Bioerodable properties

Phosphazene polymers can act as biomaterials in several different ways [401, 402,407]. What is important in the consideration of skeletal properties is that the -P=N- backbone can be considered as an extremely stable substrate when fluorinated alcohols [399,457] or phenoxy [172] substituents are used in the substitution process of the chlorine atoms of (NPCl2)n> but it becomes highly hydrolytically unstable when simple amino acid [464] or imidazole [405-407] derivatives are attached to the phosphorus. In this case, an extraordinary demolition reaction of the polymer chain takes place under mild hydrolytic conditions transforming skeletal nitrogen and phosphorus into ammonium salts and phosphates, respectively [405-407,464]. This opens wide perspectives in biomedical sciences for the utilization of these materials, for instance, as drug delivery systems [213,401,405,406,464] and bioerodible substrates [403,404]. 

J Heller. Bioerodible hydrogels. In NA Peppas, ed. Hydrogels in Medicine and Pharmacy, Vol III Properties and Applications. Boca Raton, FL CRC Press, 1987, pp 137-149. 

Bioerodible polymers offer a unique combination of properties that can be tailored to suit nearly any controlled drug delivery application. By far the most common bioerodible polymers employed for biomedical applications are polyesters and polyethers (e.g., polyethylene glycol), polylactide, polyglycolide and their copolymers). These polymers are biocompatible, have good mechanical properties, and have been used in... 

Long-term inertness without loss of strength, flexibility, or other necessary physical property is needed for use in artificial organs, prostheses, skeletal joints, etc. Bioerodability is needed when the polymer is used as a carrier such as in controlled release of drugs, removal of unwanted materials, or where the materials purpose is short-lived, such as in their use as sutures and frames for natural growth. 

Polyanhydrides are a class of bioerodible polymers that have shown excellent characteristics as drug delivery carriers. The properties of these biomaterials can be tailored to obtain desirable controlled release characteristics. Extensive research in this promising area of biomaterials is the focus of this entry. In the first part of the entry, the chemical structures and synthesis methods of various polyanhydrides are discussed. This is followed by a discussion of the physical, chemical, and thermal properties of polyanhydrides and their effect on the degradation mechanism of these materials. Finally, a description of drug release applications from polyanhydride systems is presented, highlighting their potential in biomedical applications. 

Most bioinert rigid polymers are commodity plastics developed for nonmedical applications. Due to their chemical stability and nontoxic nature, many commodity plastics have bwn used for implantable materials. This subsection on rigid polymers is separated into bioinert and bioerodable materials. Table 11.6 contains mechanical property data for bioineit polymers and is roughly ordered by elastic modulus. Polymers such as the nylons and poly(ethylene terephthalate) slowly degrade by hydrolysis of the polymer backbone. However, they are considered bioinert since a significant decrease in properties takes years. 

Most rigid degradable polymers degrade without the aid of enzymes and are therefore bioerodable. Table 11.7 shows mechanical property data for bioerodable polymers. 

This chapter focuses on biodegradable polymers used in the health domain. Some examples of biodegradable and bioerodible polymers are presented in Table 4.1, and some of their thermomechanical properties are given in Table 4.2. 

Sawhney, A.S., C.P. Pathak, J.J.w Rensburg, R.C. Dunn andJ.A. Hubbell, Optimization of photopolymerized bioerodible hydrogel properties for adhesion prevention, Jotimal of Biomedical Materials Research, 28 (1994) 831-838. 

Outstanding properties - biocompatible, bioerodible, easily metabolized ... 

The meaning and definition of the words biodegradable, bioerodable, bioresorbable and bioabsorbable, which are often used misleadingly in the tissue engineering literature, are of primary importance in discussing the rationale, function and chemical and physical properties of polymer-based scaffolds [58]. In this paper, the biorelated polymer properties are based on the definitions given by Vert etal. [58, 59] ... 

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