Electrochemical peptide nucleic acid functionalized α-Fe2O3/Fe3O4 nanosheets for detection of CYP2C19*2 gene

Magnetically induced self-assembly electrochemical biosensor with ultra-low detection limit and extended measuring range for sensitive detection of HER2 protein

An innovative electrochemical biosensor was fabricated for sensitive detection of human epidermal growth factor receptor 2 (HER2) protein, which was considered as an essential tumor marker for diagnosis and treatment evaluation of breast cancer. The sensor was constructed using Apt and PNA as recognition probes incorporated with magnetic Fe3O4/α-Fe2O3@Au nanocomposites. The sensing strategy was designed to lower the detection limit of HER2, and avoid the large steric interference caused by macromolecular HER2 on the electrode surface. Rigid structure dsDNA (Apt/ssDNA) was designed to improve the sensitivity of the sensor. Apt captured the macromolecular HER2 protein, and ssDNA chains were simultaneously released, causing a sensitive change in the electrochemical signal. PNA captured the released ssDNA chains, which converted the electrochemical signal changes caused by HER2 to those caused by the number of short strand ssDNA, so the detection range was extended. Under optimized conditions, this sensing strategy realized an ultra-low detection LOD of HER2 (4.1 fg·mL-1), and the detection range was 10 fg·mL-1-5 × 106 fg·mL-1. The experimental results confirmed that the electrochemical biosensor had excellent selectivity, reproducibility, and storage stability. Analysis of spiked serum samples exhibited a recovery rate of 95.9-115.7 %, which indicated great promise for HER2 detection in serum samples.

Nucleic acid aptasensor with magnetically induced self-assembly for the detection of EpCAM glycoprotein

A "turn-on" aptasensor for label-free and cell-free EpCAM detection was constructed by employing magnetic α-Fe2O3/Fe3O4@Au nanocomposites as a matrix for signal amplification and double-stranded complex (SH-DNA/Apt probes) immobilization through Au-S binding. α-Fe2O3/Fe3O4@Au could be efficiently assembled into uniform and stable self-assembly films via magnetic-induced self-assembly technique on a magnetic glassy carbon electrode (MGCE). The effectiveness of the platform for EpCAM detection was confirmed through differential pulse voltammetry (DPV). Under optimized conditions, the platform exhibited excellent specificity for EpCAM, and a strong linear correlation was observed between the current and the logarithm of EpCAM protein concentration in the range 1 pg/mL-1000 pg/mL (R2 = 0.9964), with a limit of detection (LOD) of 0.27 pg/mL. Furthermore, the developed platform demonstrated good stability during a 14-day storage test, with fluctuations remaining below 93.33% of the initial current value. Promising results were obtained when detecting EpCAM in spiked serum samples, suggesting its potential as a point-of-care (POC) testing.

Precise Differentiation of Wobble-Type Allele via Ratiometric Design of a Ligase Chain Reaction-Based Electrochemical Biosensor for CYP2C19*2 Genotyping of Clinical Samples

Due to the comparable stability between the perfect-base pair and the wobble-base pair, a precise differentiation of the wobble-type allele has remained a challenge, often leading to false results. Herein, we proposed a ligase chain reaction (LCR)-based ratiometric electrochemical DNA sensor, namely, R-eLCR, for a precise typing of the wobble-type allele, in which the traditionally recognized "negative" signal of wobble-base pair-mediated amplification was fully utilized as a "positive" one and a ratiometric readout mode was employed to ameliorated the underlying potential external influence and improved its detection accuracy in the typing of the wobble-type allele. The results showed that the ratio between current of methylene blue (IMB) and current of ferrocene (IFc) was partitioned in three regions and three types of wobble-type allele were thus precisely differentiated (AA homozygote: IMB/IFc > 2; GG homozygote: IMB/IFc < 1; GA heterozygote: 1 < IMB/IFc < 2); the proposed R-eLCR successfully discriminated the three types of CYP2C19*2 allele in nine cases of human whole blood samples, which was consistent with those of the sequencing method. These results evidence that the proposed R-eLCR can serve as an accurate and robust alternative for the identification of wobble-type allele, which lays a solid foundation and holds great potential for precision medicine.