Browsing by Author "Griffo, Alessandra"

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Adhesion Properties of Freestanding Hydrophobin Bilayers
(2018-07-24) Hähl, Hendrik; Vargas, Jose Nabor; Jung, Michael; Griffo, Alessandra; Laaksonen, Päivi; Lienemann, Michael; Jacobs, Karin; Seemann, Ralf; Fleury, Jean Baptiste
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Hydrophobins are a family of small-sized proteins featuring a distinct hydrophobic patch on the protein's surface, rendering them amphiphilic. This particularity allows hydrophobins to self-assemble into monolayers at any hydrophilic/hydrophobic interface. Moreover, stable pure protein bilayers can be created from two interfacial hydrophobin monolayers by contacting either their hydrophobic or their hydrophilic sides. In this study, this is achieved via a microfluidic approach, in which also the bilayers' adhesion energy can be determined. This enables us to study the origin of the adhesion of hydrophobic and hydrophilic core bilayers made from the class II hydrophobins HFBI and HFBII. Using different fluid media in this setup and introducing genetically modified variants of the HFBI molecule, the different force contributions to the adhesion of the bilayer sheets are studied. It was found that in the hydrophilic contact situation, the adhesive interaction was higher than that in the hydrophobic contact situation and could be even enhanced by reducing the contributions of electrostatic interactions. This effect indicates that the van der Waals interaction is the dominant contribution that explains the stability of the observed bilayers.
Binding Forces of Cellulose Binding Modules on Cellulosic Nanomaterials
(2019-02-11) Griffo, Alessandra; Rooijakkers, Bart J.M.; Hähl, Hendrik; Jacobs, Karin; Linder, Markus B.; Laaksonen, Päivi
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
In this study, the interaction forces between different cellulosic nanomaterials and a protein domain belonging to cellulose binding modules family 1 (CBM1) were investigated at the molecular scale. Cellulose binding modules are protein domains found in carbohydrate active enzymes having an affinity toward cellulosic materials. Here, the binding force of a fusion protein containing a cellulose binding module (CBM1) produced recombinantly in E. coli was quantified on different cellulose nanocrystals immobilized on surfaces. Adhesion of the CBM on cellulose with different degrees of crystallinity as well as on chitin nanocrystals was examined. This study was carried out by single molecule force spectroscopy using an atomic force microscope, which enables the detection of binding force of individual molecules. The study contains a preliminary quantification of the interactions at the molecular level that sheds light on the development of new nanocellulose-based nanocomposites with improved strength and elasticity.
Deposition of indigo thin films by Langmuir-Schaefer technique
(2019-01-29) Lim, Woojae
Kemian tekniikan korkeakoulu | Master's thesis
The main purpose of this thesis is to explore an opportunity to create a conductive thin film on the substrate for organic semiconductors with non-amphiphilic molecules of indigo by Langmuir-Schaefer deposition. The hypothesis of this study was that high surface pressure of a Langmuir film of indigo leaded to an ordered Langmuir-Schaefer film. To do the experiment, Indigo powders were dissolved in a chloroform solvent and stirred at room temperature. The substrates of glass and SiO$_2$ for deposition were silanized to imitate a dielectric layer between a gate and a semiconducting film. After Langmuir-Schaefer deposition, the samples were mainly characterized by ultraviolet–visible spectroscopy (UV-Vis) and atomic force microscopy (AFM). In UV-Vis characterization, the max absorption peak of the indigo film on the glass substrate was red-shifted to 670 nm from 600 nm of indigo solution due to the hydrogen bond between indigo molecules. The max absorption peak of an indigo film was red-shifted as decreasing surface pressure of Langmuir film and/or the number of deposition cycles. The AFM characterization revealed that the thickness of indigo thin film was around 5nm. It was also found that aggregates of indigo covered the surfaces of the samples and calculated root-mean-square surface roughness lay in between 2.6 to 18 nm. In sum, this study showed that Langmuir-Schaefer deposition succeeded in creating an indigo thin film, and low surface pressure of a Langmuir film consisting of non-amphiphilic molecules of indigo has a positive impact to have an ordered Langmuir-Schaefer film.
Design and Testing of a Bending-Resistant Transparent Nanocoating for Optoacoustic Cochlear Implants
(2019-01-01) Griffo, Alessandra; Liu, Yingying; Mahlberg, Riitta; Alakomi, Hanna L.; Johansson, Leena S.; Milani, Roberto
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
A nanosized coating was designed to reduce fouling on the surface of a new type of cochlear implant relying on optoacoustic stimulation. This kind of device imposes novel design principles for antifouling coatings, such as optical transparency and resistance to significant constant bending. To reach this goal we deposited on poly(dimethylsiloxane) a PEO-based layer with negligible thickness compared to the curvature radius of the cochlea. Its antifouling performance was monitored upon storage by quartz crystal microbalance, and its resistance upon bending was tested by fluorescence microscopy under geometrical constraints similar to those of implantation. The coating displayed excellent antifouling features and good stability, and proved suitable for further testing in real-environment conditions.
Effect of Phosphate on the Molecular Properties, Interactions, and Assembly of Engineered Spider Silk Proteins
(2024-07-08) Yin, Yin; Griffo, Alessandra; Gutiérrez Cruz, Adrián; Hähl, Hendrik; Jacobs, Karin; Linder, Markus B.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Phosphate plays a vital role in spider silk spinning and has been utilized in numerous artificial silk spinning attempts to replicate the remarkable mechanical properties of natural silk fiber. Its application in artificial processes has, however, yielded varying outcomes. It is thus necessary to investigate the origins and mechanisms behind these differences. By using recombinant silk protein SC-ADF3 derived from the garden spider Araneus diadematus, here, we describe its conformational changes under various conditions, elucidating the effect of phosphate on SC-ADF3 silk protein properties and interactions. Our results demonstrate that elevated phosphate levels induce the irreversible conformational conversion of SC-ADF3 from random coils to β-sheet structures, leading to decreased protein solubility over time. Furthermore, exposure of SC-ADF3 to phosphate stiffens already formed structures and reduces the ability to form new interactions. Our findings offer insights into the underlying mechanism through which phosphate-induced β-sheet structures in ADF3-related silk proteins impede fiber formation in the subsequent phases. From a broader perspective, our studies emphasize the significance of silk protein conformation for functional material formation, highlighting that the formation of β-sheet structures at the initial stages of protein assembly will affect the outcome of material forming processes.
On the Nanoscale Interactions and the Self-Assembly of Recombinant Proteins and Hybrid Nanostructures: an AFM Study
(2019) Griffo, Alessandra
School of Chemical Technology | Doctoral dissertation (article-based)
The study presented in this Thesis is focussed on the characterization and the design of new polymeric materials, taking inspiration from the Nature. Here, new hybrid architectures in which adhesive and elastic proteins coexist with inorganic or cellulosic surfaces, or where ligand capped metal nanoclusters self-assemble in monolayer films, are investigated. Genetic engineering is used to produce new synthetic fusion proteins having specific functionalities starting from microbes. The particle self-assembly is indeed inspired on the symmetrical and directional arrangement of natural architectures such as globular proteins and viral capsids. The study is fundamental and performed at nanoscale level. Single molecular interactions on surfaces are analysed as well as the structure and the conformation of individual fusion proteins. The self-assembly process of protein films is deeply studied as well as the stiffness and elastic modulus of self-assembled silver nanocluster composite films. The candidate proteins for making biohybrids are hydrophobins, cellulose binding modules and resilins. Hydrophobins (HFB), with their unique assembly mechanism, are well known for their hydrophobic patch, that strongly bind to hydrophobic surfaces. Cellulose binding modules (CBMs), turned out to be highly interesting domains for their binding affinity to their primary substrate, the cellulose. On the other hand, resilin, for its ability to dissipate energy upon tensile stress, could find use as a sacrificial bond in high strength materials. Atomic force microscope (AFM) is here used for detecting the binding and interaction forces between proteins and surfaces. For the resilin, this such powerful tool is also used to characterize the length of the biopolymer under different environments, upon stretching. AFM was also employed for determining the elastic modulus of the nanocluster monolayers. According to the results achieved, HFBI ranged a quite high adhesion force value near 100 pN on the chosen hydrophobic surfaces, whereas the CBMs reported a binding affinity for different kind of cellulosic surfaces between 40-50 pN. The silver nanoclusters ligand-capped films revealed an elastic modulus value around 20 GPa. The Thesis sheds light on the importance of replacing plastic materials with new bio hybrids for a more sustainable approach, in an age where the ecosystem risks to be compromised by pollution and not biodegradable waste.
Single-Molecule Force Spectroscopy Study on Modular Resilin Fusion Protein
(2017-10-19) Griffo, Alessandra; Hähl, Hendrik; Grandthyll, Samuel; Müller, Frank; Paananen, Arja; Ilmen, Marja; Szilvay, Géza R.; Landowski, Christopher P.; Penttilä, Merja; Jacobs, Karin; Laaksonen, Päivi
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The adhesive and mechanical properties of a modular fusion protein consisting of two different types of binding units linked together via a flexible resilin-like-polypeptide domain are quantified. The adhesive domains have been constructed from fungal cellulose-binding modules (CBMs) and an amphiphilic hydrophobin HFBI. This study is carried out by single-molecule force spectroscopy, which enables stretching of single molecules. The fusion proteins are designed to self-assemble on the cellulose surface, leading into the submonolayer of proteins having the HFBI pointing away from the surface. A hydrophobic atomic force microscopy (AFM) tip can be employed for contacting and lifting the single fusion protein from the HFBI-functionalized terminus by the hydrophobic interaction between the tip surface and the hydrophobic patch of the HFBI. The work of rupture, contour length at rupture and the adhesion forces of the amphiphilic end domains are evaluated under aqueous environment at different pHs.
Strong and Elastic Membranes via Hydrogen Bonding Directed Self-Assembly of Atomically Precise Nanoclusters
(2022-08) Som, Anirban; Griffo, Alessandra; Chakraborty, Indranath; Hähl, Hendrik; Mondal, Biswajit; Chakraborty, Amrita; Jacobs, Karin; Laaksonen, Päivi; Ikkala, Olli; Pradeep, Thalappil; Nonappa
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
2D nanomaterials have provided an extraordinary palette of mechanical, electrical, optical, and catalytic properties. Ultrathin 2D nanomaterials are classically produced via exfoliation, delamination, deposition, or advanced synthesis methods using a handful of starting materials. Thus, there is a need to explore more generic avenues to expand the feasibility to the next generation 2D materials beyond atomic and molecular-level covalent networks. In this context, self-assembly of atomically precise noble nanoclusters can, in principle, suggest modular approaches for new generation 2D materials, provided that the ligand engineering allows symmetry breaking and directional internanoparticle interactions. Here the self-assembly of silver nanoclusters (NCs) capped with p-mercaptobenzoic acid ligands (Na4Ag44-pMBA30) into large-area freestanding membranes by trapping the NCs in a transient solvent layer at air–solvent interfaces is demonstrated. The patchy distribution of ligand bundles facilitates symmetry breaking and preferential intralayer hydrogen bondings resulting in strong and elastic membranes. The membranes with Young's modulus of 14.5 ± 0.2 GPa can readily be transferred to different substrates. The assemblies allow detection of Raman active antibiotic molecules with high reproducibility without any need for substrate pretreatment.