The delivery of nanoparticles. Hashim AA, ed., Rijeka, Croatia: InTech, 2012 May; :271-292
During the past several years, nanotechnology based on novel nanomaterials has gained considerable attention in various scientific disciplines such as biotechnology, medicine and material engineering (McCarthy and Weissleder 2008). According to British Standards Institute Report (2007), nanoparticles are those particles with at least one dimension of less than or equal to 100 nm (1 nm = 1 x 10-6 m) in size. Since particle size is directly related to surface area and associated surface energy, nanoscaled materials relatively exhibit unique physicochemical, optical and electrical properties than micron-sized particles. Nanomaterials have exceptional properties and are beneficial in a wide range of applications. Nanotechnology based on these novel nanomaterials is fueling the modern industrial revolution which is already a multi-billion dollar market capitalization. Among the different types of nanomaterials, carbon nanoparticles have gained much attention in recent years due to their exceptional physicochemical properties. Some of the most popular carbon-based nanomaterials are fullerene (C60), carbon nanohorn, single wall carbon nanotubes (SWCNT), and multi wall carbon nanotubes (MWCNT). Carbon nanotubes (CNT) are one of the most commonly used nanomaterials possessing unique physicochemical properties such as high aspect ratio and a diameter of less than 100 nm (Iijima 1991). Due to their exceptional characteristics, CNT, if incorporated will enhance the efficiency of a number of applications including electronics (Bandaru 2007), biosensors (Le Goff, Holzinger et al. 2011), drug and biomolecule carriers (Prato, Kostarelos et al. 2007). Other potential biomedical applications of CNT include bone scaffold, dental tissue support, and neuronal cell growth scaffold (Li, Fan et al. 2010). Increasing evidence has shown that certain CNT properties such as nano-sized dimension, high surface energy, and large reactive surface area are directly correlated to their biological activities (Oberdorster, Ferin et al. 1994; Oberdorster, Oberdorster et al. 2005). The bioactivity of nanoparticles differs from micron-size particles of the same material. Although the underlying mechanism remains to be understood, small size, high surface area and chemical composition of nanomaterials play an important role. Recent studies have shown that CNT could be harmful to human health. Fiber morphology and high surface energy of CNT raise health concerns among scientists due to their structural similarities with asbestos fibers (Donaldson, Murphy et al. 2010). The biological properties of nanoparticles are currently under intense investigations and are the subject of this review.