Drug-based magnetic imprinted nanoparticles: Enhanced lysozyme amyloid fibrils cleansing and anti-amyloid fibrils toxicity

Current amyloid inhibitors: Therapeutic applications and nanomaterial-based innovations

Amyloid proteins have long been in the spotlight for being involved in many degenerative diseases including Alzheimer´s, Parkinson´s or type 2 diabetes, which currently cannot be prevented and for which there is no effective treatment or cure. Here we provide a comprehensive review of inhibitors that act directly on the amyloidogenic pathway (at the monomer, oligomer or fibril level) of key pathological amyloids, focusing on the most representative amyloid-related diseases. We discuss the latest advances in preclinical and clinical trials, focusing on cutting-edge developments, particularly on nanomaterials-based inhibitors, which offer unprecedented opportunities to address the complexity of protein misfolding disorders and are revolutionizing the landscape of anti-amyloid therapeutics. Notably, nanomaterials are impacting critical areas such as bioavailability, penetrability and functionality of compounds currently used in biomedicine, paving the way for more specific therapeutic solutions tailored to various amyloid-related diseases. Finally, we highlight the window of opportunity opened by comparative analysis with so-called functional amyloids for the development of innovative therapeutic approaches for these devastating diseases.

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.

Synthesis and Properties of Cefixime Core-Shell Magnetic Nano-Molecularly Imprinted Materials

Novel core-shell magnetic molecularly imprinted polymers (MMIPs) were synthesized using the sol-gel method for the adsorption of cefixime (CFX). Fe3O4@SiO2 is the core, and molecularly imprinted polymers (MIPs) are the shell, which can selectively interact with CFX. The preparation conditions, adsorption kinetics, adsorption isotherms, selective adsorption ability, and reutilization performance of the MMIPs were investigated. The adsorption capacity of MMIPs for CFX was 111.38 mg/g, which was about 3.5 times that of MNIPs. The adsorption equilibrium time was 180 min. The dynamic adsorption experiments showed that the adsorption process of MMIPs to CFX conformed to the pseudo-second-order model. Through static adsorption study, the Scatchard analysis showed that MMIPs had two types of binding sites-the high-affinity binding sites and the low-affinity binding sites-while the Langmuir model fit the adsorption isotherms well (R2 = 0.9962). Cefepime and ceftiofur were selected as the structural analogs of CFX for selective adsorption studies; the adsorption of CFX by MMIPs was higher than that of other structural analogs; and the imprinting factors of CFX, cefepime, and ceftiofur were 3.5, 1.7, and 1.4, respectively. Furthermore, the MMIPs also showed excellent reusable performance.

Structural Remodeling Mechanism of the Toxic Amyloid Fibrillary Mediated by Epigallocatechin-3-gallate

Numerous therapeutic agents and strategies were designed targeting the therapies of Alzheimer's disease, but many have been suspended due to their severe clinical side effects (such as encephalopathy) on patients. The attractiveness for small molecules with good biocompatibility is therefore restarted. Epigallocatechin-3-gallate (EGCG), extracted from green tea, is expected to be a promising small-molecule drug candidate, which can remodel the structure of preformed β-sheet-rich oligomers/fibrils and then effectively interfere with neurodegenerative processes. However, as the structure of non-fibrillary aggregates cannot be directly characterized, the atomic details of the underlying inhibitory and destructive mechanisms still remain elusive to date. Here, all-atom molecular dynamics simulations and experiments were carried out to elucidate the EGCG-induced remodeling mechanism of amyloid β (Aβ) fibrils. We showed that EGCG was indeed an effective Aβ fibril inhibitor. EGCG was capable of mediating conformational rearrangement of Aβ_1-42 fibrils (from a β-sheet to a random coil structure) and triggering the disintegration of fibrils in a dose-dependent manner. EGCG redirected the structure of Aβ by breaking the β-sheet structure and hydrogen bonds between peptide chains within the Aβ protofibrils, especially the parallel β-strand (L₁₇VFFAEDVGS₂₆). Moreover, reduced solvent exposure and multisite binding patterns all tended to induce the conformation conversion of Aβ_17-42 pentameric protofibrils, destroying pre-formed fibrils and inhibiting continued fibril growth. Detailed data analysis revealed that structural features of EGCG with abundant benzene ring and phenolic hydroxyl moieties preferentially interact with the parallel β-strands to effectually hinder the interaction of the interpeptide chain and the growth of the ordered β-sheet structure. Furthermore, experimental studies confirmed that EGCG was able to disaggregate the preformed fibrils and alter the protein structure. This study will enable a deeper understanding of fundamental principles for design of structural-based inhibitors.

Advanced nanomaterials for modulating Alzheimer's related amyloid aggregation

Alzheimer's disease (AD) is a common neurodegenerative disease that brings about enormous economic pressure to families and society. Inhibiting abnormal aggregation of Aβ and accelerating the dissociation of aggregates is treated as an effective method to prevent and treat AD. Recently, nanomaterials have been applied in AD treatment due to their excellent physicochemical properties and drug activity. As a drug delivery platform or inhibitor, various excellent nanomaterials have exhibited potential in inhibiting Aβ fibrillation, disaggregating, and clearing mature amyloid plaques by enhancing the performance of drugs. This review comprehensively summarizes the advantages and disadvantages of nanomaterials in modulating amyloid aggregation and AD treatment. The design of various functional nanomaterials is discussed, and the strategies for improved properties toward AD treatment are analyzed. Finally, the challenges faced by nanomaterials with different dimensions in AD-related amyloid aggregate modulation are expounded, and the prospects of nanomaterials are proposed.

Curcumin-loaded protein imprinted mesoporous nanosphere for inhibiting amyloid aggregation

Some natural variants of human lysozyme are associated with systemic non-neurological amyloidosis that leads to amyloid protein fibril deposition in different tissues. Inhibition of amyloid fibrillation by nanomaterials is considered to be an effective approach to treating amyloidosis. Here, we prepared a targeted, highly loaded curcumin lysozyme-imprinted nanosphere (CUR-MIMS) that could effectively inhibit the aggregation of lysozyme with lysozyme adsorption capacity of 193.57 mg g^-1 and the imprinting factor (IF) of 3.72. CUR-MIMS could bind to lysozyme through hydrophobic interactions and effectively reduce the hydrophobicity of the total solvent-exposed surface in lysozyme fibrillation, thus reducing the self-assembly process triggered by hydrophobic interactions. Thioflavin T (ThT) analysis demonstrated that CUR-MIMS inhibited the aggregation of amyloid fibrils in a dose-dependent manner (inhibition efficiency of 56.07 %). Circular dichroism (CD) spectrum further illustrated that CUR-MIMS could significantly inhibit the transition of lysozyme from α-helix structure to β-sheet. More importantly, biological experiments proved the good biocompatibility of CUR-MIMS, which indicated the potential of our system as a future therapeutic platform for amyloidosis.

Lysozyme amyloid fibril: Regulation, application, hazard analysis, and future perspectives

Self-assembly of misfolded proteins into ordered fibrillar aggregates known as amyloid results in various human diseases. However, more and more proteins, whether in human body or in food, have been found to be able to form amyloid fibrils with in-depth researches. As a model protein for amyloid research, lysozyme has always been the focus of research in various fields. Firstly, the formation mechanisms of amyloid fibrils are discussed concisely. Researches on the regulation of lysozyme amyloid fibrils are helpful to find suitable therapeutic drugs and unfriendly substances. And this review article summarizes a number of exogenous substances including small molecules, nanoparticles, macromolecules, and polymers. Small molecules are mainly connected to lysozyme through hydrophobic interaction, electrostatic interaction, π-π interaction, van der Waals force and hydrogen bond. Nanoparticles inhibit the formation of amyloid fibers by stabilizing lysozyme and fixing β-sheet. Besides, the applications of lysozyme amyloid fibrils in food-related fields are considered furtherly due to outstanding physical and mechanical properties. Nevertheless, the potential health threats are still worthy of our attention. Finally, we also give suggestions and opinions on the future research direction of lysozyme amyloid fibrils.

Anti-Amyloidogenic and Fibril-Disaggregating Potency of the Levodopa-Functionalized Gold Nanoroses as Exemplified in a Diphenylalanine-Based Amyloid Model

The phenomenon of proteins/peptide assembly into amyloid fibrils is associated with various neurodegenerative and age-related human disorders. Inhibition of the aggregation behavior of amyloidogenic peptides/proteins or disruption of the pre-formed aggregates is a viable therapeutic option to control the progression of various protein aggregation-related disorders such as Alzheimer's disease (AD). In the current work, we investigated both the amyloid inhibition and disaggregation proclivity of levodopa-functionalized gold nanoroses (GNRs) against various peptide-based amyloid models, including the amyloid beta peptide [Aβ (1-42) and Aβ (1-40)] and the dipeptide phenylalanine-phenylalanine (FF). Our results depicted the anti-aggregation behavior of the GNR toward FF and both forms of Aβ-derived fibrils. The peptides demonstrated a variation in their fiber-like morphology and a decline in thioflavin T fluorescence after being co-incubated with the GNR. We further demonstrated the neuroprotective effects of the GNR in neuroblastoma cells against FF and Aβ (1-42) fiber-induced toxicity, exemplified both in terms of regaining cellular viability and reducing production of reactive oxygen species. Overall, these findings support the potency of the GNR as a promising platform for combating AD.

Nano-Strategies for Enhancing the Bioavailability of Tea Polyphenols: Preparation, Applications, and Challenges

Tea polyphenols (TPs) are among the most abundant functional compounds in tea. They exhibit strong antioxidant, anti-inflammatory, and anti-cancer effects. However, their instability and low bioavailability limits their applications. Nanotechnology, which involves the use of nanoscale substances (sizes ranging from 1 to 100 nm) to improve the properties of substances, provides a solution for enhancing the stability and bioavailability of TPs. We reviewed the preparation, performance, effects, and applications of different types of TPs nanocarriers. First, we introduced the preparation of different nanocarriers, including nanoparticles, nanoemulsions, nanomicelles, and nanolipids. Then, we discussed various applications of tea polyphenol-loaded nanocarriers in functional ingredient delivery, food quality improvement, and active food packaging. Finally, the challenges and future development directions of TPs nanocarriers were elucidated. In conclusion, a nano-strategy may be the “key” to break the application barriers of TPs. Therefore, the use of nano-strategies for the safe, stable, and efficient release of TPs is the direction of future research.

(-)-Epigallocatechin-3-Gallate Diminishes Intra-and Extracellular Amyloid-Induced Cytotoxic Effects on Cholinergic-like Neurons from Familial Alzheimer's Disease PSEN1 E280A

Alzheimer’s disease (AD) is a complex neurodegenerative disease characterized by functional disruption, death of cholinergic neurons (ChNs) because of intracellular and extracellular Aβ aggregates, and hyperphosphorylation of protein TAU (p-TAU). To date, there are no efficient therapies against AD. Therefore, new therapies for its treatment are in need. The goal of this investigation was to evaluate the effect of the polyphenol epigallocatechin-3-gallate (EGCG) on cholinergic-like neurons (ChLNs) bearing the mutation E280A in PRESENILIN 1 (PSEN1 E280A). To this aim, wild-type (WT) and PSEN1 E280A ChLNs were exposed to EGCG (5–50 μM) for 4 days. Untreated or treated neurons were assessed for biochemical and functional analysis. We found that EGCG (50 μM) significantly inhibited the aggregation of (i)sAPPβf, blocked p-TAU, increased ∆Ψm, decreased oxidation of DJ-1 at residue Cys106-SH, and inhibited the activation of transcription factor c-JUN and P53, PUMA, and CASPASE-3 in mutant ChLNs compared to WT. Although EGCG did not reduce (e)Aβ42, the polyphenol reversed Ca²⁺ influx dysregulation as a response to acetylcholine (ACh) stimuli in PSEN1 E280A ChLNs, inhibited the activation of transcription factor NF-κB, and reduced the secretion of pro-inflammatory IL-6 in wild-type astrocyte-like cells (ALCs) when exposed to mutant ChLNs culture supernatant. Taken together, our findings suggest that the EGCG might be a promising therapeutic approach for the treatment of FAD.

Dual-targeted carbon-dot-drugs nanoassemblies for modulating Alzheimer's related amyloid-β aggregation and inhibiting fungal infection

Amyloid aggregation and fungal infection, especially amyloid beta (Aβ) peptide and Candida albicans are considered as two of the crucial pathogenic agents in Alzheimer's disease (AD). In this work, we propose an innovative treatment strategy for AD, targeting at not only Aβ aggregation but also Candida albicans infection. Here, a high-performance nanomaterial, namely gCDs-E, have been prepared by self-assembled of glycosylated carbon dots (gCDs) and epigallocatechin-3-gallate (EGCG). Surprisingly, gCDs-E can not only suppress the fibrillation of Aβ and disaggregate Aβ fibrils, but also effectively inhibit the activity of Candida albicans. More importantly, the prepared gCDs-E can effectively cut down the cytotoxicity of amyloid aggregations, and the cell viability reached to 99.2%. In addition, the capability of the gCDs-E for blood brain barrier (BBB) penetration was also observed using a normal mice model. Above all, the gCDs-E greatly cleaned Aβ deposition and improved memory impairment in APP/PS1 transgenic AD model mice, confirming its potential as therapeutic agent for AD treatment.

Chitosan modified ultra-thin hollow nanoparticles for photosensitizer loading and enhancing photodynamic antibacterial activities

Antibacterial photodynamic therapy (PDT) has attracted extremely attention due to not inducing bacteria to generate resistance. However, the poor utilization and low reactive oxygen species (ROS) field of photosensitizers hinder their further application for antibacterial. Here, we designed ultra-thin hollow silica nanoparticles (UHSN), followed by pore-engineering including covalent anchoring of chitosan (UHSN@CS) for enhanced loading and photodynamic property of photosensitizer. The UHSN@CS exhibit high loading efficiency (80.6%, pH = 6.0) and controllable pH-responsive release for Ce6. Additionally, UHSN@CS can enhance the ROS yield of photosensitizers and effectively adhere to S. aureus, thus enormously enhancing antibacterial performance toward bacteria. Moreover, UHSN@CS-Ce6 can obliterate mature S. aureus biofilm and cause an 81% decrease in the biomass, showing a better therapeutic effect than Ce6 (59.2%) under laser irradiation. In vivo results confirm that UHSN@CS-Ce6 is effective to promote infectious wound regeneration. As photodynamic-based nanoplatforms, UHSN@CS-Ce6 are potential antibacterial agents for skin infection therapy.

Surface-modified magnetite nanoparticles affect lysozyme amyloid fibrillization

BACKGROUND

The surface of nanoparticles (NPs) is an important factor affecting the process of poly/peptides' amyloid aggregation. We have investigated the in vitro effect of trisodium citrate (TC), gum arabic (GA) and citric acid (CA) surface-modified magnetite nanoparticles (COAT-MNPs) on hen egg-white lysozyme (HEWL) amyloid fibrillization and mature HEWL fibrils.

METHODS

Dynamic light scattering (DLS) was used to characterize the physico-chemical properties of studied COAT-MNPs and determine the adsorption potential of their surface towards HEWL. The anti-amyloid properties were studied using thioflavin T (ThT) and tryptophan (Trp) intrinsic fluorescence assays, and atomic force microscopy (AFM). The morphology of amyloid aggregates was analyzed using Gwyddion software. The cytotoxicity of COAT-MNPs was determined utilizing Trypan blue (TB) assay.

RESULTS

Agents used for surface modification affect the COAT-MNPs physico-chemical properties and modulate their anti-amyloid potential. The results from ThT and intrinsic fluorescence showed that the inhibitory activities result from the more favorable interactions of COAT-MNPs with early pre-amyloid species, presumably reducing nuclei and oligomers formation necessary for amyloid fibrillization. COAT-MNPs also possess destroying potential, which is presumably caused by the interaction with hydrophobic residues of the fibrils, resulting in the interruption of an interface between β-sheets stabilizing the amyloid fibrils.

CONCLUSION

COAT-MNPs were able to inhibit HEWL fibrillization and destroy mature fibrils with different efficacy depending on their properties, TC-MNPs being the most potent nanoparticles.

GENERAL SIGNIFICANCE

The study reports findings regarding the general impact of nanoparticles' surface modifications on the amyloid aggregation of proteins.

Amino acid-functionalized carbon quantum dots for selective detection of Al3+ ions and fluorescence imaging in living cells

Carbon quantum dots (CQDs) are drawing tremendous attention due to their unique photoluminescence property and fascinating functions. Herein, we prepared novel CQDs functionalized with amino acids (AA-CQDs) by a one-pot hydrothermal method for selective detection of Al³⁺ ions and fluorescence imaging. The prepared AA-CQDs exhibit a novel triple-excitation and single-colour emission for fluorescent property. In addition, the AA-CQDs have a high absolute quantum yield (24.23%) and quantum lifetime (13.29 ns). Moreover, the AA-CQDs exhibit high selectivity and sensitivity for Al³⁺ by fluorescence enhancement. In pH 7.4 PBS solution, there was a good linear relation between the fluorescence intensity and the concentration of Al³⁺ in the range of 1-20 μmol L^-1; the limit of detection (3σ) was only 0.32 μmol L^-1. Furthermore, an AA-CQD probe was also utilized for detection of Al³⁺ in living cells based on excellent biocompatibility and endocytosis. Based on the concentration of Al³⁺ ions in cells and apoptosis data, there will be a quick reflect of apoptosis induced by aluminium ions via the fluorescence intensity of the AA-CQD probe. This work will set the stage for developing novel CQD-based biosensors in cell research.

Lasting Tracking and Rapid Discrimination of Live Gram-Positive Bacteria by Peptidoglycan-Targeting Carbon Quantum Dots

Selective discrimination and lasting tracking of live bacteria are primary steps for microbiology research and treatment of bacterial infection. However, conventional detection methods, such as the gold standard of Gram staining, are being challenged under actual test conditions. Herein, we provided a novel method, namely, three excitation peaks and single-color emission carbon quantum dots (T-SCQDs) for the rapid (5 min) peptidoglycan-targeting discrimination of Gram-positive bacteria and lasting tracking (24 h) through one-step staining. Bacterial viability testing indicates that T-SCQDs can achieve nondestructive identification of Gram-positive bacteria within 50-500 μg mL^-1. Interestingly, the fluorescence imaging system suggests that T-SCQDs can also selectively distinguish the type of colonies based on fluorescence intensity. Furthermore, T-SCQDs were successfully used to visually distinguish Gram-positive bacteria from the microbial environment of A549 cells by confocal fluorescence microscopy. These properties endow T-SCQDs with excellent functions for the diagnosis of infection and other biological applications.

Preparation and characterization of carboxymethylated cotton fabrics as hemostatic wound dressing

Uncontrolled hemorrhage is a large cause of death in the global scope, thus leading to an urgent demand to develop efficient hemostatic materials. In this study, a series of modified cotton fabrics (MCFs) with different carboxymethyl group contents were prepared from cotton fabric (CF) by a carboxymethylation process to choose the appropriate one with the best hemostatic performance. The carboxymethyl group contents of MCFs rose up as the dosages of ClCH₂COOH increased. The crystallinity of CF decreased after carboxymethylation, and MCFs can dissolve slightly with the phenomenon that there were vague boundaries between fibers after being treated with water. Furthermore, the MCF with the carboxymethyl group content at 0.77 mmol/g (MCF-0.77) could absorb the blood quickly, achieve dense distribution of blood cells and have high viscosity of leaching liquor. In addition, the MCF-0.77 with good biocompatibility accelerated the hemostasis time to 46.6 ± 8.4 s compared with the CF (88.8 ± 31.5 s) in a rat model of liver injury. In summary, the prepared MCF-0.77 is a potential hemostatic wound dressing for clinical use since every second counts for pre-hospital care.

Rational design and latest advances of codelivery systems for cancer therapy

Current treatments have limited effectiveness in treating tumors. The combination of multiple drugs or treatment strategies is widely studied to improve therapeutic effect and reduce adverse effects of cancer therapy. The codelivery system is the key to realize combined therapies. It is necessary to design and construct different codelivery systems in accordance with the variable structures and properties of cargoes and vectors. This review presented the typical design considerations about codelivery vectors for cancer therapy and described the current state of codelivery systems from two aspects: different types of vectors and collaborative treatment strategies. The commonly used loading methods of cargoes into the vectors, including physical and chemical processes, are discussed in detail. Finally, we outline the challenges and perspectives about the improvement of codelivery systems.

Europium-functionalized luminescent titania nanotube arrays: Utilizing interactions with glucose, cholesterol and triglycerides for rapid detection application

In this work, titania nanotube arrays (TiO₂-NTs) were prepared by anodization, and the Eu(III) complexes (Eu (TTA)₃ phen with 2-thenoyltrifluoroacetone (TTA) and 1, 10-phenanthroline (phen)) were successfully coated onto the walls of the nanotubes. When a solution of glucose, cholesterol or triglycerides was dropped onto Eu(III) complex-modified TiO₂-NTs, the fluorescence intensity of this material changes (glucose enhances fluorescence, cholesterol and triglycerides quench fluorescence). These phenomena are explained via an energy transfer process. The sensitivity of the fluorescence intensity to glucose, cholesterol or triglycerides concentration enables design of a multifunctional solid sheet-like detector. Under optimized experimental conditions, the change in fluorescence intensity ratio (ΔF/F₀) is linear with the concentration of glucose, cholesterol or triglycerides. To test the utility of the detector, glucose in orange juice, cholesterol in milk powder, and triglycerides in coconut oil were measured using this method and the results were in good agreement analytical data provided by a food testing company. The new method proposed here is simple, sensitive, reliable and suitable for practical applications.