Natural/biodegradable polymers poly

There are many kinds of natural biodegradable polymers. They are classified into three types according to their chemical structures, i.e., polysaccharides, polypeptides/proteins and polynucleotides/nucleic acids. Among them, polysaccharides, such as cellulose, chitin/chitosan, hyaluronic acid and starch, and proteins, such as silk, wool, poly( y-glutamic acid), and poly(e-lysin), are well known and particularly important industrial polymeric materials. 

The C4 aldol intermediate of the Weizmann process is also key in the aerobic fermentation of sugars to poly(3-hydroxybutyric acid) or PHB (-0[-CH(CH3)-CH2-COO - [70]. This natural and biodegradable polymer is produced inside microorganisms, e.g., Ralstonia eutropha. A complex processing is required to extract and purify the polymer granules from the microorganism. 

Biodegradable polymers, both synthetic and natural, have gained more attention as carriers because of their biocompatibility and biodegradability and therewith the low impact on the environment. Examples of biodegradable polymers are synthetic polymers, such as polyesters, poly(orfho-esters), polyanhydrides and polyphosphazenes, and natural polymers, like polysaccharides such as chitosan, hyaluronic acid and alginates. 

Early development of polymers in injectable drug delivery primarily involved PLA and poly(lactic-co-glycolic) acid (PLGA) due to the prior use of these polymers in biomedical applications as sutures. Besides the safe and biocompatible nature of these polymers, their ease of availability made them ideal first candidates for screening parenteral CR formulations. Some of the early biodegradable polymer-based products for injectable sustained release used these polymers. However because... 

A number of reviews cover what has been achieved over the past 20 years in the field of soluble polymers as potential drug carriers.The polymers selected for preparing macromolecular prodrugs can be categorized according to (1) the chemical nature (vinylic or acrylic polymers, polysaccharides, poly(a-amino acids)) (2) the back bone stability (biodegradable polymers, stable polymers) (3) the origin (natural polymers, synthetic polymers) and (4) the... 

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