Hydroxyapatite, porous silicon

Fig. 16.7. SEM micrographs of hydroxyapatite (b) Cross-section of substrate shown in (a), (c) spherulites deposited upon porous silicon Deposition adjacent to anodized region after...

The term biocompatibility is defined as the ability of a material to perform with an appropriate host response in a specific situation" (Williams 2008). A biocompatible material can be inert, where it would not induce a host immune response and have little or no toxic properties. A biocompatible material can also be bioactive, initiating a controlled physiological response. For porous silicon, bioactive properties were initially suggested based on the observation that hydroxyapatite (HA) crystals grow on microporous silicon films. HA has implications for bone tissue implants and bone tissue engineering (Canham 1995). An extension of this work showed that an applied cathodic current was able to further promote calcification on the surface (Canham et al. 1996). More recently, Moxon et al. showed another example of bioactive porous silicon where the material promoted neuron viability when inserted into rat brains as a potential neuronal biosensor, whereas planar silicon showed significantly fewer viable neurons surrounding the implant site (Moxon et al. 2007). 

In the previous chapter, two examples of multifunetional drag delivery systems applying PSi luminescent and photonic properties were described, but there are many other possibilities to include additional functionalities to the delivery systems. One of the most studied applications is PSi-poljuner composite structures in which PSi have a dual role as a hydroxyapatite growth activator and drag carrier (Mukheijee et al. 2006 Fan et al. 2009, 2011). The composite structures are described in detail in chapter Poljnner-Porous Silicon Composites. ... 

Zhang, E. and Zou, C.M. (2009) Porous titanium and silicon-substituted hydroxyapatite biomodification prepared by a biomimetic process characterization and in vivo evaluation. Acta Biomater., 5 (5), 1732-1741. 

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