| 1. |
- Bäcklund, Fredrik, et al.
(författare)
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Amyloid fibrils as dispersing agents for oligothiophenes: control of photophysical properties through nanoscale templating and flow induced fibril alignment
- 2014
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 1364-5501 .- 0959-9428 .- 2050-7526 .- 2050-7534. ; 2:37, s. 7811-7822
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Tidskriftsartikel (refereegranskat)abstract
- Herein we report that protein fibrils formed from aggregated proteins, so called amyloid fibrils, serve as an excellent dispersing agent for hydrophobic oligothiophenes such as alpha-sexithiophene (6T). Furthermore, the protein fibrils are capable of orienting 6T along the fibril long axis, as demonstrated by flow-aligned linear dichroism spectroscopy and polarized fluorescence microscopy. The materials are prepared by solid state mixing of 6T with a protein capable of self-assembly. This results in a water soluble composite material that upon heating in aqueous acid undergoes self-assembly into protein fibrils non-covalently functionalized with 6T, with a typical diameter of 5-10 nm and lengths in the micrometre range. The resulting aqueous fibril dispersions are a readily available source of oligothiophenes that can be processed from aqueous solvent, and we demonstrate the fabrication of macroscopic structures consisting of aligned 6T functionalized protein fibrils. Due to the fibril induced ordering of 6T these structures exhibit polarized light emission.
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| 2. |
- Bäcklund, Fredrik, et al.
(författare)
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Conducting microhelices from self-assembly of protein fibrils
- 2017
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Ingår i: Soft Matter. - : Royal Society of Chemistry. - 1744-683X .- 1744-6848. ; 13:25, s. 4412-4417
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Tidskriftsartikel (refereegranskat)abstract
- Herein we utilize insulin to prepare amyloid based chiral heliceswith either right or left handed helicity. We demonstrate that thehelices can be utilized as structural templates for the conductingpolymer alkoxysulfonate poly(ethylenedioxythiophene) (PEDOT-S).The chirality of the helical assembly is transferred to PEDOT-S asdemonstrated by polarized optical microscopy (POM) and CircularDichroism (CD). Analysis of the helices by conductive atomic force(c-AFM) shows significant conductivity. In addition the morphologyof the template structure is stabilized by PEDOT-S. Theseconductive helical structures represent promising candidates in ourquest for THz resonators.
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| 3. |
- Bäcklund, Fredrik, et al.
(författare)
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Development and Application of Methodology for Rapid Screening of Potential Amyloid Probes
- 2014
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Ingår i: ACS COMBINATORIAL SCIENCE. - : ACS Publications. - 2156-8952 .- 2156-8944. ; 16:12, s. 721-729
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Tidskriftsartikel (refereegranskat)abstract
- Herein, we demonstrate that it is possible to rapidly screen hydrophobic fluorescent aromatic molecules with regards to their properties as amyloid probes. By grinding the hydrophobic molecule with the amyloidogenic protein insulin, we obtained a water-soluble composite material. When this material is dissolved and exposed to conditions promoting amyloid formation, the protein aggregates into amyloid fibrils incorporating the hydrophobic molecule. As a result, changes in the fluorescence spectra of the hydrophobic molecule can be correlated to the formation of amyloid fibrils, and the suitability of the hydrophobic molecular skeleton as an amyloid probe can thus be assessed. As a result, we discovered two new amyloid probes, of which one is the well-known laser dye DCM. The grinding method can also be used for rapid preparation of novel composite materials between dyes and proteins, which can be used in materials science applications such as organic electronics and photonics.
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| 4. |
- Bäcklund, Fredrik G., et al.
(författare)
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An Image-Analysis-Based Method for the Prediction of Recombinant Protein Fiber Tensile Strength
- 2022
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Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 15:3
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Tidskriftsartikel (refereegranskat)abstract
- Silk fibers derived from the cocoon of silk moths and the wide range of silks produced by spiders exhibit an array of features, such as extraordinary tensile strength, elasticity, and adhesive properties. The functional features and mechanical properties can be derived from the structural composition and organization of the silk fibers. Artificial recombinant protein fibers based on engineered spider silk proteins have been successfully made previously and represent a promising way towards the large-scale production of fibers with predesigned features. However, for the production and use of protein fibers, there is a need for reliable objective quality control procedures that could be automated and that do not destroy the fibers in the process. Furthermore, there is still a lack of understanding the specifics of how the structural composition and organization relate to the ultimate function of silk-like fibers. In this study, we develop a new method for the categorization of protein fibers that enabled a highly accurate prediction of fiber tensile strength. Based on the use of a common light microscope equipped with polarizers together with image analysis for the precise determination of fiber morphology and optical properties, this represents an easy-to-use, objective non-destructive quality control process for protein fiber manufacturing and provides further insights into the link between the supramolecular organization and mechanical functionality of protein fibers.
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| 5. |
- Bäcklund, Fredrik G., et al.
(författare)
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Controlling Amyloid Fibril Formation by Partial Stirring
- 2016
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Ingår i: Biopolymers. - : Wiley-Blackwell. - 0006-3525 .- 1097-0282. ; 105:5, s. 249-259
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Tidskriftsartikel (refereegranskat)abstract
- Many proteins undergoes self-assembly into fibrillar structures known as amyloid fibrils. During the self-assembly process related structures, known as spherulites, can be formed. Herein we report a facile method where the balance between amyloid fibrils and spherulites can be controlled by stirring of the reaction mixture during the initial stages of the self-assembly process. Moreover, we report how this methodology can be used to prepare non-covalently functionalized amyloid fibrils. By stirring the reaction mixture continuously or for a limited time during the lag phase the fibril length, and hence the propensity to form liquid crystalline phases, can be influenced. This phenomena is utilized by preparing films consisting of aligned protein fibrils incorporating the laser dye Nile red. The resulting films display polarized Nile red fluorescence.
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| 6. |
- Bäcklund, Fredrik Gustaf, et al.
(författare)
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Convection Induced Air-Water Interface Assembly of Amyloid Fibrils
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We report that hydrophobically modified amyloid fibrils form macroscopic films at the air-water interface. The hydrophobically modified fibrils are prepared in a two step process. First bovine insulin is ground with a hydrophobic compound. The resulting material is dissolved in acidic water and heated to induce assembly into fibrils incorporating the hydrophobic compounds. Upon dilution followed by asymmetric heating, resulting in convection flow, the fibrills form highly ordered films with thicknesses from 80 nm and up. The thickness of the film can be controlled by the fibril concentration and/or reaction time. The films contain anisotropic domains spanning several square centimeters. In addition, the films contains ordered assemblies of dyes that display emission of polarized light.
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| 7. |
- Bäcklund, Fredrik G., et al.
(författare)
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Tuning the aqueous self-assembly process of insulin by a hydrophobic additive
- 2015
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Ingår i: RSC ADVANCES. - : Royal Society of Chemistry. - 2046-2069. ; 5:112, s. 92254-92262
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Tidskriftsartikel (refereegranskat)abstract
- Biomolecular self-assembly is an efficient way of preparing soft-matter based materials. Herein we report a novel method, based on the use of insoluble additives in aqueous media, for influencing the self-assembly process. Due to their low solubility, the use of hydrophobic additives in aqueous media is problematic; however, by mixing the additive with the biomolecule in the solid state, prior to solvation, this problem can be circumvented. In the investigated self-assembly system, where bovine insulin self-assembles into spherical structures, the inclusion of the hydrophobic material α-sexithiophene (6T) results in significant changes in the self-assembly process. Under our reaction conditions, in the case of materials prepared from insulin-only the growth of spherulites typically stops at a diameter of 150μm. However, by adding 2 weight % of hydrophobic material, spherulite growth continues up to diameters in the mm-range. The spherulites incorporate 6T and are thus fluorescent. The method reported herein should be of interest to all scientists working in the field of self-assembly as the flexible materials preparation, based simply on co-grinding of commercially available materials, adds another option to influence the structure and properties of products formed by self-assembly reactions.
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| 8. |
- Bäcklund, Fredrik, et al.
(författare)
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PEDOT-S coated protein fibril microhelices
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We show here the preparation and characterization of micrometer sized conductive helices. We utilize protein fibrils as structural templates to create chiral helices with either right or left handed helicity. The helices are coated with the conductive polymer alkoxysulfonate poly(ethylenedioxythiophene) (PEDOT-S) to create micrometer sized conductive helices. The coating acts as a stabilizer for the template structure, facilitates the preparation of solid state films and shows significant conductivity. The helices have been investigated using Circular Dichroism (CD) and scanning electron microscopy (SEM) and the conductivity have been measured for solid state films.
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| 9. |
- Bäcklund, Fredrik
(författare)
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Preparation and Application of Functionalized Protein Fibrils
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Many proteins have an innate ability to self-assemble into fibrous structures known as amyloid fibrils. From a material science perspective, fibrils have several interesting characteristics, including a high stability, a distinct shape and tunable surface properties. Such structures can be given additional properties through functionalization by other compounds such as fluorophores. Combination of fibrils with a function yielding compound can be achieved in several ways. Covalent bond attachment is specific, but cumbersome. External surface adhesion is nonspecific, but simple. However, in addition, internal non-covalent functionalization is possible. In this thesis, particular emphasis is put on internal functionalization of fibrils; by co-grinding fibril forming proteins with a hydrophobic molecule, a protein-hydrophobic compound molecule composite can be created that retains the proteins innate ability to form fibrils. Subsequently formed fibrils will thus have the structural properties of the protein fibril as well as the properties of the incorporated compound. The functionalization procedures used throughout this thesis are applicable for a wide range of chromophores commonly used for organic electronics and photonics. The methods developed and the prepared materials are useful for applications within optoelectronics as well as biomedicine.Regardless of the methodology of functionalization, using functionalized fibrils in a controlled fashion for material design requires an intimate understanding of the formation process and knowledge of the tools available to control not only the formation but also any subsequent macroscale assembly of fibrils. The development and application of such tools are described in several of the papers included in this thesis. With the required knowledge in hand, the possible influence of fibrils on the functionalizing agents, and vice versa, can be probed. The characteristic traits of the functionalized fibril can be customized and the resulting material can be organized and steered towards a specific shape and form. This thesis describes how control over the process of formation, functionalization and organization of functionalized fibrils can be utilized to influence the hierarchical assembly of fibrils – ranging from spherical structures to spirals; the function – fluorescent or conducting; and macroscopic properties – optical birefringence and specific arrangement of functionalized fibrils in the solid state. In conclusion, the use of amyloid fibrils in material science has great potential. Herein is presented a possible route towards a fully bottom up approach ranging from the nanoscale to the macroscale.
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| 10. |
- Bäcklund, Tomas, et al.
(författare)
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Novel, clinically applicable method to measure step-width during the swing phase of gait
- 2020
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Ingår i: Physiological Measurement. - : Institute of Physics Publishing (IOPP). - 0967-3334 .- 1361-6579. ; 41:6
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Step-width during walking is an indicator of stability and balance in patients with neurological disorders, and development of objective tools to measure this clinically would be a great advantage. The aim of this study was to validate an in-house-developed gait analysis system (Striton), based on optical and inertial sensors and a novel method for stride detection, for measuring step-width during the swing phase of gait and temporal parameters.Approach: The step-width and stride-time measurements were validated in an experimental setup, against a 3D motion capture system and on an instrumented walkway. Further, test-retest and day-to-day variability were evaluated, and gait parameters were collected from 87 elderly persons (EP) and four individuals with idiopathic normal pressure hydrocephalus (iNPH) before/after surgery.Main results: Accuracy of the step-width measurement was high: in the experimental setup mean error was 0.08 +/- 0.25 cm (R = 1.00) and against the 3D motion capture system 0.04 +/- 1.12 cm (R = 0.98). Test-retest and day-to-day measurements were equal within +/- 0.5 cm. Mean difference in stride time was -0.003 +/- 0.008 s between Striton and the instrumented walkway. The Striton system was successfully applied in the clinical setting on individuals with iNPH, which had larger step-width (6.88 cm, n = 4) compared to EP (5.22 cm, n = 87).Significance: We conclude that Striton is a valid, reliable and wearable system for quantitative assessment of step-width and temporal parameters during gait. Initial measurements indicate that the newly defined step-width parameter differs between EP and patients with iNPH and before/after surgery. Thus, there is potential for clinical applicability in patients with reduced gait stability.
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