Growth of spherical clusters of hydroxyapatite in gelatin which resemble deposits in biofilms

Gelatin gels were prepared which incorporated triammonium orthophosphate solution at pH 8.5—9.5. Hydroxyapatite was precipitated within these gels by covering their surfaces with calcium nitrate solution. When the hydroxyapatite within the surface layer was examined by scanning electron microscopy, it appeared as roughly spherical clusters with internal structure; this structure arises because the clusters were composed of plate‐like crystals. The clusters were closely similar to bodies in published electron micrographs of marine surfaces fouled by bacteria. They also resembled clusters of poorly crystalline hydroxyapatite formed on the surfaces of urinary catheters which encrust as a result of bacterial colonisation.

Key words:

• calcium phosphate
• hydroxyapatite
• protein