Nanogold amplified electrochemiluminescence/electrochemistry in bipolar silica nanochannel array for ultrasensitive detection of SARS-CoV-2 pseudoviruses.

The prompt and accurate point-of-care test (POCT) for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in infected persons or virus-containing environmental samples is of great importance. The present work reports a highly integrated electrochemiluminescence/electrochemical (ECL/EC) sensor for determination of SARS-CoV-2 pseudoviruses, in which bio-recognition element (SARS-CoV-2 IgG antibody), bifunctional probe (tris (2,2'-bipyridyl) ruthenium (Ru(bpy)32+)), and amplification material (gold nanoparticles (Au NPs)) are designed into bipolar silica nanochannel array (bp-SNA). bp-SNA consisting of homogeneous two-layer mesoporous silica films bears inner silanol groups and outer amino groups, generating a solid "electrostatic nanocage" for stable confinement of Ru(bpy)32+ and Au NPs inside the nanochannels and further providing functional sites for covalent modification of SARS-CoV-2 IgG antibody. Owing to the preconcentration capacity of bp-SNA and amplified effect of Au NPs, ECL or EC signals of Ru(bpy)32+ can be remarkably promoted and thereby increase the analytical performance, which can be diminished by immunorecognization of target SARS-CoV-2 pseudoviruses on the sensing interface. The developed integrated ECL/EC sensor based on Ru@AuNPs/bp-SNA modified solid indium tin oxide electrode enables the sensitive analysis of SARS-CoV-2 pseudoviruses by ECL mode with a linear range of 50 TU mL-1-5000 TU mL-1, as well as the EC mode with a linear range of 100 TU mL-1-5000 TU mL-1. Moreover, the designed sensor showed satisfactory results in the analyses of saliva and pond water samples. When flexible electrode substate (polyethylene terephthalate) is employed, Ru@AuNPs/bp-SNA has great potential to integrate with KN95 face masks for direct detection of SARS-CoV-2 pseudoviruses produced from breathing, talking and coughing processes, which could provide an efficient platform for POCT diagnosis.

A highly sensitive electrochemical biosensor for protein based on a tetrahedral DNA probe, N- and P-co-doped graphene, and rolling circle amplification.

A tetrahedral DNA probe can effectively overcome the steric effects of a single-stranded probe to obtain well-controlled density and minimize nonspecific adsorption. Herein, a highly sensitive electrochemical biosensor is fabricated for determination of protein using a tetrahedral DNA probe and rolling circle amplification (RCA). N- and P-co-doped graphene (NP-rGO) is prepared, and AuNPs are then electrodeposited on it for DNA probe immobilization. Benefitting from the synergistic effects of the excellent electrical conductivity of NP-rGO, the stability of the tetrahedral DNA probe and the signal amplification of RCA, the biosensor achieves a low limit of 3.53 × 10-14 M for thrombin and a wide linear range from 1 × 10-13 to 1 × 10-7 M. This study provides a sensitive and effective method for the detection of protein in peripheral biofluids, and paves the way for future clinical diagnostics and treatment of disease. Graphical abstract.

Fe3O4 nanoparticles coated with double imprinted polymers for magnetic solid phase extraction of lead(II) from biological and environmental samples.

Double imprinted polymer coated magnetic nanoparticles were fabricated with 4-nm size ZnO nanoparticles acting as the sacrifice templates, which were co-imprinted with template Pb(II) ions. After template removal, abundant transfer pores derived from ZnO nanoparticles were left around the selective adsorption sites derived from Pb(II) ions. The magnetic sorbent exhibit good selectivity, rapid adsorption kinetic and large adsorption capacity for Pb(II). They were used to extract trace Pb(II) followed by graphite furnace atomic absorption spectrometry detection. After the optimization of extraction conditions, following merits are found: (a) rapid extraction (10 min), (b) high preconcentration factor (100 fold), (c) sensitive detection with the detection limit of 9.4 ng·L-1, and (d) low relative standard deviation (6.9%) at a level of 50 ng·L-1 of Pb(II) analyzed 7 times. The method was employed in extraction and quantification of trace Pb in biological and environmental samples with satisfactory recoveries of 87.5-104%. Graphical abstractDouble imprinted polymer coated magnetic nanoparticles (MNPs@DIP) were fabricated and used for extraction of Pb(II) followed by graphite furnace atomic absorption spectrometry (GFAAS) detection. The method was successfully applied for the determination of Pb in environmental and biological samples.

Highly specific and sensitive determination of propyl gallate in food by a novel fluorescence sensor.

Propyl gallate (PG), one of the most widely used synthetic phenolic antioxidants in edible oil, cookies and fried food, has received extensive concern due to its possible toxic effects on human health. Herein, a novel fluorescence analytical method is firstly proposed to sensitively and selectively determine propyl gallate (PG) by utilizing the unique fluorescence quenching property of organic molybdate complex (OMC) formed by the specific reaction between MoO42- and PG to g-C3N4 nanosheets. Under the optimum conditions, the developed fluorescence sensor allows highly sensitive detection of PG in a wide range from 0.5 to 200 µg mL-1 with a detection limit of 0.11 µg mL-1, and possesses excellent specificity and good recoveries. All the analytical results indicate the present method provides an effective approach for rapid detection of PG in common products, which is beneficial for monitoring and reducing the risk of overuse of PG.

Simultaneous and sensitive electrochemical detection of dihydroxybenzene isomers with UiO-66 metal-organic framework/mesoporous carbon.

The zirconium-based MOF (UiO-66)/mesoporous carbon (MC) composite was synthesized using conventional hydrothermal method for the first time. The surface morphology and structure of UiO-66/MC composite were characterized by scanning electron microscopy (SEM), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). A novel electrochemical sensor based on UiO-66/MC was constructed for simultaneous and sensitive determination of dihydroxybenzene isomers (DBIs) of hydroquinone (HQ), catechol (CT) and resorcinol (RS). The proposed sensor displays excellent electrocatalytic activity toward the oxidation of HQ, CT and RS. The peak-to-peak potential separations between CT and HQ, and RS and CT are 0.130V and 0.345V, respectively. Under the optimized conditions, the electrochemical sensor shows a wide linear response in the concentration range of 0.5-100µM, 0.4-100µM and 30-400µM with a detection limit of 0.056µM, 0.072µM and 3.51µM (S/N = 3) for HQ, CT and RS, respectively. In addition, the sensor has superior sensitivity and electrochemical stability along with good reproducibility and anti-interference properties. The fabricated sensor was also applied for the determination of DBIs in the real water samples with satisfying results.