Titrimetric method for determination of O-desulfated heparin in physiological samples using protamine-sensitive membrane electrode as endpoint detector

O-Desulfated heparin (ODSH) is a promising new anti-inflammatory agent for the prevention of reperfusion injury following myocardial infarction or stroke. This partially desulfated heparin derivative has less anticoagulant activity than unfractionated heparin but retains the inherent anti-inflammatory properties of heparin. Thus, ODSH could be administered at the high doses needed to achieve desired anti-inflammatory function without risk of hemorrhage. However, given the very low anticoagulant activity of this species, traditional methods for heparin determination in clinical samples might not be well suited for ODSH measurements. In this article, a novel titrimetric method for detection of ODSH in buffer and plasma is described using a protamine-sensitive polymer membrane electrode as the detector. Titrations of ODSH with the heparin antagonist protamine yield sharp endpoints with sensitivity to ODSH in the micrograms per milliliter range for plasma samples. The stoichiometry for protamine interaction with ODSH is determined to average 1.39 μg protamine/μg ODSH in plasma. This technology is further applied to a toxicokinetic study of ODSH in an animal model, demonstrating the ability to detect the changes in ODSH concentrations in biological samples.