Biodegradable polymers abilities

The design of biodegradable nano-hybrids has also been reported by Rhee et al. by the combination of a CaO-Si02 component with the biodegradable polymer, poly (epsilon-caprolactone) [30]. These nano-hybrids show hydroxyapatite-forming ability and are expected to show bioactivity and biodegradability. 

The response reaction of the host to a foreign material remaining in the body for an extended period of time is a concern. Thus, any polymeric material to be integrated into such a delicate system as the human body must be biocompatible. Biocompatibility is defined as the ability of a material to perform with an appropriate host response in a specific application [79]. The concept include all aspects of the interfacial reaction between a material and body tissues initial events at the interface, material changes over time, and the fate of its degradation products. To be considered bio compatible, a biodegradable polymer must meet a number of requirements, given in Table 2. 

Polymer-based systems offer numerous advantages, such as biocompatibility, biodegradability, and ability to incorporate functional groups for attachment of drugs. Drugs can be incorporated into the polymer matrix or in the cavity created by the polymeric architecture, from which the drug molecule can be released with an element of temporal control, and controlled pharmacokinetic profile with almost zero-order release achievable. 

Clearly thermoplastic starch based polymers offer a very attractive base for new biodegradable polymers due to their low material cost and ability to be processed on conventional plastic processing equipment. The engineering of more advanced properties into these low cost base materials will continue to be... 

A much more desirable erosion mechanism is surface erosion, where hydrolysis is confined to a narrow zone at the periphery of the device. Then, if the drug is weU-immobihzed in the matrix so that drug release due to diffusion is minimal, the release rate is completely controlled by polymer erosion, and an ability to control erosion rate would translate into an ability to control dmg delivery rate. For a polymer matrix that is very hydrophobic so that water penetration is limited to the surface (thus Hmiting bulk erosion), and at the same time, allowing polymer hydrolysis to proceed rapidly, it should be possible to achieve a drug release rate that is controlled by the rate of surface erosion. Two classes of biodegradable polymers successfully developed based on this rationale are the polyanhydrides [31] and poly (ortho esters) [32], the latter of which is the subject of this chapter. 

An interesting application of biocompatible and biodegradable polymers is in the field of tissue engineering, which involves the creation of natural tissue with the ability to restore missing organ function. 

As poly(ethylenimine) (PEI) is one of the most widely studied non-viral vectors due to its high transfection ability, and much effort has been contributed to decrease its toxicity, we mainly focus on the current progress of PEI and its derivatives as the gene carrier. In addition, biodegradable polymers, which have gained increasing attention during the past decade for their reduced toxicity and prevention of polymer accumulation in the body, are also discussed. 

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