In this paper, a novel electrochemical sensor was developed for the rapid detection of G-G mismatched DNA based on hexaammineruthenium(III) chloride ([Ru(NH 3 ) 6 ]C l3 ) as a redox indicator. The sensor platform was constructed by immobilizing small molecules (NC-linker) on the gold electrode via amide bonds. The as-prepared NC-linker as the nucleic acids recognition molecule can interact with the G base of DNA. After the sensor was incubated with G-G mismatched DNA, the double-stranded DNA (dsDNA) acted as carriers of the signal tags-[Ru(NH3)6]Cl3, which resulted in a remarkable electrochemical signal. More binding of [Ru(NH 3 ) 6 ]C l3 led to increases of the electrochemical signal. Other mismatched DNA produced only a low response, as well as complementary DNA. Thus G-G mismatched DNA can be easily discriminated from other mismatched and complementary DNA based on the sensor. Furthermore, the method was simple, rapid and repeatable for the detection of G-G mismatched DNA. The selective detection of target dsDNA was achieved by a relative current ratio of the target and control DNA. These results demonstrated that this strategy could provide great promise for the rapid and specific detection of other sequence-specific DNA.
Yihui Ma,Nianzu Liu,Zhenying Xu,Jingjing Wang,Xiliang Luo
The rapid, selective and ultrasensitive assaying of biomarkers remains a challenge relevant to biosensor/diagnostic applications. Herein, a promising electrochemical biosensor based on three-dimensional (3D) nanoporous conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) decorated with gold nanoparticles (AuNPs) was developed, in which methylene blue (MB) was employed as redox indicator for microRNA24 (miRNA24) detection. The unique porous construction was fabricated by a simple hard-template method and cyclic voltammetry (CV) electrochemical technique. AuNPs were electrodeposited onto the porous PEDOT surface to increase the interface conductivity and provide more active sites to load identification elements. The obtained porous biosensor based on conducting polymer PEDOT and AuNPs exhibited significantly enlarged specific surface area (about 2.4 times) and enhanced sensitivity (about 2.1 times), compared to the biosensor based on planar PEDOT. The developed porous biosensor achieved a miRNA24 quantification range from 1 fM to 10 nM with satisfying stability, high selectivity, and a low limit of detection (0.38 fM). The construction of biosensors based on porous conducting polymers decorated with AuNPs offers an effective strategy to increase the electroactive surface area of the sensing interfaces, so as to effectively enhance the sensitivity.
Low-density lipoprotein (LDL) is a key biomarker involved in cardiovascular disease (CVD) risk assessment. Early-stage diagnosis of CVD complications by monitoring LDL levels could be a significant clinical tool and the first step toward adopting efficient therapy. Herein, a novel label-free electrochemical aptasensor for LDL detection was developed via the molybdenum disulfide-gold nanoparticle- ferrocene-carboxylic acid nanosheets (MoS 2 -Au-Fc NSs) enhanced signal amplification strategy. The MoS 2 -Au-Fc NSs were used not only as the biocompatible substrate for LDL aptamer (LDLapt) stabilization due to the increasing electrical conductivity and effective surface area, but also as a redox probe for monitoring the changes of the electrochemical signal because of good electroactive properties of Fc . The aptasensor fabrication steps were investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). When LDL was captured onto the sensor via the specific affinity of the LDLapt, the formed LDLapt-LDL complexes shed from the electrode and enhanced the electron transfer rate on the electrode surface, resulting in an increase of the peak current. Thus, LDL can be easily detected by measuring the changes of peak current. Under ideal circumstances, the aptasensor was linearly correlated with logarithm LDL concentration from 0.001 to 100.0 μg/mL with R 2 of 0.9914, and a low detection limit of 0.42 ng/mL. Furthermore, the LDL detected by aptasensor in actual serum samples with good actual errors (0.73%–5.00%) and satisfactory relative standard deviations (RSDs) (0.04%–0.84%). This study provides a new analytical method for measuring the level of LDL which is specifically up-regulated in CVD patients at an early stage.
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