Читать книгу Nanobiotechnology in Diagnosis, Drug Delivery and Treatment - Группа авторов - Страница 63

The GI tract is one of the portals for nanoparticles to get across the human body. However, inhaled nanoparticles can also be ingested by the GI tract once they are cleared through the respiratory tract (Hoet et al. 2004; Gaur et al. 2008). The kinetics of particle uptake in the GI tract depends on diffusion through the mucus layer, initial contact with enterocytes, cellular trafficking, and post‐translocation events (Medina et al. 2007). Once ingested, nanoparticles readily penetrate the mucus layer and come into contact with enterocytes of the intestinal lining. The smaller the particle diameter is, the faster they can diffuse through the mucus layer and reach the colonic enterocytes. However, nanoparticles may escape from active uptake by enterocytes as they are scavenged by M‐cells overlying the intestinal mucosa. Due to cellular transposition they can reach the bloodstream and distribute all over the body (Szentkuti 1997; Gaur et al. 2008).

It is suggested that similar to the lungs, the GI tract is also easily exposed to stimuli that can induce an inflammatory response. IBD, which is a group of inflammatory chronic disorders of the gut, can result from a combination of genetic predisposition and environmental factors (Podolsky 2002; Gaur et al. 2008). However, none of the published studies have reported direct toxicological effects of nanoparticles in the GI tract (Gaur et al. 2008).

On the one hand, the successful action of nanomaterials used for diagnosis or therapy of GI diseases depends heavily on their size, size distribution, morphology, hydrophilic–hydrophobic balance, and surface functionalization (Laroui et al. 2011). However, this action of nanomaterials also depends on conditions in each part of the digestive tract. These distinct conditions introduce many challenges to the application of therapeutics to GI tract. It should be highlighted that physicochemical properties and aggregation of nanomaterials will be also affected by co‐ingested material present in the gut, namely food matrices, proteins, mucus, and bile acids secreted within the gut (Walczak et al. 2015; Bouwmeester et al. 2018). Studies by Peters et al. (2012) and Walczak et al. (2013) reported that properties of 60 nm silver nanomaterials and nanometer‐sized silica were affected by the food matrix during transit before they were available for uptake in the small intestine.

The knowledge about the properties of nanomaterials is required for successful application of nanotechnology in diagnosis and therapy of GI tract disorders. The nanomaterials can be designed and their behavior regulated according to conditions of changing pH, transport time, pressure, enzyme‐catalyzed degradation, and content of bacterial population to reach the target site (Laroui et al. 2011).