Versatile MXene composite probe-mediated homogeneous electrochemiluminescence biosensor with integrated signal transduction and near-infrared modulation strategy for concanavalin A detection.

Based on the highly specific interaction between concanavalin A (Con A) and glucose (Glu), a competitive electrochemiluminescence (ECL) biosensor was constructed for ultrasensitive detection of Con A. Nanocomposites with excellent electrocatalytic and photothermal properties were obtained by covalently bonding zinc oxide quantum dots (ZnO QDs) to vanadium carbide MXene (V2C MXene) surfaces. The modification of ZnO QDs hinders the aggregation of V2C MXene and increases the catalytic activity of oxygen reduction reaction, thus amplifying the luminol cathodic emission. In addition, the excellent photothermal performance of the V2C MXene-ZnO QDs can convert light energy into heat energy under the irradiation of 808 nm near infrared laser, thus increasing the temperature of the reaction system and accelerating the electron transfer process to realize the synergistic amplified homogeneous ECL system. This innovative work not only enriches the fundamental research on multifunctional MXene nanomaterials for biosensing, but also provides an effective strategy for ECL signal amplification.

A pressure-colorimetric multimode system with photothermal activated multiple rolling signal amplification for ovarian cancer biomarker detection.

Utilizing the photothermal effect to activate enzyme activity, realize signal conversion and amplification show promising prospects in biosensing. Herein, a pressure-colorimetric multi-mode bio-sensor was proposed through the multiple rolling signal amplification strategy of photothermal control. Under NIR light radiation, the Nb2C MXene labeled photothermal probe caused notable temperature elevation on a multi-functional signal conversion paper (MSCP), leading to decomposition of thermal responsive element and in-situ formation of Nb2C MXene/Ag-Sx hybrid. The generation of Nb2C MXene/Ag-Sx hybrid accompanied with valid color change from pale yellow to dark brown on MSCP. Moreover, the Ag-Sx as a signal amplification element enhanced the NIR light absorption to further improve the photothermal effect of Nb2C MXene/Ag-Sx thereby induce cyclic in situ production of Nb2C MXene/Ag-Sx hybrid with rolling enhanced photothermal effect. Subsequently, the continuously enhanced photothermal effect rolling activated catalase-like activity of Nb2C MXene/Ag-Sx, which accelerated the decomposition of H2O2 and promoted the pressure elevation. Therefore, the rolling-enhanced photothermal effect and rolling activated catalase-like activity of Nb2C MXene/Ag-Sx considerately amplified the pressure and color change. Making full use of multi-signal readout conversion and rolling signal amplification, accurate results can be obtained in a short time, whether in the laboratory or in the patient's homes.

A self-enhanced electrochemiluminescent ratiometric zearalenone immunoassay based on the use of helical carbon nanotubes.

A self-enhanced electrochemiluminescent ratiometric immunoassay for zearalenone is described. A system composed of N-aminobutyl-N-ethylisoluminol (ABEI) and glutathione (GSH) produces a strong electrochemiluminescence (ECL) at an applied potential of 0.8 V, probably because of short electron transfer distance and reduced energy loss. The method also uses octahedral anatase mesocrystals (OAM) with a large specific surface facilitating immobilization of ABEI and GSH. Helical carbon nanotubes, possessing a large specific surface, superior mechanical stability, and excellent electrical conductivity which serve as a solid support, greatly enhanced the loading capacity for g-C3N4 nanosheets and horseradish peroxidase-labeled anti-antibody. The peroxidase accelerates the decomposition of H2O2 to produce reactive oxygen species (ROSs), amplifying the blue ECL of ABEI and the green ECL of g-C3N4. The ratiometric sandwich immunoassay (performed by the ratio of ECL intensity at - 1.3 V and 0.8 V) allows for sensitive and reliable determination of ZEN in a wide linear range from 1.0 × 10-4 ng/mL to 10 ng/mL. The method was successfully applied to the analysis of corn hazelnut samples for ZEN. Graphical abstract Schematic presentation of a self-enhanced electrochemiluminescent ratiometric immunosensor based on octahedral anatase mesocrystals (OAM) supported ABEI-glutathione (GSH) and g-C3N4 functionalized helical carbon nanotubes (HCNT) for zearalenone (ZEN) determination.

Photoelectrochemical biosensor constructed using TiO2 mesocrystals based multipurpose matrix for trypsin detection.

Herein, a delicate photoelectrochemical biosensor for quantitative detection of trypsin was successfully established by virtue of polyethylenimine-sensitized TiO2 mesocrystal as the photoactive matrix integrated with Boron-doped carbon quantum dots labeled peptide as the signal amplification tags. Specifically, polyethylenimine with fine photo-stability was introduced here as the electron transporting layer to reduce the energy barrier of TiO2 mesocrystal, thereby facilitating the carriers transfer and improving the photocurrent response. Moreover, the Boron-doped carbon dots-peptide bioconjugates could noticeably decrease the photocurrent due to the competitively light harvesting by Boron-doped carbon dots and the steric hindrance of peptide chains, leading to less light energy arriving at the TiO2 mesocrystal and hindering the electrons transfer between the electrolyte and electrode. The anchored conjugates synergistically promoted the decline of photocurrent signal, evidently enhancing the sensitivity of this detection protocol. When trypsin was incubated, the photoelectric signal was obviously re-promoting because arginine-containing peptide chains could be specifically cleaved by trypsin and the Boron-doped carbon quantum dots was affranchised from the electrode, making the most of the previous suppression effects released. Therefore, the intensity of photocurrent signal was proportional to the trypsin concentration in a wide linger range from 1×10-7mg/mL to 1.0mg/mL. This practical and elegant "on-off-on" biosensor with high sensitivity offered a promising scheme to monitor various proteases and the inhibitors screening for early diagnoses of different diseases.

An electrochemical impedimetric sensor based on biomimetic electrospun nanofibers for formaldehyde.

Herein, simple molecular recognition sites for formaldehyde were designed on electrospun polymer nanofibers. In order to improve the conductivity of the electrospun polymer nanofibers, carbon nanotubes were introduced into the resulting nanofibers. By employing these functionalized nanocomposite fibers to fabricate a biomimetic sensor platform, an obvious change caused by recognition between recognition sites and formaldehyde molecules was monitored through electrochemical impedance spectroscopy (EIS). The experimental conditions were optimized and then a quantitative method for formaldehyde sensing in low concentration was established. The relative results demonstrated that the sensor based on biomimetic recognition nanofibers displays an excellent recognition capacity toward formaldehyde. The linear response range of the sensor was between 1 × 10(-6) mol L(-1) and 1 × 10(-2) mol L(-1), with the detection limit of 8 × 10(-7) mol L(-1). The presented research provided a fast, feasible and sensitive method for formaldehyde with good anti-interference capabilities and good stability, which could meet the practical requirement for formaldehyde assay.