Glucose-Responsive Capsules Based on (Phenylboronic-modified Poly(Lysine)/Alginate) System

Developing "smart" systems that respond to chemical stimuli is of major interest. The physico-chemical properties of such a system would enable it to detect and respond to changes in the concentrations of targeted molecules. Saccharides are one member of a challenging class of chemical stimuli that are particularly important with respect to both medical applications and industrial processes. In this context, a new glucose-responsive, multilayer system based on electrostatic interaction has been created via the layer-by-layer deposition of biopolymers. The studied polymers are poly(lysine) derivatives and alginate and are used as polycation and polyanion respectively. The system detected glucose at levels approximating 0.5 g.L−1 at which point the chemical modification of poly(lysine) with phenylboronic acid groups (known to form complexes with diol derivatives) occured. Herein, we have shown, using wetting contact and quartz crystal microbalance (QCM) measurements, that the poly(lysine) derivatives self-assemble with alginate through the formation of electrostatic bonding throughout the layer-by-layer assembly. QCM measurement revealed that introducing boronic acid moieties inside a macromolecular chain leads to glucose-responsiveness. This strategy was then extended to the fabrication of responsive particles using gold nanoparticles as a core template, and even to the fabrication of the capsule. As evidenced by measuring zeta potential, electrostatic interactions between the protonated amine groups of poly (lysine) derivative macromolecules (+40 mV) and the carboxylate groups of alginate (−20 mV) are the driving attraction force driving the fabrication of well-ordered multilayer films onto the spherical substrate. Transmission electron microscopy (TEM) was used to confirm that nanocapsules had been formed. This novel responsive capsule may further be used for specific biological purposes such as the detection of diabetes and/or enhancing treatment of the disease through sensing sugar levels.