Exposure via the Gastrointestinal Tract

Exposure to nanomaterials via the gastrointestinal tract is inevitable as food products may be contaminated by synthetic nanomaterials present in the environment. In addition, nanomaterials or particulate matter cleared through the mucociliary escalator in the respiratory system will relocate to the gastrointestinal tract [14, 35, 51, 84). Thus, it is important to understand particulate invasion via the gastrointestinal tract, and the factors that dominate the tract s absorption processes. 

The uptake of nanomaterials in the gastrointestinal tract is greatly affected by the nanomaterials size and surface properties [32, 51, 94], with small nanoparticles being more easily absorbed than larger nanoparticles. The rate of uptake for different-sized polystyrene particles showed a distinctive pattern of efficiencies, with 6.6% and 5.8% of small particles (50 and lOOnm) being absorbed, respectively, but almost none of the micrometer-sized particles (0.8% and 0% for 1 pm and 3 pm particles, respectively) [94]. 

The surface charges of the nanomaterials can also affect their rate of uptake. Typically, positively charged particles are absorbed more efficiently than neutral and negatively charged particles, although most particles in the gastrointestinal tract will be quickly expelled via the feces [84]. 

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Type I, or immediate immune, response involves the body s production of immunoglobulin E (IgE) antibodies in lymphatic tissue that bind to the surface of mast cells and basophils and prime them for action. The antibodies are produced in B lymphocytes during the period of sensitization. Sensitization occurs as the result of exposure to appropriate antigens through the respiratory tract, dermally, or by exposure via the gastrointestinal tract. Subsequent cross-linking of the antibodies... 

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