Characterization of Multiblock (Segmented) Copolyurethane- Imides and Nanocomposites Based Thereof Using AFM, Nanotribology, and Nanoindentation Methods

This chapter reviews our results on the morphology, tribological, and local mechanical property investigations of new copoly(urethane-imide)s (coPUIs) and nanocomposites based thereof using atomic force microscopy (AFM) and nanoindentation (NI) methods. AFM in the contact mode of lateral forces revealed the presence of different contrast phases on the surface of synthesized films which depends on the chemical structure of monomers used. Single-walled carbon nanotubes (SWCNTs), carbon nanofibers, graphene, tungsten disulfide and tungsten diselenide were introduced into coPUI matrices. Dependencies of microhardness and modulus of elasticity on the depth of indentation have been obtained. It was found that for each synthesized coPUI, there is only one type of carbon nanomaterials that exerts the greatest influence on their characteristics. The improvement of mechanical properties is found to mainly depend on the nature of the polymer matrix and filler. Our results showed that effective methods for improving of tribological characteristics can be either modification by SWCNTs (up to 1 wt.%) or heating at 30°C. Synthesized coPUI films and nanocomposites are very promising materials and can be used as thermoplastic elastomers for tribological applications, and their physical-mechanical properties can be controlled both by temperature and by mechanical action

Polyurethane–poly(2-hydroxyethyl methacrylate) semi- IPN–nanooxide composites

Two sets of hybrid polyurethane–poly(2-hydroxyethyl methacrylate) semi-interpenetrating polymer network–nanooxide composites with 0.25 or 3 wt% nanosilica or nanoalumina functionalised with OH, NH2 or CHLCH2 groups were prepared. A combination of atomic force microscopy, infrared spectroscopy, thermally stimulated depolarisation current measurement, differential scanning calorimetry and creep rate spectroscopy analysis of the nanostructure and properties of the composites was performed. The pronounced dynamic heterogeneity and the strong impact of oxide additives, basically suppression of the dynamics and temperature-dependent increasing modulus of elasticity, were observed. The effects correlated with either interfacial interactions (for silica) or the nanostructure (for alumina). A low oxide content strongly affected the matrix due to the formation of an unusual cross-linked, via double covalent hybridisation of three components, structure of the nanocomposites

Plasma etched carbon microelectrode arrays for bioelectrical measurements

Carbon-based materials have attracted much attention in biological applications like interfacing electrodes with neurons and cell growth platforms due to their natural biocompatibility and tailorable material properties. Here we have fabricated sputtered carbon thin film electrodes for bioelectrical measurements. Reactive ion etching (RIE) recipes were optimized with Taguchi method to etch the close field unbalanced magnetron sputtered carbon thin film (nanocarbon, nC) consisting of nanoscale crystalline sp(2)-domains in amorphous sp(3)-bonded backbone. Plasma etching processes used gas mixtures of Ar/O-2/SF6/CHF3 for RIE and O-2/SF6 for ICP-RIE. The highest achieved etch rate for nanocarbon was >> 389 nm/min and best chromium etch mask selectivity was 135:1. Biocompatibility of the material was tested with rat neuronal cultures. Next, we fabricated multielectrode arrays (MEA) with carbon recording electrodes and metal wiring. Organotypic brain slices grown on the MEAs were viable and showed characteristic spontaneous electrical network activity. The results demonstrate that interactions with nanocarbon substrate support neuronal survival and maturation of functional neuronal networks. Thus the material can have wide applications in biomedical research.Peer reviewe

Novel carbon film induces precocious calcium oscillation to promote neuronal cell maturation

Different types of carbon materials are biocompatible with neural cells and can promote maturation. The mechanism of this effect is not clear. Here we have tested the capacity of a carbon material composed of amorphous sp3 carbon backbone, embedded with a percolating network of sp2 carbon domains to sustain neuronal cultures. We found that cortical neurons survive and develop faster on this novel carbon material. After 3 days in culture, there is a precocious increase in the frequency of neuronal activity and in the expression of maturation marker KCC2 on carbon films as compared to a commonly used glass surface. Accelerated development is accompanied by a dramatic increase in neuronal dendrite arborization. The mechanism for the precocious maturation involves the activation of intracellular calcium oscillations by the carbon material already after 1 day in culture. Carbon-induced oscillations are independent of network activity and reflect intrinsic spontaneous activation of developing neurons. Thus, these results reveal a novel mechanism for carbon material-induced neuronal survival and maturation.Peer reviewe

Plasma etched carbon microelectrode arrays for bioelectrical measurements

Carbon-based materials have attracted much attention in biological applications like interfacing electrodes with neurons and cell growth platforms due to their natural biocompatibility and tailorable material properties. Here we have fabricated sputtered carbon thin film electrodes for bioelectrical measurements. Reactive ion etching (RIE) recipes were optimized with Taguchi method to etch the close field unbalanced magnetron sputtered carbon thin film (nanocarbon, nC) consisting of nanoscale crystalline sp2-domains in amorphous sp3-bonded backbone. Plasma etching processes used gas mixtures of Ar/O2/SF6/CHF3 for RIE and O2/SF6 for ICP-RIE. The highest achieved etch rate for nanocarbon was ≫389 nm/min and best chromium etch mask selectivity was 135:1. Biocompatibility of the material was tested with rat neuronal cultures. Next, we fabricated multielectrode arrays (MEA) with carbon recording electrodes and metal wiring. Organotypic brain slices grown on the MEAs were viable and showed characteristic spontaneous electrical network activity. The results demonstrate that interactions with nanocarbon substrate support neuronal survival and maturation of functional neuronal networks. Thus the material can have wide applications in biomedical research.Peer reviewe

Gamma-Synuclein Dysfunction Causes Autoantibody Formation in Glaucoma Patients and Dysregulation of Intraocular Pressure in Mice

Dysregulation of intraocular pressure (IOP) is one of the main risk factors for glaucoma. γ-synuclein is a member of the synuclein family of widely expressed synaptic proteins within the central nervous system that are implicated in certain types of neurodegeneration. γ-synuclein expression and localization changes in the retina and optic nerve of patients with glaucoma. However, the mechanisms by which γ-synuclein could contribute to glaucoma are poorly understood. We assessed the presence of autoantibodies to γ-synuclein in the blood serum of patients with primary open-angle glaucoma (POAG) by immunoblotting. A positive reaction was detected for five out of 25 patients (20%) with POAG. Autoantibodies to γ-synuclein were not detected in a group of patients without glaucoma. We studied the dynamics of IOP in response to IOP regulators in knockout mice (γ-KO) to understand a possible link between γ-synuclein dysfunction and glaucoma-related pathophysiological changes. The most prominent decrease of IOP in γ-KO mice was observed after the instillation of 1% phenylephrine and 10% dopamine. The total protein concentration in tear fluid of γ-KO mice was approximately two times higher than that of wild-type mice, and the activity of neurodegeneration-linked protein α2-macroglobulin was reduced. Therefore, γ-synuclein dysfunction contributes to pathological processes in glaucoma, including dysregulation of IOP