Читать книгу Nanobiotechnology in Diagnosis, Drug Delivery and Treatment - Группа авторов - Страница 64

The digestive system consists of the GI tract, liver, pancreas, and gallbladder (Giau et al. 2019). This system allows the body to digest and break down the food into nutrients, which are subsequently used for energy, growth, and cell repair (Angsantikul et al. 2018). The digestive system diseases and disorders can be acute and last for a short time (e.g. various bacterial or viral infections), while others are chronic or long‐lasting (e.g. cancers, Helicobacter pylori infection, etc.) (Giau et al. 2019). Irritable bowel syndrome (IBS) belongs to the functional GI disorder group as it shows a group of symptoms such as abdominal pain and changes in the pattern of bowel movements but without any evidence of underlying damage (Lacy et al. 2016). Some of the reports available proposed the use of nanodelivery systems as carriers for the delivery of active compounds in the treatment of IBS (Collnot et al. 2012; Xiao and Merlin 2012). These reports demonstrate promising results showing physiological changes in IBS, after application of such nanoconjugates with drugs and exploiting these differences to enhance specific delivery of drugs to affected tissue.

GI tract disorders are statistically noticed in 5 to 50% of patients with primary immunodeficiencies (PIDs) which include rare, chronic, and serious disorders of the immune system. Patients suffering from PIDs cannot mount a sufficiently protective immune response, leading to an increased susceptibility to infections. The gut is the largest lymphoid organ in the body, containing the majority of lymphocytes and producing large amounts of immunoglobulin (Ig), therefore patients with PIDs might suffer from various GI disorders caused by microorganisms or parasites. Dysfunction of the regulatory mechanisms responsible for the balance between active immunity and tolerance in the gut may lead to mucosal inflammation and damage, and also lead to GI diseases (Agarwal and Mayer 2013).

Overall, nanoparticle and nanomolecule drug‐delivery mechanisms can be classified into active and passive targeting. Active targeting highly depends on the interaction between the target cell receptors and nanoparticles, whereas passive targeting relies on a number of factors such as longer biological half‐life, long‐circulating time at tumor locations, and the flow rate of nanoparticles to the impaired lymphatic system (Hong et al. 1999; Kaasgaard et al. 2001; Mishra et al. 2004; Gryparis et al. 2007; Romberg et al. 2008; Gholami and Engel 2018). Moreover, the effectiveness of the nanoplatform drug‐delivery system is determined by the enhanced permeability, retention effects, and nanoparticle clearance by the mononuclear phagocyte system (Maeda et al. 2000; Greish 2007). The reticuloendothelial system (RES) effect is one of the most common problems among all different types of nanoparticles used for diagnosis and therapy of various diseases. The RES effect refers to the quick absorption of nanoparticles by macrophages which usually results in clearing nanoparticles from the circulation in vivo (Owens and Peppas 2006; Torchilin 2007; Howard et al. 2008). Therefore, modification of nanomaterials, e.g. specific types of nanoparticle coating, may prevent and minimize the RES effect (Gholami and Engel 2018). Kovacevic et al. (2011) reported that nanoparticles with surfactants or covalent linkage of polyoxyethylene have shown to effectively minimize the RES effect. Similarly, the size of nanoparticles was found to affect the delivery of conventional therapeutics to solid tumors. Nanoparticles larger than 500 nm are shown to be rapidly removed from the circulation in vivo (Maeda et al. 2000; Cho et al. 2009).

Although the application of diagnostics and therapeutics to the targeted sites along the GI tract and endoscopy are sometimes complicated, especially into the distal small intestine, it has been tried in many types of diseases, with varied success. The targeted delivery of therapeutic agents to the terminal ileum and colon was performed in the case of IBD and to the stomach in gastrin ulcers, while the theranostic probe was tried in the diagnostics of pancreatic, gastric and colonic cancers, or genes in gene therapy of gastric and colonic cancers (Jha et al. 2012). It suggests that application of nanomaterials in diagnosis and therapy of GI disorders is a very promising approach in nanomedicine.