Find in Library

The world of medicinal therapies has been historically, and remains to be, dominated by the use of elegant organic molecular structures. Now, a novel medical treatment is emerging based on CeO₂ nano-crystals that are discrete clusters of a few hundred atoms. This development is generating a great deal of exciting and promising research activity, as evidenced by this Special Issue of <i>Biomolecules</i>. In this paper, we provide both a steady-state and time-dependent mathematical description of a sequence of reactions: superoxide generation, superoxide dismutase, and hydrogen peroxide catalase and ceria regeneration. This sequence describes the reactive oxygen species (ROS); superoxide, O₂^&#8722;, molecular oxygen, O₂, hydroxide ion OH^&#8722; and hydrogen peroxide, H₂O₂, interacting with the Ce^3+, and Ce⁴⁺ surface cations of nanoparticle ceria, CeO₂. Particular emphasis is placed on the predicted time-dependent role of the Ce³⁺/Ce⁴⁺ ratio within the crystal. The net reaction is succinctly described as: H₂O₂ + 2O₂^&#8722; + 2H⁺ &#8594; 2H₂O + 2O₂. The chemical equations and mathematical treatment appears to align well with several critical in vivo observations such as; direct and specific superoxide dismutase (SOD), ROS control, catalytic regeneration, ceria self-regulation and self-limiting behavior. However, in contrast to experimental observations, the model predicts that the 4+ ceric ion state is the key SOD agent. Future work is suggested based on these calculations.