From Drug-Eluting Stents to Biopharmaceuticals : Poly(ester amide) a Versatile New Bioabsorbable Biopolymer

New biodegradable and tissue-resorbable co-poly(ester amides) (PEAs) useful for biomedical applications were prepared using a versatile Active PolyCondensation (APC) method, which involves di-p-toluenesulfonic acid salts of bis-(L-α-amino acid)-α,ω-alkylene diesters and active diesters of dicarboxylic acids as monomers. APC reactions were carried out at mild temperatures (40-60°C) and allowed the synthesis of regular, linear, polyfunctional PEAs with high molecular weights. The physical properties of PEAs are critically dependent upon the structure of the polymer backbone. A wide range of mechanical properties and biodegradation rates can be achieved by varying the three components in the backbone: α-amino acids, diols and dicarboxylic acids. Indeed, there is a growing need for wider variations of biocompatible PEA compositions and methods for the delivery of different therapeutic molecules at controlled rates, while affording enhanced mechanical and physical properties. Therefore, various types of new non-toxic building blocks based upon bulky diols (isosorbide, 17β-estradiol), unsaturated (fumaric) and aromatic diacids (hydroxycinnamic acid, 1,3-bis(4-carboxyphenoxy)-propane) were developed and successfully incorporated into the main backbone of PEA. In vitro biodegradation tests with enzymes have shown that changes in the polymer backbone and functional groups resulted in a wide range of degradation rates that further exemplify the usefulness of these compositions in biomedical applications.