The synthesis of nanosized calcium-hydroxyapatite particles by the catalytic decomposition of urea with urease

Abstract

In this paper, the synthesis of nanosized calcium-hydroxyapatite particles by the catalytic decomposition of urea with urease is presented. As reagents for the Ca-hydroxyapatite synthesis, the various amounts of CaCl2, NaH2PO4 urea and urease were used. The urease catalyzed decomposition of urea leads to more homogenic precipitation of hydroxyapatite, due to pH changes because of urea hydrolysis. During urea hydrolysis, the CO32- ion is released and can be incorporated in the crystal structure of hydroxyapatite, as it appears in human bones. The influence of synthesis parameters: temperature concentrations of solution to urease concentration ratio on the particle size and morphology of nanostuctured Ca-hydroxyapatite, were investigated. It was found that at temperature range from 30 to 40oC, the low crystallized carbonate hydroxyapatite formed in all case. It was also concluded that decreasing the solution to urease concentration ratio lead to decreasing in the particle size below 100 nm and morphology changes from sponge like to spherical.

U ovom radu je prikazana sinteza nanostrukturnih čestica kalcijum-hidroksiapatita metodom katalitičke razgradnje uree ureazom. Kao polazna jedinjenja korišćene su različite količine CaCl2, NaH2PO4, urea i ureaze. Katalitička razgradnja uree ureazom dovodi do povećanja pH vrednosti rastvora što za posledicu ima homogenu precipitaciju kalcijum-hidroksiapatita. Tokom razgradnje uree takođe dolazi do oslobađanja CO32- i njihove ugradnje u kristalnu strukturu, sličnu onoj koja se javlja u apatitima prisutnim u kostima. U radu je takođe ispitan uticaj parametara sinteze: temperature i odnosa koncentracije rastvora prema koncentraciji ureaze na morfologiju i veličinu nastalih čestica. Utvrđeno je da u temperaturnom intervalu od 30 do 40 oC dolazi do formiranja karbonatnog kalcijum-hidroksiapatita. Smanjenjem odnosa koncentracija rastvora prema koncentraciji ureaze dolazi do smanjenja veličine čestica do ispod 100 nm i promene morfologije čestica od sunđeraste lisnate ka sfernim.