Bioactive composites produced in situ on the basis of calcium phosphates and lactic acid oligomers

Composites based on lactic acid oligomers, calcium hydrophosphate and hydroxyapatite synthesized under the action of microwave radiation were obtained in situ. The appearance of a new band associated with stretching vibrations of >C=O in spectra of the chloroform-insoluble fraction is indicative of the chemical interaction between lactic acid and hydroxyapatite. To determine whether a calcium phosphate layer can be formed on the surface of composite samples, biomimetic studies in a physiological SBF solution were carried out during 28 days at 37°C. It was found that all samples containing calcium phosphates promote active formation of a new calcium phosphate layer, whereas lactic acid oligomer in samples containing no inorganic component undergoes destruction in the SBF solution as a result of hydrolysis. The estimate of the resorption rate demonstrated that the solubility of calcium phosphates contained in the composites at 20°C in the physiological solution is 3–7 times that of pure hydroxyapatite.