Interactions of Calcium Phosphates with Chitosan

摘要

The hybrid composite materials (CMs) possess high potential for medical applications related to replacement or regeneration of damaged bone tissue. Of particular interest are the CMs in the calcium phosphate— biopolymer system, whose structure can be organized directly during the synthesis of calcium phosphate in a biopolymer solution similarly to biom-ineralization, i.e., the formation of bone tissue consisting of hydroxyapatite nanoparticles and collagen fibrils. The microstructure and properties of these CMs depend on the interaction between the mineral and biopolymer phases, which determines the conditions of nucleation and the subsequent growth of the mineral phase on the functional groups of biopolymer macromolecules [1,2]. Of interest are CMs with chitosan, which is a biocompatible and biodegradable polysaccharide having high antimicrobial, chemotac-tic, and immunostimulating activity [1]. The medium- and high-molecular mass chitosans are soluble in acids; this corresponds to the synthesis conditions of calcium phosphates such as dicalcium phosphate dihydrate (DCPD, CaHPO4 · 2H2O) and amorphous calcium phosphate (ACP, Ca3PO4 · nH2O), which are possible crystallization precursors of hydroxyapatite, the key mineral constituent of the bone tissue. Studies on the calcium phosphate synthesis in chitosan solutions have been reported (e.g., [4, 5]). However, the question of chemical interaction of chitosan macromolecules with mother liquor ions and with reaction products remains open. The purpose of this work was to study this interaction by IR spectrometry.