Bioresorbable polymers and infiltrated carbon foams for biomedical applications

In a holistic quest to introduce more body responsive elements in biomedical applications to accelerate the healing of bone fractures and reinforcing tissue growth, an innovative composite material system of carbon foam infiltrated with bioresorbable polymer is introduced. Changes in mass, stiffness and strength as a function of exposure time are crucial parameters to explore in enabling the successful design of non-metallic, fully biocompatible and bioresorbable orthopedic plates, pins and grafting scaffolds. Preliminary studies to observe the time and rate dependent degradation mechanisms and their subsequent impact on the material and mechanical properties of bio-devices are undertaken with (a) poly(L-lactide) (PLLA) membranes and (b) polycaprolactone (PCL) infiltrated carbon foam specimens. Porous, particulate, and dense PLLA membrane specimens approximately 50 μm thick are cast and then incubated in phosphate buffered saline (PBS, pH of 7.4) at temperatures of 50 °C and 70 °C. Mass loss measurements, gel permeation chromatography (GPC) for molecular weight measurements (M_w, M_w/M_n), and scanning electron microscopy (SEM) analysis to characterize surface morphology are conducted for the period of twenty four days. All three morphologies of PLLA membranes exhibited surface erosion as the primary degradation mechanism. The porous PLLA specimens' degradation rates were approximately three times those of the particulate and dense specimens. In order to tailor in high stiffness and strength, carbon foam is infiltrated with PCL to form a two phase composite. This approach led to an as processed composite with a tenfold increase in compressive modulus and strength of the neat foam. These specimens are then submersed in simulated body fluid (SBF) up to ten weeks. Subsequent tests revealed about twenty percent decrease in its properties.