Measurement of fluid ingress into calcium polyphosphate bioceramics using nuclear magnetic resonance microscopy

A MR microscopy experiment is developed and used to characterize fluid ingress and microstructural transformation in degradable calcium polyphosphate (CPP) bioceramics. High-resolution (49 μm) maps of fluid density and spin-lattice relaxation rate were obtained as a function of time for CPP immersed in phosphate buffered saline. These results demonstrate clear differences in fluid transport rates and solid matrix microstructure in two differing CPP formulations. CPP has been proposed as a potential implantable device for the delivery of pharmaceuticals, and the magnetic resonance imaging (MRI) data are used in conjunction with previously reported bulk elution results to develop a hypothesis explaining microstructural evolution in these materials. This type of non-destructive evaluation of the structure-transport of fluids in CPP is important to improved design of these functionalized biomaterials for long-term, localized delivery of sustained levels of therapeutic agents.