Biocompatibility and toxicity of nanocomposites

Nanotechnology research is growing at an exponential rate and is predicted to change the face of the world in which we live. There are many products including sunscreens, anti-wrinkle face creams, sports equipment, bone, and muscular replacement materials which employ nanomaterials to improve functions above those currently observed in conventional or microstructured materials (Henig, 2007). 

Nanocomposites are multiphase solid materials which have one to three dimensions less than lOOnm, or structures with nanosized repeat distances in different phases that compose the material (Ajayan et al., 2003). Nanocomposites can be divided into bioceramic nanocomposites, metallic nanocomposites, and polymer nanocomposites. The structure of nanocomposites can be nanoflbers, nanoparticles, nanotubes, or scaffolds 

Of course, one of the most popular cerantics used in orthopedic tissue engineering is hydroxyapatite (HA). Several researchers have developed HA ceramic-based composites for bone replacements. With different loading conditions of nanohydroxyapatite (nHA) particles, the nanocomposites showed great bioactivity toward bone cells and consequently new bone formation. The bioactivity of HA is due to the close matching of the chemical composition of the ceranuc with the natural inorgauic phase of bone (Alothman et al., 2013). However, poor resorbability and brittle constructs 

ZnO and MgO nanoparticles have been shown to increase bone cell functions and decrease infection (Liu et al., 2015 Weng and Webster, 2012). Nano zinc oxide (ZnO) also can induce osteogenic properties from stem cells (Liu et al., 2015). Composites incorporating ZnO nanoparticles with a diameter near 60 nm can form a scaffold for tissue regeneration. The size of laminin, collagen, and fibronectin, which are all major components of the natural ECM, is on the same order of magnitude as a ZnO nanoparticle. Moreover, the piezoelectric and antibacterial properties of ZnO particles make it a good choice for orthopedic implant applications (Sell and Webster, 2(X)8). 

Although some potential cytotoxicity occurs with some polymers or metallic ions, there is some research using polymer-based bioactive ceramic composites combined with metals to improve the mechanical and bioactive properties for biomaterials. 

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