PAA influence on chitosan membrane calcification

This work discusses the influence of polyacrylic acid (PAA) on chitosan in vitro calcification. Calcium phosphate deposition on porous and dense (non-porous) chitosan membranes treated or not with PAA has been studied using scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray diffraction, potentiometric titration and attenuated total reflectance infrared spectroscopy (ATR-IR). The experiments were carried out by soaking chitosan membranes in simulated body fluids (SBF), 1.0 and 1.5 times the human serum salt concentration, at 36.5 °C during 7 days at pH 7.4 or 7.8. SEM micrographs showed that the use of these growth solutions resulted in substrates with significant coverage with calcium phosphate. PAA led to a higher coverage even at lower pH (7.4), but the morphological and chemical nature of deposits was remarkably different if compared to deposits on pure chitosan membranes. Although PAA has shown to promote a more intense deposition, probably by offering ion-binding sites adequate for nucleation, it does not necessarily determine a well-defined crystal growth orientation.