Effects of amelogenin on the transforming surface microstructures of Bioglass((R)) in a calcifying solution

Topographies of a bioactive glass (45S5 type Bioglass(R)) during 0-4 h of i mmersion in a supersaturated calcifying solution (SCS) and the SCS containi ng recombinant porcine amelogenin rP172 (SCSrP172) were observed by atomic force microscopy. Other techniques including X-ray diffraction, scanning el ectron microscopy coupled with energy ergy dispersive X-ray spectroscopy, a nd transmission electron microscopy were used for some complementary micros tructural investigations. The smooth Bioglass surface changed to-be very ro ugh after 0.5 h of SCS immersion because of glass network dissolution. Sphe rical silica-gel particles with diameters of 150-300 nm consisting of subst ructures of 20-60 nm across had formed on the sample surfaces after 1 h of SCS immersion. The chemisorption of amorphous calcium phosphate and crystal lization of nanophase apatite were seen to occur epitaxially on the silica- gel structures during 1-4 h of SCS immersion. During the first 0.5 h of SCS rP172 immersion, more than 95% of rP172 protein in solution was adsorbed on to the sample surfaces and generated spherical assemblies of 10-60 nm diame ters. During 0.5-4 h of SCSrP172 immersion, the protein assemblies of rP172 remarkably induced the formation of orientated silicagel plates (approxima tely 100-nm wide and 50-nm thick) and subsequently of long and thin apatite needle crystals. The recombinant amelogenin rP172-modulated apatite crysta ls resembled those formed in the early stage of tooth enamel biomineralizat ion, suggesting the functional roles of amelogenins during the oriented gro wth of enamel crystallites and a great potential for amelogenins in applica tions designed to fabricate enamel-like calcium phosphate biomaterials. (C) 2000 John Wiley & Sons, Inc.