The mechanisms of oxidative degradation of biomedical polymers by free radicals

Abstract

Degradation is an essential factor in polymer biocompatibility. The physiological environment of the human body can be aggressive to polymers. Most implanted polymers suffer degradation and the kinetics and mechanisms of the processes can be significantly affected by various biologically active species, especially enzymes, lipids, peroxides, free radicals, and phagocytic cells. Iron enhances the toxicity of oxygen free radicals. Superoxide and hydrogen peroxide can interact to form the very toxic hydroxyl radical in the presence of iron. The data have shown that the hydroxyl radical is likely to be one of the main causes of polymer degradation in implantable devices.

Effect of zinc oxide nanoparticles on thein vitrodegradation of electrospun polycaprolactone membranes in simulated body fluid

“…The data have shown that the hydroxyl radical is likely to be one of the main causes of polycaprolactone degradation in implantable devices [52]. …”

A review of biodegradable polymers: uses, current developments in the synthesis and characterization of biodegradable polyesters, blends of biodegradable polymers and recent advances in biodegradation studies

“…It suggests that the human body can therefore produce very toxic hydroxyl radicals, which may be one of the main causes of degradation in implanted polymeric devices. 159 The mechanism for the biodegradation of PE was presented in 1987,160 involving initial abiotic oxidation. Hydroperoxides are introduced into the polymer chain with a gradual increase in "in-chainÏ keto groups, followed by a decrease as short-chain carboxylic acids are released ; the Ðnal stage involves microbial biodegradation by a b-oxidation mechanism.…”

Hydrolysis of biodegradable polymers by superoxide ions

“…19 -21 Williams and coworkers investigated the degradation mechanisms of biodegradable biomedical polymers by using the free radical species like hydroxyl radicals in an aqueous Fenton solution. [22][23][24][25] It should be mentioned that the reaction of free radicals with the biodegradable polymers like glycolic acid/lactic acid copolymer (Vicryl) could not be definitely confirmed since an equal amount of •OH and OH Ϫ were generated in Fenton reagents. The observed changes in morphological, mechanical, and thermal properties of Vicryl could be partially attributed to the action of OH Ϫ ions as well as •OH radicals.…”