Thin Film Elastic Modulus of Degradable Tyrosine-Derived Polycarbonate Biomaterials and Their Blends

The integrity, function, and performance of biomedical devices having thin polymeric coatings are critically dependent on the mechanical properties of the film, including the elastic modulus. In this report, the elastic moduli of several tyrosine-derived polycarbonate thin films, specifically desaminotyrosyl ethyl tyrosine polycarbonates p(DTE carbonate), an iodinated derivative p(I(2)-DTE carbonate), and several discrete blends are measured using a method based on surface wrinkling. The data shows that the elastic modulus does not vary significantly with the blend composition as the weight percentage of p(I(2)-DTE carbonate) increases for films of uniform thickness in the range of 67 to 200 nm. As a function of film thickness, the observed elastic moduli of p(DTE carbonate), p(I(2)-DTE carbonate) and their 50:50 by mass blend show little variation over the range 30 to 200 nm.

Polymers derived from the amino acid L-tyrosine: polycarbonates, polyarylates and copolymers with poly(ethylene glycol)

The natural amino acid L-tyrosine is a major nutrient having a phenolic hydroxyl group. This feature makes it possible to use derivatives of tyrosine dipeptide as a motif to generate diphenolic monomers, which are important building blocks for the design of biodegradable polymers. Particularly useful monomers are desaminotyrosyl-tyrosine alkyl esters (abbreviated as DTR, where R stands for the specific alkyl ester used). Using this approach, a wide variety of polymers have been synthesized. Here, tyrosine-derived polycarbonates, polyarylates, and polyethers are reviewed with special emphasis on recent developments relating to cellular and in vivo responses, sterilization techniques, surface characterization, drug delivery, and processing and fabrication techniques. The commercial development of tyrosine-derived polycarbonates is most advanced, with one polymer, poly(DTE carbonate) (E=ethyl), being under review by the USA Federal Drug Administration.