Influence of solution chemistry on the deposition and detachment kinetics of RNA on silica surfaces

Deposition kinetics of bacteriophage MS2 on Microcystis aeruginosa and kaolin surface

Waterborne virus contamination might easily adsorb on the organic or inorganic surface in the complex aquatic environment. A quartz crystal microbalance coupled with dissipation monitoring was used to investigate the effects of the ionic strength of monovalent cation and divalent cation and pH on the deposition kinetics of bacteriophage MS2 on silica surface coated with Microcystis aeruginosa or kaolin, which represents organic or inorganic particle, respectively. Derjaguin-Landau-Verwey-Overbeek theory was used to illustrate the deposition mechanisms of MS2. The increased concentration of Na⁺ significantly enhanced the deposition rates of MS2 on both coated silica surfaces due to the reduction of repulsive electrostatic interactions. However, the MS2 deposition rates decreased at higher ionic strength of Ca²⁺, which accounted for the steric and hydrophobic interactions. And the higher MS2 deposition rates on both surfaces occurred at pH 3. In addition, the deposition rates of MS2 on kaolin-coated silica surfaces were higher than on the Microcystis-coated surface under all studied conditions. Furthermore, the Derjaguin-Landau-Verwey-Overbeek theory could elucidate the deposition mechanism in Na⁺ solution, whereas the steric and hydrophobic interactions should be considered for the presence of high concentration of Ca²⁺.

The detection and characterization techniques for the interaction between graphene oxide and natural colloids: A review

The high dispersibility of graphene oxide (GO) and the universality of natural colloids (clay minerals, (hydr)oxides of Al, Fe, silica, etc.) make them interact easily. Many kinds of analytical methods have been used to study the interaction between GO and natural colloids. This review provides a comprehensive overview of analytical methods for the detection and quantification of interaction process. We highlighted the influence of the most relevant environmental factors (ionic strength, pH, etc.) on batch experiment, quartz crystal microbalance with dissipation monitoring measurements, and column experiments. Besides, the benefits and drawbacks of spectroscopic, microscopic techniques, theoretical models, calculation and time-resolved dynamic light scattering methods also have discussed in this work. This review can give some guidance to researchers in their selection and combination of the technique for the research of the interaction between GO and natural colloids.

Looking for Hidden Enemies of Metabarcoding: Species Composition, Habitat and Management Can Strongly Influence DNA Extraction while Examining Grassland Communities

Despite the raising preoccupation, the critical question of how the plant community is composed belowground still remains unresolved, particularly for the conservation priority types of vegetation. The usefulness of metabarcoding analysis of the belowground parts of the plant community is subjected to a considerable bias, that often impedes detection of all species in a sample due to insufficient DNA quality or quantity. In the presented study we have attempted to find environmental factors that determine the amount and quality of DNA extracted from total plant tissue from above- and belowground samples (1000 and 10,000 cm2). We analyzed the influence of land use intensity, soil properties, species composition, and season on DNA extraction. The most important factors for DNA quality were vegetation type, soil conductometry (EC), and soil pH for the belowground samples. The species that significantly decreased the DNA quality were Calamagrostis epigejos, Coronilla varia, and Holcus lanatus. For the aboveground part of the vegetation, the season, management intensity, and certain species-with the most prominent being Centaurea rhenana and Cirsium canum-have the highest influence. Additionally, we found that sample size, soil granulation, MgO, organic C, K2O, and total soil N content are important for DNA extraction effectiveness. Both low EC and pH reduce significantly the yield and quality of DNA. Identifying the potential inhibitors of DNA isolation and predicting difficulties of sampling the vegetation plots for metabarcoding analysis will help to optimize the universal, low-cost multi-stage DNA extraction procedure in molecular ecology studies.

Improve sample preparation process for miRNA isolation from the culture cells by using silica fiber membrane

In clinical applications of miRNAs, the purity and quality of the testing samples are very critical, especially the obtained tissue sample volume is limited. If the extracted miRNAs are contaminated or different in quality before analysis, it will increase the variance of the analysis result and make the medical information judgment incorrect and cannot be portable. Herein, we improved the commercially extraction kit by realizing the fundamental mechanism and hoped to serve finding optimal procedures for increasing the recovery of miRNAs extracted from cultured cells. In the adsorption process, the factors, like increasing the ethanol concentration or adding Ca²⁺, could influence the RNA adsorption were investigated. For the elution process, the effect caused by raising the elution temperature and raising the pH value of elution buffer was studied. Finally, the conditions for miRNA extraction are optimal modified by using a 65% (v/v) solution of ethanol in the adsorption process, and using TE buffer with the pH value of 8.0 and raising the temperature to 55 °C in the elution. According to the quantified results, the improved extraction kit can promote the recovery of endogenous miR-21 by about 6 times by using the optimal extraction conditions comparing with the miRNeasy Mini Kit.

Sulfide reduction can significantly enhance transport of biochar fine particles in saturated porous medium

The release of fine particles from biochar materials applied in the environment may have important environmental implications, such as mobilization of environmental contaminants. In natural environments biochar fine particles can undergo various transformation processes, which may change their surface chemistry and consequently, the mobility of the particles. Here, we show that sulfide reduction can significantly alter the transport of wheat-straw- and pine-wood-derived biochar fine particles in saturated porous media. Counterintuitively, the sulfide-reduced biochar particles exhibited greater mobility in artificial groundwater than their non-reduced counterparts, even though reduction led to decrease of surface charge negativity and increase of hydrophobicity (from the removal of surface O-functional groups), both should favor particle deposition, as predicted based on extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory. Using transport experiments conducted in single-cation background solutions containing K⁺, Mg²⁺ or Ca²⁺ under different pH conditions, we show that the surprisingly greater mobility of sulfide-reduced biochar particles was attributable to the removal of surface carboxyl groups during reduction, as this markedly alleviated particle deposition through cation bridging, wherein Ca²⁺ acted as the bridging agent in linking the surface O-functional groups of biochar particles and quartz sand. These findings show the critical roles of surface properties in dictating the mobility of biochar fine particles and call for further understanding of their transport properties, which apparently cannot be simply extrapolated based on the findings of other (engineered) carbonaceous nanomaterials.

New insights into the humic acid fouling mechanism of ultrafiltration membranes for different Ca2+ dosage ranges: results from micro- and macro-level analyses

To reveal the mechanisms of the influence of Ca²⁺ on membrane fouling with humic acid (HA), the adhesion forces of HA with both other HA molecules and the membrane, the HA fouling layer structure, HA fouling experiments, and the HA rejections at a wide range of Ca²⁺ dosages were investigated. The results indicated that the effect of Ca²⁺ on HA fouling can be divided into three stages. At lower ionic strength (IS) of CaCl₂, the change in electrostatic forces is the main factor in controlling HA fouling behavior; i.e., increasing Ca²⁺ dosages resulted in more serious membrane fouling. When the IS of CaCl₂ reached 10 mM, HA aggregates became the dominant factor in the fouling process, which could result in a porous fouling layer accompanied by less membrane fouling. Interestingly, much weaker membrane fouling was observed when the IS increased to 100 mM and the HA rejection began to decline. This was because a stronger hydration repulsion force was generated, which could weaken the compactness of the fouling layer and the adhesion forces of HA with both the membrane and HA, while enabling smaller-sized HA to pass more easily into the permeate, which led to less membrane fouling and a lower HA rejection.

Probing the interactions of organic molecules, nanomaterials, and microbes with solid surfaces using quartz crystal microbalances: methodology, advantages, and limitations

Quartz crystal microbalances (QCMs) provide a new analytical opportunity and prospect to characterize many environmental processes at solid/liquid interfaces, thanks to their almost real-time measurement of physicochemical changes on their quartz sensor. This work reviews the applications of QCMs in probing the interactions of organic molecules, nanomaterials (NMs) and microbes with solid surfaces. These interfacial interactions are relevant to critical environmental processes such as biofilm formation, fate and transport of NMs, fouling in engineering systems and antifouling practices. The high sensitivity, real-time monitoring, and simultaneous frequency and dissipation measurements make QCM-D a unique technique that helps reveal the interaction mechanisms for the abovementioned processes (e.g., driving forces, affinity, kinetics, and the interplay between surface chemistry and solution chemistry). On the other hand, QCM measurement is nonselective and spatially-dependent. Thus, caution should be taken during data analysis and interpretation, and it is necessary to cross-validate the results using complementary information from other techniques for more quantitative and accurate interpretation. This review summarizes the general methodologies for collecting and analyzing raw QCM data, as well as for evaluating the associated uncertainties. It serves to help researchers gain deeper insights into the fundamentals and applications of QCMs, and provides new perspectives on future research directions.

The attachment of colloidal particles to environmentally relevant surfaces and the effect of particle shape

Despite the prevalence of nonspherical colloidal particles, the role of particle shape in the transport of colloids is largely understudied. This study investigates the attachment of colloidal particles onto environmentally relevant surfaces while varying particle shape and ionic strength. Using quartz crystal microbalance and atomic force microscopy measurements, the role of particle shape was elucidated and possible mechanisms discussed. The attachment of both spherical and stretched polystyrene colloidal particles onto a smooth alginate-coated silica surface showed qualitative agreement with DLVO theory. Attachment onto a Harpeth humic acid (HHA) surface, however, significantly deviated from DLVO theory due to its high surface heterogeneity and extended confirmation from the silica surface. This extended confirmation provided increased potential for spherical particle entanglement, while the enlarged major axis of the stretched particles hindered their ability to attach. As ionic strength increased, the HHA layer condensed and provided less potential for spherical particle entanglement and therefore the selectivity for spherical particle attachment vanished. The findings presented in this study suggest that colloidal particle shape may play a complex and important role in predicting the transport of colloidal particles, especially in the presence of natural organic matter-coated surfaces.