Dual Antibody-Conjugated Amyloid Nanorods to Promote Selective Cell-Cell Interactions

Bioengineered self-assembled nanofibrils for high-affinity SARS-CoV-2 capture and neutralization

The recent coronavirus disease 2019 (COVID-19) pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spurred intense research efforts to develop new materials with antiviral activity. In this study, we genetically engineered amyloid-based nanofibrils for capturing and neutralizing SARS-CoV-2. Building upon the amyloid properties of a short Sup35 yeast prion sequence, we fused it to SARS-CoV-2 receptor-binding domain (RBD) capturing proteins, LCB1 and LCB3. By tuning the reaction conditions, we achieved the spontaneous self-assembly of the Sup35-LCB1 fusion protein into a highly homogeneous and well-dispersed amyloid-like fibrillar material. These nanofibrils exhibited high affinity for the SARS-CoV-2 RBD, effectively inhibiting its interaction with the angiotensin-converting enzyme 2 (ACE2) receptor, the primary entry point for the virus into host cells. We further demonstrate that this functional nanomaterial entraps and neutralizes SARS-CoV-2 virus-like particles (VLPs), with a potency comparable to that of therapeutic antibodies. As a proof of concept, we successfully fabricated patterned surfaces that selectively capture SARS-CoV-2 RBD protein on wet environments. Collectively, these findings suggest that these protein-only nanofibrils hold promise as disinfecting coatings endowed with selective SARS-CoV-2 neutralizing properties to combat viral spread or in the development of sensitive viral sampling and diagnostic tools.

Silver Mineralized Protein Hydrogel with Intrinsic Cell Proliferation Promotion and Broad-Spectrum Antimicrobial Properties for Accelerated Infected Wound Healing

The presence of multidrug-resistant bacteria has challenged the clinical treatment of bacterial infection. There is a real need for the development of novel biocompatible materials with broad-spectrum antimicrobial activities. Antimicrobial hydrogels show great potential in infected wound healing but are still being challenged. Herein, broad-spectrum antibacterial and mechanically tunable amyloid-based hydrogels based on self-assembly and local mineralization of silver nanoparticles are reported. The mineralized hydrogels are biocompatible and have the advantages of sustained release of silver, prolonged antimicrobial effect, and improved adhesion capacity. Moreover, the mineralized hydrogels display a significant antimicrobial effect against both Gram-positive and Gram-negative bacteria in cells and mice by inducing membrane damage and reactive oxygen species toxicity in bacteria. In addition, the mineralized hydrogels can rapidly accelerate wound healing by the synergy between their antibacterial activity and intrinsic improvement for cell proliferation and migration. This study provides a modular approach to developing a multifunctional protein hydrogel platform based on biomolecule-coordinated self-assembly for a wide range of biomedical applications.

Functional Amyloids: The Biomaterials of Tomorrow?

Functional amyloid (FAs), particularly the bacterial proteins CsgA and FapC, have many useful properties as biomaterials: high stability, efficient, and controllable formation of a single type of amyloid, easy availability as extracellular material in bacterial biofilm and flexible engineering to introduce new properties. CsgA in particular has already demonstrated its worth in hydrogels for stable gastrointestinal colonization and regenerative tissue engineering, cell-specific drug release, water-purification filters, and different biosensors. It also holds promise as catalytic amyloid; existing weak and unspecific activity can undoubtedly be improved by targeted engineering and benefit from the repetitive display of active sites on a surface. Unfortunately, FapC remains largely unexplored and no application is described so far. Since FapC shares many common features with CsgA, this opens the window to its development as a functional scaffold. The multiple imperfect repeats in CsgA and FapC form a platform to introduce novel properties, e.g., in connecting linkers of variable lengths. While exploitation of this potential is still at an early stage, particularly for FapC, a thorough understanding of their molecular properties will pave the way for multifunctional fibrils which can contribute toward solving many different societal challenges, ranging from CO2 fixation to hydrolysis of plastic nanoparticles.

gp120-derived amyloidogenic peptides form amyloid fibrils that increase HIV-1 infectivity

Apart from mediating viral entry, the function of the free HIV-1 envelope protein (gp120) has yet to be elucidated. Our group previously showed that EP2 derived from one β-strand in gp120 can form amyloid fibrils that increase HIV-1 infectivity. Importantly, gp120 contains ~30 β-strands. We examined whether gp120 might serve as a precursor protein for the proteolytic release of amyloidogenic fragments that form amyloid fibrils, thereby promoting viral infection. Peptide array scanning, enzyme degradation assays, and viral infection experiments in vitro confirmed that many β-stranded peptides derived from gp120 can indeed form amyloid fibrils that increase HIV-1 infectivity. These gp120-derived amyloidogenic peptides, or GAPs, which were confirmed to form amyloid fibrils, were termed gp120-derived enhancers of viral infection (GEVIs). GEVIs specifically capture HIV-1 virions and promote their attachment to target cells, thereby increasing HIV-1 infectivity. Different GAPs can cross-interact to form heterogeneous fibrils that retain the ability to increase HIV-1 infectivity. GEVIs even suppressed the antiviral activity of a panel of antiretroviral agents. Notably, endogenous GAPs and GEVIs were found in the lymphatic fluid, lymph nodes, and cerebrospinal fluid (CSF) of AIDS patients in vivo. Overall, gp120-derived amyloid fibrils might play a crucial role in the process of HIV-1 infectivity and thus represent novel targets for anti-HIV therapeutics.

Local environment in biomolecular condensates modulates enzymatic activity across length scales

The mechanisms that underlie the regulation of enzymatic reactions by biomolecular condensates and how they scale with compartment size remain poorly understood. Here we use intrinsically disordered domains as building blocks to generate programmable enzymatic condensates of NADH-oxidase (NOX) with different sizes spanning from nanometers to microns. These disordered domains, derived from three distinct RNA-binding proteins, each possessing different net charge, result in the formation of condensates characterized by a comparable high local concentration of the enzyme yet within distinct environments. We show that only condensates with the highest recruitment of substrate and cofactor exhibit an increase in enzymatic activity. Notably, we observe an enhancement in enzymatic rate across a wide range of condensate sizes, from nanometers to microns, indicating that emergent properties of condensates can arise within assemblies as small as nanometers. Furthermore, we show a larger rate enhancement in smaller condensates. Our findings demonstrate the ability of condensates to modulate enzymatic reactions by creating distinct effective solvent environments compared to the surrounding solution, with implications for the design of protein-based heterogeneous biocatalysts.

OligoBinders: Bioengineered Soluble Amyloid-like Nanoparticles to Bind and Neutralize SARS-CoV-2

The coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has become a primary health concern. Molecules that prevent viral entry into host cells by interfering with the interaction between SARS-CoV-2 spike (S) protein and the human angiotensin-converting enzyme 2 receptor (ACE2r) opened a promising avenue for virus neutralization. Here, we aimed to create a novel kind of nanoparticle that can neutralize SARS-CoV-2. To this purpose, we exploited a modular self-assembly strategy to engineer OligoBinders, soluble oligomeric nanoparticles decorated with two miniproteins previously described to bind to the S protein receptor binding domain (RBD) with high affinity. The multivalent nanostructures compete with the RBD-ACE2r interaction and neutralize SARS-CoV-2 virus-like particles (SC2-VLPs) with IC50 values in the pM range, preventing SC2-VLPs fusion with the membrane of ACE2r-expressing cells. Moreover, OligoBinders are biocompatible and significantly stable in plasma. Overall, we describe a novel protein-based nanotechnology that might find application in SARS-CoV-2 therapeutics and diagnostics.

Novel, Inexpensive, and Scalable Amyloid Fibril Formation Method

Wheat flour was used as a source of protein for the in vitro synthesis of Amyloid fibrils to develop a novel and inexpensive fabrication method. Amyloid fibrillation was confirmed by Thioflavin T Fluorescence, using confocal microscopy. A morphological study was carried out by transmission electron microscopy (TEM), which revealed the high aspect ratio of the amyloid fibrils formed via a novel process. An application of the amyloid fibers produced by the novel method is shown to be melatonin sensing. Tests showed that the amyloid samples had a measurable color variation dependent on the melatonin concentration. This newly derived process could prove to be a cost-effective tool for future nano-biomaterial applications in commercial and research settings.

AlphaFold and the amyloid landscape

Protein aggregation is a widespread phenomenon with important implications in many scientific areas. Although amyloid formation is typically considered as detrimental, functional amyloids that perform physiological roles have been identified in all kingdoms of life. Despite their functional and pathological relevance, the structural details of the majority of molecular species involved in the amyloidogenic process remains elusive. Here, we explore the application of AlphaFold, a highly accurate protein structure predictor, in the field of protein aggregation. While we envision a straightforward application of AlphaFold in assisting the design of globular proteins with improved solubility for biomedical and industrial purposes, the use of this algorithm for predicting the structure of aggregated species seems far from trivial. First, in amyloid diseases, the presence of multiple amyloid polymorphs and the heterogeneity of aggregation intermediates challenges the "one sequence, one structure" paradigm, inherent to sequence-based predictions. Second, aberrant aggregation is not the subject of positive selective pressure, precluding the use of evolutionary-based approaches, which are the core of the AlphaFold pipeline. Instead, amyloid polymorphism seems to be constrained by the need for a defined structure-activity relationship in functional amyloids. They may thus provide a starting point for the application of AlphaFold in the amyloid landscape.