Читать книгу Nanobiotechnology in Diagnosis, Drug Delivery and Treatment - Группа авторов - Страница 58

Nanomaterials are characterized by their small size, commonly defined to be of diameter in the range of 1–100 nm and large surface area to volume ratio. However, in principle, NMs are described as materials with a length of 1–1000 nm in at least one dimension. Size is an important feature of nanomaterials as it affects their cellular uptake, physical properties, and interactions with biomolecules. It is observed that the smaller the size the easier the penetration of nanoparticles through the cell envelope (Jeevanandam et al. 2018). Kumar et al. (2016) reported that nanoparticles in the range of 1–10 nm have the capacity to diffuse into tumor cells. This helps to overcome limitations related to chemotherapy using free drugs such as poor in vivo/in vitro correlation and other possible resistances exhibited by tumors.

Powers et al. (2007) demonstrated that decrease in the size of any materials leads to an exponential increase in surface area to volume ratio, thereby making the nanomaterial surface more reactive to itself and to its contiguous environments. Moreover, it is suggested that size‐dependent toxicity of nanoparticles can be attributed to its ability to enter into the biological systems and then modify the structure of various macromolecules, thereby interfering with critical biological functions (Lovrić et al. 2005; Aggarwal et al. 2009). Small particles in the size range of 5–110 nm can be used as potential carriers of anticancer drugs via intracellular drug delivery (Laroui et al. 2011). However, evaluation of other physicochemical properties of nanomaterials including surface area, solubility, chemical composition, shape, agglomeration state, crystal structure, surface energy, surface charge, surface morphology, and surface coating are essential for their safe use in clinical applications. Therefore, the role of individual, characteristic properties of nanomaterials in imparting toxic manifestations is so important (Gatoo et al. 2014).

Nanomaterials possess good stability and much longer shelf life compared with molecular carriers (Laroui et al. 2011). The drugs can be loaded into nanoparticles at a specific concentration, and such nanoconjugates may avoid digestive processes in the GI tract, which ultimately helps in efficient drug delivery at targeted sites. Moreover, the kinetics of drug release can be modulated, and nanomaterial surfaces may be modified with ligands to affect site‐specific drug delivery (Laroui et al. 2011). Similarly, nanostructures can be conjugated to biological molecules, including hormones and antibodies, which enable their targeting to tissues expressing their cognate receptors (Fortina et al. 2007).

These capabilities of nanomaterials allow design and use of nanostructures in various fields of medicine including gastroenterology that help in diagnosis, bioimaging, and treatment processes, and can favorably compete with conventional methods (Laroui et al. 2011).