Schiff Base Complexes with Covalently Anchored Luminophores: Self-Enhanced Electrochemiluminescence Detection of Neomycin.

A novel electrochemiluminescence (ECL) amplification strategy was established aiming to overcome the inherent shortcomings of the current oxygen (O2) coreactant ECL systems. Macrocyclic Schiff base Fe complexes were rationally designed as a novel integrated ECL emitter by iminium linkage between N-(4-aminobutyl)-N-ethylisoluminol (ABEI) and 1,10-phenanthroline-2,9-dicarbaldehyde (PDL) and postmetalation of the macrocyclic Schiff base. Covalently combining luminophore ABEI with a catalytic center endowed the novel ECL emitter with both remarkable redox electrocatalytic properties and significantly enhanced ECL efficiency. The high content of ferrous iron and the dominantly active low-spin Fe state greatly contributed to the inherent catalytic activity for O2 activation. The rational modification of luminophore optimized the spatial distribution and simultaneously shortened the species transport distance of coreactant radicals generated in situ from dissolved O2, resulting in significantly self-enhanced ECL efficiency. Neomycin, which posed a growing threat to aquatic biodiversity and environmental safety, as the model antibiotic was successfully detected with a detection limit of 0.21 pM (S/N = 3), clarifying a promising application prospect of this new luminophore-embedded ECL amplification strategy in biological analysis and environmental monitoring.

Rational Design of a Highly Dispersed Fe-N-C Nanosheet with 1,10-Phenanthroline-2,9-Dicarboxylic Acid as a Preorganized Ligand: Boosted Electrochemiluminescence Detection of Tetracycline.

In view of the shortcomings of the current coreactant electrochemiluminescence (ECL) and inspired by natural oxygen (O2) reduction metalloenzymes, a novel ECL amplification strategy was established. A pyrolytic iron- and nitrogen-doped (Fe-N-C) nanosheet rich in singly ionized oxygen vacancy (VO•) defects was rationally designed by destroying the highly saturated coordination with a preorganized ligand 1,10-phenanthroline-2,9-dicarboxylic acid (PDA). Extraordinary catalytic activity for O2 activation was obtained via screening a special pyrolysis temperature using spectroscopic and electrochemical methods. The high-spin ferric centers of highly dispersed FeC nanoclusters and abundant carbon and oxygen vacancy defects fully contributed to the inherent catalytic activity. ECL amplification was achieved by integrating the material with luminol to generate redox-active radicals in situ from dissolved O2 and simultaneously shorten the transferring distance of radicals. Tetracycline (TC), which posed a growing threat to aquatic biodiversity and environmental safety, as a model antibiotic was successfully detected with a detection limit of 3.88 nM (S/N = 3), clarifying a promising application prospect of this new effective ECL amplification strategy in biological analysis and environmental monitoring.

Fe-MOGs-based enzyme mimetic and its mediated electrochemiluminescence for in situ detection of H2O2 released from Hela cells.

Enzyme mimetics have attracted wide interest due to their inherent enzyme-like activity and unique physicochemical properties, as well as promising applications in disease diagnosis, treatment and monitoring. Inspired by the attributes of nonheme iron enzymes, synthetic models were designed to mimic their capability and investigate the catalytic mechanisms. Herein, metal-organic gels (Fe-MOGs) with horseradish peroxidase (HRP) like Fe-NX structure were successfully synthesized though the coordination between iron and 1,10-phenanthroline-2,9-dicarboxylic acid (PDA) and exhibited excellent peroxidase-like activity. Its structure-activity relationship and the in-situ electrochemiluminescence (ECL) detection of H2O2 secreted by Hela cells were further investigated. The highly dispersed Fe-NX active sites inside Fe-MOGs were able to catalyze the decomposition of H2O2 into large amounts of reactive oxygen species (ROS) via a Fenton-like reaction under a low overpotential. Due to the accumulation of ROS free radicals, the luminol ECL emission was significantly amplified. A proof-of-concept biosensor was constructed with a detection limit as low as 2.2 nM and a wide linear range from 0.01 to 40 µM. As a novel metal organic gels based enzyme mimetic, Fe-MOGs show great promises in early cancer detection and pathological process monitoring.

Uniform and Easy-To-Prepare Glycopolymer-Brush Interface for Rapid Protein (Anti-)Adhesion Sensing.

Glycopolymers have emerged as powerful and versatile glycan analogues for the investigation of cellular signal transduction. In this study, a layer of the glycopolymer-brush (GlyB) interface was functionalized on the surface of gold substrates. In order to enhance the capability and accessibility of this transducer interface, a combined protocol of copper(0)-mediated living radical polymerization (Cu(0)-LRP) with subsequent "CuAAC" click reaction was utilized to synthesize a set of novel glycopolymer precursors with a tunable scaffold structure and pyranose ligands. The resulting glycopolymer exhibited a fine-tuned molecular weight with a minor dispersity of 1.27. Through surface plasmon resonance (SPR) analysis, various GlyB interfaces exhibiting different saccharide moieties (glucose, mannose, and galactose) were examined to study their adhesion or antiadhesion potential toward three types of proteins, concanavalin A, bovine serum albumin, and peanut agglutinin (PNA). The strong affinity between poly(galactose) and PNA was further employed to construct a proof-of-concept aggregation-mediated sensing system. This minimal naked-eye sensor that consisted of only two substances, namely, gold nanoparticles and glycopolymers, was characterized and tested for its potential in protein quantification.