Calcium polyphosphate precipitation - A strategy to tune the chain length of the glass and control the subsequent release of vancomycin

Using a multi-variable design approach this study sought to determine whether calcium polyphosphate (CPP) could be precipitated with a significantly higher chain length than achieved with conventional melt-derived glass and subsequently enhance the performance of the CPP-based drug delivery matrix. Manipulating aqueous sodium polyphosphate concentration, order of reactant addition, and Ca/P molar ratio at mix of reactants across a minimum of two levels was found to significantly influence the chain length, Ca/P ratio, and residual sodium of the resulting CPP precipitates. The various interactions of these three variables were also found to have a significant impact on the aforementioned properties of the precipitates and we successfully fabricated a precipitate with a 6-fold increase in chain length over that achieved by conventional melting. Despite not seeing a significant improvement in drug release properties, our systematic preparation of calcium polyphosphate from aqueous sodium polyphosphate solutions yielded valuable mechanistic data on this interesting fabrication strategy.