show that the proposed graphene in prism and planar waveguide based SPR biosensors have 1 + 0.40L and 1 + 0.45L; (where L is the number of graphene layers) times more sensitivity than the conventional SPR biosensor respectively. The enhanced sensitivity is due to increased SPR angle change about 40L% and 45L% by adding graphene layer and using the optical property of graphene. We also investigate the performance of proposed biosensors in terms of sensitivity using graphene sublayers.

Highly birefringent single mode spiral shape photonic crystal fiber based sensor for gas sensing applications

Abstract: This article represents a gas sensor based on spiral photonic crystal fiber (S-PCF) for detecting harmful or colorless gasses and monitoring air pollution by metering gas condensate elements in production facilities. The proposed micro-structured S-PCF contains two layers porous core encircled by a spiral shape cladding. The geometrical parameters are tuned to fix the optimized S-PCF structure. The numerical analysis of the proposed S-PCF is performed by utilizing finite element method (FEM) with circular perfectly match layer (C-PML). The relative sensitivity and birefringence of the recommended structure are 57.61% and 7.53 × 10 − 3 respectively at 1.33 μm wavelength on the absorption line of toxic gasses (methane and hydrogen fluoride). The exhibited beam divergence is about 4.1° at the same wavelength. Besides, beat length, nonlinear coefficient, effective area and V parameters are also described briefly for optimized S-PCF structure over broader wavelength range from 1 μm to 1.8 μm.

High performance supercapacitor and non-enzymatic hydrogen peroxide sensor based on tellurium nanoparticles

Abstract: Tellurium nanoparticles (Te Nps) were synthesized by wet chemical method and characterized by XRD, Raman, FESEM, TEM, XPS, UV–Vis and FL. The Nps were coated on graphite foil and Glassy carbon electrode to prepare the electrodes for supercapacitor and biosensor applications. The supercapacitor performance is evaluated in 2 M KOH electrolyte by both Cyclic Voltammetry (CV) and galvanostatic charge-discharge method. From charge-discharge method, Te Nps show a specific capacitance of 586 F/g at 2 mA/cm2 and 100 F/g at 30 mA/cm2 as well as an excellent cycle life (100% after 1000 cycles). In addition, the H2O2 sensor performance of Te Nps modified glassy carbon electrode is checked by CV and Chronoamperometry (CA) in phosphate buffer solution (PBS). In the linear range of 0.67 to 8.04 μM of hydrogen peroxide (H2O2), Te NPs show a high sensitivity of 0.83 mA mM− 1 cm− 2 with a correlation coefficient of 0.995. The detection limit is 0.3 μM with a response time less than 5 s.

Synthesis and characterization of ZnS quantum dots and application for development of arginine biosensor

Abstract: Arginine deiminase co-immobilized with ZnS QDs coupled micro-disk was applied for the sensing of arginine in real and spiked fruit samples. Intracellular arginine deiminase from Lactococcus lactis MTCC 460 was partially purified by ammonium sulphate precipitation and co-immobilized on hydrosol gel disk with ZnS quantum dots. Surface study and topology of immobilized ZnS QDs were characterized by SEM. The size of MPA capped ZnS quantum dots was achieved up to 200 nm. Excitation and emission wavelength of synthesized ZnS QDs was observed to be 259 and 580 nm respectively. Linear range of detection of arginine was found to be 1.0 to 10 − 4 M and developed biosensor was used to monitor arginine in water melon and pomegranate fruit juices. Main advantage of the developed system is there is no need of pretreatment of sample for the estimation of arginine content.

Electrochemical sensing and bio-sensing of bisphenol A and detection of its damage to DNA: A comprehensive review

Abstract: This review is aimed at providing comprehensive information on the applications of electrochemical sensors and biosensors to the determination of bisphenol A (BPA) and detection of its damage to DNA as one of the most important endocrine disrupting chemicals (EDCs). The BPA exhibits endocrine disruption in binding to estrogen receptors, such as alterations in endogenous hormone synthesis, hormone metabolism and hormone concentrations in blood which can cause cancerous tumors, birth defects and other developmental disorders. Therefore, sensitive and selective determination of BPA and its damage to DNA is needed and interesting. Electrochemical sensors and biosensors are very suitable for monitoring because of their excellent selectivity and sensitivity, automation, fast response and good repeatability and reproducibility. In this review, we have provided valuable information about electrochemical sensors and biosensors applied for determination of BPA and detection of its damage to DNA.

CTAB immobilized carbon paste electrode for the determination of mesalazine: A cyclic voltammetric method

Abstract: The electrochemical behavior of mesalazine (MSZ) was investigated at CTAB immobilized CPE in 0.2 M PBS of pH 7.4 by cyclic voltammetric technique. The modified electrode was exhibited a good electrochemical activity towards the oxidation of mesalazine, which results in the noticeable improvement of the peak currents and feasible oxidation as compared to the bare carbon paste electrode. Under optimal experimental conditions the electrochemical response to MSZ was linear in the concentration range from 60 μM to 140 μM with a detection limit of 1.9 nM by cyclic voltammetric technique. The sensitivity, long-term stability, reproducibility was shown by the modified electrode. Overall, the proposed method was successfully applied to determine MSZ in pharmaceutical samples and satisfactory results were obtained.

Porous shaped photonic crystal fiber with strong confinement field in sensing applications: Design and analysis

Abstract: In this article, porous core porous cladding photonic crystal fiber (P-PCF) has been proposed for aqueous analytes sensing applications. Guiding properties of the proposed P-PCF has been numerically investigated by utilizing the full vectorial finite element method (FEM). The relative sensitivity and confinement loss are obtained by varying distinct geometrical parameters like the diameter of air holes, a pitch of the core and cladding region over a wider range of wavelength. The proposed P-PCF is organized with five rings air hole in the cladding and two rings air hole in a core territory which maximizes the relative sensitivity expressively and minimizes confinement loss depressively compare with the prior-PCF structures. After completing all investigations, it is also visualized that the relative sensitivity is increasing with the increment of the wavelength of communication band (O + E + S + C + L + U). Higher sensitivity is gained by using higher band for all applied liquids. Finally the investigating effects of different structural parameters of the proposed P-PCF are optimized which shows the sensitivity of 60.57%, 61.45% and 61.82%; the confinement loss of 8.71 × 10 − 08 dB/m, 1.41 × 10 − 10 dB/m and 6.51 × 10 − 10 dB/m for Water (n = 1.33), Ethanol (n = 1.354) and Benzene (n = 1.366) respectively at 1.33 μm wavelength. The optimized P-PCF with higher sensitivity and lower confinement loss has high impact in the area of the chemical as well as gas sensing purposes.

Electrochemical study of hydrochlorothiazide on electrochemically pre-treated pencil graphite electrode as a sensor

Abstract: An electrochemical anodic behavior of hydrochlorothiazide (HCTZ) was studied by using electrochemically pretreated pencil graphite electrode (EPPGE) using cyclic voltammetry (CV), differential pulse voltammetry (DPV) and square wave voltammetry (SWV). Two anodic peaks were observed at peak potential 842 mV and 1091 mV on EPPGE at phosphate buffer (pH 7.0). Electrooxidation process of HCTZ shows diffusion-controlled process on EPPGE. DPV and SWV show a good linearity in the concentration range 4 μM to 140 μM and 1 μM to 20 μM, respectively. The limits of detection were found to be 3.25 μM L− 1 and 0.421 μM L− 1, respectively. Electrochemical impedance spectra (EIS) gave the charge transfer resistance at EPPGE (32.3 kΩ) and PGE (867 kΩ), which shows an increase in the electron transfer rate at EPPGE than that of PGE. Surface area, sensitivity and electron transfer kinetic parameters were studied. Electrochemical pretreatment is a simpler method compared to other modifications for the electrodes and this method could be applied for the sensitive determination of HCTZ present in pharmaceutical formulations and urine samples.

Extremely sensitive multiple sensing ring PCF sensor for lower indexed chemical detection

Abstract: In this article, we have designed and analysed a photonic crystal fiber with multiple sensing ring in core for chemical and biochemical sensing applications. In this proposed design, three and four sensing ring describe in core which offers remarkable high sensitivity and spiral cladding pattern confines large fraction of power in core region and thus reduce the overall confinement loss. This novel proposed model exhibits simultaneously ultra high relative sensitivity 95.40%, 93.13% and minimum confinement loss 7.108 × 10 − 08 , 2.47 × 10 − 08 dB/km for four and three ring pattern. These sensing rings are filled with different sensing liquid. Multiple sensing rings as compared to multiple air holes are desirable feature from fabrication point of view. This proposed PCF design overcomes some experimental challenge such as PCF probe needs some displacement after filling the sensing liquid. These uniform circular sensing rings around the solid core overcome the losses and support better evanescent field matter interaction for sensing application. Multiple sensing rings as compared to multiple tiny air holes are desirable feature from fabrication point of view.

CTAB functionalized multiwalled carbon nanotube composite modified electrode for the determination of 6-mercaptopurine

Abstract: In this work the electrochemical behavior of 6-mercaptopurine (6-MP) on MWCNT-CTAB modified glassy carbon electrode (GCE) is reported in a phosphate buffer solution, pH 3.0. Cyclic voltammetric studies indicated that the oxidation process is irreversible and diffusion-controlled. The number of electrons exchanged in the electro-oxidation process was obtained, and the data indicated that 6-MP is oxidized via a two-electron step. The results revealed that MWCNT-CTAB modified GCE promotes the rate of oxidation compared to the bare GCE, by increasing the peak current. The electron-transfer coefficients and heterogeneous electron-transfer rate constants for 6-MP were reported using modified GCE. A sensitive, simple, and timesaving linear sweep voltammetric procedure was developed for the analysis of 6-MP, using the MWCNT-CTAB/GC electrode. 6-MP can be determined with a detection limit of 8.41 × 10− 9 M in the range of 5.0 × 10− 7 M to 3.0 × 10− 6 M with the proposed method. The developed method was successfully applied in real sample analysis.

Spectroscopic ellipsometry study of gold nanostructures for LSPR bio-sensing applications

Abstract: This main aim of this work is the development of optical biosensors based on the LSPR phenomenon in nano-structured gold films suitable for detection of low molecular weight analytes such as mycotoxins. A simple technology of annealing thin gold films was utilized for the formation of gold nano-islands exhibiting the LSPR effect. The morphology of gold nano-structures produced was studied with SEM and AFM, and their optical properties were analysed with UV-visible absorption spectroscopy and spectroscopic ellipsometry (SE). The position of LSPR band appeared to depend on the dimensions of gold nano-islands. The dependence of the LSPR band spectral shift on the refractive index of a medium was studied with both UV-vis absorption and SE, and the refractive index sensitivity (RIS) was evaluated. The method of SE gave from two to three times higher values of RIS as compared to those obtained by absorption spectroscopy. LSPR bio-sensing tests were attempted using total internal reflection ellipsometry (TIRE); a noticeable spectral shift was recorded on course of immune binding of Aflatoxin B1 to specific antibodies immobilized on the surface of gold.

PDMS membranes as sensing element in optical sensors for gas detection in water

Abstract: Polydimethylsiloxane (PDMS) has been introduced the first time about 20 years ago. This polymer is worldwide used for the rapid prototyping of microfluidic device through a replica molding process. However, the great popularity of PDMS is not only related to its easy processability, but also to its chemical and physical properties. For its interesting properties, the polymer has been implied for several applications, including sensing. In this work, we investigated how to use functionalized PDMS membranes as sensing elements in optical sensors for gas detection in water samples.

Extending the capability of forensic electrochemistry to the novel psychoactive substance benzylpiperazine.

Abstract: Benzylpiperazine (BZP) is a novel psychoactive substance that is commonly abused in tablet form as an “ecstasy-type” drug. Electroanalysis offers genuine potential for field testing of bulk drug samples. This research is the first to investigate the viability of voltammetric analysis of BZP. Initial cyclic voltammetry in 0.1 M KCl showed an oxidative peak at a glassy carbon electrode for BZP at approximately 0.8 V (scan rate 205 mV s− 1). Next an optimised electrode/electrolyte combination (viz. 80:20 W:W glassy carbon beads:nujol and pH 9.5, 40 mM, Britton-Robinson buffer) was developed using K3Fe(CN)6 to test the electrode material. The oxidation of BZP involves two electrons and two protons and a mechanism has been proposed. An anodic stripping square wave voltammetric method was optimised by factorial design with the conditions of deposition: − 0.8 V for 135 s, and stripping: step height 10 mV, amplitude 50 mV and frequency 13 Hz. A limit of detection of 6 μM was achieved. The resolution against 3,4-methylenedioxymethylamphetamine (MDMA) was also verified.

Simplified immunoassay for rapid Dengue serotype diagnosis, revealing insensitivity to non-specific binding interference

Abstract: Proof of concept of an immunoassay, which is easy to implement, for rapid Dengue virus (DENV) serotype diagnosis, in the early infection stage, is reported. The four-layer assay is immobilized onto a thin gold film and relies on a low cost, disposable polymer biochip for optical surface plasmon resonance sensing and detection. The protocol comprises Neutravidin-Biotin mediated monoclonal antibody (MAB) attachment as the functionalized sensing element. Formation of the MAB-DENV complex results in a pronounced thickness change that is optically recorded in real time, employing a microfluidic set-up. Virus presence is confirmed by atomic force microscopy from the same sample. Serum samples were collected from a patient in acute febrile state. Simultaneous serological analysis by means of the reverse transcription polymerase chain reaction, independently, confirmed presence of DENV2 and DENV3. The protocol proved applicable in presence of strong non-specific binding interference that originates from, and is caused by, various blood, serum and other body fluid constituents. False positive indications for both, negative serum and blood control samples were not observed. The achievable limit of detection was estimated to be 2 × 104 particles/ml. Eventually, the method can be modified towards detection of other viruses by using the same protocol.

Development of electrochemical inhibition biosensor based on bacteria for detection of environmental pollutants

Abstract: The main aim of this work is to develop a simple inhibition electrochemical sensor array for detection of heavy metals using bacteria. A series of electrical measurements (cyclic voltammograms) were carried out on samples of two types of bacteria, namely Escherichia coli and Shewanella oneidensis along with optical measurements (fluorescence microscopy, optical density, and flow cytometry) for comparison purposes. As a first step, a correlation between DC electrical conductivity and bacteria concentration in solution was established. The study of the effect of heavy metal ions (Hg2 +) on DC electrical characteristics of bacteria revealed a possibility of pattern recognition of inhibition agents. Electrical properties of bacteria in solution were compared to those for immobilized bacteria.