Semi-Permeable Microcapsules for Use in Fluorescence-Based Glucose Sensing

Abstract

Due to the pain associated with conventional blood sugar monitoring techniques and the rising prevalence of diabetes, the development of noninvasive glucose sensing techniques is desirable. Towards this aim, implantable fluorescence-based glucose sensors are being developed. One strategy used in these sensors is to create a competitive binding scheme between fluorescent-labeled dextran and glucose using a fluorescent-labeled binding protein, such as glucose binding protein (GBP) or Concanavalin A (ConA), so that the protein and dextran create a Fluorescence Resonance Energy Transfer (FRET) pair. The sensing chemistry is then encapsulated in microcapsules with walls of nanoscale thickness formed using the Layer-by-Layer (LbL) method. This work involved two principal objectives: 1) to measure the permeability of capsules comprising different materials to dextran, as a means of identifying materials that allow the diffusion of glucose into the sensor while preventing release of the other components; and 2) evaluating the effects of different core formation methods on encapsulation. Results indicate that adding salt to the LbL solutions can decrease the permeability of the films to dextran and [PAH-GPTS/PSS]10 films made with salt had the lowest overall diffusion coefficient. Also, both the time frame between core precipitation and the beginning of the LbL and the core precursor solution compositions affect encapsulation of ConA but not dextran. The development of the capsules described in this work represents an important first step towards the fabrication of a noninvasive glucose monitoring system.