Global regulatory agencies seem increasingly active in the debate over nanotechnology definitions and are engaged in discussing applications in food, agriculture, and medicine. Perhaps the most promising public health application of nanotechnology lies in reducing nutrient insufficiencies and the associated illnesses.
Global insufficiencies of certain micronutrients may be corrected through the use of nanoparticles as carriers. Most iron fortificants are relatively biologically inert in humans. While most of these compounds are compatible in food systems, the physical and chemical properties provide product development, stability, and sensory challenges (Clemens and Mercurio, 1981). Iron salts such as gluconate, fumarate, and sulfate demonstrate high bioavailability and high reactivity in foods. Some of these issues may be moderated or resolved through the introduction of nanostructured powders, depending on the particle size, molar ratios of some minerals, and the physical dimensions of the particle (Rohner et al., 2007; Hilty et al., 2009; Hilty et al., 2010).
Dispersing lipid soluble nutrients such as vitamins A and D may be improved through nanoparticulation or through the introduction of nanostructured lipid carriers, nanoencapsulation, or engineered nanoliposomes (Hentschel et al., 2008; Bernardy et al., 2010; Jølck et al., 2010). These carrier systems may be equally valuable in the delivery of medications and nutrients targeted to specific cell types and receptors. This approach, often referred to as nanotherapy, may improve intervention efficiency, significantly reduce classic inhibitory concentration doses, and possibly improve apoptotic index (apoptotic cells/1,000 tumor cells). These favorable outcomes were recently demonstrated through the use of nanoparticles transporting encapsulated grape seed extract and folic acid (Narayanan et al., 2010).
One biological challenge associated with phytochemicals is the apparently rapid plasma clearance. Hepatic cytochrome P450 readily metabolizes phytochemicals such as polyphenols, thus minimizing the potential effectiveness often ascribed to antioxidants. Developing a time-release approach through encapsulation technologies may assist in thwarting the hostile gastric environment and aid the delivery of bioactive food components as well as medications (Siddiqui et al., 2010).
Applying the traditional toxicological principles of absorption, distribution, metabolism, and excretion (ADME), it is incumbent to assess the pharmacodynamics of nanoparticles. Rodent studies indicate orally administered nanoparticles are absorbed through the small intestinal wall and readily distributed through organs and tissues via the circulatory and lymphatic systems (des Rieux et al., 2006; Hagens et al., 2007). This is consistent with increased bioavailability of iron phosphate-containing nanoparticles, which may reflect its amorphous state, irregular porous structure, and high surface area (Rohner et al., 2007). These findings are further supported through the use of physiologically based pharmacokinetic (PBPK) models (Li et al., 2010). Using the PBPK model, the ADME of nanoparticles, potential applications and toxicity of these components may explain similarities and differences among species, tissues, exposure routes, and doses (Evans et al., 2008). Importantly, several pharmacokinetic studies indicate the absence of bioaccumulation of nanoparticles in gut or other tissues (Hilty et al., 2010).
Among the many aspects of the ADME model not yet fully addressed in the consideration of nanotechnology are potential oxidative stress mechanisms that may compromise the safety of nanoparticles (Mocan et al., 2010). A recent study suggested that nanoparticles of iron oxide can alter microvascular cell permeability through the activation of reactive oxygen species and the modulation of specific kinases that mediate this permeability (Apopa et al., 2009).
Some in biomedical research contend iron nanoparticles may be useful in advancing imaging and in the fabrication of biological materials as well as targeted drug delivery and directed chemotherapeutic and antibiotic therapies. Some investigations demonstrate that nanosized particles with unique structures and physical characteristics may concentrate in targeted cells, such as cancer cells, through altered membrane permeability properties. The results of enhanced selective permeability and concentration may improve therapeutic effects while minimizing negative side effects (Greish, 2010).
Nanotechnology, whether its application is in nanosized nutrients or nanomedicine, marks a new era in research and a new challenge in consumer communications and public health policy Pautler and Brenner, 2010).
References cited in this article are available from the authors.
Roger Clemens, Dr.P.H.,
Chief Scientific Officer, ETHorn, La Mirada, Calif.
Peter Pressman, M.D.,
LCDR, Medical Corps, U.S. Navy, Director Expeditionary Medicine, Task Force for Business & Stability Operations