Search

Electrochemical biosensors based on structure‐switching aptamers offer many advantages because they can operate directly in complex samples and offer the potential to integrate with miniaturized electronics. Unfortunately, these biosensors often suffer from cross‐reactivity problems when measuring a target in samples containing other chemically similar molecules, such as precursors or metabolites. While some progress has been made in selecting highly specific aptamers, the discovery of these reagents remains slow and costly. In this work, a novel strategy is demonstrated to distinguish molecules with miniscule difference in chemical composition (such as a single hydroxyl group)—with cross reactive aptamer probes—by tuning the charge state of the surface on which the aptamer probes are immobilized. As an exemplar, it is shown that the strategy can distinguish between DOX and many structurally similar analytes, including its primary metabolite doxorubicinol (DOXol). Then the ability to accurately quantify mixtures of these two molecules based on their differential response to sensors with different surface‐charge properties is demonstrated. It is believed that this methodology is general and can be extended to a broad range of applications. [ABSTRACT FROM AUTHOR]

The ability to control the mobility and function of droplets is fundamental to developing open surface microfluidics. Despite notable progress in the manipulation of droplets, the existing strategies are still limited in functionalizing droplets. Herein, the coupling of droplet motion and functionalization elicited by an invisible charge wall is reported. The charged superamphiphobic surface is overlapped with a conductor to induce free charge, creating the invisible charge wall at the overlapping boundary. The charge wall can trap droplets and polarize them into Janus charged state. It is found that the trapping degree and the charge distribution in the Janus charged droplet depend on the original surface charge on the superamphiphobic surface. The invisible charge wall can also be established at diverse boundary curvatures, allowing to design pathways for droplet manipulations. Furthermore, the enrichment of protein and nanomaterial in the manipulated Janus charged droplet is demonstrated. The strategy provides a potential microfluidic platform with orthogonal functionalities. [ABSTRACT FROM AUTHOR]

Background: Limited information is available on the changes in surface electrochemical properties of different‐sized particles of an Anthrosol, compared with the corresponding parental upland soil. Aims: Our overarching goal was to clarify the contribution of different‐sized particles to the soil surface charge. The specific objectives of this work were to examine the differences in the surface charge properties between the Anthrosol and its upland parental Gleysol and to reveal the properties of the different‐sized fractions separated from the Anthrosol, compared with those of the upland Gleysol. Materials and methods: The properties (e.g., negative surface charge, zeta potential, and particle sedimentation) of different‐sized fractions of nanoparticle (NP), coarse colloid, silt, and sand fractions separated from an upland Gleysol and its derived Anthrosol were compared. Results: NPs in both the Anthrosol and the Gleysol carried more negative charge than did the coarse colloids, with cation exchange capacities (CEC) being 186.5% and 58.8% greater, respectively. On the other hand, the presence of more positively charged Fe/Al (hydr)oxides compensated for the negative charge, resulted in a zeta potential of the NPs similar to that of the coarse colloids. More secondary minerals were observed in the coarse colloids of the Anthrosol than in the same fraction of the Gleysol, resulting in more negative charge on the surface of the Anthrosol coarse colloids. The coarse colloid fraction of the Anthrosol, therefore, had a greater CEC, despite representing a smaller mass fraction than in the Gleysol. Overall, the CEC of the Anthrosol was 21% lower than that of the parent Gleysol, which was consistent with the findings of the surface charge, using the cesium (Cs+)‐adsorption method. The sedimentation observations demonstrated that the suspension stability of the NPs was higher than that of the coarse colloids, and that they tended to disperse particularly under high pH conditions. Conclusions: Although the surface charge potential of the Anthrosol was lower than that of the upland Gleysol, the accumulation of organic matter and formation of secondary phyllosilicates resulted in maintenance of the nutrient‐ and pollutant‐binding capacity and agricultural productivity of the Anthrosol. [ABSTRACT FROM AUTHOR]

This study was designed to evaluate and compare the stability, antioxidant and anticancer activities of selenium nanoparticles (SeNPs) decorated with different molecular weight (MW) of chitosan (CS) (1500 Da, 48 kDa, 510 kDa). The size range of well‐dispersed SeNPs was effectively controlled by I− first and then coated with CS. The morphology, size and surface charge of generated SeNPs were characterised by several technologies. Fourier transform infrared spectroscopy was used to investigate the relationship between SeNPs and CS. SeNPs decorated with CS (510 kDa) can keep stable for more than 45 days. As observed from the results of a simple photometric system, the antioxidant activities of decorated SeNPs were enhanced compared to undecorated SeNPs. SeNPs coated with higher MW of CS (510 kDa) showed the strongest antioxidant activities. Moreover, the treatments of SeNPs decorated with CS inhibited the growth of HepG2 cells in a time‐ and dose‐dependent manner. The proposed results demonstrated the critical roles of the MW of CS on the stability, antioxidant and anticancer properties of CS‐coated SeNPs, which provided an important design cue for future applications of functional foods and additives. [ABSTRACT FROM AUTHOR]

Synthesis of iron nanoparticles (INPs) with a biocompatible coating usually is a multistep process which requires harsh, special and protected reaction conditions. In the current experiment, the authors used Xanthomonas campestris cells to develop a facile method for fabrication of biocompatible INPs. Bacterial cells were supplied with ferric citrate as an iron precursor. Transmission electron microscopy micrographs exhibited that xanthan gum‐coated INPs are synthesised and deposited on the surface of X. campestris cells and produced nanoparticles were 20–80 nm in diameter with 41.7 nm mean particle size. Xanthan gum coating with about 7 nm thickness formed a clear hollow around each nanoparticle. According to thermogravimetric analysis, the coating was about 13.4% of the total INPs weight. Prepared particles had a zeta potential of −114 mv which is an ideal surface charge to make particles colloidally stable in aqueous matrixes. Xanthan gum‐coated INPs were non‐crystalline with low saturation magnetisation value of about 0.26 emu/g. [ABSTRACT FROM AUTHOR]

Tailoring Electrode Surface Charge to Achieve Discrimination and Quantification of Chemically Similar Small Molecules with Electrochemical Aptamers (Adv. Funct. Cross-reactivity, drug discrimination, drug quantification, electrochemical aptamer biosensors, nanostructured electrodes, surface charge Keywords: cross-reactivity; drug discrimination; drug quantification; electrochemical aptamer biosensors; nanostructured electrodes; surface charge EN cross-reactivity drug discrimination drug quantification electrochemical aptamer biosensors nanostructured electrodes surface charge 1 1 1 01/05/23 20230103 NES 230103 B Electrochemical Aptamer Biosensors b In article number 2208534, Fu, Soh, and co-workers report an electrochemical biosensor to distinguish molecules with a minuscule difference in chemical composition by tuning the charge state of the surface on which the aptamer probes are immobilized. [Extracted from the article]