Advanced Functional Materials

Cover image for Vol. 26 Issue 36

17_16b/2007Inside Front Cover: Thermally Responsive Biomineralization on Biodegradable Substrates (Adv. Funct. Mater. 16/2007)

Biomineralization offers an elegant example of how nature can design complex, hierarchical, and structurally/morphologically controllable materials. João Mano and co-workers of the University of Minho, Portugal report on p. 3312 that modifying the surface of bioactive substrates, together with the effect of temperature, triggers the formation of apatite upon immersion in simulated body fluid. This “smart” biomineralization concept could be combined with patterning methodologies by controlling the microstructure of the surface. Such a concept could be extended in the biomimetic production of other minerals, being triggered by other kind of stimuli (e.g., pH or ionic strength), in substrates with more complex geometries.

Biomineralization offers an elegant example of how nature can design complex, hierarchical, and structurally/morphologically controllable materials. In this work, the surface of bioactive substrates prepared from poly(L-lactic acid) and reinforced with Bioglass are modified by the graft polymerization of poly(N-isopropylacrylamide), (PNIPAAm) after plasma activation. It is found that such treatment, together with temperature, could trigger the formation of apatite on the biodegradable substrate upon immersion in simulated body fluid above the PNIPAAm lower critical solution temperature (LCST); in contrast, no apatite is formed at room temperature. A control experiment on a material that is not subjected to surface treatment does not show any evidence of mineral deposition at the two analyzed temperatures. This “smart” biomineralization concept is combined with patterning methodologies to control the microstructure of the surface onto which PNIPAAm is grafted. In this case, the apatite is formed at 37 °C in the modified regions. We suggest that this concept could be extended in the biomimetic production of other minerals, where it would be triggered by another kind of stimulus (e.g., pH or ionic strength) in substrates with more complex geometries.

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