Cross-linking of a charged polysaccharide using polyions as electrostatic staples

Abstract

Charged polysaccharides play an essential role in biology and also serve as a promising class of biomaterials. We demonstrate, at the single molecule level, a simple method to cross-link anionic polysaccharides using polyions as electrostatic staples; positive charges on the polyion bridge opposite charges on the polysaccharide and trap its conformation. Cross-linking is detected by measuring step-like conformational transitions when the polysaccharides are stretched using an Atomic Force Microscope (AFM). The probability of cross-linking can be tuned by either titrating or screening the polysaccharide charges; this probability is measured from the width of transitions in the AFM force–extension curves. Polyion mediated cross-linking can be used to reversibly fold polysaccharides and engineer carbohydrates as a stimuli-responsive material that responds to changes in pH and ionic environment.