Scaffold systems, porous

Bioresorbable poly(ester urethanes) have been developed by reacting lysine diisocyanate (LDI) with polyester diols or triols based on D,L-lactide, caprolac-tone, and other copolymers [45]. In these systems, aliphatic polyesters such as PLGA or PCL form the soft segments and the polypeptides form the hard segments [46]. A resorbable elastomeric poly(ester urethane) called Degrapol is available commercially. It is currently being used to develop porous scaffolds for tissue engineering applications. 

Owing to its outstanding biological, chemical, and pharmaceutical applications, a variety of CS-graft copolymers have been synthesized to extend the utilization of CS in different areas such as drug delivery systems, hydrogels, and porous scaffolds. 

A third approach is to use the scaffolds intended for cell attachment and proliferation as a drug-delivery system (Figure 42.5c). Many of these materials provide tremendous opportunities to control the release of drugs. Especially biodegradable polymers and hydrogel materials have been used extensively as porous scaffolds to allow for erosion controlled drug or DNA release. 

An approach related to the use of emulsions as a raw material for scaffolding is the use of emulsions for coating. Sohier et al. [221] used a W/O emulsion of poly(ethylene glycol) terephthalate/poly(butylene terephthalate) multiblock copolymer loaded with lysozyme as a model protein to coat porous scaffolds made of the same material. They could release the protein over several days and were able to show that the activity of lysozyme was maintained. While the use of emulsions has the advantage of creating an even distribution of drugs inside the material, in some cases, sensitive drugs may not be stable in such an emulsion system [222-224]. 

Scaffold-mediated gene delivery. Plasmid DNA condensed with cationic polymers can be encapsulated into various types of 3D polymeric scaffold systems (micro/nanospheres, porous sponges, or hydrogels) for sustained gene delivery. Source Reprinted and adapted from Reyes etal., 2013, copyright 2013, with permission from Elsevier B.V.)... 

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