Direct Measurement of Supra-Physiological Levels of Ascorbate in Plasma using a Nanophotometer

High dose intravenously administered vitamin C (ascorbate) is currently being tested in clinical trials as an adjuvant to current standard of care therapies in a variety of cancers. Intravenous infusion is used with a goal to achieve supraphysiological ascorbate concentrations in blood of at least 20 mM, 300 to 500 times normal healthy concentrations (0.04-0.08 mM). These trials need quick and easy access to information on the levels of ascorbate achieved in the blood to make clinical decisions. Previous methods that quantify ascorbate levels in blood require extensive preparation, time, and materials that may not always be present in clinical settings. We developed a new approach to meet this need using direct UV spectroscopy with a nanophotometer. The only preparation required is centrifugation of whole blood to separate the red blood cells from plasma. No more than 3 microliters of plasma are needed; the approach can determine the concentration of ascorbate in the range of 3 – 35 mM; the method is fast and efficient. This approach has already been deployed to gather this information in a clinical trial with lung cancer patients