Peer reviewed article authored by (Baek M, Chung HE, Yu J, Lee JA, Kim TH, Oh JM, Lee WJ, Paek SM, Lee JK, Jeong J, Choy JH, Choi SJ). Read article or submit your manuscript for publishing.

In the present study, the effects of particle size (20 nm or 70 nm) and surface charge (negative or positive) on the pharmacokinetics, tissue distributions, and excretion of ZnO nanoparticles were examined following the administration of a single oral dose to rats. Pharmacokinetic profiles and biodistributions were not affected by particle size or gender. However, ZnO (−) particles were markedly more absorbed by the systemic circulation than ZnO (+) particles. Furthermore, the kinetic behaviors of ZnO nanoparticles differed from those of zinc ions, as evidenced by the low dissolution (13–14%) of ZnO nanoparticles under gastric conditions. The kidneys, liver, and lungs were found to be target organs. However, the major biological fate of ZnO nanoparticles in tissues was the ionic form, not the particulate form, and this was independent of exposure routes (oral and intravenous). Particle size was only found to affect excretion kinetics, and 20 nm particles were more rapidly eliminated. Most nanoparticles were excreted via the biliary and fecal routes, but a small amount of the nanoparticles was excreted via urine. The study shows that surface charge, rather than particle size or gender, is the critical modulator of the pharmacokinetic behavior of ZnO nanoparticles.

Food additive zinc oxide (ZnO) nanoparticles (NPs) are widely used as a Zn supplement in the food and agriculture industries. However, ZnO NPs are directly added to complex food-matrices and orally taken through the gastrointestinal (GI) tract where diverse matrices are present. Hence, the dissolution properties, interactions with bio- or food-matrices, and the ionic/particle fates of ZnO NPs in foods and under physiological conditions can be critical factors to understand and predict the biological responses and oral toxicity of ZnO NPs. In this review, the solubility of ZnO NPs associated with their fate in foods and the GI fluids, the qualitative and quantitative determination on the interactions between ZnO NPs and bio- or food-matrices, the approaches for the fate determination of ZnO NPs, and the interaction effects on the cytotoxicity and oral toxicity of ZnO NPs are discussed. This information will be useful for a wide range of ZnO applications in the food industry at safe levels.

A methotrexate (MTX)-layered double hydroxide (LDH) hybrid have been developed as a drug delivery system, in which an anticancer drug, MTX, was intercalated into a 2-dimensional LDH nanovehicle to form a nanohybrid. According to the comparative cell viability studies between MTX only and its LDH nanohybrid on MTX sensitive and resistant cell culture lines, it was found that the MTX-LDH nanohybrid could bypass the MTX resistance and eventually inhibit cancer cell proliferation very effectively compared to free MTX, due to an enhanced permeability and retention effect of MTX-LDH nanoparticles even in dihydrofolate reductase-overexpressing MTX-resistant cells. This is definitely associated with the uptake mechanism via a clathrin-mediated endocytic pathway for the MTX-LDH nanohybrid particles, the same as for the LDH nanocarrier only, which is completely different from the cellular uptake mechanism for MTX only, the reduced folate carrier (RFC) and/or the folate receptor entries.