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Xu Y, Jacquat RPB, Shen Y, Vigolo D, Morse D, Zhang S, Knowles TPJ. Microfluidic Templating of Spatially Inhomogeneous Protein Microgels. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2020; 16:e2000432. [PMID: 32529798 DOI: 10.1002/smll.202000432] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Revised: 04/20/2020] [Accepted: 05/18/2020] [Indexed: 05/20/2023]
Abstract
3D scaffolds in the form of hydrogels and microgels have allowed for more native cell-culture systems to be developed relative to flat substrates. Native biological tissues are, however, usually spatially inhomogeneous and anisotropic, but regulating the spatial density of hydrogels at the microscale to mimic this inhomogeneity has been challenging to achieve. Moreover, the development of biocompatible synthesis approaches for protein-based microgels remains challenging, and typical gelation conditions include UV light, extreme pH, extreme temperature, or organic solvents, factors which can compromise the viability of cells. This study addresses these challenges by demonstrating an approach to fabricate protein microgels with controllable radial density through microfluidic mixing and physical and enzymatic crosslinking of gelatin precursor molecules. Microgels with a higher density in their cores and microgels with a higher density in their shells are demonstrated. The microgels have robust stability at 37 °C and different dissolution rates through enzymolysis, which can be further used for gradient scaffolds for 3D cell culture, enabling controlled degradability, and the release of biomolecules. The design principles of the microgels could also be exploited to generate other soft materials for applications ranging from novel protein-only micro reactors to soft robots.
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127
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Hakala T, Bialas F, Toprakcioglu Z, Bräuer B, Baumann KN, Levin A, Bernardes GJL, Becker CFW, Knowles TPJ. Continuous Flow Reactors from Microfluidic Compartmentalization of Enzymes within Inorganic Microparticles. ACS APPLIED MATERIALS & INTERFACES 2020; 12:32951-32960. [PMID: 32589387 PMCID: PMC7383928 DOI: 10.1021/acsami.0c09226] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Compartmentalization and selective transport of molecular species are key aspects of chemical transformations inside the cell. In an artificial setting, the immobilization of a wide range of enzymes onto surfaces is commonly used for controlling their functionality but such approaches can restrict their efficacy and expose them to degrading environmental conditions, thus reducing their activity. Here, we employ an approach based on droplet microfluidics to generate enzyme-containing microparticles that feature an inorganic silica shell that forms a semipermeable barrier. We show that this porous shell permits selective diffusion of the substrate and product while protecting the enzymes from degradation by proteinases and maintaining their functionality over multiple reaction cycles. We illustrate the power of this approach by synthesizing microparticles that can be employed to detect glucose levels through simultaneous encapsulation of two distinct enzymes that form a controlled reaction cascade. These results demonstrate a robust, accessible, and modular approach for the formation of microparticles containing active but protected enzymes for molecular sensing applications and potential novel diagnostic platforms.
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128
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Dear AJ, Meisl G, Michaels TCT, Zimmermann MR, Linse S, Knowles TPJ. The catalytic nature of protein aggregation. J Chem Phys 2020; 152:045101. [PMID: 32007046 PMCID: PMC7377910 DOI: 10.1063/1.5133635] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The formation of amyloid fibrils from soluble peptide is a hallmark of many
neurodegenerative diseases such as Alzheimer’s and Parkinson’s diseases. Characterization
of the microscopic reaction processes that underlie these phenomena have yielded insights
into the progression of such diseases and may inform rational approaches for the design of
drugs to halt them. Experimental evidence suggests that most of these reaction processes
are intrinsically catalytic in nature and may display enzymelike saturation effects under
conditions typical of biological systems, yet a unified modeling framework accounting for
these saturation effects is still lacking. In this paper, we therefore present a universal
kinetic model for biofilament formation in which every fundamental process in the reaction
network can be catalytic. The single closed-form expression derived is capable of
describing with high accuracy a wide range of mechanisms of biofilament formation and
providing the first integrated rate law of a system in which multiple reaction processes
are saturated. Moreover, its unprecedented mathematical simplicity permits us to very
clearly interpret the effects of increasing saturation on the overall kinetics. The
effectiveness of the model is illustrated by fitting it to the data of in
vitro Aβ40 aggregation. Remarkably, we find that primary nucleation becomes
saturated, demonstrating that it must be heterogeneous, occurring at interfaces and not in
solution.
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129
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Pansieri J, Iashchishyn IA, Fakhouri H, Ostojić L, Malisauskas M, Musteikyte G, Smirnovas V, Schneider MM, Scheidt T, Xu CK, Meisl G, Knowles TPJ, Gazit E, Antoine R, Morozova-Roche LA. Templating S100A9 amyloids on Aβ fibrillar surfaces revealed by charge detection mass spectrometry, microscopy, kinetic and microfluidic analyses. Chem Sci 2020; 11:7031-7039. [PMID: 34122996 PMCID: PMC8159403 DOI: 10.1039/c9sc05905a] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Accepted: 06/16/2020] [Indexed: 12/16/2022] Open
Abstract
The mechanism of amyloid co-aggregation and its nucleation process are not fully understood in spite of extensive studies. Deciphering the interactions between proinflammatory S100A9 protein and Aβ42 peptide in Alzheimer's disease is fundamental since inflammation plays a central role in the disease onset. Here we use innovative charge detection mass spectrometry (CDMS) together with biophysical techniques to provide mechanistic insight into the co-aggregation process and differentiate amyloid complexes at a single particle level. Combination of mass and charge distributions of amyloids together with reconstruction of the differences between them and detailed microscopy reveals that co-aggregation involves templating of S100A9 fibrils on the surface of Aβ42 amyloids. Kinetic analysis further corroborates that the surfaces available for the Aβ42 secondary nucleation are diminished due to the coating by S100A9 amyloids, while the binding of S100A9 to Aβ42 fibrils is validated by a microfluidic assay. We demonstrate that synergy between CDMS, microscopy, kinetic and microfluidic analyses opens new directions in interdisciplinary research.
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130
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Ruggeri FS, Mannini B, Schmid R, Vendruscolo M, Knowles TPJ. Single molecule secondary structure determination of proteins through infrared absorption nanospectroscopy. Nat Commun 2020; 11:2945. [PMID: 32522983 PMCID: PMC7287102 DOI: 10.1038/s41467-020-16728-1] [Citation(s) in RCA: 74] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Accepted: 05/11/2020] [Indexed: 12/21/2022] Open
Abstract
The chemical and structural properties of biomolecules determine their interactions, and thus their functions, in a wide variety of biochemical processes. Innovative imaging methods have been developed to characterise biomolecular structures down to the angstrom level. However, acquiring vibrational absorption spectra at the single molecule level, a benchmark for bulk sample characterization, has remained elusive. Here, we introduce off-resonance, low power and short pulse infrared nanospectroscopy (ORS-nanoIR) to allow the acquisition of infrared absorption spectra and chemical maps at the single molecule level, at high throughput on a second timescale and with a high signal-to-noise ratio (~10-20). This high sensitivity enables the accurate determination of the secondary structure of single protein molecules with over a million-fold lower mass than conventional bulk vibrational spectroscopy. These results pave the way to probe directly the chemical and structural properties of individual biomolecules, as well as their interactions, in a broad range of chemical and biological systems.
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131
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Dear AJ, Meisl G, Šarić A, Michaels TCT, Kjaergaard M, Linse S, Knowles TPJ. Identification of on- and off-pathway oligomers in amyloid fibril formation. Chem Sci 2020; 11:6236-6247. [PMID: 32953019 PMCID: PMC7480182 DOI: 10.1039/c9sc06501f] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Accepted: 05/26/2020] [Indexed: 12/22/2022] Open
Abstract
A general non-binary definition for on- and off-pathway intermediates is developed, enabling comparison of amyloid oligomers' contributions to fibril formation.
The misfolding and aberrant aggregation of proteins into fibrillar structures is a key factor in some of the most prevalent human diseases, including diabetes and dementia. Low molecular weight oligomers are thought to be a central factor in the pathology of these diseases, as well as critical intermediates in the fibril formation process, and as such have received much recent attention. Moreover, on-pathway oligomeric intermediates are potential targets for therapeutic strategies aimed at interrupting the fibril formation process. However, a consistent framework for distinguishing on-pathway from off-pathway oligomers has hitherto been lacking and, in particular, no consensus definition of on- and off-pathway oligomers is available. In this paper, we argue that a non-binary definition of oligomers' contribution to fibril-forming pathways may be more informative and we suggest a quantitative framework, in which each oligomeric species is assigned a value between 0 and 1 describing its relative contribution to the formation of fibrils. First, we clarify the distinction between oligomers and fibrils, and then we use the formalism of reaction networks to develop a general definition for on-pathway oligomers, that yields meaningful classifications in the context of amyloid formation. By applying these concepts to Monte Carlo simulations of a minimal aggregating system, and by revisiting several previous studies of amyloid oligomers in light of our new framework, we demonstrate how to perform these classifications in practice. For each oligomeric species we obtain the degree to which it is on-pathway, highlighting the most effective pharmaceutical targets for the inhibition of amyloid fibril formation.
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132
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Arter WE, Yusim Y, Peter Q, Taylor CG, Klenerman D, Keyser UF, Knowles TPJ. Digital Sensing and Molecular Computation by an Enzyme-Free DNA Circuit. ACS NANO 2020; 14:5763-5771. [PMID: 32293175 DOI: 10.1021/acsnano.0c00628] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
DNA circuits form the basis of programmable molecular systems capable of signal transduction and algorithmic computation. Some classes of molecular programs, such as catalyzed hairpin assembly, enable isothermal, enzyme-free signal amplification. However, current detection limits in DNA amplification circuits are modest, as sensitivity is inhibited by signal leakage resulting from noncatalyzed background reactions inherent to the noncovalent system. Here, we overcome this challenge by optimizing a catalyzed hairpin assembly for single-molecule sensing in a digital droplet assay. Furthermore, we demonstrate digital reporting of DNA computation at the single-molecule level by employing ddCHA as a signal transducer for simple DNA logic gates. By facilitating signal transduction of molecular computation at pM concentration, our approach can improve processing density by a factor of 104 relative to conventional DNA logic gates. More broadly, we believe that digital molecular computing will broaden the scope and efficacy of isothermal amplification circuits within DNA computing, biosensing, and signal amplification in general.
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133
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Ruggeri FS, Flagmeier P, Kumita JR, Meisl G, Chirgadze DY, Bongiovanni MN, Knowles TPJ, Dobson CM. The Influence of Pathogenic Mutations in α-Synuclein on Biophysical and Structural Characteristics of Amyloid Fibrils. ACS NANO 2020; 14:5213-5222. [PMID: 32159944 DOI: 10.1021/acsnano.9b09676] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Proteinaceous deposits of α-synuclein amyloid fibrils are a hallmark of human disorders including Parkinson's disease. The onset of this disease is also associated with five familial mutations of the gene encoding the protein. However, the mechanistic link between single point mutations and the kinetics of aggregation, biophysical properties of the resulting amyloid fibrils, and an increased risk of disease is still elusive. Here, we demonstrate that the disease-associated mutations of α-synuclein generate different amyloid fibril polymorphs compared to the wild type protein. Remarkably, the α-synuclein variants forming amyloid fibrils of a comparable structure, morphology, and heterogeneity show similar microscopic steps defining the aggregation kinetics. These results demonstrate that a single point mutation can significantly alter the distribution of fibrillar polymorphs in α-synuclein, suggesting that differences in the clinical phenotypes of familial Parkinson's disease could be associated with differences in the mechanism of formation and the structural characteristics of the aggregates.
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134
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Hakala TA, Davies S, Toprakcioglu Z, Bernardim B, Bernardes GJL, Knowles TPJ. A Microfluidic Co-Flow Route for Human Serum Albumin-Drug-Nanoparticle Assembly. Chemistry 2020; 26:5965-5969. [PMID: 32237164 PMCID: PMC7318336 DOI: 10.1002/chem.202001146] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Indexed: 12/13/2022]
Abstract
Nanoparticles are widely studied as carrier vehicles in biological systems because their size readily allows access through cellular membranes. Moreover, they have the potential to carry cargo molecules and as such, these factors make them especially attractive for intravenous drug delivery purposes. Interest in protein-based nanoparticles has recently gained attraction due to particle biocompatibility and lack of toxicity. However, the production of homogeneous protein nanoparticles with high encapsulation efficiencies, without the need for additional cross-linking or further engineering of the molecule, remains challenging. Herein, we present a microfluidic 3D co-flow device to generate human serum albumin/celastrol nanoparticles by co-flowing an aqueous protein solution with celastrol in ethanol. This microscale co-flow method resulted in the formation of nanoparticles with a homogeneous size distribution and an average size, which could be tuned from ≈100 nm to 1 μm by modulating the flow rates used. We show that the high stability of the particles stems from the covalent cross-linking of the naturally present cysteine residues within the particles formed during the assembly step. By choosing optimal flow rates during synthesis an encapsulation efficiency of 75±24 % was achieved. Finally, we show that this approach achieves significantly enhanced solubility of celastrol in the aqueous phase and, crucially, reduced cellular toxicity.
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135
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Sanguanini M, Baumann KN, Preet S, Chia S, Habchi J, Knowles TPJ, Vendruscolo M. Complexity in Lipid Membrane Composition Induces Resilience to Aβ 42 Aggregation. ACS Chem Neurosci 2020; 11:1347-1352. [PMID: 32212722 DOI: 10.1021/acschemneuro.0c00101] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The molecular origins of Alzheimer's disease are associated with the aggregation of the amyloid-β peptide (Aβ). This process is controlled by a complex cellular homeostasis system, which involves a variety of components, including proteins, metabolites, and lipids. It has been shown in particular that certain components of lipid membranes can speed up Aβ aggregation. This observation prompts the question of whether there are protective cellular mechanisms to counterbalance this effect. Here, to address this issue, we investigate the role of the composition of lipid membranes in modulating the aggregation process of Aβ. By adopting a chemical kinetics approach, we first identify a panel of lipids that affect the aggregation of the 42-residue form of Aβ (Aβ42), ranging from enhancement to inhibition. We then show that these effects tend to average out in mixtures of these lipids, as such mixtures buffer extreme aggregation behaviors as the number of components increases. These results indicate that a degree of quality control on protein aggregation can be achieved through a mechanism by which an increase in the molecular complexity of lipid membranes balances opposite effects and creates resilience to aggregation.
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136
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Michaels TCT, Šarić A, Curk S, Bernfur K, Arosio P, Meisl G, Dear AJ, Cohen SIA, Dobson CM, Vendruscolo M, Linse S, Knowles TPJ. Dynamics of oligomer populations formed during the aggregation of Alzheimer's Aβ42 peptide. Nat Chem 2020; 12:445-451. [PMID: 32284577 DOI: 10.1038/s41557-020-0452-1] [Citation(s) in RCA: 186] [Impact Index Per Article: 46.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Accepted: 03/02/2020] [Indexed: 01/10/2023]
Abstract
Oligomeric species populated during the aggregation of the Aβ42 peptide have been identified as potent cytotoxins linked to Alzheimer's disease, but the fundamental molecular pathways that control their dynamics have yet to be elucidated. By developing a general approach that combines theory, experiment and simulation, we reveal, in molecular detail, the mechanisms of Aβ42 oligomer dynamics during amyloid fibril formation. Even though all mature amyloid fibrils must originate as oligomers, we found that most Aβ42 oligomers dissociate into their monomeric precursors without forming new fibrils. Only a minority of oligomers converts into fibrillar structures. Moreover, the heterogeneous ensemble of oligomeric species interconverts on timescales comparable to those of aggregation. Our results identify fundamentally new steps that could be targeted by therapeutic interventions designed to combat protein misfolding diseases.
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137
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Toprakcioglu Z, Hakala TA, Levin A, Becker CFW, Bernandes GJL, Knowles TPJ. Correction: Multi-scale microporous silica microcapsules from gas-in water-in oil emulsions. SOFT MATTER 2020; 16:3586. [PMID: 32219268 DOI: 10.1039/d0sm90059a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Correction for 'Multi-scale microporous silica microcapsules from gas-in water-in oil emulsions' by Zenon Toprakcioglu et al., Soft Matter, 2020, DOI: 10.1039/c9sm02274k.
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138
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Arter WE, Levin A, Krainer G, Knowles TPJ. Microfluidic approaches for the analysis of protein-protein interactions in solution. Biophys Rev 2020; 12:575-585. [PMID: 32266673 PMCID: PMC7242286 DOI: 10.1007/s12551-020-00679-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Accepted: 03/02/2020] [Indexed: 12/15/2022] Open
Abstract
Exploration and characterisation of the human proteome is a key objective enabling a heightened understanding of biological function, malfunction and pharmaceutical design. Since proteins typically exhibit their behaviour by binding to other proteins, the challenge of probing protein-protein interactions has been the focus of new and improved experimental approaches. Here, we review recently developed microfluidic techniques for the study and quantification of protein-protein interactions. We focus on methodologies that utilise the inherent strength of microfluidics for the control of mass transport on the micron scale, to facilitate surface and membrane-free interrogation and quantification of interacting proteins. Thus, the microfluidic tools described here provide the capability to yield insights on protein-protein interactions under physiological conditions. We first discuss the defining principles of microfluidics, and methods for the analysis of protein-protein interactions that utilise the diffusion-controlled mixing characteristic of fluids at the microscale. We then describe techniques that employ electrophoretic forces to manipulate and fractionate interacting protein systems for their biophysical characterisation, before discussing strategies that use microdroplet compartmentalisation for the analysis of protein interactions. We conclude by highlighting future directions for the field, such as the integration of microfluidic experiments into high-throughput workflows for the investigation of protein interaction networks.
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139
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Toprakcioglu Z, Hakala TA, Levin A, Becker CFW, Bernandes GGL, Knowles TPJ. Multi-scale microporous silica microcapsules from gas-in water-in oil emulsions. SOFT MATTER 2020; 16:3082-3087. [PMID: 32140697 DOI: 10.1039/c9sm02274k] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Controlling the surface area, pore size and pore volume of microcapsules is crucial for modulating their activity in applications including catalytic reactions, delivery strategies or even cell culture assays, yet remains challenging to achieve using conventional bulk techniques. Here we describe a microfluidics-based approach for the formation of monodisperse silica-coated micron-scale porous capsules of controllable sizes. Our method involves the generation of gas-in water-in oil emulsions, and the subsequent rapid precipitation of silica which forms around the encapsulated gas bubbles resulting in hollow silica capsules with tunable pore sizes. We demonstrate that by varying the gas phase pressure, we can control both the diameter of the bubbles formed and the number of internal bubbles enclosed within the silica microcapsule. Moreover, we further demonstrate, using optical and electron microscopy, that these silica capsules remain stable under particle drying. Such a systematic manner of producing silica-coated microbubbles and porous microparticles thus represents an attractive class of biocompatible material for biomedical and pharmaceutical related applications.
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140
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Schnaider L, Toprakcioglu Z, Ezra A, Liu X, Bychenko D, Levin A, Gazit E, Knowles TPJ. Biocompatible Hybrid Organic/Inorganic Microhydrogels Promote Bacterial Adherence and Eradication in Vitro and in Vivo. NANO LETTERS 2020; 20:1590-1597. [PMID: 32040332 DOI: 10.1021/acs.nanolett.9b04290] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Self-assembling peptides and proteins have the potential to serve as multifunctional building blocks for the generation of versatile materials for a wide range of biomedical applications. In particular, supramolecular hydrogels comprised of self-assembled protein nanofibrils, have been used in contexts ranging from tissue engineering to drug delivery. Due to the rapid emergence of multidrug resistant bacteria, development of biomaterials with intrinsic antimicrobial properties has been continuously increasing. Here, we describe hybrid organic/inorganic nanofibrillar silk microgels decorated with silver nanoparticles that display potent antimicrobial activity in vitro and in vivo and are able to adhere bacterial cells to their surfaces while subsequently eradicating them, through a two-step mechanism of action. Importantly, in contrast to treatments involving conventional silver, these silk-silver microgels are nonhemolytic and noncytotoxic toward mammalian cell lines. Finally, we show that these hybrid microgels display substantial efficacy as topical antimicrobial agents in a murine model of surgical site infections.
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141
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Kong L, Levin A, Toprakcioglu Z, Xu Y, Gang H, Ye R, Mu BZ, Knowles TPJ. Lipid-Stabilized Double Emulsions Generated in Planar Microfluidic Devices. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:2349-2356. [PMID: 32045250 DOI: 10.1021/acs.langmuir.9b03622] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Microemulsions have found a wide range of applications exploiting their chemical and physical properties. Development of microfluidic-based approaches has allowed for the controlled production of highly monodispersed emulsions, including the formation of multiple and hierarchical emulsions. Conventional poly(dimethylsiloxane)-based microfluidic systems require tight spatial control over the surface chemistry when used for double emulsion generation, which can be challenging to achieve on the micrometer scale. Here, we present a two-dimensional device design, which can selectively be surface-treated in a straightforward manner and allows for the formation of uniform water/oil/water double emulsions by combining two distinct hydrophilic and hydrophobic surface properties. These surfaces are sufficiently separated in space to allow for imparting their functionalization without the requirement for lithographic approaches or complex flow control. We demonstrate that a mismatch between the wettability requirements of the continuous phase and the channel wall inherent in this approach can be tolerated over several hundreds of micrometers, opening up the possibility to use simple pressure-driven flows to achieve surface functionalization. The design architecture exhibits robust efficiency in emulsion generation while retaining simple device fabrication. We finally demonstrate the potential of this approach by generating water in oil in water emulsions with lipid molecules acting as surfactants.
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142
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Zhou J, Ruggeri FS, Zimmermann MR, Meisl G, Longo G, Sekatskii SK, Knowles TPJ, Dietler G. Effects of sedimentation, microgravity, hydrodynamic mixing and air-water interface on α-synuclein amyloid formation. Chem Sci 2020; 11:3687-3693. [PMID: 34094057 PMCID: PMC8152616 DOI: 10.1039/d0sc00281j] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Accepted: 03/06/2020] [Indexed: 12/28/2022] Open
Abstract
The formation of amyloid fibrils is a characterizing feature of a range of protein misfolding diseases, including Parkinson's disease. The propensity of native proteins to form such amyloid fibril, both in vitro and in vivo, is highly sensitive to the surrounding environment, which can alter the aggregation kinetics and fibrillization mechanisms. Here, we investigate systematically the influence of several representative environmental stimuli on α-synuclein aggregation, including hydrodynamic mixing, the presence of an air-water interface and sedimentation. Our results show that hydrodynamic mixing and interfacial effects are critical in promoting several microscopic steps of α-synuclein aggregation and amyloid fibril formation. The presence of an air-water interface under agitation significantly promoted primary nucleation. Secondary processes were facilitated by hydrodynamic mixing, produced by 3D rotation and shaking either in the presence or in the absence of an air-water interface. Effects of sedimentation, as investigated in a microgravity incubator, of α-synuclein lead only to minor changes on the aggregation kinetics rates in comparison to static conditions. These results forward the understanding of α-synuclein fibrillization, paving the way for the development of high-throughput assays for the screening of pharmacological approaches targeting Parkinson's disease.
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143
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Kamada A, Levin A, Toprakcioglu Z, Shen Y, Lutz-Bueno V, Baumann KN, Mohammadi P, Linder MB, Mezzenga R, Knowles TPJ. Modulating the Mechanical Performance of Macroscale Fibers through Shear-Induced Alignment and Assembly of Protein Nanofibrils. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2020; 16:e1904190. [PMID: 31595701 DOI: 10.1002/smll.201904190] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Revised: 09/27/2019] [Indexed: 05/09/2023]
Abstract
Protein-based fibers are used by nature as high-performance materials in a wide range of applications, including providing structural support, creating thermal insulation, and generating underwater adhesives. Such fibers are commonly generated through a hierarchical self-assembly process, where the molecular building blocks are geometrically confined and aligned along the fiber axis to provide a high level of structural robustness. Here, this approach is mimicked by using a microfluidic spinning method to enable precise control over multiscale order during the assembly process of nanoscale protein nanofibrils into micro- and macroscale fibers. By varying the flow rates on chip, the degree of nanofibril alignment can be tuned, leading to an orientation index comparable to that of native silk. It is found that the Young's modulus of the resulting fibers increases with an increasing level of nanoscale alignment of the building blocks, suggesting that the mechanical properties of macroscopic fibers can be controlled through varying the level of ordering of the nanoscale building blocks. Capitalizing on strategies evolved by nature, the fabrication method allows for the controlled formation of macroscopic fibers and offers the potential to be applied for the generation of further novel bioinspired materials.
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144
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Baumann K, Piantanida L, García-Nafría J, Sobota D, Voïtchovsky K, Knowles TPJ, Hernández-Ainsa S. Coating and Stabilization of Liposomes by Clathrin-Inspired DNA Self-Assembly. ACS NANO 2020; 14:2316-2323. [PMID: 31976654 PMCID: PMC7302506 DOI: 10.1021/acsnano.9b09453] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2019] [Accepted: 01/24/2020] [Indexed: 05/17/2023]
Abstract
The self-assembly of the protein clathrin on biological membranes facilitates essential processes of endocytosis and has provided a source of inspiration for materials design by the highly ordered structural appearance. By mimicking the architecture of the protein building blocks and clathrin self-assemblies to coat liposomes with biomaterials, advanced hybrid carriers can be derived. Here, we present a method for fabricating DNA-coated liposomes by hydrophobically anchoring and subsequently connecting DNA-based triskelion structures on the liposome surface inspired by the assembly of the protein clathrin. Dynamic light scattering, ζ-potential, confocal microscopy, and cryo-electron microscopy measurements independently demonstrate successful DNA coating. Nanomechanical measurements conducted with atomic force microscopy show that the DNA coating enhances the mechanical stability of the liposomes relative to uncoated ones. Furthermore, we provide the possibility to reverse the coating process by triggering the disassembly of the DNA coats through a toehold-mediated displacement reaction. Our results describe a straightforward, versatile, and reversible approach for coating and stabilizing lipid vesicles through the assembly of rationally designed DNA structures. This method has potential for further development toward the ordered arrangement of tailored functionalities on the surface of liposomes and for applications as hybrid nanocarriers.
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145
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Ghadami SA, Chia S, Ruggeri FS, Meisl G, Bemporad F, Habchi J, Cascella R, Dobson CM, Vendruscolo M, Knowles TPJ, Chiti F. Transthyretin Inhibits Primary and Secondary Nucleations of Amyloid-β Peptide Aggregation and Reduces the Toxicity of Its Oligomers. Biomacromolecules 2020; 21:1112-1125. [PMID: 32011129 PMCID: PMC7997117 DOI: 10.1021/acs.biomac.9b01475] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
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Alzheimer’s
disease is associated with the deposition of
the amyloid-β peptide (Aβ) into extracellular senile plaques
in the brain. In vitro and in vivo observations have indicated that
transthyretin (TTR) acts as an Aβ scavenger in the brain, but
the mechanism has not been fully resolved. We have monitored the aggregation
process of Aβ40 by thioflavin T fluorescence, in
the presence or absence of different concentrations of preformed seed
aggregates of Aβ40, of wild-type tetrameric TTR (WT-TTR),
and of a variant engineered to be stable as a monomer (M-TTR). Both
WT-TTR and M-TTR were found to inhibit specific steps of the process
of Aβ40 fibril formation, which are primary and secondary
nucleations, without affecting the elongation of the resulting fibrils.
Moreover, the analysis shows that both WT-TTR and M-TTR bind to Aβ40 oligomers formed in the aggregation reaction and inhibit
their conversion into the shortest fibrils able to elongate. Using
biophysical methods, TTR was found to change some aspects of its overall
structure following such interactions with Aβ40 oligomers,
as well as with oligomers of Aβ42, while maintaining
its overall topology. Hence, it is likely that the predominant mechanism
by which TTR exerts its protective role lies in the binding of TTR
to the Aβ oligomers and in inhibiting primary and secondary
nucleation processes, which limits both the toxicity of Aβ oligomers
and the ability of the fibrils to proliferate.
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146
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Dobson CM, Knowles TPJ, Vendruscolo M. The Amyloid Phenomenon and Its Significance in Biology and Medicine. Cold Spring Harb Perspect Biol 2020; 12:cshperspect.a033878. [PMID: 30936117 DOI: 10.1101/cshperspect.a033878] [Citation(s) in RCA: 80] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The misfolding of proteins is now recognized to be the origin of a large number of medical disorders. One particularly important group of such disorders is associated with the aggregation of misfolded proteins into amyloid structures, and includes conditions ranging from Alzheimer's and Parkinson's diseases to type II diabetes. Such conditions already affect over 500 million people in the world, a number that is rising rapidly, and at present these disorders cannot be effectively treated or prevented. This review provides an overview of this field of science and discusses recent progress in understanding the nature and properties of the amyloid state, the kinetics and mechanism governing its formation, the origins of its links with disease, and the manner in which its formation may be inhibited or suppressed. This latter topic is of particular importance, both to enhance our knowledge of the maintenance of protein homeostasis in living organisms and also to address the development of therapeutic strategies through which to combat the loss of homeostasis and the associated onset and progression of disease.
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Baum J, Chiti F, De Simone A, Knowles TPJ, Kumita JR, Radford SE, Robinson CV, Salvatella X, Valelli K, Vendruscolo M, Pastore A, Tartaglia GG. Homage to Chris Dobson. Front Mol Biosci 2020; 6:137. [PMID: 31921887 PMCID: PMC6921691 DOI: 10.3389/fmolb.2019.00137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Accepted: 11/18/2019] [Indexed: 11/25/2022] Open
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148
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Chakraborty T, Chen B, Daetwyler S, Chang BJ, Vanderpoorten O, Sapoznik E, Kaminski CF, Knowles TPJ, Dean KM, Fiolka R. Converting lateral scanning into axial focusing to speed up three-dimensional microscopy. LIGHT, SCIENCE & APPLICATIONS 2020; 9:165. [PMID: 33024553 PMCID: PMC7501866 DOI: 10.1038/s41377-020-00401-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Revised: 08/25/2020] [Accepted: 09/02/2020] [Indexed: 05/04/2023]
Abstract
In optical microscopy, the slow axial scanning rate of the objective or the sample has traditionally limited the speed of volumetric imaging. Recently, by conjugating either a movable mirror to the image plane in a remote-focusing geometry or an electrically tuneable lens (ETL) to the back focal plane, rapid axial scanning has been achieved. However, mechanical actuation of a mirror limits the axial scanning rate (usually only 10-100 Hz for piezoelectric or voice coil-based actuators), while ETLs introduce spherical and higher-order aberrations that prevent high-resolution imaging. In an effort to overcome these limitations, we introduce a novel optical design that transforms a lateral-scan motion into a spherical aberration-free axial scan that can be used for high-resolution imaging. Using a galvanometric mirror, we scan a laser beam laterally in a remote-focusing arm, which is then back-reflected from different heights of a mirror in the image space. We characterize the optical performance of this remote-focusing technique and use it to accelerate axially swept light-sheet microscopy by an order of magnitude, allowing the quantification of rapid vesicular dynamics in three dimensions. We also demonstrate resonant remote focusing at 12 kHz with a two-photon raster-scanning microscope, which allows rapid imaging of brain tissues and zebrafish cardiac dynamics with diffraction-limited resolution.
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149
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Toprakcioglu Z, Challa P, Xu C, Knowles TPJ. Label-Free Analysis of Protein Aggregation and Phase Behavior. ACS NANO 2019; 13:13940-13948. [PMID: 31738513 DOI: 10.1021/acsnano.9b05552] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Phase transitions of protein molecules are central to biological function and malfunction. One such transition commonly encountered in nature is the conversion of soluble monomeric states into solid phases, which include crystals and amyloid fibrils, the latter of which are associated with the onset and development of neurodegenerative diseases. Monitoring aggregate formation and protein phase behavior is essential in gaining mechanistic insights into these fundamental processes. Fluorescence techniques have proven invaluable in observing biological molecules; yet, most such approaches rely on the use of an extrinsic fluorophore that binds to the molecule of interest, the installation of which can perturb the molecular systems under study. However, most proteins also possess aromatic amino acids within their peptide sequence and therefore exhibit intrinsic fluorescence. Here, we show that by measuring in space and time tryptophan autofluorescence for three proteins, reconstituted silk fibroin, β-lactoglobulin, and lysozyme, fibrillar self-assembly can be monitored accurately and without the need for extrinsic dyes. When fibrillar protein self-assembly takes place, hydrophobic burial occurs, resulting in the minimization of exposed tryptophan residues to the solvent and consequently leading to an increase in protein autofluorescence. Moreover, by employing a droplet-microfluidic approach to confine protein self-assembly in space, we demonstrate that intrinsic fluorescence can be used to image protein nanofibrils in a label-free manner and that the microstructural analysis obtained from intrinsic fluorescence microscopy correlates well with that from samples treated with extrinsic dyes. Finally, our results show that protein autofluorescence is not limited to the observation of β-sheet-rich structures, but can also be used to distinguish between different types of solid phases including spherulites and crystals, making this approach suitable for overall characterization of protein phase transition phenomena.
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150
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Michaels TCT, Dear AJ, Knowles TPJ. Universality of filamentous aggregation phenomena. Phys Rev E 2019; 99:062415. [PMID: 31330719 DOI: 10.1103/physreve.99.062415] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Indexed: 12/24/2022]
Abstract
We use perturbative renormalization group theory to study the kinetics of protein aggregation phenomena in a unified manner across multiple timescales. Using this approach, we find that, irrespective of the specific molecular details or experimental conditions, filamentous assembly systems display universal behavior in time. Moreover, we show that the universality classes for protein aggregation correspond to simple autocatalytic processes and that the diversity of behavior in these systems is determined solely by the reaction order for secondary nucleation with respect to the protein concentration, which labels all possible universality classes. We validate these predictions on experimental data for the aggregation of several different proteins at several different initial concentrations, which by appropriate coordinate transformations we are able to collapse onto universal kinetic growth curves. These results establish the power of the perturbative renormalization group in distilling the ultimately simple temporal behavior of complex protein aggregation systems, creating the possibility to study the kinetics of general self-assembly phenomena in a unified fashion.
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