Robert Yokel

Contact Information

335 Bio Pharm Complex
789 South Limestone Street
Lexington, KY 40536-0596

Phone: 859-257-4855
Fax: 859-257-7564

Contact by email


  • Provost Distinguished Service Professor
    Department of Pharmaceutical Sciences

Robert Yokel, Ph.D.

Dr. Yokel's research focuses on neurotoxic metals, their toxicokinetics and chelation. Specific interests include entry into and exit from the brain, oral bioavailability, in vitro and biological assessment of chelators, mechanisms of neurotoxicity, and the role of physico-chemical properties of nanoscale materials in their ability to enter the brain. Preparations used include whole-animal preparations and cells in culture. Analytical techniques include radiation counting and accelerator mass spectrometric quantification of isotopic tracers.

Selected Publications/Presentations

  • Dan, M., Cochran, D.B., Yokel, R.A., Dziubla, T.D. Binding, transcytosis and biodistribution of anti-PECAM-1 iron oxide nanoparticles for brain-targeted delivery, PLOS ONE. 
  • Hardas, S.S, Sultana, R., Warrier, G., Dan, M., Wu, P., Grulke, E.A., Tseng, M.T., Unrine, J.M., Graham, U.M., Yokel, R.A., Butterfield, D.A. Rat hippocampal responses up to 90 days after a single nanoceria dose extend a hierarchical oxidative stress model for nanoparticle toxicity, Nanotoxicology.
  • Yokel, R., Grulke, E., MacPhail, R. Metal-based nanoparticle interactions with the nervous system: the challenge of brain entry and the risk of retention in the organism, WIREs Nanomed Nanobiotechnol. 5:346-373, 2013.
  • Dan, M., Scott, D.F., Hardy, P.A.,  Wydra, R.J.,  Hilt, J.Z., Yokel, R.A., Bae, Y. Block copolymer cross-linked nanoassemblies improve particle stability and biocompatibility of superparamagnetic iron oxide nanoparticles, Pharmaceutical Research, 30(2): 552-561, 2013.
  • Yokel, R.A., Tseng, M.T., Dan, M., Unrine, J.M., Graham, U.M., Wu, P., Grulke, E.A., Biodistribution and biopersistence of ceria engineered nanomaterials: Size dependence, Nanomedicine: Nanotechnology, Biology, and Medicine,9(3), 398-407, 2013.
  • Hardas, S.S., Sultana, R., Warrier, G., Dan, M., Florence, R.L., Wu, P., Grulke, E.A., Tseng, M.T., Unrine, J.M., Graham, U.M, Yokel, R.A., Butterfield, D.A, Rat brain pro-oxidant effects of peripherally administered 5 nm ceria 30 days after exposure, Neurotoxicology, 33, 1147-1155, 2012.
  • Dan, M., Tseng, M.T., Wu, P., Unrine, J.M., Grulke, E.A., Yokel, R.A., Brain microvascular endothelial cell association and distribution of a 5 nm ceria engineered nanomaterial, International Journal of Nanomedicine, 7,4023-4036, 2012.
  • Tseng, M.T., Lu, X., Duan, X., Hardas, S.S., Sultana, R., Wu, P., Unrine, J.M., Graham, U.M., Butterfield, D.A., Grulke, E.A., Yokel, R.A., Alteration of hepatic structure and oxidative stress induced by intravenous nanoceria, Toxicology and Applied Pharmacology, 260,173-182, 2012.
  • Yokel, R.A., Au, T.C., MacPhail, R.C., Hardas, S.S., Butterfield, D.A., Sultana, R., Goodman, M., Tseng, M.T., Dan, M., Haghnazar, H., Unrine, J.M., Graham, U.M., Wu, P., Grulke, E.A., Distribution, elimination and biopersistence to 90 days of a systemically-introduced 30 nm ceria engineered nanomaterial in rats, Toxicological Sciences, 127, 256-268, 2012.
  • Dan, M., We, P., Grulke, E.A., Graham, U.M., Unrine, J.M., Yokel, R.A., Ceria engineered nanomaterial distribution in and clearance from blood: Size matters, Nanomedicine, 7(1), 95-110, 2012.
  • Boyes, W.K., Chen, R., Chen, C., Yokel, R.A., The neurotoxic potential of engineered nanomaterials, NeuroToxicology, 33, 902-910, 2012.
  • Yokel, R.A., MacPhail, R.C., Engineered Nanomaterials: Exposures, hazards and risk prevention, Journal of Occupational Medicine and Toxicology, 6:7 (21 March 2011).
  • Hardas, S.S., Butterfield, D.A., Sultana, R.L., Tseng, M.T., Dan, M., Florence, R., Unrine, J.M., Graham, U.M., Wu, P., Grulke, E.A., Yokel, R.A., Brain distribution and toxicological evaluation of a systemically delivered engineered nanoscale ceria, Toxicological Sciences 116(2), 562-576, 2010; doi: 10.1093/toxsci/kfq137.
  • Yokel, R.A. Manganese flux across the blood-brain barrier. NeuroMolecular Medicine, 2009, 11(4), 297-310, 2009.
  • Yokel, R.A., Florence, R.L., Unrine, J.M., Tseng, M.T., Graham, U.M., Wu, P., Grulke, E.A., Sultana, R., Hardas, S.S., Butterfield, D.A. Biodistribution and oxidative stress effects of a systemically-introduced commercial ceria engineered nanomaterial. Nanotoxicology, 3(3), 2009. DOI: 10.1080/17435390902974496.
  • Yokel, R.A., and Florence R.L. Aluminum bioavailability from tea infusion. Food and Chemical Toxicology, 46:3659-3663, 2008.
  • Yokel, R.A., Hicks, C.L., Florence R. L. Aluminum bioavailability from basic sodium aluminum phosphate, an approved food additive emulsifying agent, incorporated in cheese. Food and Chemical Toxicology, 46:2261-2266, 2008.
  • Krewski, D., Yokel, R.A., Nieboer, E., Borchelt, D., Cohen, J., Harry, J., Kacew, S., Lindsay, J., Mahfouz, A.M., Rondeau, V., Human health risk assessment for aluminium, aluminium oxide, and aluminium hydroxide, J. Toxicol. Environ. Health, B. 10(Suppl 1):1-269, 2007.
  • Zhou, Y., Harris, W. R., Yokel, R.A. The influence of citrate, maltolate and fluoride on the gastrointestinal absorption of aluminum at a drinking water-relevant concentration: A 26Al and 14C study. J. Inorganic Biochem.
  • Sjögren, B., Iregren, A., Elinder, C-G., Yokel, R.A. Aluminum, Ch. 17 in: L. Friberg, G. Nordberg, B. Fowler, M. Nordberg (eds), Handbook on the Toxicology of Metals, 3rd Edition, Academic Press, 2007, pp 339-352.
  • Yokel, R.A., Blood-brain barrier flux of aluminum, manganese, iron and other metals suspected to contribute to metal-induced neurodegeneration, Journal of Alzheimer's Disease, 10:223-253, 2006.
  • Yokel, R.A., and Florence R. L. Aluminum bioavailability from the approved food additive leavening agent acidic sodium aluminum phosphate, incorporated into a baked good, is lower than from water, Toxicology, 227:86-93, 2006.
  • Yokel, R.A., Lasley, S.M., Dorman, D.C. The speciation of metals in mammals influences their toxicokinetics and toxicodynamics and therefore human health risk assessment. J. Toxicol. Environ. Health, B, 9:63-85, 2006.
  • Zhou, Y., Yokel, R.A. The chemical species of aluminum influences its paracellular flux across and uptake into Caco-2 cells, a model of gastrointestinal absorption. Toxicol. Sci., 87, 15-26, 2005.
  • Saiyed, Salim M., and Yokel, R.A. Aluminium content of some foods and food products in the USA, with aluminium food additives. Food Addit. Contam., 22:234-244, 2005.
  • Crossgrove, J.S., Yokel, R.A. Manganese distribution across the blood-brain barrier. IV. Evidence for brain influx through store-operated calcium channels. NeuroToxicology, 26:297-307, 2005.
  • Crossgrove, J.S., Yokel, R.A. Manganese distribution across the blood-brain barrier. III. The divalent metal transporter-1 is not the major mechanism mediating brain manganese uptake. NeuroToxicology, 25:451-460, 2004.
  • Yokel, R.A. and Crossgrove, J.S., Manganese toxicokinetics at the blood-brain barrier, Health Effects Institute Research Report 119, January, 2004, available at
  • Yokel, R.A., Crossgrove, J.S., Bukaveckas, B.L Manganese distribution across the blood-brain barrier. II. Manganese efflux from the brain does not appear to be carrier mediated. NeuroToxicology, 24:15-22, 2003.
  • Crossgrove, J.S., Allen, D.D., Bukaveckas, B.L., Rhineheimer, S.S., Yokel, R.A. Manganese distribution across the blood-brain barrier. I. Evidence for carrier-mediated influx of manganese citrate as well as manganese and manganese transferrin. NeuroToxicology, 24:3-13, 2003.
  • Yokel, R.A., Aluminum chelation principles and recent advances. Coordination Chemistry Reviews, 228:97-113, 2002.

Website Links

page last modified: November 19 2013     

© University of Kentucky College of Pharmacy
Official Site of the University of Kentucky College of Pharmacy