The effect of processing on the structural characteristics of vancomycin-loaded amorphous calcium phosphate matrices

Calcium polyphosphate antibiotic delivery matrices were prepared using a unique processing technique involving the exposure of calcium polyphosphate pastes to high humidity for 0, 5, 24 or 48 h to induce gelling. Subsequently, samples were dried for a minimum of 24 h. The mild conditions associated with matrix fabrication readily allowed for vancomycin incorporation within an environment that did not disrupt antibiotic activity. While reproducible from a processing standpoint, the gelling and drying process did contribute to a decrease in matrix tensile strength and the formation of significant pores near the surface of the matrices. Generally, the core of the gelled matrices appeared to be denser than their non-gelled counterparts. The degree of phosphate chain lysis during the gelling and drying stages was quantified using solution 31P nuclear magnetic resonance (NMR) spectroscopy. Both NMR and Raman spectroscopy indicated that the presence of vancomycin did not appreciably alter the matrix formation process. The ability to incorporate clinically relevant levels of antibiotic within this degradable bone substitute matrix suggests the potential of this approach for creating a localized antibiotic delivery system to treat osteomyelitis infections.