Heating promoted super sensitive electrochemical detection of p53 gene based on alkaline phosphatase and nicking endonuclease Nt.BstNBI-assisted target recycling amplification strategy at heated gold disk electrode

An ultrasensitive electrochemical biosensor for detecting p53 gene was fabricated based on heated gold disk electrode coupling with endonuclease Nt.BstNBI-assisted target recycle amplification and alkaline phosphatase (ALP)-based electrocatalytic signal amplification. For biosensor assembling, biotinylated ssDNA capture probes were first immobilized on heated Au disk electrode (HAuDE), then combined with streptavidin-alkaline phosphatase (SA-ALP) by biotin-SA interaction. ALP could catalyze the hydrolysis of ascorbic acid 2-phosphate (AAP) to produce ascorbic acid (AA). While AA could induce the redox cycling to generate electrocatalytic oxidation current in the presence of ferrocene methanol (FcM). When capture probes hybridized with p53, Nt.BstNBI would recognize and cleave the duplexes and p53 was released for recycling. Meanwhile, the biotin group dropt from the electrode surface and subsequently SA-ALP could not adhere to the electrode. The signal difference before and after cleavage was proportional to the p53 gene concentration. Furthermore, with electrode temperature elevated, the Nt.BstNBI and ALP activities could be increased, greatly improving the sensitivity and efficiency for p53 detection. A detection limit of 9.5 × 10^-17 M could be obtained (S/N = 3) with an electrode temperature of 40 °C, ca. four magnitudes lower than that at 25 °C.

Temperature-Controllable Electrodes with a One-Parameter Calibration

Electrically heated electrodes have been applied for various chemical and biological sensors. However, previous electrically heated electrodes, including microwires and microdiscs, are usually small and often suffer from the requirement of frequent calibrations of the electrode surface temperature ( T_s) at different environment temperatures. Here, we fabricate a temperature-controllable disk electrode (TCDE) with a conventional size (3-5 mm in diameter). A one-parameter temperature calibration is proposed using a temperature transfer coefficient α and a structural model ( T_s = T_e + α ( T_h - T_e)) to estimate T_s ( T_h and T_e are the temperature of the heating element and environment, respectively). The value of α is unique for a TCDE and mainly dependent on the structure and materials of the electrodes and the solution in nature. Once α is experimentally determined, T_s can be calibrated and found to be applicable to wide fluctuations in room temperature (15.0-33.0 °C) with errors below 1.5% for three types of disk electrodes (gold, glassy carbon, and platinum). The required T_s can be obtained by just setting T_h without thermal characterization between the heating power and T_s. A simple relationship for exploring the dependence of α on the height ( H) and radius ( R) of the electrode materials and other constants ( a, b, c, and R₀), α = 1 - c - aH - b ( R - R₀)², is revealed by numerical simulations (COMSOL). The impact of the radii of both the insulating materials of the electrode and the electrochemical cells on T_s is also considered. The effect of the solution thermal conductivity on α is studied. TCDEs are expected to be used as a sensor platform with enhanced performance.

Integration of thermocouple microelectrode in the scanning electrochemical microscope at variable temperatures: simultaneous temperature and electrochemical imaging and its kinetic studies

We describe herein a method for the simultaneous measurement of temperature and electrochemical signal with a new type of thermocouple microelectrode. The thermocouple microelectrode can be used not only as a thermometer but also as a scanning electrochemical microscope (SECM) tip in the reaction between tip-generated bromine and a heated Cu sample. The influence of temperature on the SECM imaging process and the related kinetic parameters have been studied, such as kinetic constant and activation energy.

Electrochemical methods in conjunction with capillary and microchip electrophoresis

Electromigrative techniques such as capillary and microchip electrophoresis (CE and MCE) are inherently associated with various electrochemical phenomena. The electrolytic processes occurring in the buffer reservoirs have to be considered for a proper design of miniaturized electrophoretic systems and a suitable selection of buffer composition. In addition, the control of the electroosmotic flow plays a crucial role for the optimization of CE/MCE separations. Electroanalytical methods have significant importance in the field of detection in conjunction with CE/MCE. At present, amperometric detection and contactless conductivity detection are the predominating electrochemical detection methods for CE/MCE. This paper reviews the most recent trends in the field of electrochemical detection coupled to CE/MCE. The emphasis is on methodical developments and new applications that have been published over the past five years. A rather new way for the implementation of electrochemical methods into CE systems is the concept of electrochemically assisted injection which involves the electrochemical conversions of analytes during the injection step. This approach is particularly attractive in hyphenation to mass spectrometry (MS) as it widens the range of CE-MS applications. An overview of recent developments of electrochemically assisted injection coupled to CE is presented.