Electrochemical aptasensor based on DNA-templated copper nanoparticles and RecJf exonuclease-assisted target recycling for lipopolysaccharide detection.

An electrochemical aptasensor for detecting lipopolysaccharides (LPS) was fabricated based on DNA-templated copper nanoparticles (DNA-CuNPs) and RecJf exonuclease-assisted target recycling. The DNA-CuNPs were synthesized on a double-stranded DNA template generated through the hybridization of the LPS aptamer and its complementary chain (cDNA). In the absence of LPS, the CuNPs were synthesized on DNA double-strands, and a strong readout corresponding to the CuNPs was achieved at 0.10 V (vs. SCE). In the presence of LPS, the fabricated aptamer could detach from the DNA double-strand to form a complex with LPS, disrupting the template for the synthesis of CuNPs on the electrode. Meanwhile, RecJf exonuclease could hydrolyze the cDNA together with this single-stranded aptamer, releasing the LPS for the next round of aptamer binding, thereby enabling target recycling amplification. As a result, the electrochemical signal decreased and could be used to indicate the LPS content. The fabricated electrochemical aptasensor exhibited an extensive dynamic working range of 0.01 pg mL-1 to 100 ng mL-1, and its detection limit was 6.8 fg mL-1. The aptasensor also exhibited high selectivity and excellent reproducibility. Moreover, the proposed aptasensor could be used in practical applications for the detection of LPS in human serum samples.

A dual-mode of electrochemical-colorimetric biosensing platform for kanamycin detection based on self-sacrifice beacon and magnetic separation technique.

In this work, iron-based metal organic frameworks (Fe-MOF) are used as a self-sacrifice beacon to produce Prussian blue (PB). Then, a dual-mode electrochemical-colorimetric biosensing platform for kanamycin (KAN) detection is established considering the prominent redox activity and blue color of PB. CoFe2O4 magnetic nanobeads (CoFe2O4 MBs) are employed for immobilization and separation of the signal beacon in the complex matrix, and the combination between CoFe2O4 MBs and magnetic electrodes simplifies the electrochemical testing process. The linear range of the electrochemical mode is 0.1 nM-1.0 µM with a detection limit of 39 pM, and that of the colorimetric mode is 10 nM-2.0 µM with a detection limit of 3.6 nM. Furthermore, the dual-mode strategy shows satisfactory specificity and enhanced applicability for KAN detection in real samples. Compared with known dual-mode determination methods, the proposed design employs the same reaction to produce two signal output modes, thus eliminating the effect of different reactive pathways on the outcome and in turn promoting greater accuracy.

Rapid synthesis and characterization of silver-loaded graphene oxide nanomaterials and their antibacterial applications.

With the promising potential application of Ag/graphene-based nanomaterials in medicine and engineering materials, the large-scale production has attracted great interest of researchers on the basis of green synthesis. In this study, water-soluble silver/graphene oxide (Ag/GO) nanomaterials were synthesized under ultrasound-assisted conditions. The structural characteristics of Ag/GO were confirmed by Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, scanning electron microscopy and energy dispersion spectroscopy, respectively. The results showed the silver particles (AgNPs) obtained by reduction were attached to the surface of GO, and there was a strong interaction between AgNPs and GO. The antibacterial activity was primarily evaluated by the plate method and hole punching method. Antibacterial tests indicated that Ag/GO could inhibit the growth of Gram-negative and Gram-positive bacteria, special for the Staphylococcus aureus.

Cellulose nanocrystal assisted trace silver nitrate to synthesize green silver nanocomposites with antibacterial activity.

Cellulose nanocrystals (CNCs) with silver nanoparticles (AgNPs) are used for applications ranging from chemical catalysis to environmental remediation, and generation of smart electronics and biological medicine such as antibacterial agents. To reduce the synthesis cost of AgNPs and environmental pollution, microwave-assisted generation of AgNPs on the CNC surface (AgNPs@CNC) has been found to be useful, because microwave reaction has the advantages of simple reaction conditions, short reaction time and high reaction efficiency. The silver ions (Ag+) could be added to the CNC suspension and placed in the microwave reactor for a few minutes to produce AgNPs. AgNP generation was affected by factors such as the concentrations of Ag+ and CNC, and the power of the microwave, as well as the time of reaction. In this study, we used trace amounts of AgNO3 to rapidly synthesize AgNPs using a green microwave-based method instead of Tollen's reagent, and the antibacterial activity of the T1 sample showed that only using 0.03 mM (∼0.01 wt%) AgNO3 to synthesize AgNPs@CNC could achieve good antibacterial properties.