Rapid and ultrasensitive electrochemical detection of DNA methylation for ovarian cancer diagnosis.

Alterations in DNA methylation, a stable epigenetic marker, are important components in the development of cancer. It is vital to develop diagnostic systems with the ability to rapidly quantify DNA methylation with high sensitivity and selectivity. However, the analysis of DNA methylation must address two main challenges: (i) ultralow abundance and (ii) differentiating methylated cytosine from normal cytosine on target DNA sequence in the presence of an overwhelming background of circulating cell-free DNA. Here we report the development of an ultrasensitive and highly-selective electrochemical biosensor for the rapid detection of DNA methylation in blood. The sensing of DNA methylation involves the hybridization on a network of probe DNA modified gold-coated magnetic nanoparticles (DNA-Au@MNPs) complementary to target DNA, and subsequently enzymatic cleavage to differentiate methylated DNA strands from corresponding unmethylated DNA strands. The biosensor presents a dynamic range from 2 aM to 20 nM for 110 nucleotide DNA sequences containing a single-site methylation with the lowest detected concentration of 2 aM. This DNA-Au@MNPs based sensor provides a promising method to achieve 35 min response time and minimally invasive diagnosis of ovarian cancer.

Rapid and ultrasensitive electrochemical detection of circulating tumor DNA by hybridization on the network of gold-coated magnetic nanoparticles.

An accurate and robust method for quantifying the levels of circulating tumor DNA (ctDNA) is vital if this potential biomarker is to be used for the early diagnosis of cancer. The analysis of ctDNA presents unique challenges because of its short half-life and ultralow abundance in early stage cancers. Here we develop an ultrasensitive electrochemical biosensor for rapid detection of ctDNA in whole blood. The sensing of ctDNA is based on hybridization on a network of probe DNA modified gold-coated magnetic nanoparticles (DNA-Au@MNPs). This DNA-Au@MNPs biosensor can selectively detect short- and long-strand DNA targets. It has a broad dynamic range (2 aM to 20 nM) for 22 nucleotide DNA target with an ultralow detection limit of 3.3 aM. For 101 nucleotide ctDNA target, a dynamic range from 200 aM to 20 nM was achieved with a detection limit of 5 fM. This DNA-Au@MNPs based sensor provides a promising method to achieve 20 min response time and minimally invasive cancer early diagnosis.

Advances in the Application of Magnetic Nanoparticles for Sensing.

Magnetic nanoparticles (MNPs) are of high significance in sensing as they provide viable solutions to the enduring challenges related to lower detection limits and nonspecific effects. The rapid expansion in the applications of MNPs creates a need to overview the current state of the field of MNPs for sensing applications. In this review, the trends and concepts in the literature are critically appraised in terms of the opportunities and limitations of MNPs used for the most advanced sensing applications. The latest progress in MNP sensor technologies is overviewed with a focus on MNP structures and properties, as well as the strategies of incorporating these MNPs into devices. By looking at recent synthetic advancements, and the key challenges that face nanoparticle-based sensors, this review aims to outline how to design, synthesize, and use MNPs to make the most effective and sensitive sensors.

Acetylcholinesterase biosensor based on multi-walled carbon nanotubes-SnO2-chitosan nanocomposite.

A sensitive amperometric acetylcholinesterase (AChE) biosensor was developed based on the nanocomposite of multi-walled carbon nanotubes (MWCNTs), tin oxide (SnO2) nanoparticles and chitosan (CHIT). Acetylcholinesterase (AChE) and Nafion were immobilized onto the nanocomposite film to prepare AChE biosensor for pesticide residues detection. The morphologies and electrochemistry properties of the surface modification were investigated using cyclic voltammetry, differential pulse voltammetry, and scanning electron microscopy, respectively. Compared with individual MWCNTs-CHIT, SnO2-CHIT and bare gold electrode, this nanocomposite showed the most obvious electrochemical signal in the presence of [Fe(CN)6](3-/4-) as a redox couple. Incorporating MWCNTs and SnO2 into 0.2% CHIT solution can promote electron transfer, enhance the electrochemical response, and improve the microarchitecture of the electrode surface. All variables involved in the preparation process and analytical performance of the biosensor were optimized. Under optimized conditions, the AChE biosensor exhibited a wide linear range from 0.05 to 1.0 × 10(5 )µg/L and with a detection limit for chlorpyrifos was 0.05 µg/L. Based on the inhibition of pesticides on the AChE activity, using chlorpyrifos as model pesticide, the proposed biosensor exhibited a wide range, low detection limit, good reproducibility, and high stability. Using cabbages, lettuces, leeks, and pakchois as model samples, acceptable recovery of 98.7-105.2% was obtained. The proposed method was proven to be a feasible quantitative method for chlorpyrifos analysis, which may open a new door ultrasensitive detection of chlorpyrifos residues in vegetables and fruits.