engleski

Biomimetic organic-inorganic nanocomposite coatings for titanium implants

A new class of organic - inorganic nanocomposites, to be used as coatings for surface enhancement of metal implants for bone replacement and repair, has been prepared by a biomimetic procedure, which involves three steps: (1) embedding amorphous calcium phosphate (ACP) particles between organic polyelectrolyte multilayers (PE MLs), (2) "In situ” transformation of ACP to OCP and/or poorly crystalline apatite nanocrystals by immersion of the material into a metastable calcifying solution (MCS) and (3) deposition of a final polyelectrolyte multilayer. The organic polyelectrolytes used were poly-L-glutamic acid (PGA) and poly-L-lysine (PLL). The nanocomposites obtained by each successive step were characterized by scanning electron microscopy, EDX and XRD and their suitability as coatings for metal implants was examined by mechanical and "in vitro" biological tests. Coatings obtained as a result of the first deposition step are mechanically unstable and therefore not suitable. During the second step - i.e. upon immersion of the (PE ML - ACP) composite into MCS, ACP particles were transformed into crystalline calcium phosphate, with large plate-like OCP crystals as the top layer. After the phase transformation the nanocomposite was strongly attached to the titanium, but the top layer did not promote cell proliferation. However, when the coating was topped with an additional polyelectrolyte multilayer (step 3), smoother surfaces were obtained, which facilitated cell adhesion and proliferation as shown by "in vitro" biological tests using primary human osteoblast directly seeded onto the nanocomposites. In fact cell proliferation on nanocomposites with top polyelectrolyte multilayers was far superior than on any of the individual components i.e. on chemically etched titanium, organic multilayer film and/or inorganic crystals and was equivalent to proliferation on the golden standard (plastic).

bioimplants ; amorphous calcium phosphate ; apatite ; composite coatings ; polyelectrolyte multilayers

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