Biological response, influencing factors

Throughout the text we will relate polymer structure to the properties of the polymer. Polymer properties are related not only to the chemical nature of the polymer, but also to such factors as extent and distribution of crystallinity, distribution of polymer chain lengths, and nature and amount of additives, such as fillers, reinforcing agents, and plasticizers, to mention a few. These factors influence essentially all the polymeric properties to some extent including hardness, flammability, weatherability, chemical stability, biological response, comfort, flex life, moisture retention, appearance, dyeability, softening point, and electrical properties. 

However, it was immediately recognized by peptide chemists that, even in the cases where a direct (backbone)peptide -protein(backbone) interaction is not operative, the backbone conformation may dramatically influence the biological response. It is evident that the introduction of new, promising peptidomimetics is based primarily on the combined knowledge of the complementary conformational, topochemical, and electronic properties of the native peptide and of its address (in other words, of the receptor or the active site of the enzyme with which it interacts). Then, the design of peptidomimetics as potential bioactive compounds must take into particular account two structural factors (i) a favorable fit (tertiary structure) with respect to the corresponding complementary spatial situation at the active site (ii) the placement of structural elements (e.g., functional groups, polar and... 

Cell filterability is influenced by a variety of biological and technological factors (Nordt, 1983). Thus, in order to be reliable and reproducible, Nucleopore filtration techniques must fulfil certain criteria, and namely (1) the most part of the input cells must be recovered in the filtrate (2) cellular aggregation should be minimized by choosing conditions which permit relatively short filtration times (3) cell viability should be high and not lost on filtration (4) cell size distribution should not be influenced by filtration and (5) differences in cell to filter and cell to cell adhesion of different cell lines should not be responsible for differences in filterability. In order to fulfil these criteria, experimental parameters such as cell to pore ratio, filtration pressure and cell culmre conditions have to be standardized. The following optimal conditions have been established for filtration of B16 melanoma cells (mean cell diameter 17.4 0.21 /xm, mean diameter of cell nuclei 9.8 0.27/xm) 20 cm H2O driving pressure, cell-to-pore ratio 1 1, temperature 22°C (Ochalek et al., 1988). Care has to be taken to derive tumor cells from similar culture conditions, since cell density has been found to influence filterability. 

Table 2-8 illustrates several items that must be kept in mind when selecting. substituents to be evaluated in terms nf the type of factors that influence a biological response. Fur electronic parameters such as aromatic ring is important because of resonance versus inductive effects. Notice the twofold differences seen between and fur the three aliphatic substituents and iodo. and scvcralfold difference for methuxy, amino. Huoru, and phenolic hydroxyl. 

Apart from the presence of proteins, several other factors can influence NM behavior in culture media, including the salt composition, the pH, or the buffer capacity. Using gold nanoparticles (AuNP) of three sizes Maiorano et al. [24] demonstrated that the nanoparticle-protein interactions are differendy mediated when AuNP are suspended in two common cell culture media (DMEM and RPMI) supplemented with fetal bovine serum. An increased protein coating and different size distribution were observed in AuNP suspended in DMEM in comparison to RPMI. Most impor-tantiy, differences were also found in the biological responses of two cell lines (HeLa and U937), as the intracellular internalization and cytotoxicity were higher in cells exposed to AuNP in RPMI, where the protein corona was less abundant. 

There are numerous biotic and abiotic parameters which influence metal uptake and accumulation. The abiotic factors (salinity, temperature, light, pH, Eh, and ligand concentration) influence the relationship between metal species distribution and organisms. Using the available speciation techniques (see Part IV, Chapter 3 Raspor 1980), biological responses can often be pre-... 

This chapter will focus on the factors concerning dental implants which affect biologic properties of currently available dental implant materials. As pertains to each major topic, the influence of the materials properties on biologic responses will be emphasized. 

Rutkowska and co-workers reported a complete defragmentation of PCL samples in sea water (Baltic sea) at temperatures between 9 C and 21 °C [7] within 8 weeks. Temperature was stated to be a major influence factor for the degradation. For PCL, chemical hydrolysis and enzymic surface erosion are responsible in parallel for the polymer degradation. The same research group found for poly(ester urethanes) a significant weight loss in sea water (Baltic sea) within 12 months, while a poly(ether urethane) was not biologically attacked under the same experimental conditions [8]. 

Biological factors that may influence pharmacological response and side effects include pharmacokinetics such as protein binding, distribution, metabolism, or... 

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