Investigating Heparin Dynamics through Solid-State Nanopores: Toward Nanopore-based Methods for Glycomics

Abstract

Solid-state nanopores have become a fast-rising technique in single-molecule sensing, especially in DNA and protein sensing. Carbohydrates, as one of the most important biomacromolecules for human life, have posed challenges in related research and analysis due to their complexities, and solid-state nanopores have shown great potential in glycan sensing and analysis because of their stability, cost-effectiveness, fast results and high sensitivity. The kinetics, conformation, and identification of heparin molecules were investigated. Heparin is a widely used anticoagulant in medical practices, and a large-scale contamination scandal in 2008 has attracted more attention, as a quick and effective method to differentiate heparin and OSCS (oversulphated chondroitin sulphate) needs to be developed. A series of experiments was done in different salts and salt concentrations, at different pH levels, to find an optimized sensing condition for maximum capture. By a simulation tool developed in the lab and the experimental results, we also investigated conformations of heparin as they pass through a solid-state nanopore. However, the negatively charged small particles pass through the nanopores too fast for the state-of-the-art instruments to fully resolve. An attempt was also made to differentiate heparin and OSCS, but no significant differences were seen. In an effort to slow down the molecules, a specialized flow cell that incorporates a pressure system was adopted. However, under a small counterpressure, heparin molecules were not seen to slow down. Lectin, a human protein that has proved to be heparin-binding, was also experimented with. It was shown that at 3.6 M LiCl, pH 4, heparin and lectin molecules could bind and form a compound that translocates through the nanopore as one, which produces significantly slower and deeper signals.