Search results for "atomic force"
showing 10 items of 308 documents
Force measurements and tip shape approximation with the atomic force microscope
2011
The Atomic Force Microscope (AFM) is an instrument with huge impact on modern research in the nanosciences and in nanotechnology. In AFM, a tip which is sharp on a scale of nanometers or tens of nanometers, is scanning along the surface which is imaged. A few among the large numbers of factors that potentially affect the interaction between the tip and the surface were studied in the experimental work that form this Thesis. Friction and elasticity measurements with AFM and the approximation of the tip shape are discussed. Also the contribution of the imaging environment is studied. A commercial AFM was modified into a so called environmental-AFM (env- AFM) , where the imaging conditions, su…
Synthetic/ECM-inspired hybrid platform for hollow microcarriers with ROS-triggered nanoporation hallmarks
2017
Reactive oxygen species (ROS) are key pathological signals expressed in inflammatory diseases such as cancer, ischemic conditions and atherosclerosis. An ideal drug delivery system should not only be responsive to these signals but also should not elicit an unfavourable host response. This study presents an innovative platform for drug delivery where a natural/synthetic composite system composed of collagen type I and a synthesized polythioether, ensures a dual stimuli-responsive behaviour. Collagen type I is an extracellular matrix constituent protein, responsive to matrix metalloproteinases (MMP) cleavage per se. Polythioethers are stable synthetic polymers characterized by the presence o…
Langmuir-Blodgett films of biocompatible poly(HPMA)-block-poly(lauryl methacrylate) and poly(HPMA)-random-poly(lauryl methacrylate): influence of pol…
2010
Membranes based on functional biocompatible polymers can be regarded as a useful model system to study biological interactions, e.g. antibody-antigen interactions or protein polymer interactions. These model systems may give a better insight into these processes and may help to find suitable polymeric structures offering biocompatibility as well as reduced polymer protein interaction. In this respect, Langmuir-Blodgett (LB) layer formation at the air/water (A/W) interface is studied in respect to polymer architecture in this article. For this purpose, narrowly distributed N-(2-hydroxypropyl)-methacrylamide (HPMA) random and block copolymers have been prepared by the RAFT polymerization meth…
On-Surface Synthesis of Oligo(indenoindene)
2020
Fully conjugated ladder polymers (CLP) possess unique optical and electronic properties, and are considered promis-ing materials for applications in (opto)electronic devices. Poly(indenoindene) is a CLP consisting of an alternating array of five- and six-membered rings, which has remained elusive so far. Here, we report an on-surface synthesis of oligo(indenoindene) on Au(111). Its structure and a low elec-tronic bandgap have been elucidated by low-temperature scanning tunneling microscopy and spectroscopy and non-contact atomic force microscopy, complemented by density functional theory calculations. Achieving defect-free seg-ments of oligo(indenoindene) offers an exclusive insight into th…
Hierarchical structure formation of cylindrical brush polymer-surfactant complexes.
2009
The complex formation of cylindrical brush polymers with poly(l-lysine) side chains (PLL) and sodium dodecyl sulfate (SDS) can induce a helical conformation of the cylindrical brush polymer in aqueous solution (Gunari, N.; Cong, Y.; Zhang, B.; Fischer, K.; Janshoff, A.; Schmidt, M. Macromol. Rapid Commun. 2008, 29, 821-825). Herein, we have systematically investigated the influence of surfactant, salt, and pH on the supramolecular structure formation. The cylindrical brush polymers and their complexes with surfactants were directly visualized by atomic force microscopy in air and in aqueous solution. The alkyl chain length (measured by the carbon number, n) of the surfactant plays a key rol…
Redox Materials by the Covalent Entrapment of Redox-Active Dirhodium(II,II) Species in a Siloxane Network
2004
Hydrolysis and polycondensation of the coupling agent (aminopropyl)triethoxysilane (APS), axially coordinated to the redox-active complex [Rh 2 (form) 2 (CH 3 COO) 2 -(APS) 2 ], lead to the insertion of redox-active inorganic microdomains into a siloxane network; the new polymers undergo cyclic redox reactions indicating that dirhodium(II,II) centres retain their redox activity even when incorporated into siloxane networks.
Controllable membrane remodeling by a modified fragment of the apoptotic protein Bax.
2021
Intrinsic apoptosis is orchestrated by a group of proteins that mediate the coordinated disruption of mitochondrial membranes. Bax is a multi-domain protein that, upon activation, disrupts the integrity of the mitochondrial outer membrane by forming pores. We strategically introduced glutamic acids into a short sequence of the Bax protein that constitutively creates membrane pores. The resulting BaxE5 peptide efficiently permeabilizes membranes at acidic pH, showing low permeabilization at neutral pH. Atomic force microscopy (AFM) imaging showed that at acidic pH BaxE5 established several membrane remodeling modalities that progressively disturbed the integrity of the lipid bilayer. The AFM…
Micropatterning of neurons using organic substrates in culture
1997
Abstract In this study, we have used spatially defined surfaces of organic thin films to micropattern the outgrowth of central nervous system neurons in culture. Glass substrates were first chemically modified with synthetic peptides derived from an extra-cellular matrix protein laminin to couple a functionality that promotes a neuron-substrate interaction. The modification procedure was verified using X-ray photoelectron spectroscopy. The functionality of the modified glass surfaces was examined by growing neurons dissociated from mammalian central nervous tissues in culture. Spatially defined surfaces of the peptide were then fabricated by selectively attaching the peptide to coplanar sur…
Photosensitive polyurethanes for optical record
2011
The method of synthesis of photosensitive polyurethanes polymers on glycerine, toluenediisocyanate and Disperse Red 1 base has been described. Two types of polymers with different amount of Disperse Red 1 fragments in macromolecules were compared. Films of the polymers were obtained from solutions in organic solvents on glass substrate. The dry film thickness was in the range of 3,5 - 4.5 μm. The transmission spectrums of the films were studied. Possibility of formation of side product in the process of synthesis was observed. The photobirefringence measurements of polymers films were performed. Surface relief grating (SRG) formation was observed during polarization holographic recording pr…
On the Use of the Nanoindentation Unloading Curve to Measure the Young's Modulus of Polymers on a Nanometer Scale
2005
Summary: The nanoindentation test is a fundamental tool to assess the link between morphology and mechanical properties. The preliminary results of a more exhaustive study about the applicability to polymers of the most used procedure to determine elastic modulus by indentation are reported in this short communication. A departure of the experimental conditions from the theoretical assumptions and results that give rise to the Oliver and Pharr analysis is shown to occur under a wide range of experimental conditions, with applied loads and penetration depths covering several orders of magnitude and using different indenter geometries. Unloading curves with exponents significantly larger than…