Biodegradable polymers approaches

The aim of this chapter is to put in evidence the evolution of nanostructured biodegradable polymer approaches in pharmaceutical and biomedical applications. 

Since the purpose of this book is to describe applications of biodegradable polymers to drug delivery systems, particularly from the perspective of the materials employed, the approach taken in this chapter has been to focus on the natural biodegradable polymers which have been used most extensively as matrices for the delivery of drugs. Consideration was also given to the fact that collagen has not been the subject of any recent reviews. 

One approach to compartmentalize hemoglobin is to encapsulate hemoglobin in biodegradable polymer-PEG-polylactide (30). These nanocapsules have a diameter of 80-150 nm and contain superoxide dismutase, catalase, carbonic anhydrase, and other enzymes of Embden-Meyerhof pathway that are needed for long-term function of an oxygen carrier (31,32). The polylactide capsules are metabolized in vivo to water and carbon... 

Polymer blends, particularly olefins with biodegradable polymers, are gaining popularity as an approach to degradable packaging plastics. The materials are at best only partially biodegraded, but will lose form and bulk as the plastic disintegrates. This may be sufficient in landfill as volume diminishes, leaving room... 

Several other novel biodegradable polymer systems were also developed. One of these stems from the observation that many polymers used in medicine today were not initially designed for that purpose. It may be particularly useful to have available biodegradable polymers that are composed of, and will break down into, naturally occurring substances. One example is the synthesis of structurally new polyfamino acids) in which L-amino acids or dipeptides are polymerized by nonamide bonds (e.g., ester, iminocarbonate) involving the functional groups located on the amino acid side chains, rather than the extensively used approach involving the amino acid termini. 

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