Barbieri Thesis - BioMedical Materials program (BMM)

Chapter 7 – Polymer molecular weight and instructive composites
ADDENDUM
7a.1. Introduction
As seen in 7.3.7. the osteoinductive composite containing poly(D,L–lactide) had low
stiffness and its damping properties were not stable over the frequency sweep. Thus, a
separated and independent study has been performed using 70%mol. L–lactide/30%mol.
D,L–lactide copolymer as organic phase of the composites. This polymer is expected to
have higher mechanical,performances thanks to the higher L–lactide content, and to be
sufficiently degradable to allow osteoinduction thanks to its D,L–lactide component. To
evaluate their osteoinductive potential, a different animal model has been used for
longer implantation period (i.e. 6 months in sheep). As explained in Chapter 6, a 5–week
accelerated degradation study at high temperature has been done to simulate a long–
term degradation at physiological temperature. The results herein presented confirmed
the conclusions previously described in this Chapter.
7a.2. Materials and methods
7a.2.1. Preparation and characterization of composites
The used apatite powder was the same of the one described in §7.2.1. Copolymers of
70%mol. L–lactide/30%mol. D,L–lactide with different molecular weights (declared
inherent viscosity 3.85 dL g –1 with residual monomer