Polymer biocompatibility and toxicity

More than a dozen biocompatible and biodegradable polymers have been described and studied for their potential use as carriers for therapeutic proteins (Table 13.5). However, some of the monomer building blocks such as acrylamide and its derivatives are neurotoxic. Incomplete polymerization or breakdown of the polymer may result in toxic monomer. Among the biopolymers, poly-lactide cofabricated with glycolide (PLG) is one of the most well studied and has been demonstrated to be both biocompatible and biodegradable [12]. PLG polymers are hydrolyzed in vivo and revert to the monomeric forms of glycolic and lactic acids, which are intermediates in the citric acid metabolic pathway. 

Clinical applications of thermosensitive hydrogels based on NIPAAm and its derivatives have limitations [121], The monomers and cross-linkers used in the synthesis of the hydrogels are still not known to be biocompatible and biodegradable. The observation that acrylamide-based polymers activate platelets upon contact with blood, together with the unclear metabolism of poly(NIPAAm), requires extensive toxicity studies before clinical applications can merge. 

Chitosan, a biocompatible and biodegradable polycationic polymer with low toxicity, is known for its swelling ability and permeation-enhancing properties and represents a polymer of choice for the preparation of microspheres intended for nasal administration [74],... 

Applications in medicine take advantage of the combination of such properties as biocompatibility and degradability. Neither the polymers themselves nor their degradation products can set free toxic materials or cause tissue-damaging processes. 

Chitosan is a biodegradable, biocompatible, non-toxic and very abundant marine-based natural polymer. It has enormous applications in different branches of modern science such as the nanobiotecnology, biotechnology, biomedical and pharmaceutical fields. 

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