Polymers Biological Effects

Radioactivity The ability possessed by some natural and synthetic isotopes to undergo nuclear transformation to other isotopes, 513 applications, 516-518 biological effects, 528-529 bombardment reactions, 514-516 diagnostic uses, 516t discovery of, 517 modes of decay, 513-514 nuclear stability and, 29-30 rate of decay, 518-520,531q Radium, 521-522 Radon, 528 Ramsay, William, 190 Random polymer 613-614 Randomness factor, 452-453 Raoult s law A relation between the vapor pressure (P) of a component of a solution and that of the pure component (P°) at the same temperature P — XP°, where X is the mole fraction, 268... 

The potential of sonochemistry was identified over sixty years ago in a wide ranging paper entitled The Physical and Biological Effects of High Frequency Sound-Waves of Great Intensity [13]. Over the few years which followed this paper a great deal of pioneering work in sonochemistry was carried out and, as a result of this, two reviews on the applications of ultrasound in polymer and chemical processes were published... 

Fluorine is an essential element involved in several enzymatic reactions in various organs, it is present as a trace element in bone mineral, dentine and tooth enamel and is considered as one of the most efficient elements for the prophylaxis and treatment of dental caries. In addition to their direct effect on cell biology, fluoride ions can also modify the physico-chemical properties of materials (solubility, structure and microstructure, surface properties), resulting in indirect biological effects. The biological and physico-chemical roles of fluoride ions are the main reasons for their incorporation in biomaterials, with a pre-eminence for the biological role and often both in conjunction. This chapter focuses on fluoridated bioceramics and related materials, including cements. The specific role of fluorinated polymers and molecules will not be reviewed here. 

Fluorinated polymers are by nature inert and nontoxic materials. A certain toxicity may however be incorporated from additives added, e.g. perfluorooctanoic acid or traces of monomers. In addition, toxic organo-fluorine compounds may be generated from these polymers by high temperature decomposition.6-64- 16-118 Biological effects of fluorocarbon fibers have been described.119 Toxicities of polychlorotrifluoroethylenc oils (hydraulic fluids) have also been discussed.202... 

The direct absorption of moderate to low frequency, nonionizing, electromagnetic radiation - microwaves - by DNA polymer molecules is a potential source of biological effects. As an introductory study of this question, we have evaluated the absorption of isolated homopolymer straight chains of poly dG-poly dC. For some absorption processes we have also investigated some effects of a surrounding aqueous medium. 

The evaluation of laminate dispensers based on lure contents of aged samples has shown that the release rate for a given pheromone can be widely altered by formulation in various types of polymer membranes of differing thicknesses. The C and Cj aldehyde pheromones are chemically stable in the laminate, and a laminate can be selected for these aldehydes to give a half-life, t.from 1 to 8 weeks, depending on the duration of biological effectiveness needed. The C g alcohol is... 

The basic biology and pharmacology of Epo B (as the most potent and most widely studied natural epothilone) have been summarized in several previous review articles.As indicated in Section 1.1, the biological effects of the compound are based on its ability to bind to microtubules and alter the intrinsic stabihty and dynamic properties of these supramolecular structures. In cell-free in vitro systems, this is demonstrated by the prevention of Ca - or cold-induced depolymerization of preformed microtubule polymers as well as by the promotion of tubuhn polymerization (to form microtubule-like polymers) in the absence of either microtubule-associated proteins (MAPs) and/or guanosine triphosphate (GTP), at temperatures significantly below 37 °C, and in the presence of The latter... 

Chisty MNA, Bellantone RA, Taft DR, Plakogiannis FM. In vitro evaluation of the release of albuterol sulfate from polymer gels effect of fatty acids on drug transport across biological membranes. Drug Dev Ind Pharm 2002 28(10) 1221—1229. 

Figure 4 Typical radiation dose ranges for thedifferent utilizations of high-energy radiation in polymer processing. Doses for desinfection, sterilization and sprout prevention (biological effects) are given for comparison.

ZZ) this may be due to the fact that these authors used serum-containing culture media. Our results demonstrate that even chemically modified DIVEMA causes - at least in vitro - the same biological effect (release of cytotoxic factors) as DIVEMA itself. This aspect is especially important if one uses DIVEMA as a carrier polymer for antitumour agents hoping to retain immune stimulating properties. 

A number of polymer systems were tested for tissue biocompatibility and release kinetics. The best long-term release results were obtained with hydrophobic polymers. Examples included non-degradable ethylene-vinyl acetate or biodegradable polylactic acid. Certain hydrogels such as polyhy-droxyethylmethacrylate or polyvinylalcohol also worked effectively, but released proteins for shorter time periods. With the hydrophobic polymers, biologically active protein was released for more than 100 days (2). In other tests, larger molecules (2 million MW), such as polysaccharides and polynucleotides, were also successfully released for long time periods (2). 

The biological effects of radiation, both positive and negative, have been important, and this is reflected by chapters on the effects of radiation on porphyrins, carbohydrates, nucleobases, proteins and DNA. These are followed by the use of radiation chemistry in the development of anti-cancer drugs, in the treatment of water pollution, polymers and in food pasteurization and sterilization. 

Duncan R. Biological effects of soluble synthetic polymers as drug carriers. CRC Critical Rev Therap Drug Carrier Sys 1985 1(4) 281-310. 

Unlike the influence of morphology on mechanical behavior, the effect on biological behavior is a less mature area of endeavor. For absorbable polymers, the effect of crystalline structure on diffusion and reaction rates provides insight. The relative amount of crystalline phase influences the rate of diffusion of water into a hydrolytically unstable polymer. Furthermore, the rate of hydrolysis of a given ester group in the polymeric chain will depend on whether the group resides in a self-protecting crystal or whether it exists in an unprotected, easily accessed, amorphous phase. 

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