Food amyloid fibrils are safe nutrition ingredients based on in-vitro and in-vivo assessment

Food protein amyloid fibrils have superior technological, nutritional, sensorial, and physical properties compared to native monomers, but there is as yet insufficient understanding of their digestive fate and safety for wide consumption. By combining SDS-PAGE, ELISA, fluorescence, AFM, MALDI-MS, CD, microfluidics, and SAXS techniques for the characterization of β-lactoglobulin and lysozyme amyloid fibrils subjected to in-vitro gastrointestinal digestion, here we show that either no noticeable conformational differences exist between amyloid aggregates and their monomer counterparts after the gastrointestinal digestion process (as in β-lactoglobulin), or that amyloid fibrils are digested significantly better than monomers (as in lysozyme). Moreover, in-vitro exposure of human cell lines and in-vivo studies with C. elegans and mouse models, indicate that the digested fibrils present no observable cytotoxicity, physiological abnormalities in health-span, nor accumulation of fibril-induced plaques in brain nor other organs. These extensive in-vitro and in-vivo studies together suggest that the digested food amyloids are at least equally as safe as those obtained from the digestion of corresponding native monomers, pointing to food amyloid fibrils as potential ingredients for human nutrition.

Renewable Energy from Livestock Waste Valorization: Amyloid-Based Feather Keratin Fuel Cells

Increasing carbon emissions have accelerated climate change, resulting in devastating effects that are now tangible on an everyday basis. This is mirrored by a projected increase in global energy demand of approximately 50% within a single generation, urging a shift from fossil-fuel-derived materials toward greener materials and more sustainable manufacturing processes. Biobased industrial byproducts, such as side streams from the food industry, are attractive alternatives with strong potential for valorization due to their large volume, low cost, renewability, biodegradability, and intrinsic material properties. Here, we demonstrate the reutilization of industrial chicken feather waste into proton-conductive membranes for fuel cells, protonic transistors, and water-splitting devices. Keratin was isolated from chicken feathers via a fast and economical process, converted into amyloid fibrils through heat treatment, and further processed into membranes with an imparted proton conductivity of 6.3 mS cm-1 using a simple oxidative method. The functionality of the membranes is demonstrated by assembling them into a hydrogen fuel cell capable of generating 25 mW cm-2 of power density to operate various types of devices using hydrogen and air as fuel. Additionally, these membranes were used to generate hydrogen through water splitting and in protonic field-effect transistors as thin-film modulators of protonic conductivity via the electrostatic gating effect. We believe that by converting industrial waste into renewable energy materials at low cost and high scalability, our green manufacturing process can contribute to a fully circular economy with a neutral carbon footprint.

Two-photon excited lasing for detection of amyloids in brain tissue

Two-photon excitation of emissive markers with near-infrared (NIR) light is of a particular interest for imaging in biology and medicine because NIR light is relatively weakly absorbed and scattered by tissues. At the same time the mechanism of two-photon absorption allows excitation of molecules located deep inside a scattering medium. In this work we demonstrate that the two-photon excitation combined with the effect of light amplification in the stimulated emission process provides a sensitive method for detecting amyloids of different forms. We investigate the two-photon excited amplified spontaneous emission (ASE) of a fluorescent dye, coumarin 307, in the brain tissue infiltrated with various amyloid phantoms i.e. oligomers, protofibrils and mature fibrils. All these forms of amyloids can be detected by observation of ASE and determination of thresholds for light amplification. On this basis we suggest that a relatively simple extension of currently used emission-based optical spectroscopy techniques can provide key information on pathogenic amyloid structures in tissue.

Laser Emission of Thioflavin T Uncovers Protein Aggregation in Amyloid Nucleation Phase

There is currently no definitive test for early detection of neurodegeneration which is linked with protein aggregation. Finding methods capable of detecting intermediate states of protein aggregates, named oligomers, is critical for the early stage diagnosis of over 30 neurodegenerative diseases including Alzheimer's or Parkinson's. Currently, fluorescence-based imaging using Thioflavin T (ThT) dye is the gold standard for detecting protein aggregation. It is used to detect aggregation in vitro and in various tissues, including the cerebrospinal fluid (CSF), whereby the disease-related protein recombinant is seeded with the patient's fluid. The major drawback of ThT is its lack of sensitivity to oligomeric forms of protein aggregates. Here, we overcome this limitation by transferring a ThT-oligomer mixture into solid state thin films and detecting fluorescence of ThT amplified in the process of stimulated emission. By monitoring the amplified spontaneous emission (ASE) we achieved a remarkable recognition sensitivity to prefibrillar oligomeric forms of insulin and lysozyme aggregates in vitro, to Aβ42 oligomers in the human protein recombinants seeded with CSF and to Aβ42 oligomers doped into brain tissue. Seeding with Alzheimer patient's CSF containing Aβ42 and Tau aggregates revealed that only Aβ42 oligomers allowed generating ASE. Thus, we demonstrated that, in contrast to the current state-of-the-art, ASE of ThT, a commonly used histological dye, can be used to detect and differentiate amyloid oligomers and evaluate the risk levels of neurodegenerative diseases to potential patients before the clinical symptoms occur.

An α-Cyanostilbene Derivative for the Enhanced Detection and Imaging of Amyloid Fibril Aggregates

The aggregation of proteins into amyloid fibrils has been implicated in the pathogenesis of a variety of neurodegenerative diseases, including Alzheimer's disease and Parkinson's disease. Benzothiazole dyes such as Thioflavin T (ThT) are well-characterized and widely used fluorescent probes for monitoring amyloid fibril formation. However, existing dyes lack sensitivity and specificity to oligomeric intermediates formed during fibril formation. In this work, we describe the use of an α-cyanostilbene derivative (called ASCP) with aggregation-induced emission properties as a fluorescent probe for the detection of amyloid fibrils. Similar to ThT, ASCP is fluorogenic in the presence of amyloid fibrils and, upon binding and excitation at 460 nm, produces a red-shifted emission with a large Stokes shift of 145 nm. ASCP has a higher binding affinity to fibrillar α-synuclein than ThT and likely shares the same binding sites to amyloid fibrils. Importantly, ASCP was found to also be fluorogenic in the presence of amorphous aggregates and can detect oligomeric species formed early during aggregation. Moreover, ASCP can be used to visualize fibrils via total internal reflection fluorescence microscopy and, due to its large Stokes shift, simultaneously monitor the fluorescence emission of other labelled proteins following excitation with the same laser used to excite ASCP. Consequently, ASCP possesses enhanced and unique spectral characteristics compared to ThT that make it a promising alternative for the in vitro study of amyloid fibrils and the mechanisms by which they form.

Amyloid fibril systems reduce, stabilize and deliver bioavailable nanosized iron

Iron-deficiency anaemia (IDA) is a major global public health problem. A sustainable and cost-effective strategy to reduce IDA is iron fortification of foods, but the most bioavailable fortificants cause adverse organoleptic changes in foods. Iron nanoparticles are a promising solution in food matrices, although their tendency to oxidize and rapidly aggregate in solution severely limits their use in fortification. Amyloid fibrils are protein aggregates initially known for their association with neurodegenerative disorders, but recently described in the context of biological functions in living organisms and emerging as unique biomaterial building blocks. Here, we show an original application for these protein fibrils as efficient carriers for iron fortification. We use biodegradable amyloid fibrils from β-lactoglobulin, an inexpensive milk protein with natural reducing effects, as anti-oxidizing nanocarriers and colloidal stabilizers for iron nanoparticles. The resulting hybrid material forms a stable protein-iron colloidal dispersion that undergoes rapid dissolution and releases iron ions during acidic and enzymatic in vitro digestion. Importantly, this hybrid shows high in vivo iron bioavailability, equivalent to ferrous sulfate in haemoglobin-repletion and stable-isotope studies in rats, but with reduced organoleptic changes in foods. Feeding the rats with these hybrid materials did not result in abnormal iron accumulation in any organs, or changes in whole blood glutathione concentrations, inferring their primary safety. Therefore, these iron-amyloid fibril hybrids emerge as novel, highly effective delivery systems for iron in both solid and liquid matrices.

On the Molecular Form of Amyloid Marker, Auramine O, in Human Insulin Fibrils

Designing extrinsic fluorescence sensors for amyloid fibrils is a very active and important area of research. Recently, an ultrafast molecule rotor dye, Auramine O (AuO), has been projected as a fluorescent amyloid marker. It has been claimed that AuO scores better than the most extensively utilized gold-standard amyloid probe, Thioflavin-T (ThT). This advantage arises from the fact that AuO, in addition to its usual emission band (∼500 nm), also displays a large red-shifted emission band (∼560 nm), exclusively in the presence of human insulin fibril medium and not in the native protein or buffer media. On the contrary, for ThT, the emission maximum (∼490 nm) largely remains unchanged while going from protein to fibril. This otherwise unknown large red-shifted emission band of AuO, observed in the presence of human insulin fibrils, was tentatively attributed to a species formed upon fast proton dissociation from excited AuO. It was proposed that because of the long excited-state lifetime (∼1.8 ns) of AuO upon association with human insulin fibrils, this fast proton dissociation from excited AuO could be observed, which is otherwise not observed in buffer or native protein media, owing to its very short excited-state lifetime (∼1 ps). Herein, we show that despite the long excited-state lifetime of AuO in other fibrillar media (human serum albumin and lysozyme), the new red-shifted emission band at 560 nm is not observed, thus possibly suggesting a different origin of the red-shifted emission band of AuO in human insulin fibril medium. We convincingly show that this red-shifted band of AuO (∼560 nm) could be observed under conditions that promote dye aggregation, such as a premicellar concentration of surfactants and polyelectrolytes. These AuO aggregates display strong emission wavelength dependence of transient decay traces, similar to that for AuO in human insulin fibril medium. Detailed time-resolved emission spectral (TRES) measurements suggest that the AuO/premicellar surfactant and AuO/human insulin fibril system share similar features, such as a dynamic red-shift in TRES and an isoemissive point in the time-resolved area-normalized emission spectra, suggesting that the characteristic red-shifted emission band of AuO in human insulin fibril medium may arise from AuO aggregates.

PicoGreen: a better amyloid probe than Thioflavin-T

PicoGreen, an ultrafast molecular rotor, binds strongly with amyloid fibrils and shows much higher sensitivity than Thioflavin-T, a gold standard fluorescence amyloid probe.

Effect of sodium salicylate and sodium deoxycholate on fibrillation of bovine serum albumin: comparison of fluorescence, SANS and DLS techniques

Adsorbed sodium salicylate (NaSal) and sodium deoxycholate (NaDC) retard the thermal denaturation of bovine serum albumin.