Highly Sensitive Potentiometric Strip Test for Detecting High Charge Density Impurities in Heparin

Abstract

Contamination of heparin with oversulfated chondroitin sulfate (OSCS) became a matter of grave concern in the medical field after many fatal responses to OSCS tainted heparin products occurred during the 2007 – 2008 period. Even though standard lab-based analytical techniques such as nuclear magnetic resonance (NMR) and strong anion-exchange high performance liquid chromatography (SAX-HPLC) have proven useful for monitoring the OSCS content in heparin products, an easy-to-use, quick, portable, and cost-efficient method is still needed for on-site monitoring during and after the heparin production. In this report, a disposable strip-type electrochemical polyion sensor is described for detection of low levels of OSCS contamination in heparin. A magnetic actuator is incorporated into this simple electrode-based microfluidic device in order to create the mixing effect necessary to achieve equilibrium potential changes of the sensor within a microfluidic channel. The planar membrane electrode detector within the sample channel is prepared with a tridodecylmethylammonium chloride (TDMAC)-doped PVC membrane essentially equivalent to previously reported polyanion-sensitive electrodes. When the concentration of heparin applied to the single-use strip device is 57 mg/mL (in only 20 μl of sample), the same concentration recommended in the NMR analysis protocol for detecting OSCS in heparin, the detection limit is 0.005 wt% of OSCS, which is ca. 20 times lower than the reported detection limit of the NMR method.

Pharmacology of Heparin and Related Drugs

“…Methods for quantification and detection of OSCS include a Taq polymerase inhibition assay (Tami et al, 2008), enzyme immunoassay (Bairstow et al, 2009), and potentiometric methods (Wang and Meyerhoff, 2010) that can be developed into sensor technology (Gemene and Meyerhoff, 2010;Kang et al, 2011). Other ingenious methods for detection and quantification of OSCS in heparin include a heparinase inhibition assay (Aich et al, 2011), a convenient disposable strip-type electrochemical polyanion sensor (Kang et al, 2011), pyrolysis MS (Nemes et al, 2013), and spectropolarimetry (Chmielewski et al, 2011;Stanley et al, 2011).…”

“…Other ingenious methods for detection and quantification of OSCS in heparin include a heparinase inhibition assay (Aich et al, 2011), a convenient disposable strip-type electrochemical polyanion sensor (Kang et al, 2011), pyrolysis MS (Nemes et al, 2013), and spectropolarimetry (Chmielewski et al, 2011;Stanley et al, 2011).…”

A moving-part-free protamine-sensitive polymeric membrane electrode for sensitive biomedical analyses

“…Potentiometric polyion sensitive electrodes are a kind of ion exchanger-based polymeric membrane electrodes showing sensitive and reproducible potential responses toward polyionic macromolecules Kang et al, 2011). One of the most commonly used polyion-sensitive electrodes is the electrode responsive to protamine, a small polycationic protein isolated from fish sperm.…”

“…Among them, the analysis of heparin, a widely used injectable anticoagulant in surgical procedures, is of special importance. The accurate monitoring of heparin levels in blood prevents patients from fatal heparin overdose effects such as bleeding during or after the open-heart surgery (Olson et al, 1992) and the discrimination of heparin with its analog, oversulfated chondroitin sulfate is an imperative task for the control of heparin purity (Wang et al, 2008;Kang et al, 2011).…”

“…To solve these problems, an oscillating pressure source generated by a motor-driven syringe was used to move the sample solution in a cartridge back and forth across the protamine-sensitive polymeric membrane, thus ensuring effective sample mixing and the mass transport of protamine into the sensing membrane (Qin et al, 2010). More recently, in a microfluidic device for potentiometric polyion sensing, an electromagnet-driven actuator was designed to control a permanent magnet to squeeze and release sample solution on the sensing membrane, by which sample convection was fulfilled (Kang et al, 2011). However, these configurations, in essence, still rely on complex moving components and a potentiometric polyion-sensitive electrode truly free of moving parts is highly desirable to enable the fabrication of a simple, integrated, cost-and energy-effective polyion-based detection unit.…”