TiO2 و کامپوزیت های آن به عنوان مواد زیست شناختی TiO2 and its composites as promising biomaterials: a review

Introduction Biomaterials are biocompatible substances used in biological world for analysis, treatment and support to the living beings. They may be originated naturally or synthesized in laboratory. Among synthesized materials, TiO2 is one of the well-known semiconductor material used in the biological world. Utilization of TiO2, in water splitting (Fujishima and Honda 1972) and in photokilling of various microorganisms (Matsunaga et al. 1985) revolutionized the chemical and biological world respectively to a great extent. In the present scenario TiO2 is widely used in cosmetics, paints, ceramics, photocatalysis, solar cell, food coloring etc. TiO2 and TiO2 based conjugates exhibit antimicrobial activity and are also being applied in various biological applications like biosensing, blood clotting, drug delivery and photodynamic therapy due to their stability, sensitivity, selectivity, biocompatibility and non-toxic nature to the living beings. Titanium and its alloys have good mechanical properties, low density and excellent biocompatibility (Hunt and Shoichet 1985; Olmedo’ et al. 2008) which make these compounds highly applicable in the field of implants such as osteointegrated dental and orthopedic implants (Sahar et al. 1988). TiO2 exists in three forms i.e. anatase (tetragonal), rutile (tetragonal) and brookite (orthorhombic). TiO2 when synthesized is found in amorphous state and becomes crystalline on calcination. Its anatase phase is formed in the temperature range 400–500 C (Cordero-Garcı´a et al. 2016; Mattle and Thampi 2013). Further increase in the temperature pushes it into rutile phase that completes in the temperature range of 800–900 C (Zheng et al. 2008). It is a general perception that the key property of semiconductor functioning is their electronic properties, especially the band gap. The band gap of anatase and rutile are 3.2 and 3.0 eV respectively, (Dette et al. 2014; Scanlon et al. 2013) which is responsible for the antimicrobial activity and biosensing property. To achieve desired properties and applications, band gap of TiO2 can be altered by incorporation of various elements (metals and nonmetals) in TiO2 (Chenga and Sunb 2012; Yu et al. 2014; Souza et al. 2014; SoteloVazquez et al. 2015; Wang et al. 2011; Li et al. 2009). Absorption shift to visible region is highly appreciable regarding efficiency and cost effective purposes i.e. for the fabrication of self sterilizing materials and biosensors. Recently improved properties of TiO2, like low band gap and charge separation have been achieved by making their composites with carbon. Carbon materials are highly environment friendly and cheaper as compared to inorganic materials because carbon is one of the major elements present in the earth crust (Jo et al. 2014).