Dendrimer-encapsulated copper as a novel oligonucleotides label for sensitive electrochemical stripping detection of DNA hybridization

Simple electrochemical sensing for mercury ions in dairy product using optimal Cu2+-based metal-organic frameworks as signal reporting

A convenient sensor is developed for electrochemical assay of Hg²⁺ in dairy product using the optimal Cu²⁺-based metal-organic frameworks (Cu-MOFs) as signal reporting. Benefiting from specific recognition between Hg²⁺ and thymine (T)-rich DNA strands, the interferences of milk matrices are effectively eliminated, thereby greatly improving the accuracy of test results. Moreover, the suitable Cu-MOFs offer an efficient carrier for probe design, and the contained Cu²⁺ ions could be directly detected to output electrochemical signal of Hg²⁺ presence without labor- or time-intensive operations. Compared with previous methods, this sensor substantially simplifies the process of electrochemical measurement and facilitates highly sensitive, selective and rapid analysis of Hg²⁺ with detection limit of 4.8 fM, offering a valuable means for monitoring dairy product contamination with Hg²⁺.

Silver-dendrimer nanocomposites as oligonucleotide labels for electrochemical stripping detection of DNA hybridization

Silver-dendrimer nanocomposites were synthesized and used as oligonucleotide labels for electrochemical stripping detection of DNA hybridization. The synthesized silver-dendrimer nanocomposites were characterized by UV-vis spectrophotometry, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Ratios of silver/dendrimer were optimized in order to obtain stable nanocomposites with maximal silver loading in the interior of a polymeric shell. The silver-dendrimer nanocomposites were attached to sequence-known DNA probes specific to colitoxin, and used to detect probe hybridization by dissolution of the silver nanoparticles in the interior of dendrimer in a diluted nitric acid, followed by measurement of Ag⁺ ions by anodic stripping voltammetry (ASV). Use of differential pulse voltammetry for the stripping step, along with optimization of the ASV conditions, enabled a detection limit of 0.78 pM. The present strategy, in combination with dendrimer-encapsulated copper labeled oligonucleotides probe reported previously, could potentially be used to detect single or multiple DNA targets in one sample.

Development of an electrochemical surface-enhanced Raman spectroscopy (EC-SERS) aptasensor for direct detection of DNA hybridization

Rapid detection of disease biomarkers at the patient point-of-care is essential to timely and effective treatment. The research described herein focuses on the development of an electrochemical surface-enhanced Raman spectroscopy (EC-SERS) DNA aptasensor capable of direct detection of tuberculosis (TB) DNA. Specifically, a plausible DNA biomarker present in TB patient urine was chosen as the model target for detection. Cost-effective screen printed electrodes (SPEs) modified with silver nanoparticles (AgNP) were used as the aptasensor platform, onto which the aptamer specific for the target DNA was immobilized. Direct detection of the target DNA was demonstrated through the appearance of SERS peaks characteristic for adenine, present only in the target strand. Modulation of the applied potential allowed for a sizeable increase in the observed SERS response and the use of thiol back-filling prevented non-specific adsorption of non-target DNA. To our knowledge, this work represents the first EC-SERS study of an aptasensor for the direct, label-free detection of DNA hybridization. Such a technology paves the way for rapid detection of disease biomarkers at the patient point-of-care.

Direct detection of OTA by impedimetric aptasensor based on modified polypyrrole-dendrimers

Ochratoxin A (OTA) is a carcinogenic mycotoxin that contaminates food such as cereals, wine and beer; therefore it represents a risk for human health. Consequently, the allowed concentration of OTA in food is regulated by governmental organizations and its detection is of major agronomical interest. In the current study we report the development of an electrochemical aptasensor able to directly detect trace OTA without any amplification procedure. This aptasensor was constructed by coating the surface of a gold electrode with a film layer of modified polypyrrole (PPy), which was thereafter covalently bound to polyamidoamine dendrimers of the fourth generation (PAMAM G4). Finally, DNA aptamers that specifically binds OTA were covalently bound to the PAMAM G4 providing the aptasensor, which was characterized by using both Atomic Force Microscopy (AFM) and Surface Plasmon Resonance (SPR) techniques. The study of OTA detection by the constructed electrochemical aptasensor was performed using Electrochemical Impedance Spectroscopy (EIS) and revealed that the presence of OTA led to the modification of the electrical properties of the PPy layer. These modifications could be assigned to conformational changes in the folding of the aptamers upon specific binding of OTA. The aptasensor had a dynamic range of up to 5 μg L(-1) of OTA and a detection limit of 2 ng L(-1) of OTA, which is below the OTA concentration allowed in food by the European regulations. The efficient detection of OTA by this electrochemical aptasensor provides an unforeseen platform that could be used for the detection of various small molecules through specific aptamer association.

One step synthesis of silane-capped copper clusters as a sensitive optical probe and efficient catalyst for reversible color switching

Luminescent silane-functionalized copper clusters are developed as a highly efficient catalyst to build up a recyclable and photoreversible color switching system based on the redox reactions of methylene blue.

A label-free electrochemistry biosensor based flower-like 3-dimensional ZnO superstructures for detection of DNA arrays

A highly sensitive electrochemical DNA sensor was constructed by homogenously distributing Au nanoparticles (AuNPs) on a flower-like 3D ZnO superstructure–chitosan (CS) matrix.

Label and indicator free electrochemical nanobiosensing of DNA hybridization based on MnO2 nanomaterial modified GCPE

A label and indicator free electrochemical DNA hybridization detection method based on MnO₂-Nps/GCPE was developed. Compared to plain GCPE, a very robust and sensitive genosensor was obtained.