26 research outputs found
Chemical kinetic theory of aging
A theory of aging based on the principles of the kinetics of chemical
reactions and the rules of natural selection of organisms is proposed. The
theory is based on a hypothesis that the biochemical processes in the organism
can be described in the terms of chemical reaction kinetics. The evolutionary
process of organisms is determined by the goal of continuing life, and the
natural selection forced organisms to develop in an optimized way for survival
and reproduction, after which any further development of the organisms did not
matter for natural selection and therefore was not regulated by it.
Accordingly, the ongoing biochemical processes in the organism after giving
birth were not stabilised and continued casual, which, in the case of complex
systems of biochemical processes, led to imbalances and biochemical processes
that did not contribute to health in the organism, resulting in aging. Based on
this view, it is necessary to look for the key biochemical processes that
regulate the vital activity of the organism. Balancing of these processes in
the period after giving birth can artificially lead to the stabilization of the
kinetics of biochemical reactions, and consequently, the continuation of life
almost indefinitely
Composite Materials With Uncured Epoxy Matrix Exposed in Stratosphere During NASA Stratospheric Balloon Flight
A cassette of uncured composite materials with epoxy resin matrixes was exposed in the stratosphere (40 km altitude) over three days. Temperature variations of -76 to 32.5C and pressure up to 2.1 torr were recorded during flight. An analysis of the chemical structure of the composites showed, that the polymer matrix exposed in the stratosphere becomes crosslinked, while the ground control materials react by way of polymerization reaction of epoxy groups. The space irradiations are considered to be responsible for crosslinking of the uncured polymers exposed in the stratosphere. The composites were cured on Earth after landing. Analysis of the cured composites showed that the polymer matrix remains active under stratospheric conditions. The results can be used for predicting curing processes of polymer composites in a free space environment during an orbital space flight
Mechanisms for covalent immobilization of horseradish peroxi-dase on ion beam treated polyethylene
The mechanism that provides the observed strong binding of biomolecules to
polymer sur-faces modified by ion beams is investigated. The surface of
polyethylene (PE) was modified by plasma immersion ion implantation with
nitrogen ions. Structure changes including car-bonization and oxidation were
observed in the modified surface layer of PE by Raman spec-troscopy, FTIR ATR
spectroscopy, atomic force microscopy, surface energy measurement and XPS
spectroscopy. An observed high surface energy of the modified polyethylene was
attributed to the presence of free radicals on the surface. The surface energy
decay with stor-age time after PIII treatment was explained by a decay of the
free radical concentration while the concentration of oxygen-containing groups
increased with storage time. Horseradish per-oxidase was covalently attached
onto the modified PE surface. The enzymatic activity of co-valently attached
protein remained high. A mechanism based on the covalent attachment by the
reaction of protein with free radicals in the modified surface is proposed.
Appropriate blocking agents can block this reaction. All aminoacid residues can
take part in the covalent attachment process, providing a universal mechanism
of attachment for all proteins. The long-term activity of the modified layer to
attach protein (at least 2 years) is explained by stabilisa-tion of unpaired
electrons in sp2 carbon structures. The native conformation of attached
pro-tein is retained due to hydrophilic interactions in the interface region. A
high concentration of free radicals on the surface can give multiple covalent
bonds to the protein molecule and de-stroy the native conformation and with it
the catalytic activity. The universal mechanism of protein attachment to free
radicals could be extended to various methods of radiation damage of polymers
EPDM Rubber Modified by Nitrogen Plasma Immersion Ion Implantation
Ethylene-propylene diene monomer rubber (EPDM) was treated by plasma immersion ion implantation (PIII) with nitrogen ions of 20 keV energy and fluence from 1013 to 1016 ions/cm2. The Fourier-transform infrared attenuated total reflection spectra, atomic force microscopy and optical microscopy showed significant structure changes of the surface. The analysis of an interface of PIII treated EPDM rubber with polyurethane binder showed a cohesive character of the adhesion joint fracture at the presence of solvent and interpreted as covalent bond network formation between the PIII treated rubber and the adhesive
Bound (“Glassy”) Rubber as a Free Radical Cross-linked Rubber Layer on a Carbon Black
A model of rubber with a cross-linked rubber layer on a carbon black filler has been proposed. The cross-links are the result of free radical reactions generated by carbon atoms with unpaired electrons at the edge of graphitic sheets in a carbon black filler. The experimental study of the cross-linking reactions in polyisoprene was done on a flat carbonized surface after ion beam implantation. The cross-linking process in the polyisoprene macromolecules between two particles was simulated. The model with a cross-linked rubber layer on a carbon filler as a “glassy layer” explains the mechanical properties of the rubber materials
Effect of plasma immersion ion implantation on polycaprolactone with various molecular weights and crystallinity
Polycaprolactone with five different molecular weights was spin-coated on silicon wafers and plasma immersion ion implanted (PIII) with ion fluence in the range 5 × 1014–2 × 1016 ions/cm2. The effects of PIII treatment on the optical properties, chemical structure, crystallinity, morphology, gel fraction formation and wettability were investigated. As in the case of a number of previously studied polymers, oxidation and hydrophobic recovery of the PIII treated PCL follow second order kinetics. CAPA 6250, which has the lowest molecular weight and the highest degree of crystallinity of the untreated PCL films studied, has the highest carbonization of the modified layer after PIII treatment. Untreated medical grade PCL films, mPCL PC12 (Perstorp) and mPCL OsteoporeTM have similar chemical structures and crystallinity. Accordingly, the chemical and structural transformations caused by PIII treatment and post-treatment oxidation are almost identical for these two polymers. In general, PIII treatment destroys the nano-scale lamellar structure and results in a reduction of PCL crystallinity. Examination after washing PIII treated PCL films in toluene confirmed our hypothesis that cross-linking due to PIII treatment is significantly higher in semi-crystalline PCL as compared with amorphous polymers
Extracellular Vesicle-Based Coatings Enhance Bioactivity of Titanium Implants—SurfEV
Extracellular vesicles (EVs) are nanoparticles released by cells that contain a multitude of biomolecules, which act synergistically to signal multiple cell types. EVs are ideal candidates for promoting tissue growth and regeneration. The tissue regenerative potential of EVs raises the tantalizing possibility that immobilizing EVs on implant surfaces could potentially generate highly bioactive and cell-instructive surfaces that would enhance implant integration into the body. Such surfaces could address a critical limitation of current implants, which do not promote bone tissue formation or bond bone. Here, we developed bioactive titanium surface coatings (SurfEV) using two types of EVs: secreted by decidual mesenchymal stem cells (DEVs) and isolated from fermented papaya fluid (PEVs). For each EV type, we determined the size, morphology, and molecular composition. High concentrations of DEVs enhanced cell proliferation, wound closure, and migration distance of osteoblasts. In contrast, the cell proliferation and wound closure decreased with increasing concentration of PEVs. DEVs enhanced Ca/P deposition on the titanium surface, which suggests improvement in bone bonding ability of the implant (i.e., osteointegration). EVs also increased production of Ca and P by osteoblasts and promoted the deposition of mineral phase, which suggests EVs play key roles in cell mineralization. We also found that DEVs stimulated the secretion of secondary EVs observed by the presence of protruding structures on the cell membrane. We concluded that, by functionalizing implant surfaces with specialized EVs, we will be able to enhance implant osteointegration by improving hydroxyapatite formation directly at the surface and potentially circumvent aseptic loosening of implants