Search

Here, screen-printed carbon electrodes (SPCEs) were modified with ultrafine and mainly monodisperse sea urchin-like tungsten oxide (SUWO3) nanostructures synthesized by a simple one-pot hydrothermal method for highly sensitive and selective detection of dopamine (DA) and uric acid (UA). Sea urchin-like nanostructures were clearly observed in scanning electron microscope images and WO3 composition was confirmed with XRD, FTIR and UV-Vis spectrophotometer. Modification SPCEs with SUWO3 nanostructures via the drop-casting method clearly reduced the R𝑐𝑡 value of the electrodes, lowered the ΔEp and enhanced the DA oxidation current due to high electrocatalytic activity. As a result, SUWO3/SPCEs enabled highly sensitive detection of DA (LOD: 51.4 nM and sensitivity: 127 μAmM−1cm−2) and UA (LOD: 253 nM and sensitivity: 55.9 μAmM−1cm−2) at low concentration. Lastly, SUWO3/SPCEs were tested with artificial urine, in which acceptable recoveries for both molecules were obtained. Given the high selectivity, the sensor has the potential to be used for highly sensitive simultaneous detection of DA and UA in real biological samples

In this study, a stable, flexible, cheap and disposable multiwalled carbon nano tubes (MWCNT)-based screen-printed carbon electrode was developed for fast and sensitive sensor applications. A novel ink was prepared by mixing MWCNT, varnish and liquid paraffin in certain ratios. The ink was then was transferred to an acetate paper using a stencil pattern which had a working, an auxiliary and a reference electrode in its design. Commercial silver paste was used to pattern the reference electrode using the same stencil. First, the ink composition was optimizes and then the electrodes were characterized based on physical stress and electrochemical behavior at different scan rates. According to the results, the flexible electrode exhibited an excellent electrochemical behavior and expected to contribute to wearable biosensor applications due to its stability, sensitivity and flexible structure.

Here, a dual ITO microchip was fabricated for high sensitive detection of dopamine (DA) based on redox-cycling. The ITO electrodes with 3×3 mm working areas were made via photolithography and dry etching processes. The microchip was obtained by first aligning the working areas of two ITO electrodes to overlap and then fixing them in that position using a double-sided tape, which also formed a sealed microchannel between the ITO electrodes for test solution delivery. The ITO electrodes and microchips were electrochemically characterized using EIS, cyclic voltammetry and chronoamperometry. Compared to a single ITO electrode in a microchannel, the microchip had a significantly higher signal due to redox cycling. The microchip was lastly used for the detection of DA at varying concentrations. According to the results, the microchip had an LOD of 0.15 μM in a linear detection region of 0.1 to 50 μM. The microchip requires less than 1 μl of solution to complete the analysis and has great potential to be applied for immunosensing.

Here, an extended – gate field effect transistor (EGFET) pH microsensor was developed for use in fast and sensitive pH measurement applications. The system consisted of two components; a pH sensitive modified gold electrode and a simple and cheap metal oxide semiconductor field-effect transistor (MOSFET). Polypyrrole, a semiconductor and pH responsive polymer, was formed by electropolymerization of pyrrole monomer at the surface of the gold electrode in galvostanic mode. Then, measurements were made in PBS at different pH values using the pH sensitive electrode. In this context, the pH sensitivity of polypyrrole with respect to electropolymerization and incubation time were studied. According to the results, the EGFET pH microsensor formed by 4-min pyrrole electropolymerization showed at pH 6-12 the highest pH sensitivity with 67 mV/pH

Paper-based sensors have great potential for use in a variety of areas, from environmental monitoring to clinical and pointof-care testings. Here, a microfluidic paper-based analytical device (µPAD) was integrated with a smartphone app capable of offline (without internet access) image processing and analysis for rapid colorimetric detection of glucose. A self-inking stamp was used to form hydrophobic channels on a piece of paper-towel due to its superior water absorption efficiency. As demonstrated, the developed sensor was employed for colorimetric detection of glucose in artificial saliva in the linear scope of 0-1 mM with a calculated detection limit of 29.65 µM. In addition, experimental results show that quantitative analysis of glucose with the proposed smartphone platform could be completed in less than one minute. The app developed for the smartphone platform is capable of extracting the color changing area with an embedded image processing tool which could address the problem of color uniformity in detection zones of µPAD. The total cost of a µPAD is less than $0.2. By integrating µPAD with a smartphone and user-friendly app together, the proposed smartphone-based platform could be used for the quantitative analysis of glucose with advantages such as portability, simple operation, rapid response, ultra-low cost, field-deployable, selectivity and sensitivity. The results show that the integrated platform has great potential to be used for non-invasive measurement of glucose in body fluids like a tear, sweat and saliva.

Paper-based sensors have great potential to be used in a variety of fields ranging from environmental monitoring to clinical and point-of-care diagnostics. These sensors are disposable, cost effective, flexible and easy to use. The aim of this study was to fabricate a low cost, disposable, reliable and easy to use paper-based electrochemical sensor and its electrochemical modification with nanostructured Au for glucose detection in alkaline solutions.

Here, we report a facile method for electro-addressable functionalization of a probe comprising of closely spaced three individually addressable carbon fiber electrodes for detection of nucleic acids. First, a multi electrode array probe comprising three adjacent carbon fiber electrodes was fabricated through pulling a three-barrel glass capillary with a single carbon fiber in each barrel using a micropuller. Second, electropolymerization based doping was used for electro-addressable functionalization of the multi-electrode array probe. To demonstrate that the current strategy works, anti-miR-34a was electrografted on only one of three electrodes by electropolymerization of pyrrole on the specific electrode. A second electrode was coated only with polypyrrole (PPy) and the third was left unmodified. Electrochemical impedance spectroscopy (EIS) was used for analysis and the results clearly showed charge transfer resistance of the PPy + anti-miR-34a modified electrode increased significantly after hybridization, while charge transfer resistance of the other two electrodes remained almost constant. The results demonstrate that the present strategy has great potential for constructing multiplex nucleic acid micro/nano biosensors for local and in situ detection of multiple nucleic acid molecules such as miRNAs at a time., Comment: Sen, Mustafa (2017), Using electropolymerization based doping for electro-addressable functionalization of a multi-electrode array probe for nucleic acid detection, submitted to Chemistry Letters

We fabricated a platinum-based double barrel probe for scanning electrochemical microscopy-scanning ion conductance microscopy (SECM-SICM) by electrodepositing platinum onto the carbon nanoelectrode of the double barrel probe. The deposition conditions were optimized to attain highly sensitive electrochemical measurements and imaging. Simultaneous SECM-SICM imaging of electrochemical features and noncontact topography by using the optimized probe afforded high-resolution images of epidermal growth factor receptors (EGFR) on the membrane surface of the A431 cells.