Effects of nanobubbles on peptide self-assembly

Hydroxide and Hydronium Ions Modulate the Dynamic Evolution of Nitrogen Nanobubbles in Water

It has been widely recognized that the pH environment influences the nanobubble dynamics and hydroxide ions adsorbed on the surface may be responsible for the long-term survival of the nanobubbles. However, understanding the distribution of hydronium and hydroxide ions in the vicinity of a bulk nanobubble surface at a microscopic scale and the consequent impact of these ions on the nanobubble behavior remains a challenging endeavor. In this study, we carried out deep potential molecular dynamics simulations to explore the behavior of a nitrogen nanobubble under neutral, acidic, and alkaline conditions and the inherent mechanism, and we also conducted a theoretical thermodynamic and dynamic analysis to address constraints related to simulation duration. Our simulations and theoretical analyses demonstrate a trend of nanobubble dissolution similar to that observed experimentally, emphasizing the limited dissolution of bulk nanobubbles in alkaline conditions, where hydroxide ions tend to reside slightly farther from the nanobubble surface than hydronium ions, forming more stable hydrogen bond networks that shield the nanobubble from dissolution. In acidic conditions, the hydronium ions preferentially accumulating at the nanobubble surface in an orderly manner drive nanobubble dissolution to increase the entropy of the system, and the dissolved nitrogen molecules further strengthen the hydrogen bond networks of systems by providing a hydrophobic environment for hydronium ions, suggesting both entropy and enthalpy effects contribute to the instability of nanobubbles under acidic conditions. These results offer fresh insights into the double-layer distribution of hydroxide and hydronium near the nitrogen-water interface that influences the dynamic behavior of bulk nanobubbles.

Nanobubble technologies: Applications in therapy from molecular to cellular level

Nanobubbles are gaseous entities suspended in bulk liquids that have widespread beneficial usage in many industries. Nanobubbles are already proving to be versatile in furthering the effectiveness of disease treatment on cellular and molecular levels. They are functionalized with biocompatible and stealth surfaces to aid in the delivery of drugs. At the same time, nanobubbles serve as imaging agents due to the echogenic properties of the gas core, which can also be utilized for controlled and targeted delivery. This review provides an overview of the biomedical applications of nanobubbles, covering their preparation and characterization methods, discussing where the research is currently focused, and how they will help shape the future of biomedicine.

Cooking Delicacy with Ice-Nanobubble Isolation Switches Stewing to 'BBQ'

The key role of ice in cooking has been neglected. Here, we found negatively charged bulk nanobubbles (BNBs: average size ~60 nm and zeta potential <-20 mV) can be generated in ice-melted water through freeze/thaw-induced cavitation when we studied a local delicacy, 'ice-stewed mutton'. Freeze/thaw-induced BNBs are so robust that they can, in turn, isolate food from water; in this way, they protect and enhance the delicacy by protecting protein structures and preventing flavorful components from being lost. In comparison to cooking with ordinary water, cooking with ice can switch 'stewing' to 'BBQ', which has been proved experimentally via diverse characterization from the nano to micro scale. This study not only provides a novel mechanism for ice-based cooking but also might shed light on the design of potential applications of BNBs in chemical engineering and biomedicine.

Gelation of a Pentapeptide in Alcohols

Properties of solvents such as polarity and H-bond-forming ability are critical for the formation of an organogel and have a significant impact on the gel behavior, as solvents are the majority of organogel systems. However, so far, there is still a lack of systematic studies regarding the effects of molecular structures of solvents on the characteristics of organogels. Motivated by revealing such a relationship, in this paper, we studied the morphologies of assemblies, gelation behaviors, and secondary structures of a pentapeptide termed EAF-5 in a wide variety of alcohols. The side chains and lengths of carbon chains of the solvent molecules were found to play a critical role in the self-assembly and gelation of EAF-5. EAF-5 was capable of self-assembling into fibers and entangling into a network in alcohols including ethanol, propanol, butanol, n-pentanol, and n-hexanol, which further immobilized the corresponding alcohols to form gels. In these organogels, increasing β-sheet secondary structures of the peptides were formed by introducing side chains and extending the length of primary alcohol molecules. We hypothesized that alcohol molecules with extended lengths and side chains reduced the gelator-solvent interactions and promoted the gelator-gelator interactions, resulting in the self-assembly of EAF-5 into fibril structures and development of gels. These findings provide a new sight into the interactions between gelators and solvents and are helpful for designing peptide-based organogelators.

The effects of nanobubbles on the assembly of glucagon amyloid fibrils

Some recent studies have shown that the surface and interface play an important role in the assembly and aggregation of amyloid proteins. However, it is unclear how the gas-liquid interface affects the protein assembly at the nanometer scale although the presence of gas-liquid interfaces is very common in in vitro experiments. Nanobubbles have a large specific surface area, which provides a stage for interactions with various proteins and peptides on the nanometer scale. In this work, nanobubbles produced in solution were employed for studying the effects of the gas-liquid interface on the assembly of glucagon proteins. Atomic force microscopy (AFM) studies showed that nanobubble-treated glucagon solution formed fibrils with an apparent height of 4.02 ± 0.71 nm, in contrast to the fibrils formed with a height of 2.14 ± 0.53 nm in the control. Transmission electron microscopy (TEM) results also showed that nanobubbles promoted the assembly of glucagon to form more fibrils. Thioflavin T (ThT) fluorescence and Fourier transform infrared (FTIR) analyses indicated that the nanobubbles induced the change of the glucagon conformation to a β-sheet structure. A mechanism that explains how nanobubbles affect the assembly of glucagon amyloid fibrils was proposed based on the above-mentioned experimental results. Given the fact that there are a considerable amount of nanobubbles existing in protein solutions, our results indicate that nanobubbles should be considered for fully understanding the protein aggregation events in vitro.

Effects of Dissolved Gases on the Amyloid Fibril Morphology

The onset or progression of numerous neurodegenerative diseases occurs due to aggregation of proteins that ultimately form fibrils. The assembly and morphology of fibrils are susceptible to environmental factors. In this work, we used atomic force microscopy (AFM) to investigate the effects of dissolved nitrogen and oxygen molecules on the morphology of fibrils formed by a hydrophobic amyloid peptide implicated in amyotrophic lateral sclerosis, 15 repeats of glycine-alanine, on a highly oriented pyrolytic graphite substrate. We started with preformed fibril solutions that were then diluted with buffers of different gas conditions, resulting in the aggregation of the fibrils into different morphologies that were revealed by AFM after adsorption on the substrate. Straight fibrils were observed in both degassed and ambient buffers, but a stronger lateral association was seen in degassed buffers. Smaller and softer fibrils were observed in O₂-supersaturated buffers, and plaque-like fibril aggregates of considerably large size were evident in N₂-supersaturated buffers. In overnight incubation experiments, we observed changes in both the morphology and height of the fibril aggregates, and their evolution varied with different gas conditions. These findings indicate that the gas type and concentration affect the aggregation of amyloid fibrils and may facilitate the development of biomaterial applications and treatments for amyloid-related diseases.

[Progress in extracellular vesicle imaging methods]

Extracellular vesicles (EVs), including exosomes and microvesicles, are lipid bilayer-enclosed nanovesicles secreted by cells. These EVs are important mediators of intercellular communication by serving as vehicles for transfer of proteins, mRNA, miRNA and lipids between cells. Various visualization methods have been established to explore the characteristics of EVs and their role in physiological and pathological processes. The nanoscale size and high heterogeneity of EVs hamper the identification of their biological characteristics and functions. This review presents a comprehensive overview of EV imaging methods in light of the origin, separation and dynamic tracking of EVs, and the advantages and disadvantages of different imaging strategies are discussed. We believe that studies at the levels of single vesicles and single cells will become the frontier of future researches of EVs.