scholarly journals DNAzyme-Amplified Electrochemical Biosensor Coupled with pH Meter for Ca2+ Determination at Variable pH Environments

Nanomaterials ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 4
Author(s):  
Hui Wang ◽  
Fan Zhang ◽  
Yue Wang ◽  
Fangquan Shi ◽  
Qingyao Luo ◽  
...  

For more than 50% of multiparous cows, it is difficult to adapt to the sudden increase in calcium demand for milk production, which is highly likely to cause hypocalcemia. An electrochemical biosensor is a portable and efficient method to sense Ca2+ concentrations, but biomaterial is easily affected by the pH of the analyte solution. Here, an electrochemical biosensor was fabricated using a glassy carbon electrode (GCE) and single-walled carbon nanotube (SWNT), which amplified the impedance signal by changing the structure and length of the DNAzyme. Aiming at the interference of the pH, the electrochemical biosensor (GCE/SWNT/DNAzyme) was coupled with a pH meter to form an electrochemical device. It was used to collect data at different Ca2+ concentrations and pH values, and then was processed using different mathematical models, of which GPR showed higher detecting accuracy. After optimizing the detecting parameters, the electrochemical device could determine the Ca2+ concentration ranging from 5 μM to 25 mM, with a detection limit of 4.2 μM at pH values ranging from 4.0 to 7.5. Finally, the electrochemical device was used to determine the Ca2+ concentrations in different blood and milk samples, which can overcome the influence of the pH.

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Koh Sing Ngai ◽  
Wee Tee Tan ◽  
Zulkarnain Zainal ◽  
Ruzniza Mohd Zawawi ◽  
Joon Ching Juan

A rapid, simple, and sensitive method for the electrochemical determination of paracetamol was developed. A single-walled carbon nanotube/nickel (SWCNT/Ni) nanocomposite was prepared and immobilized on a glassy carbon electrode (GCE) surface via mechanical attachment. This paper reports the voltammetry study on the effect of paracetamol concentration, scan rate, pH, and temperature at a SWCNT/Ni-modified electrode in the determination of paracetamol. The characterization of the SWCNT/Ni/GCE was performed by cyclic voltammetry. Variable pressure scanning electron microscopy (VPSEM) and energy dispersive X-ray (EDX) spectrometer were used to examine the surface morphology and elemental profile of the modified electrode, respectively. Cyclic voltammetry showed significant enhancement in peak current for the determination of paracetamol at the SWCNT/Ni-modified electrode. A linear calibration curve was obtained for the paracetamol concentration between 0.05 and 0.50 mM. The SWCNT/Ni/GCE displayed a sensitivity of 64 mA M−1and a detection limit of 1.17 × 10−7 M in paracetamol detection. The proposed electrode can be applied for the determination of paracetamol in real pharmaceutical samples with satisfactory performance. Results indicate that electrodes modified with SWCNT and nickel nanoparticles exhibit better electrocatalytic activity towards paracetamol.


Author(s):  
Pengfei Li ◽  
Nan Lei ◽  
Jie Xu ◽  
Wei Xue

Here we report the design, fabrication, and characterization of a lab-on-a-chip device using a nanotube-based sensor array. The microfluidic components are composed of an ultraviolet (UV) light-defined, cross-linked SU-8 microchannel and a polydimethylsiloxane (PDMS) top cover. The hybrid microfluidic structure provides a fully sealed microchannel, well-aligned features, and precisely positioned nanosensors. Well-organized single-walled carbon nanotube (SWNT) thin films are deposited and aligned across the electrodes on a silicon substrate with dielectrophoresis. The assembly of SWNTs is carried out in a sealed microchannel. The SWNT devices are configured as two-terminal resistor-type sensors with the metal electrodes as the probing pads and the dielectrophoretically captured SWNTs as the sensing elements. The SWNT devices are used as integrated flow sensors to monitor the flow rate in the microchannel. In addition, when exposed to aqueous solutions with various pH values, these sensors change their resistance accordingly and demonstrate high sensitivity towards pH solutions.


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