Improved protamine-sensitive membrane electrode for monitoring heparin concentrations in whole blood via protamine titration§

Abstract

An improved protamine-sensitive electrode based on a polymeric membrane doped with the charged ion exchanger dinonylnaphthalenesulfonate (DNNS) is used for monitoring heparin concentrations in whole blood. The electrode exhibits significant nonequilibrium potentiometric response to polycationic protamine over the concentration range of 0.5–20 mg/L in undiluted whole-blood samples. The sensor can serve as a simple end point detector for the determination of heparin via potentiometric titrations with protamine. Whole-blood heparin concentrations determined by the electrode method (n ≥157) correlate well with other protamine titration-based methods, including the commercial Hepcon HMS assay (r = 0.934) and a previously reported potentiometric heparin sensor-based method (r = 0.973). Reasonable correlation was also found with a commercial chromogenic anti-Xa heparin assay (r = 0.891) with corresponding plasma samples and appropriate correction for whole-blood hematocrit levels. Whereas a significant positive bias (0.62 kU/L; P <0.001) is observed between the anti-Xa assay and the protamine sensor methods, insignificant bias is observed between the protamine sensor and the Hepcon HMS tests (0.08 kU/L; P = 0.02). The possibility of fully automating these titrations offers a potentially simple, inexpensive, and accurate method for monitoring heparin concentrations in whole blood.

Reversible Sensing of the Anticoagulant Heparin with Protamine Permselective Membranes

“…A linear dosage response is observed in Figure 2 d, which suggests a quantitative protamine–heparin interaction with a well‐defined stoichiometry (65 mg L −1 heparin for 90 mg L −1 protamine concentration. This is in agreement with earlier findings where the experimental binding ratio was 1.4 to 1 5f. 8b Unlike previous reports to develop polyion‐responsive sensors, the principle reported herein yields linear calibration curves.…”

Flash chronopotentiometric sensing of the polyions protamine and heparin at ion-selective membranes

“…Detection of heparin level in blood samples is very important and is commonly attempted in clinical laboratories by the socalled the activated clotting time measurement (ACT). However, this technique is indirect and nonspecific and the results can be affected by factors other than heparin [1,2] The developments in polymeric membrane potentiometric heparin [3][4][5][6]-and protamine [7][8]-selective electrodes by the group of Meyerhoff have been major achievements for direct and titration-based measurements of heparin as well as direct measurement of protamine in clinical samples. In addition to selective recognition of the polyions, these sensors show unusually high sensitivities that cannot be explained on the basis of the Nernst equation.…”

In vitro Detection and Optimization of Streptokinase Production by Two Streptococcal Strains in a Relatively Low Cost Growth Medium

“…Protamine-sensitive membrane electrodes were prepared according to the method described by Ramamurthy et al (1998). Electrochemical EMF measurements were made vs an Ag/AgCl reference electrode using a VF-4 (World Precision Instruments, Sarasota, FL).…”