Yttrium-90

Y-90 carries the hardest mean beta in the therapy roster, near 0.93 MeV: several times the energy of a Lu-177 electron. More energy per decay means more radiolytic peroxide per decay, and Y-90 is used at gigabecquerel activity for radioembolization and radionuclide therapy, so the production rate in the vial is intense from the moment it is filled.

Its 2.7-day half-life is shorter than the multi-day betas like Lu-177 and I-131 but still firmly a multi-day clock. The result is a peroxide burden that climbs quickly (high energy meeting high activity) and then stays elevated across the whole usable window rather than burning off in hours. High per-decay intensity on a multi-day clock is the Y-90 signature.

DuraRad lines the vial wall with a sol-gel coating that holds immobilized manganese superoxide dismutase, which converts superoxide to hydrogen peroxide and oxygen, and catalase, which decomposes that peroxide to water and oxygen. Radiolysis of water generates the reactive-oxygen species throughout the solution, at random positions and in every direction; the coating acts as a distributed sink at the wall, consuming the superoxide and peroxide that diffuse to it and holding their steady-state concentration in the vial below the uncoated level. The enzymes are anchored in the coating, not dissolved into the dose as a formulation additive. Hydroxyl radicals and singlet oxygen are not enzyme substrates, so the direct effect is on superoxide and peroxide; any reduction in hydroxyl radical would be indirect, from less peroxide feeding the trace-metal Fenton reaction.

Y-90's peroxide burden is intense but spread across days: the hard 0.93-MeV mean beta deposits several times a Lu-177 electron's energy per decay, and at gigabecquerel therapy activity the production rate is high from the moment the vial is filled and stays elevated across the 2.7-day half-life rather than burning off in hours. Enzymatic turnover runs on a timescale of minutes, far faster than that multi-day production clock, so the wall sink keeps pace with each increment of peroxide the high-energy decays produce and holds the modeled steady-state peroxide well below the uncoated level. Clearing peroxide as fast as the high-energy decays produce it keeps its concentration low and lowers the oxidative burden on the drug. This behavior is modeled, not yet measured; the Q4 2026 radioactive validation at Washington University in St. Louis is designed to confirm it under continuous irradiation.