Zeta potential determination with a microchannel fabricated in solidified solvents

Probing the interaction between biomolecules under sub-zero temperature conditions by electrophoresis in ice grain boundaries

BACKGROUND

Psychrophiles can survive under cryogenic conditions because of various biomolecules. These molecules interact with cells, ice crystals, and lipid bilayers to enhance their functionality. Previous studies typically measured these interactions by thawing frozen samples and conducting biological assays at room temperature; however, studying these interactions under cryogenic conditions is crucial. This is because these biomolecules can function at lower temperatures. Therefore, a platform for measuring chemical interactions under sub-zero temperature conditions must be established.

RESULTS

The chemical interactions between biomolecules under sub-zero temperature conditions were evaluated within ice grain boundaries with a channel-like structure, which circumvents the need for thawing. An aqueous solution of sucrose was frozen within a microfluidic channel, facilitating the formation of freeze-concentrated solutions (FCSs) that functioned as size-tunable electrophoretic fields. Avidin proteins or single-stranded DNA (ssDNA) were introduced into the FCS in advance. Probe micro/nanospheres whose surfaces were modified with molecules complementary to the target analytes were introduced into the FCS. If the targets have functionalities under sub-zero temperature conditions, they interact with complementary molecules. The chemical interactions between the target molecules and nanospheres led to the aggregation of the particles. The size tunability of the diameter of the FCS channels enabled the recognition of aggregation levels, which is indicative of interaction reactivity. The avidin-biotin interaction and ssDNA hybridization served as models for chemical interactions, demonstrating interactivity under sub-zero temperature conditions. The results presented herein suggest the potential for in situ measurement of biochemical assays in the frozen state, elucidating the functionality of bio-related macromolecules at or slightly below 0 °C.

SIGNIFICANCE

This is the first methodology to evaluate chemical interactions under sub-zero temperature conditions without employing the freeze-and-thaw process. This method has the advantage of revealing the chemical interactions only at low temperatures. Therefore, it can be used to screen and evaluate the functionality of cryo-related biomolecules, including cold-shock and antifreeze proteins.

Thallium removal from wastewater using sulfidized zero-valent manganese: Effects of sulfidation method and liquid nitrogen pretreatment

Zero-valent manganese (ZVMn) possesses high reducibility in theory, while sulfide exhibits strong affinity towards a variety of heavy metals owing to the low solubility of metal sulfides. Yet the performance and mechanisms on using sulfidized zero-valent manganese (SZVMn) to remove thallium (Tl) from wastewater still remain unclear. In this study, the performance of Tl(I) removal using SZVMn synthesized by borohydrides reduction followed by sulfides modification, with and without liquid nitrogen treatment, was compared and the mechanism behind was investigated. The results show that at a S/Mn molar ratio of 1.0, liquid nitrogen modified SZVMn (LSZVMn) possessed more interior channels and pores than SZVMn, with 65.3% higher specific surface area and 73.7% higher porosity, leading to 6.4-8.1% improvement in adsorption of Tl(I) at pH 4-10. LSZVMn showed effectiveness and robustness in Tl(I) removal in the presence of co-existing ions up to 0.1 M. The adsorption of Tl(I) conformed to the pseudo-1st-order kinetic model, and followed the Langmuir isothermal model, with the maximum Tl adsorption capacity of 264.9 mg·g^-1 at 288 K. The mechanism of Tl(I) removal with SZVMn was found to include sulfidation-induced precipitation, manganese reduction, surface complexation, and electrostatic attraction. The liquid nitrogen pretreatment embrittled and cracked the outer shell of S/Mn compounds, resulted in a highly hierarchical structure, enhancing the manganese reduction and improving the Tl(I) removal. Based on the above results, the SZVMn and its liquid nitrogen-modified derivatives are novel and effective environmental materials for Tl(I) removal from wastewater, and the application of SZVMn to the removal of other pollutants merits investigation in future study.

Remediation of petroleum-contaminated soil by ball milling and reuse as heavy metal adsorbent

A simple mechanochemical (MC) method is used to treat petroleum-contaminated soil and prepare a heavy metal adsorbent in one step. XRD, Raman, FT-IR, VSM, BET, and XPS were used to characterize the adsorbent. After MC treatment, the dissolved total petroleum hydrocarbons of the adsorbent is less than 1 mg·L^-1, and a porous structure and carbonization phenomenon are evident. The specific surface area and cumulative void volume increase, and the adsorption pore size decreases. On the surface of soil, the percentages of iron oxides, carbonates, CO, -C-O-H, -COOH, and π unsaturated bonds increase. The Langmuir model shows that the maximum adsorption capacity of Pb²⁺, Cu²⁺, Cd²⁺, and Zn²⁺ are 338.58, 51.61, 32.34, and 25.05 mg·g^-1, respectively. The pseudo-second-order kinetic model fits the Pb adsorption process, indicating the domination of chemical adsorption. GC-MS shows that petroleum hydrocarbons are completely degraded. The Tessier continuous extraction result shows that heavy metals are bound to carbonate, iron manganese oxide, and organic matter. The MC treatment achieves deep cleanup and resource utilization of petroleum-contaminated soil through the formation of amorphous carbon, carbonates, and iron oxides on the surface of soil particles. The material is magnetic and can be recycled when used in wastewater treatment.

Interactions of the molecular assembly of polysaccharide-protein systems as encapsulation materials. A review

Studying the interactions of biopolymers like polysaccharides and proteins is quite important mainly due to the wide number of applications such as the stabilization and encapsulation of active compounds in complex systems. Complexation takes place when materials like proteins and polysaccharides are blended to promote the entrapment of active compounds. The interaction forces between the charged groups in the polymeric chains allow the miscibility of the components in the complex system. Understanding the interactions taking place between the polymers as well as between the wall material and the active compound is important when designing delivery systems. However, some features of the biopolymers like structure, functional groups, or electrical charge as well as extrinsic parameters like pH or ratios might affect the structure and the performance of the complex system when used in encapsulation applications. This work summarizes the recent progress of the polysaccharide/protein complexes for encapsulation and the influence of the pH on the structural modifications during the complexation process.

Regulation of Laminaria Polysaccharides with Different Degrees of Sulfation during the Growth of Calcium Oxalate Crystals and their Protective Effects on Renal Epithelial Cells

The original Laminaria polysaccharide (LP0) was sulfated using the sulfur trioxide-pyridine method, and four sulfated Laminaria polysaccharides (SLPs) were obtained, namely, SLP1, SLP2, SLP3, and SLP4. The sulfated (-OSO3 -) contents were 8.58%, 15.1%, 22.8%, and 31.3%, respectively. The structures of the polysaccharides were characterized using a Fourier transform infrared (FT-IR) spectrometer and nuclear magnetic resonance (NMR) techniques. SLPs showed better antioxidant activity than LP0, increased the concentration of soluble Ca2+ in the solution, reduced the amount of CaOx precipitation and degree of CaOx crystal aggregation, induced COD crystal formation, and protected HK-2 cells from damage caused by nanometer calcium oxalate crystals. These effects can inhibit the formation of CaOx kidney stones. The biological activity of the polysaccharides increased with the content of -OSO3 -, that is, the biological activities of the polysaccharides had the following order: LP0 < SLP1 < SLP2 < SLP3 < SLP4. These results reveal that SLPs with high -OSO3 - contents are potential drugs for effectively inhibiting the formation of CaOx stones.