Implant device, biodegradable

Gunatillake and Adhikari - have written a very useful review of current biodegradable chemistries. Their review focuses on implantable systems. It is important to keep in mind that the technologies have separated into two camps. The biodegradable people focus on implantable devices and proponents of biodurability are... 

Despite advances in hepatocyte culture, tissue engineering of the liver faces significant challenges.One important factor in the development of a self-sufficient hepatic device is vascularization. While in the early stages of development, a device can be maintained by providing sufficient void volume the device ultimately will have to provide for natural supplies of raw materials. This is one of the factors that makes the development of a biodegradable implanted device problematic. Not only must the so-called biodegradable scaffold (and its associated problems) be resorbed... 

Yang et al. discussed the basic properties of an implantable or extracorporeal artificial liver. The article focused on implantable devices but other than biodegradability, the properties of implantable devices are also applicable to extracorporeal devices. The focus of the article on implantable devices reveals an unfortunate prejudice on the part of much of the scientific community. Most researchers in this field are working on devices intended to be placed in the body. 

Figure 12.15 Methods of using biodegradable polymers in controlled release implantable devices to release the active agent, A...

Since EVAc is a non-biodegradable polymer, the implanted device has to be surgically removed from the host after completion of the immunization process. Hence, it would be advantageous to use biodegradable devices for the controlled release of antigen. 

Bulk characterization yields information on the macroscopic properties of the biomaterial such as thermal, mechanical, solubility, optical, and dielectric properties. Surface characterization yields morphological information that is critical for interfacing the implant or drug delivery device with the host tissue. This could be achieved by microscopic and spectfoscopic methods. Next in the hierarchy is the characterization of processes such as biodegradation mechanism and kinetics under biomimetic in vitro conditions. Cases of implanted device failure need to be assessed by systematic interrogation of explanted medical devices. After knowing the basic characteristics of the biomaterial, real-time investigation of in vivo processes plays a major role in the successful journey of an implant. 

Similarly, the biodegradable polyesters polyglycolic acid and poly(f-caprolactone), also used for implantable devices (degradation even slower than that of PLA), drug delivery, and suture materials, are prepared by CROP using stannous octanoate and other catalysts as cationic initiators [8]. 

PolyhydroxyaUcanoates (PHAs) are the biopolymers possessing the material properties ranging from rigid and highly crystalline to flexible, amorphous, and elastomeric. Because of such properties and inherent biodegradability, PHAs have attracted the world-wide attention of scientists and researchers as environment-friendly alternative to the conventional petroleum-based polymers. Polyhydroxybutyrate (PHB) and polyhydroxyoctanoate (PHO) have been found to possess biocompatibility in mammalian systems. Such biomaterials have got great potential as medical implantation devices [78-81]. 

---