Natural/biodegradable polymers collagen

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. 

There are several types of biodegradable polymers. A common classification is based on the distinction between natural and synthetic biodegradable polymers. Natural biodegradable polymers are typically produced directly by living organisms, and they are extracted from them a posteriori. The most common biodegradable natural polymers are collagen, elastin, fibrin, and several polysaccharide derivatives, such as... 

Bacterial cellulose (BC)/HAp nanocomposites were examined by Wan et al. [279]. The most striking features of BC are its high mechanical sdength and modulus, as well as its biodegradability. Compared with other natural biodegradable polymers, BC presents much better mechanical properties, which are required in most cases when used as scaffold in tissue engineering. Compared with animal-derived polymers, BC is free of any occurrence of cross-infection that can be associated with collagen [276]. The authors found that there are different interactions between unphosphorylated and phosphorylated BC fibres and HAp, as shown schematically in Fig. 26. 

In addition to synthetic biodegradable polymers discussed so far, naturally occurring biopolymers have also been used for fabricating implantable dmg delivery systems. Examples of natural biopolymers are proteins (e.g. albumin, casein, collagen, and gelatin) and polysaccharides (e.g. cellulose derivatives, chitin derivatives, dextran, hyaluronic acids, inulin, and starch). 

Hydroxyapatite (HA) nanoparticles are osteoconductive bioactive ceramics that can support bone cell adhesion and proliferation and accelerate bone defects healing. HA is typically added to polymeric nanofibers to increase their mechanical strength. HA, often in the form of needle-like nanoparticles, was electrospun in the presence of synthetic biocompatible and biodegradable polymers such as PLA [5, 58-60] and PLA-PEG-PLA [61], natural polymers such as chitosan [62] and collagen [63, 64], and blends of natural and synthetic polymers such as PVA/chitosan [65] and PCL/gelatin [66]. 

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