Encapsulation of a Concanavalin A/dendrimer glucose sensing assay within microporated poly (ethylene glycol) microspheres

Proper management of diabetes requires the frequent measurement of a patient's blood glucose level. To create a long-term, minimally-invasive sensor that is sensitive to physiological concentrations of glucose a fluorescent glucose sensing assay using a competitive binding approach between fluorescently tagged Concanavalin-A (Con-A) and glycodendrimer is being developed. Until now, the essential step of effectively encapsulating this aggregative sensing assay while allowing a reversible response has yet to be reported. In this paper, a microporation technique is described in which microspheres are synthesized in a manner that creates fluid-filled pores within a poly (ethylene glycol) hydrogel. This dual-nature technique creates hydrophilic, biocompatible microcapsules in which the aggregative binding kinetics of the sensing assay within the pores are not constrained by spatial fixation in the hydrogel matrix. Confocal images displaying the localization of pockets filled with the assay within the polymeric matrix are presented in this paper. In addition, fluorescent responses to varying glucose concentrations, leaching studies, and long-term functionality of the encapsulated assay are demonstrated. To our knowledge, this is the first time that the Con-A/glycodendrimer assay has been shown to be reversible and repeatable within hydrogel spheres, including the display of functionality up to fourteen days under ambient conditions. (C) 2011 Optical Society of America