Dextran-based antibacterial hydrogel-derived fluorescent sensors for the visual monitoring of AgNPs.

The unpredictable release behavior of metal nanoparticles/metal ions from metal nanoparticle-loaded hydrogels, without a suitable in situ detection method, is resulting in serious cytotoxicity. To optimize the preparation and design of antibacterial hydrogels for in situ detection of metal nanoparticles, an in-situ detection platform based on the fluorescence signal change caused by the potential surface energy transfer of silver nanoparticles (AgNPs) and carbon dots (CD) through silver mirror reaction and Schiff base reaction was established. The antimicrobial test results show that the composite antimicrobial hydrogel, with lower dosages of AgNPs and CD, exhibited a higher inhibition rate of 99.1 % against E. coli and 99.8 % against S. aureus compared to the single antimicrobial component. This suggests a potential synergistic antimicrobial activity. Furthermore, the fluorescence detection platform was established with a difference of <3 µg between detected values and actual values over a period of 72 h. This demonstrates the excellent in situ detection capability of the hydrogel in antimicrobial-related applications.

A simple photoelectrochemical aptasensor based on MoS2/rGO for aflatoxin B1 detection in grain crops.

Designing a simple and sensitive photoelectrochemical (PEC) sensor is crucial to addressing the limitations of routine analytical methods. The sensitivity of the PEC sensor, however, relies on the photoelectric material used. In this manuscript, composites of MoS2/rGO (MG) with a large area and layered structure are prepared by simple steps. This material exhibits sensitivity to visible light and demonstrates outstanding photoelectric conversion performance. The constructed PEC aptasensor using this material to detect aflatoxin B1 (AFB1) shows significantly higher sensitivity and stability compared to similar sensors. This may be attributed to the presence of surface defects in MoS2, which provide more active sites for photocatalysis. Additionally, graphene oxide (GO) is reduced to rGO by thiourea and forms a heterojunction with MoS2, enhancing charge carrier separation and interfacial electron transfer. Our research has revealed that the photocurrent intensity of the aptamer electrode decreases with an increase in AFB1 concentration, resulting in a "signal-off" PEC aptasensor. The detection limit of this aptasensor is 2.18 pg mL-1, with a linear range of 0.001 to 100 ng mL-1. This result will also provide a reference for the study of other mycotoxins in food.

High inhabitation activity of CMCS/Phytic acid/Zn2+ nanoparticles via flash nanoprecipitation (FNP) for bacterial and fungal infections.

Plant diseases prompted by fungi and bacteria are one of the most serious threats to global crop production and food security. The destruction of these infections posed a major challenge to plant protection by chemical control. Herein, we develop CMCS/PA/Zn2+ nanoparticles (NPs) using carboxymethyl chitosan (CMCS), phytic acid (PA) and metal ions (Zn2+) via flash nanoprecipitation (FNP) strategy. Metal complexes of PA with specified antibacterial and antifungal activities are expected to hold the potential and play a significant role in antimicrobial treatment. The size and size distribution of NPs was confirmed through Dynamic and Static Light Scatterer (DSLS). In acidic-infection microenvironment, the CMCS/PA/Zn2+ NPs can disintegrate and release Zn2+ in situ thus stimulated the corresponding antimicrobial activity. These CMCS/PA/Zn2+ NPs showed outstanding antibacterial efficacy (98 %) against S. aureus and E. coli bacteria in vitro, as well as an impressive antifungal efficacy of 98 % and 81 % against R. solani and B. cinerea at 50 µg/mL respectively. This study contributes a prospective idea to the development of organic-inorganic hybrid NPs as environmentally-friendly and safe agricultural antimicrobials.

Facile Preparation of Metal-Organic Framework (MIL-125)/Chitosan Beads for Adsorption of Pb(II) from Aqueous Solutions.

In this study, novel composite titanium-based metal-organic framework (MOF) beads were synthesized from titanium based metal organic framework MIL-125 and chitosan (CS) and used to remove Pb(II) from wastewater. The MIL-125-CS beads were prepared by combining the titanium-based MIL-125 MOF and chitosan using a template-free solvothermal approach under ambient conditions. The surface and elemental properties of these beads were analyzed using scanning electron microscopy, Fourier transform infrared and X-ray photoelectron spectroscopies, as well as thermal gravimetric analysis. Moreover, a series of experiments designed to determine the influences of factors such as initial Pb(II) concentration, pH, reaction time and adsorption temperature was conducted. Notably, it was found that the adsorption of Pb(II) onto the MIL-125-CS beads reached equilibrium in 180 min to a level of 407.50 mg/g at ambient temperature. In addition, kinetic and equilibrium experiments provided data that were fit to the Langmuir isotherm model and pseudo-second-order kinetics. Furthermore, reusability tests showed that MIL-125-CS retained 85% of its Pb(II)-removal capacity after five reuse cycles. All in all, we believe that the developed MIL-125-CS beads are a promising adsorbent material for the remediation of environmental water polluted by heavy metal ions.

[Prokaryotic expression and identification of human astrovirus nonstructural proteins, nsP1a and nsP1a/4].

Human astrovirus (HastV) is recognized as one of the leading causes of acute viral diarrhea in infants. The HastV non-structural protein, nsPla, and C-terminal protein, nsPla/4, contain various conserved functional domains,and may play an important role in virus replication, transcription and the virus-host interactions of HastV. This study used an E. coli system to investigate the expression of nsPla and nsPla/4 proteins. Firstly,the nsPla and nsPla/4 genes of HAstV-1 were cloned into the prokaryotic expression vector,PGEX-4T-1, to build the PGEX-4T-1a and PGEX-4T-la/4 fusion protein plasmids. Then, the recombinant plasmids were transformed into Escherichia coli BL21 (DE3) and induced with isopropyl-ß-D-thiogalactopyranoside (IPTG). The optimal expression conditions of the two fusion proteins were identified and then analyzed by polyacrylamide gel electrophoresis (SDS-PAGE) and western blotting, respectively. The results showed that the pGEX-4T-la fusion protein was maximally expressed at 30 °C after 12 hours of induction with 1.0 mM IPTG. The pGEX-4T-la/4 fusion protein was maximally expressed at 20 °C after 8 hours of induction with 0.5 mM IPTG. Western blot analysis showed that the two fusion proteins specificity reacted with the anti-nsPla and anti-GST monoclonal antibodies, respectively. This study successfully obtained the HAstV non-structural protein, nsP1a, and its C-terminal protein nsP1a/4 protein using an E. coli system. This novel study lays the foundation for future research into the pathogenic mechanisms of human astrovirus and the functions of its non-structural protein.