Pomegranate seed polyphenol-based nanosheets as an efficient inhibitor of amyloid fibril assembly and cytotoxicity of HEWL

Ankaflavin and Monascin Prevent Fibrillogenesis of Hen Egg White Lysozyme: Focus on Noncovalent and Covalent Interactions

Misfolding and amyloid fibrillogenesis of proteins have close relationships with several neurodegenerative diseases. The present work investigates the inhibitive activities of ankaflavin (AK) and monascin (MS), two yellow pigments separated from Monascus-fermented rice, on hen egg white lysozyme (HEWL) fibrillation. The results demonstrated that AK/MS suppressed HEWL fibrillation through interfering with the nucleation period and AK was more potent. Fluorescence quenching and in silico docking studies revealed that AK/MS bond to HEWL by the formation of noncovalent forces with some critical amino acid residues that tend to form fibrils. Compared to those of AK, hydrogen bonding interactions between MS and Asn46, Trp62, and Trp63 residues in HEWL were slightly weaker. Besides, the covalent interaction between MS and HEWL with the binding site of Arg68 was found. These observations offered reasonable explanations for the difference in the mechanisms of AK and MS inhibiting HEWL fibrillogenesis. In a word, all data acquired herein indicated AK/MS as potent candidates for the improvement and treatment of neurological disorders.

Controlled preparation of tannic acid-derived carbonized dots and their use to inhibit amyloid aggregation and promote aggregate disaggregation

Tannic acid (TA)-derived carbon dots (TACDs) were synthesized for the first time via a solvothermal method using TA as one of the raw materials, which may effectively inhibit amyloid fibril aggregation and disaggregate mature fibril. The fluorescent property of TACDs were modulated by adjusting the ratio of TA to o-phenylenediamine (oPD), and TACDs fabricated with the precursor ratio as 1:1 showed the best fluorescent property. Circular dichroism spectra (CD) showed that the structure of β-sheet decreased as the concentration of TACDs increased. The inhibition efficiency, as confirmed by thioflavin T (ThT) and transmission electron microscopy (TEM), is extraordinary at 98.16%, whereas disaggregation efficiency is noteworthy at 97.97%, and the disaggregated lysozyme fibrils did not reaggregate after 7 days. More critically, TACDs can also alleviate the cellular toxicity caused by Aβ fibrils and improve cell viability. This work offers a new perspective on the design of scavengers for amyloid plaques.

Polydopamine contained hydrogel nanocomposites with combined antimicrobial and antioxidant properties for accelerated wound healing

Overproduction of reactive oxygen species (ROS) in infected wounds induces a tremendous inflammatory reaction to delay wound healing. To address this problem, we designed a multifunctional polyacrylamide/PVA-based hydrogel containing synthesized poly(1-glycidyl-3-butylimidazolium salicylate) (polyGBImSal) and fabricated polydopamine-coated polyphenolic nanosheet (PDA@PNS) for wound dressing. The PDA@PNS particles were designed to induce I) antioxidant and anti-inflammatory features through ROS-scavenging and II) cell adhesive properties by the existing polydopamine into the hydrogels. The poly(ionic liquid)-based polyGBImSal was designed to allocate effective hydrogel antimicrobial activity. The fabricated hydrogel nanocomposites showed excellent properties in the swelling ratio, cell adhesiveness, protein adsorption, and anti-inflammatory, proving their general performance for application in wound healing. Furthermore, these hydrogels showed high antimicrobial activity (over 95 %) against three common wound-infecting pathogenic microbes: Escherichia coli, Staphylococcus aureus, and Candida albicans. The healing process of full-thickness dermal wounds in rats was accelerated by applying hydrogel nanocomposites with 0.5 wt% of PDA@PNS and 28 wt% of polyGBImSal. The wound closure contraction attained full closure, reaching 100 %, after 14 days, contrasted with the control group employing commercial wound dressing (Tegaderm), which achieved a closure rate of 68 % within the equivalent timeframe. These results make these hydrogel nanocomposites promising candidates for multifunctional wound dressing applications.

Enhancing anti-amyloidogenic properties and antioxidant effects of Scutellaria baicalensis polyphenols through novel nanoparticle formation

Protein aggregation and oxidative stress have gained significant research attention due to their association with a group of diseases known as amyloidosis. Among the strategies developed to prevent amyloidosis, utilization of polyphenols stands out as one of the most commonly employed approaches. Scutellaria baicalensis is renowned as one of the foremost herbal sources of polyphenols. In this study, we employed a direct oxidative pyrolysis method for polymerizing S. baicalensis's polyphenols (SBPPs) after their extraction, resulting in the formation of novel SBPPs nanoparticles. Upon polymerization, SBPPs nanoparticles showed remarkable properties including heightened water solubility, increased surface area, modified surface functional groups, and enhanced stability. As a result of these diverse factors, there was a considerable enhancement in the anti-amyloidogenic properties and antioxidant effects of SBPPs nanoparticles compared to its bulk form. The fibrillation kinetics, AFM images, and cytotoxicity assays strongly indicate that SBPPs nanoparticles are more effective than SBPPs at preventing amyloid fibril formation and associated cell toxicity. Additionally, SBPPs nanoparticles demonstrated more effective prevention of reactive oxygen species (ROS) production. In conclusion, the use of SBPPs in nanoparticle form presents a promising strategy to enhance anti-amyloidogenic properties, mitigate oxidative stress, and offer potential therapeutic benefits for amyloidosis-related diseases.

Efficient inhibition of amyloid fibrillation and cytotoxicity of α-synuclein and human insulin using biosynthesized silver nanoparticles decorated by green tea polyphenols

Green tea polyphenols (GTPs), particularly epigallocatechin-3-gallate, stand out among natural small molecules screened for their ability to target protein aggregates due to their potent anti-amyloidogenic and neuroprotective activities against various disease-related peptides and proteins. However, the clinical applications of GTPs in amyloid-related diseases have been greatly limited by drawbacks such as poor chemical stability and low bioavailability. To address these limitations, this study utilized an Iranian green tea polyphenolic extract as a reducing agent to neutralize silver ions and facilitate the formation of silver nanoparticle capped by GTPs (GTPs-capped AgNPs). The results obtained from this study demonstrate that GTPs-capped AgNPs are more effective than free GTPs at inhibiting amyloid fibrillation and reducing cytotoxicity induced by amyloid fibrils of human insulin and α-synuclein (α-syn). This improved efficacy is attributed to the increased surface/volume ratio of GTPs-capped AgNPs, which can enhance their binding affinity to amyloidogenic species and boosts their antioxidant activity. The mechanism by which GTPs-capped AgNPs inhibit amyloid fibrillation appears to vary depending on the target protein. For structured protein human insulin, GTPs-capped AgNPs hinder fibrillation by constraining the protein in its native-like state. In contrast, GTPs-capped AgNPs modulate fibrillation of intrinsically disordered proteins like α-syn by redirecting the aggregation pathway towards the formation of non-toxic off-pathway oligomers or amorphous aggregates. These findings highlight polyphenol-functionalized nanoparticles as a promising strategy for targeting protein aggregates associated with neurodegenerative diseases.

Study on the impact of photoaging on the generation of very small microplastics (MPs) and nanoplastics (NPs) and the wettability of plastic surface

Photoaging is one of the important reasons for the sharp increase of waste plastics, especially microplastics (MPs), in the environment. Therefore, studying the photoaging of plastics is of great significance for controlling plastic pollution from the source. Nevertheless, there are few studies on plastic photoaging from the perspective of polymer structure. Besides, the capacity of different types of plastics to generate MPs with small particle size is relatively little studied. In view of this, we conducted a preliminary study on the capacity of different types of plastics to generate MPs using flow cytometry. We also studied the impact of photoaging on different types of plastics. The results showed that flow cytometry can be used to quantify very small MPs (1-50 μm) and nanoplastics (NPs) (< 1 μm). Furthermore, photoaging often accelerates the generation of MPs and roughens plastic surface. Besides, photoaging can introduce some oxygen-containing groups onto plastic surface, thereby changing the wettability of plastic surface. Moreover, benzene rings in polymer structures may inhibit the generation of MPs but may promote the transformation of the plastic surface from hydrophobic to hydrophilic during photoaging. Although the changes in properties of plastics caused by photoaging have adverse effects on the environment, some new processes and materials still can be developed based on photoaging of plastics. This work contributes to a better understanding of the photoaging of plastics from the perspective of polymer structure, which has certain positive significance for controlling plastic pollution from the source.