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

  • Yokel, R.A., Unrine, J.M., Wu, P., Wang, B., Grulke, E. A. Nanoceria biodistribution and retention in the rat after its intravenous administration are not greatly influenced by dosing schedule, dose, or particle shape, Environmental Sciences: Nano, published on-line September 1, 2014.
  • Yokel, R.A., Hussain, S., Garantziotis, S., Demokritou, P., Castranova, V., Cassee, F.R. The Yin: An adverse health perspective of nanoceria: uptake, distribution, accumulation, and mechanisms of its toxicity, Environmental Sciences: Nano, 1 (5), 406-428, 2014.
  • Willhite, C.C., Karyakina, N.A., Yokel, R.A., Yenugadhati, N., Wisniewski, T.M., Arnold, I.M.F., Momoli, F., Krewski, D. Systematic review of potential health risks posed by pharmaceutical, occupational and consumer exposures to metallic and nanoscale aluminum, aluminum oxide, aluminum hydroxide and its soluble salts. Critical Reviews in Toxicology, 44, Suppl 4, 1-80, 2014.
  • Graham, U.M., Tseng, M.T., Jasinski, J.B., Yokel, R.A., Unrine, J.M., Davis, B.H., Dozier, A.K., Hardas, S.S., Sultana, R., Grulke, E.A., Butterfield, D.A. In vivo processing of ceria nanoparticles inside liver: Impact on free radical scavenging activity and oxidative stress, ChemPlusChem, 79(8), 1083-1088, 2014.
  • Yokel, R.A., Harris, W.R., Spilling, C.D., Abramov, V.P., Lone, J.L., Kuhn, R.J. A filtration system that greatly reduces aluminum in calcium gluconate injection, USP used to prepare parenteral nutrition solutions, Journal of Pediatric Pharmacology and Therapeutics, 19(3), 189-195, 2014.
  • 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 8:155-166, 2014.
  • 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 8(11): e81051. 
  • 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. Aluminum in food - The nature and contribution of food additives. In: Yehia El-Samragy (ed), Food Additive, InTech, ISBN 978-953-51-0067-6, 2012, pp. 203-228 (
  • 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.
  • 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.
  • 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., 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.
  • 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.
  • Yokel, R.A., Aluminum chelation principles and recent advances. Coordination Chemistry Reviews, 228:97-113, 2002.

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page last modified: September 24 2014     

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