Cu x O@DNA sphere-based electrochemical bioassay for sensitive detection of Pb2

A novel "on-off-on" electrochemiluminescence strategy based on RNA cleavage propelled signal amplification and resonance energy transfer for Pb2+ detection

BACKGROUND

Lead (Pb) is one of the most toxic heavy-metal pollutants. Additionally, lead ions (Pb2+) can accumulate in the human body through the food chain, causing irreversible damage through organ damage and system disorders. In the past few years, the detection of Pb2+ has mainly relied on instrumental methods such as atomic absorption spectroscopy (AAS) and inductively coupled plasma mass spectrometry (ICP-MS). Nonetheless, these techniques are complicated in terms of equipment and procedures, along with being time-intensive and expensive in terms of detection. These drawbacks have limited their wide application. Hence, there is a pressing need to develop detection techniques for Pb2+ that are not only cost-efficient but also highly sensitive and specific.

RESULTS

A novel "on-off-on" electrochemiluminescence (ECL) sensor for detecting Pb2+ was developed based on the resonance energy transfer (RET) effect between AuNPs and boron nitride quantum dots (BN QDs) and the recognition of Pb2+ by DNAzyme along with the cleavage reaction of the substrate chain. Poly(6-carboxyindole)/stannic sulfide (P6ICA/SnS2) nanocomposite was employed as a co-reaction accelerator to consequently facilitate the production of intermediate SO4•-. This effective enhancement of the reaction led to an improved ECL intensity of BN QDs and enabled the sensor platform to exhibit a higher original ECL response. Benefiting from the combination of the DNAzyme signal amplification strategy with the "on-off-on" design, the ECL sensor showed satisfactory selectivity, good stability, and high sensitivity. This ECL sensor exhibited a linear detection range (LDR) of 10-12-10-5 M and a limit of detection (LOD) of 2.6 × 10-13 M.

SIGNIFICANCE

In the present work, an "on-off-on" ECL sensor is constructed based on RET effect for ultrasensitive detection of Pb2+. P6ICA/SnS2 was investigated as the co-reaction accelerator in this sensor. Moreover, this ECL sensor exhibited excellent analytical capability for detecting Pb2+ in actual water samples, providing a method for detecting other heavy metal ions as well.

Electrochemical determination of lead(II) and copper(II) by using phytic acid and polypyrrole functionalized metal-organic frameworks

A glassy carbon electrode (GCE) was modified with a composite prepared from phytic acid, polypyrrole and a ZIF type metal-organic framework (PA/PPy)/ZIF-8@ZIF-67). The nanocomposite was prepared by in-situ chemical polymerization in the presence of ferric chloride and subsequently functionalized with PA to form PA/PPy/ZIF-8@ZIF-67. The materials were characterized by XRD, FT-IR, BET, XPS, SEM and TEM. The modified GCE was applied to individual and simultaneous detection of Pb(II) and Cu(II), with peak voltages of -0.6 and - 0.1 V, respectively (vs. SCE). The amount of PPy, the ZIF-8@ZIF-67 concentration, polymerization potential, polymerization time and pH value were optimized. Under optimized conditions, the calibration plots have two linear ranges. These are from 0.02 to 200 μM and from 200 to 600 μM for Pb(II), and from 0.2 to 200 μM and 200 to 600 μM for Cu(II). The detection limits are 2.9 nM and 14.8 nM, respectively. Simultaneous detection of Pb(II) and Cu(II) is also demonstrated. The good performance of the electrode is attributed to the large surface area of ZIF-8@ZIF-67, the good electrical conductivity of PPy, and the metal complexation power of PA. The modified GCE was successfully applied to the determination of Pb(II) and Cu(II) in real samples and gave satisfactory recoveries. Graphical abstractSchematic presentation of the construction process of PA/PPy/ZIF-8@ZIF-67/GCE sensor, and the mechanism of Pb(II) and Cu(II) at the prepared sensor.

Epitaxial Graphene Sensors Combined with 3D-Printed Microfluidic Chip for Heavy Metals Detection

In this work, we investigated the sensing performance of epitaxial graphene on Si-face 4H-SiC (EG/SiC) for liquid-phase detection of heavy metals (e.g., Pb and Cd), showing fast and stable response and low detection limit. The sensing platform proposed includes 3D-printed microfluidic devices, which incorporate all features required to connect and execute lab-on-chip (LOC) functions. The obtained results indicate that EG exhibits excellent sensing activity towards Pb and Cd ions. Several concentrations of Pb²⁺ solutions, ranging from 125 nM to 500 µM, were analyzed showing Langmuir correlation between signal and Pb²⁺ concentrations, good stability, and reproducibility over time. Upon the simultaneous presence of both metals, sensor response is dominated by Pb²⁺ rather than Cd²⁺ ions. To explain the sensing mechanisms and difference in adsorption behavior of Pb²⁺ and Cd²⁺ ions on EG in water-based solutions, we performed van-der-Waals (vdW)-corrected density functional theory (DFT) calculations and non-covalent interaction (NCI) analysis, extended charge decomposition analysis (ECDA), and topological analysis. We demonstrated that Pb²⁺ and Cd²⁺ ions act as electron-acceptors, enhancing hole conductivity of EG, due to charge transfer from graphene to metal ions, and Pb²⁺ ions have preferential ability to binding with graphene over cadmium. Electrochemical measurements confirmed the conductometric results, which additionally indicate that EG is more sensitive to lead than to cadmium.

Tailoring the dimensionality of carbon nanostructures as highly electrochemical supports for detection of carcinoembryonic antigens

Partially- and fully-unzipped nitrogen-doped carbon nanotubes (NCNTs) were prepared by unzipping pristine NCNTs and three carbon nanostructures were applied to support Au nanoparticles (AuNPs) to form nanocomposites (Au/NCNTs, Au/PU-NCNTs, and Au/FU-NCNTs). The electrochemical behavior and the electrocatalytic activities of the nanocomposite-modified electrodes were examined. The oxygen functional groups, doped N content, and AuNP loaded concentrations are dependent on the unzipping-degree and then affect the electrochemical response and electrocatalytic performance of the electrodes. Besides, the three nanocomposites were also used for the immobilization of carcinoembryonic antigen (CEA) aptamer strands and applied for the detection of CEA. The Au/FU-NCNTs possess the optimal electrocatalytic activity and biosensing performance for the biomolecules and CEA, which is attributed to the maximum loaded AuNPs, the largest specific surface areas and the most active sites. The Au/FU-NCNT-based electrochemical aptasensor exhibits high sensitivity with a low detection limit of 6.84 pg mL-1 within a broad linear range of CEA concentration from 0.01 to 10 ng mL-1. All of these results indicate that the Au/FU-NCNTs may be a potential support for construction of aptasensors with high electrochemical effect and can be employed in the fields of biosensing or biomedical diagnosis.