Carbohydrate sensing using boronic acid modified polymers

Abstract

Polyelectrolytes have attained a more prominent role in the design of supramolecular systems in recent years. In particular, commercially available poly(amidoamine) (PAMAM) dendrimers have been widely used because they have high loading capacities and good solubility in water. We focus here on using optical spectroscopy to investigate the application of PAMAM dendrimer derivatives as receptors in carbohydrate sensing, and to study the multivalent behavior of receptors covalently appended to the surface of these macromolecules. We then extended the design principles obtained from this work to linear water-soluble anionic polyelectrolytes developed in collaboration with the Kharlampieva group at the University of Alabama at Birmingham (UAB), using polymethacrylate-acrylamide co-polymers synthesized by their group. In chapters 2 and 3, we describe a carbohydrate sensing system that can operate in neutral water, using covalently modified polyelectrolytes as receptors, and common commercially available dyes as optical signaling units. Particularly, in chapter 2, boronic acid modified PAMAM dendrimers were used as receptors to differentiate common monosaccharides in water at millimolar concentration. This is a significant improvement in affinity and sensitivity over simple boronic acid receptors, particularly for work in aqueous environment, which is considered a challenging medium for carbohydrate detection. In chapter 3, these design concepts were also extended to using boronic acid modified polymethacrylate-acrylamide copolymers synthesized at UAB. Binding affinity trends of carbohydrates to boronic acid moieties were then investigated from a fundamental perspective. In chapter 4, the multivalent behavior of boronic acid moieties on surface-modified PAMAM dendrimers was characterized in detail to determine the factors influencing the onset of multivalent behavior, including the surface density of receptor sites and the overall size of the polymeric scaffold.