Biocompatible, biodegradable polymer

S. Gogolewski, Biocompatible, biodegradable polym-ethane materials with controlled hydrophobic to hydrophilic ratio, EP Patent App. 20, PCT/CH2004/000471, WO/2006/010278. 

To achieve delivery of this high cell number in close proximity to a capillary network, we needed to provide a scaffold with an immense surface area. In this context, we began to address the question of growth of multicellular organisms. The surface area of a mass of cells increases as the square of the radius, while the volume increases as the cube of the radius. In experiments involving several hundred animals, we employed branching networks of biocompatible, biodegradable polymers of several chemical compositions and physical characteristics as matrices onto which we seeded hepatocytes. 

Polymer nano- or microparticles/microcapsules used in biomedical fields are fabricated from biocompatible biodegradable polymers. The list of these materials includes both natural materials, such as natural polysaccharides (alginate, cellulose, and chitosan as well as their many derivatives, etc.) and synthetic polymers. Natural polymers are attractive for cell immobilization due to their abundance and apparent biocompatibility. Synthetic polymers are used because of the high degree of control over the structure. Unlike natural materials, whose properties can vary from batch to batch, synthetic polymers provide highly consistent starting materials for any encapsulation technique. 

A biocompatible, biodegradable polymer can be produced as follows. A poloxamer (Pluronic F68) (30) is dried in vacuo at about 105°C for 14 h. Afterwards, glycolide and then -caprolactone are added. As a catalyst stannous octoate is used (29). 

Starch is an inexpensive, hydrophilic, nontoxic, biocompatible and totally biodegradable polymer. It is a mixture of two main components amylose formed by the a-1,4 glycosidic... 

Taraargo, R. J., Epstein, J. I., Reinhard, C., Chasin, M., and Brem, H., Brain biocompatibility of a biodegradable polymer capable of sustained release of mici>omolecules, Abstracts of the 1988 Annual Meeting of the American Association of Neurological Surgeons, p. 399, 1988. 

However, PVA is also extensively used in other different forms, such as gel matrices, micro and nano spheres, aerosols, aqueous solution, films, powder etc. Although some of the different types of PVA gels have been referred in chapter 3.3, it still remains much more to say. This clearly proves that PVA is an old, yet new polymer or, in other words, an old polymer with a promising future, due to its capacity to respond to all the actual society priorities clean technologies, non-toxicity, biocompatibility, biodegradability, intelligent materials. 

B. Sitharaman, X.F. Shi, X.F. Walboomers, H.B. Liao, V. Cuijpers, L.J. Wilson, A.G. Mikos, J.A. Jansen, In vivo biocompatibility of ultra-short single-walled carbon nanotube/biodegradable polymer nanocomposites for, bone tissue engineering, Bone, vol. 43, pp. 362-3Z0, 2008. 

More than a dozen biocompatible and biodegradable polymers have been described and studied for their potential use as carriers for therapeutic proteins (Table 13.5). However, some of the monomer building blocks such as acrylamide and its derivatives are neurotoxic. Incomplete polymerization or breakdown of the polymer may result in toxic monomer. Among the biopolymers, poly-lactide cofabricated with glycolide (PLG) is one of the most well studied and has been demonstrated to be both biocompatible and biodegradable [12]. PLG polymers are hydrolyzed in vivo and revert to the monomeric forms of glycolic and lactic acids, which are intermediates in the citric acid metabolic pathway. 

Biodegradable polymers, both synthetic and natural, have gained more attention as carriers because of their biocompatibility and biodegradability and therewith the low impact on the environment. Examples of biodegradable polymers are synthetic polymers, such as polyesters, poly(orfho-esters), polyanhydrides and polyphosphazenes, and natural polymers, like polysaccharides such as chitosan, hyaluronic acid and alginates. 

Early development of polymers in injectable drug delivery primarily involved PLA and poly(lactic-co-glycolic) acid (PLGA) due to the prior use of these polymers in biomedical applications as sutures. Besides the safe and biocompatible nature of these polymers, their ease of availability made them ideal first candidates for screening parenteral CR formulations. Some of the early biodegradable polymer-based products for injectable sustained release used these polymers. However because... 

Fig. 3 Hydrolyzable, acid-sensitive and reducible bonds. Efficient and biocompatible high molecular weight polymers are created by reversible linkage of small molecular weight compounds. Thus, programmed biodegradation due to, for example, hydrolyzable ester bonds [92] (a), acid-sensitive ketal (b) or acetal linkages (c) [98] is possible. The reducing cytosolic environment can also be taken advantage of in order to create biodegradable polymers by introduction of disulfide bonds as shown in (d) [105, 106]...

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