A serious impetus always exists to exploit new methods to enrich the prospect of nanomaterials. Here, we report electrochemical conversion (ECC) of magnetic nanoparticles (MNPs) to electroactive Prussian blue (PB) analogues accompanied by three interfacial effects and its exploitation for novel label self-sacrificial biosensing of avian influenza virus H5N1. The ECC method involves a high-potential step to create strong acidic condition by splitting H2O to release Fe3+ from the MNPs, and then a low-potential step leading to the reduction of coexisting K3Fe(CN)6 and Fe3+ to K4Fe(CN)6 and Fe2+, respectively, which react to form PB analogues. Unlike conventional solid/liquid electrochemical interfaces that need a supply of reactants by transportation from bulk solution and require additional template to generate porosity, the proposed method introduces MNPs on the electrode surface and makes them natural nanotemplates and nanoconfined sources of reactants. Therefore, the method presents interesting surface templating, generation–confinement, and refreshing effects/modes, which benefit the produced PB with higher porosity and electrochemical activity, and 3 orders of magnitude lower requirement for reactant concentration compared with conventional methods. Based on the ECC methods, a sandwich immunosensor is designed for rapid detection of avian influenza virus H5N1 using MNPs as self-sacrificial labels to produce PB for signal amplification. Taking full advantages of the high abundance of Fe in MNPs and three surface effects, the ECC method endows the biosensing technology with high sensitivity and a limit of detection down to 0.0022 hemagglutination units, which is better than those of most reported analogues. The ECC method may lead to a new direction for application of nanomaterials and new electrochemistry modes.

Facile regulation and enhancing of the performance of bioimmobilization materials is a key factor for their applications for biosensing, biocatalysis, bioreactor, and so on. Here, we propose a method of combined polymerizations of chemical oxidation and metal organic coordination to develop enhanced bioimmobilization matrices for high performance biosensing. Being different from conventional methods that are based on sole polymerization, the new method elaborated chemical oxidation to one-pot obtain oligomers as ligands for metal–organic coordination polymerization. Two kinds of thiol that could be chemically oxidized by H2O2 and be coordinated with NaAuCl4 were adopted as monomers. Glucose oxidase was adopted as the representative biomolecule. Chemical oxidation was proved to be efficient to lengthen monomers to produce oligomers (ligands) with different lengths by adjusting the concentrations of monomers and oxidant, as well as reaction time. This dynamic prelengthening process not only endows the coexisting biomolecules with active and protective oligomers shell to significantly enhance the immobilization efficiency but also regulates the structure of metal–organic coordination polymer. As crucial factors of immobilization, the entrapment ratio of enzyme and mass-transfer efficiency all achieved obvious increases compared with those based on sole chemical oxidation polymerization or metal–organic coordination polymerization; the entrapment ratio even reached an extreme value of 100%. Therefore, the biosensing performance was greatly promoted with sensitivities being among the best of those reported analogues. The biosensors also exhibited satisfactory selectivity, stability, and feasibility for blood serum samples. This method may provide a universal strategy for regulating and enhancing performance of ligand-constructed polymers and their composites for entrapment-based applications.

•Exploited MWCNT-MOCPs as highly efficient matrices of enzyme immobilization•MWCNT-MOCPs one-pot entrapped GOx with ratio being close to 100%•MWCNT-MOCPs electrode presented superior enzymatic catalysis performance.New nanocomposites with multi-walled carbon nanotubes (MWCNTs) embedded in metal-organic coordination polymers (MOCPs) were successfully prepared as highly efficient matrices of enzyme immobilization for sensitive electrochemical biosensing. NaAuCl4 was pre-adsorbed on the MWCNTs to act as anchor sites to further coordinate with ligand benzenedithiol and form MOCPs. The formation of MWCNTs-MOCPs one-pot entrapped glucose oxidase (GOx) with a ratio close to 100% and exhibited enhanced mass-transfer over MOCPs. Thus MWCNTs-MOCPs-modified electrodes present superior enzymatic catalysis performance of greatly enhanced sensitivity (136 μA cm− 2 mM− 1) and magnitudes-lower detection limit (48 nM), being superior to most analogues.Download high-res image (280KB)Download full-size image

Thiols play a crucial role in various physiological functions, and the discrimination of thiols is a significant but difficult issue. Herein, we presented a new strategy for strengthening the discrimination of thiols by a facile colorimetric sensor array composed of a series of urease–metal ion pairs. The proposed sensor array was fabricated based on the interactions between thiols and metal ions and the effective activation of urease by thiols. Different thiols exhibited different affinities toward the metal ions, producing differential retentions of urease activity and generating distinct colorimetric response patterns. These response patterns are characteristic for each thiol and can be quantitatively differentiated by linear discriminant analysis (LDA). Cysteine (Cys), glutathione (GSH), and four other kinds of thiols have been well distinguished on the basis of this sensor array at a low concentration (1.0 μM). Remarkably, the practicability of the proposed sensor array was further validated by high accuracy (96.67%) identification of 30 unknown thiol samples. In this strategy, urease and its metal ion inhibitors were adapted to fabricate the sensor array, offering a facile way to develop sensitive array sensing systems based on inexpensive and commercially available enzymes and their inhibitors.