Thermally Responsive Biomineralization on Biodegradable Substrates

Abstract

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.

Stimuli‐Responsive Polymeric Systems for Biomedical Applications

“…Such technology could also be used to spatially control mineralization trough adequate surface patterning, using a mask that enables to activate by plasma just certain regions of the surface of the composite film -see scheme in Figure 6. [132] Again, in such modified films no apatite was formed at 25°C after immersion in SBF, but at 37°C apatite aggregates were formed with a shape consistent with the PNIPAAm patterning generated during surface modification (see SEM picture of Fig. 6).…”

“…[131] Shi et al showed that it is possible to produce smart surfaces that could be used to control and trigger the occurrence of biomineralization onto a biodegradable and biocompatible substrate. [132] The material consisted of a poly(L-lactic acid)/Bioglass ® composite films grafted with PNIPAAm trough plasma activation followed by polymerization in N-isopropylacrylamide: at room temperature no calcification could be observed after immersing the film in SBF for two weeks (see Fig. 5(a)).…”

Bio‐Inspired Mineral Growth on Porous Spherulitic Textured Poly(L‐lactic acid)/Bioactive Glass Composite Scaffolds

“…[15][16][17] In order to investigate the role of surface texture on the biomineralization process, a spherulitic-like pattern was produced on porous PLLA-Bioglass ® composite scaffolds. The added wt % composition of the PLLA/ Bioglass ® compact disk (t-PLLA/ Bioglass ® ) was PLLA : PEO : Bioglass ® : NaCl = 20.6 : 1.8 : 8.9 : 68.7.…”

Polymer/bioactive glass nanocomposites for biomedical applications: A review

“…combination of biodegradable polymers and bioactive glass [12,20,23], as discussed in detail further below. Moreover the surface modification of such biodegradable composites with smart polymers allows to produce substrates in which biomineralization could be triggered by the action of external stimuli, such as temperature or pH [24,25]. In this context, bioactive silicate glasses exhibit several advantages in comparison to other bioactive ceramics, e.g.…”