Disaggregation Behavior of Amyloid β Fibrils by Anthocyanins Studied by Total-Internal-Reflection-Fluorescence Microscopy Coupled with a Wireless Quartz-Crystal Microbalance Biosensor

β-Hexachlorocyclohexane triggers neuroinflammatory activity, epigenetic histone post-translational modifications and cognitive dysfunction

Persistent organic pollutants (POPs), which encompass pesticides and industrial chemicals widely utilized across the globe, pose a covert threat to human health. β-hexachlorocyclohexane (β-HCH) is an organochlorine pesticide with striking stability, still illegally dumped in many countries, and recognized as responsible for several pathogenetic mechanisms. This study represents a pioneering exploration into the neurotoxic effects induced by the exposure to β-HCH specifically targeting neuronal cells (N2a), microglia (BV-2), and C57BL/6 mice. As shown by western blot and qPCR analyses, the administration of β-HCH triggered a modulation of NF-κB, a key factor influencing both inflammation and pro-inflammatory cytokines expression. We demonstrated by proteomic and western blot techniques epigenetic modifications in H3 histone induced by β-HCH. Histone acetylation of H3K9 and H3K27 increased in N2a, and in the prefrontal cortex of C57BL/6 mice administered with β-HCH, whereas it decreased in BV-2 cells and in the hippocampus. We also observed a severe detrimental effect on recognition memory and spatial navigation by the Novel Object Recognition Test (NORT) and the Object Place Recognition Task (OPRT) behavioural tests. Cognitive impairment was linked to decreased expression of the genes BDNF and SNAP-25, which are mediators involved in synaptic function and activity. The obtained results expand our understanding of the harmful impact produced by β-HCH exposure by highlighting its implication in the pathogenesis of neurological diseases. These findings will support intervention programs to limit the risk induced by exposure to POPs. Regulatory agencies should block further illicit use, causing environmental hazards and endangering human and animal health.

Piezoelectric biosensors: shedding light on principles and applications

The three decades of experience with piezoelectric devices applied in the field of bioanalytical chemistry are shared. After introduction to principles and suitable measuring approaches, active and passive methods based on oscillators and impedance analysis, respectively, the focus is directed towards biosensing approaches. Immunosensing examples are provided, followed by other affinity sensing approaches based on hybridization of nucleic acids, aptamers, monitoring of enzyme activities, and detection of pathogenic microbes. The combination of piezosensors with cell lines and testing of drugs is highlighted, including mechanically active cells. The combination of piezosensors with other measuring techniques providing original hybrid devices is briefly discussed.

Five similar anthocyanidin molecules display distinct disruptive effects and mechanisms of action on Aβ1-42 protofibril: A molecular dynamic simulation study

Alzheimer's disease (AD) is associated with the deposition of amyloid-β (Aβ) fibrillary aggregates. Disaggregation of Aβ fibrils is considered as one of the promising AD treatments. Recent experimental studies showed that anthocyanidins, one type of flavonoids abundant in fruits/vegetables, can disaggregate Aβ fibrillary aggregates. However, their relative disruptive capacities and underlying mechanisms are largely unknown. Herein, we investigated the detailed interactions between five most common anthocyanidins (cyanidin, aurantinidin, peonidin, delphinidin, and pelargonidin) and Aβ protofibril (an intermediate of Aβ fibrillization) by performing microsecond molecular dynamic simulations. We found that all five anthocyanidins can destroy F4-L34-V36 hydrophobic core and K28-A42 salt bridge, leading to Aβ protofibril destabilization. Aurantinidin exhibits the strongest damage to Aβ protofibril (with the most severe disruption on K28-A42 salt bridges), followed by cyanidin (with the most destructive effect on F4-L34-V36 core). Detailed analyses reveal that the protofibril-destruction capacities of anthocyanidins are subtly modulated by the interplay of anthocyanidin-protofibril hydrogen bonding, hydrophobic, aromatic stacking interactions, which are dictated by the number or location of hydroxyl/methyl groups of anthocyanidins. These findings provide important mechanistic insights into Aβ protofibril disaggregation by anthocyanidins, and suggest that aurantinidin/cyanidin may serve as promising starting-points for the development of new drug candidates against AD.

Behind the Scenes of Anthocyanins-From the Health Benefits to Potential Applications in Food, Pharmaceutical and Cosmetic Fields

Anthocyanins are widespread and biologically active water-soluble phenolic pigments responsible for a wide range of vivid colours, from red (acidic conditions) to purplish blue (basic conditions), present in fruits, vegetables, and coloured grains. The pigments' stability and colours are influenced mainly by pH but also by structure, temperature, and light. The colour-stabilizing mechanisms of plants are determined by inter- and intramolecular co-pigmentation and metal complexation, driven by van der Waals, π-π stacking, hydrogen bonding, and metal-ligand interactions. This group of flavonoids is well-known to have potent anti-inflammatory and antioxidant effects, which explains the biological effects associated with them. Therefore, this review provides an overview of the role of anthocyanins as natural colorants, showing they are less harmful than conventional colorants, with several technological potential applications in different industrial fields, namely in the textile and food industries, as well as in the development of photosensitizers for dye-sensitized solar cells, as new photosensitizers in photodynamic therapy, pharmaceuticals, and in the cosmetic industry, mainly on the formulation of skin care formulations, sunscreen filters, nail colorants, skin & hair cleansing products, amongst others. In addition, we will unveil some of the latest studies about the health benefits of anthocyanins, mainly focusing on the protection against the most prevalent human diseases mediated by oxidative stress, namely cardiovascular and neurodegenerative diseases, cancer, and diabetes. The contribution of anthocyanins to visual health is also very relevant and will be briefly explored.

Practical Use of Quartz Crystal Microbalance Monitoring in Cartilage Tissue Engineering

Quartz crystal microbalance (QCM) is a real-time, nanogram-accurate technique for analyzing various processes on biomaterial surfaces. QCM has proven to be an excellent tool in tissue engineering as it can monitor key parameters in developing cellular scaffolds. This review focuses on the use of QCM in the tissue engineering of cartilage. It begins with a brief discussion of biomaterials and the current state of the art in scaffold development for cartilage tissue engineering, followed by a summary of the potential uses of QCM in cartilage tissue engineering. This includes monitoring interactions with extracellular matrix components, adsorption of proteins onto biomaterials, and biomaterial–cell interactions. In the last part of the review, the material selection problem in tissue engineering is highlighted, emphasizing the importance of surface nanotopography, the role of nanofilms, and utilization of QCM as a “screening” tool to improve the material selection process. A step-by-step process for scaffold design is proposed, as well as the fabrication of thin nanofilms in a layer-by-layer manner using QCM. Finally, future trends of QCM application as a “screening” method for 3D printing of cellular scaffolds are envisioned.

Dihydrocaffeic Acid-Decorated Iron Oxide Nanomaterials Effectively Inhibit Human Calcitonin Aggregation

To date, more than 30 human peptides or proteins have been found to form amyloid fibrils, most of which are associated with human diseases. However, currently, no cure for amyloidosis exists. Therefore, development of therapeutic strategies to inhibit amyloid formation is urgently required. Although the role of some amyloidogenic proteins has not been identified in certain diseases, their self-assembling behavior largely affects their bioactivity. Human calcitonin (hCT) is a hormone peptide containing 32 amino acids and is secreted by the parafollicular cells of the thyroid gland in the human body. It can regulate the concentration of calcium ions in the blood and block the activity of osteoclasts. Therefore, calcitonin has also been considered a therapeutic peptide. However, the aggregation of hCT hinders this process, and hCT has been replaced by salmon calcitonin in drug formulations. Recently, iron oxide nanomaterials have been developed as potential materials for various applications owing to their high biocompatibility, low toxicity, and ease of functionalization. In this study, nanoparticles (NPs) were prepared using a simple chemical coprecipitation method. We first demonstrated that dopamine-conjugated Fe₃O₄ inhibited hCT aggregation, similar to what we found when carbon dots were used as core materials in the previous study. Later, we continued to simplify the preparation process, that is, the mixing of dihydrocaffeic acid (DCA) and iron oxide NPs, to maintain their stability and inhibitory effect against hCT aggregation. Furthermore, DCA-decorated Fe₃O₄ can dissociate preformed hCT amyloid fibrils. This appears to be one of the most promising ways to stabilize hCT in solution and may be helpful for amyloidosis treatment.

Moxifloxacin Disrupts and Attenuates Aβ42 Fibril and Oligomer Formation: Plausibly Repositioning an Antibiotic as Therapeutic against Alzheimer's Disease

The aggregation of Aβ42 is established as a key factor in the development of Alzheimer's disease (AD). Consequently, molecules that inhibit aggregation of peptide may lead to therapies to prevent or control AD. Several studies suggest that oligomeric intermediates present during aggregation may be more cytotoxic than fibrils themselves. In this work, we examine the inhibitory activity of an antibiotic MXF on aggregation (fibrils and oligomers) and disaggregation of Aβ42 using various biophysical and microscopic studies. Computational analysis was done to offer mechanistic insight. The amyloid formation of Aβ42 is suppressed by MXF, as demonstrated by the decrease in both the corresponding ThT fluorescence intensity and other biophysical techniques. The lag phase of amyloid formation doubled from 4.53 to 9.66 h in the presence of MXF. The addition of MXF at the completion of the fibrillation reaction, as monitored by ThT, led to a rapid, concentration dependent, exponential decrease in fluorescence signal that was consistent with loss of fibrils. We used TEM to directly demonstrate that MXF caused fibrils to disassemble. Our docking results show that MXF binds to both monomeric and fibrillar forms of Aβ42 with significant affinities. We also observed breaking of fibrils in the presence of MXF through molecular dynamics simulation. These findings suggest that antibiotic MXF could be a promising lead compound with dual role as fibril/oligomer inhibitor and disaggregase for further development as potential repurposed therapeutic against AD.

Analysis of the Effect of Electrode Materials on the Sensitivity of Quartz Crystal Microbalance

This paper investigated the effect of electrode materials on the performance of quartz crystal microbalance (QCM) sensors by means of theoretical calculation, experiment, and finite element analysis methods. First, we calculated the particle displacement amplitude and thus obtained the mass sensitivity function distribution of QCMs with gold, silver and aluminum electrodes, and found that the QCM with the gold electrode has the highest mass sensitivity at the center of the electrode. Then, we tested the humidity-sensing performance of QCMs with gold, silver, and aluminum electrodes using graphene oxide (GO) as the sensitive material, and found that the QCM with the gold electrode has higher humidity sensitivity. Finally, we used the finite element analysis software COMSOL Multiphysics to simulate the specific electrode material parameters that affect the sensitivity of the QCMs. The simulation results show that the density and Young’s modulus of the electrode material parameters mainly affect the sensitivity. The results of this paper are instructive for optimizing QCM sensor performance and improving the capability of QCM quantitative analysis.

Dual-Mode and Label-Free Detection of Exosomes from Plasma Using an Electrochemical Quartz Crystal Microbalance with Dissipation Monitoring

The biomolecular contents of extracellular vesicles, such as exosomes, have been shown to be crucial in intercellular communication and disease propagation. As a result, there has been a recent surge in the exploration of novel biosensing platforms that can sensitively and specifically detect exosomal content such as proteins and nucleic acids, with a view toward application in diagnostic assays. Here, we demonstrate dual-mode and label-free detection of plasma exosomes using an electrochemical quartz crystal microbalance with dissipation monitoring (EQCM-D). The platform adopts a direct immunosensing approach to effectively capture exosomes via their surface protein expression of CD63. By combining QCM-D with a tandem in situ electrochemical impedance spectroscopy measurement, we are able to demonstrate relationships between mass, viscoelasticity and impedance inducing properties of each functional layer and analyte. In addition to lowering the limit of detection (by a factor of 2-4) to 6.71 × 10⁷ exosome-sized particles (ESP) per mL in 25% v/v serum, the synergy between dissipation and impedance response introduces improved sensing specificity by offering further distinction between soft and rigid analytes, thereby promoting EQCM-D as an important technique for exosome analysis.

Dual-Mode and Label-Free Detection of Exosomes from Plasma Using an Electrochemical Quartz Crystal Microbalance with Dissipation Monitoring

The biomolecular contents of extracellular vesicles, such as exosomes, have been shown to be crucial in intercellular communication and disease propagation. As a result, there has been a recent surge in the exploration of novel biosensing platforms that can sensitively and specifically detect exosomal content such as proteins and nucleic acids, with a view toward application in diagnostic assays. Here, we demonstrate dual-mode and label-free detection of plasma exosomes using an electrochemical quartz crystal microbalance with dissipation monitoring (EQCM-D). The platform adopts a direct immunosensing approach to effectively capture exosomes via their surface protein expression of CD63. By combining QCM-D with a tandem in situ electrochemical impedance spectroscopy measurement, we are able to demonstrate relationships between mass, viscoelasticity and impedance inducing properties of each functional layer and analyte. In addition to lowering the limit of detection (by a factor of 2–4) to 6.71 × 10⁷ exosome-sized particles (ESP) per mL in 25% v/v serum, the synergy between dissipation and impedance response introduces improved sensing specificity by offering further distinction between soft and rigid analytes, thereby promoting EQCM-D as an important technique for exosome analysis.