Catalysts in Biological Media

The water content in biological media is relatively high. The human body consists of more than 75% water, mainly in the form of intracellular fluid of tissue and in plasma. Thus, any plastics implanted in the body will be in constant contact with water. 

Biological media exhibit high salt concentrations. Table 5.126. Plasma and cell fluids contain proteins in anionic form due to the presence of carboxylate groups [896]. 

Electrolyte diffusion into hydrophobic plastics is similar to the diffusion mechanisms of gases and vapor. Therefore, electrolytes with high vapor pressure (e.g., hydrochloric acid) exhibit water absorption and diffusion values similar to water. By contrast, very low values are found in electrolytes with low vapor pressure (e.g., chlorides or phosphates) because of the hydrophobic character of the plastic [896]. 

1 Oxido-reductases Electron transfer (hydride ions or H-atoms) 

3 Hydrolases Hydrolytic cleavage (mainly of ester or amide(peptide) bonds [890]) 

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