Long V. Le

Background: Continuous glucose monitors (CGMs) enable people with diabetes to proactively manage their blood glucose and reduce the risk of hypoglycemia. Commercially available CGMs utilize percutaneous electrodes that, after days to weeks of implantation, are subjected to the foreign body response that severely reduces sensor accuracy. The previous work demonstrated the use of hydrogels containing a glucose-responsive viologen that quenches a nearby fluorophore. Here, we investigate the immobilization of this sensing motif onto a nanoparticle surface and optimize local surface concentrations for optical glucose sensing. Methods: A viologen quencher-fluorescent dye system was incorporated into poly(2-hydroethyl methacrylate) hydrogels in varying quantities to assess the effect of quencher-fluorophore concentration on glucose responsiveness. The sensing motif was then immobilized onto silica nanoparticles by carbodiimide chemistry. Nanosensors with a range of dye and quencher concentrations were challenged for glucose responsiveness to determine the optimal sensor formulation. Results: When incorporated into a hydrogel, high concentrations of viologen quencher and fluorophore were required to permit electron transfer between the two components and yield a detectable glucose response. Immobilization of this glucose-responsive system onto a silica nanoparticle facilitated this electron transfer to yield detectable responses at even low concentrations. Increasing quencher concentration on the nanoparticle, relative to the fluorophore, resulted in the greatest apparent glucose response. Conclusion: The nanoparticle sensors demonstrated excellent glucose response in the physiological range and are a promising tool for real-time glucose tracking.

Cell migration is regulated by several mechanotransduction pathways, which consist of sensing and converting mechanical microenvironmental cues to internal biochemical cellular signals, such as protein phosphorylation and lipid signaling. While there has been significant progress in understanding protein changes in the context of mechanotransduction, lipid signaling is more difficult to investigate. In this study, physical cues of stiffness (10, 100, 400 kPa, and glass), and microrod or micropost topography were manipulated in order to reprogram primary fibroblasts and assess the effects of lipid signaling on the actin cytoskeleton. In an in vitro wound closure assay, primary cardiac fibroblast migration velocity was significantly higher on soft polymeric substrata. Modulation of PIP2 availability through neomycin treatment nearly doubled migration velocity on 10 kPa substrata, with significant increases on all stiffnesses. The distance between focal adhesions and the lamellar membrane (using wortmannin treatment to increase PIP2 via PI3K inhibition) was significantly shortest compared to untreated fibroblasts grown on the same surface. PIP2 localized to the leading edge of migrating fibroblasts more prominently in neomycin‐treated cells. The membrane‐bound protein, lamellipodin, did not vary under any condition. Additionally, fifteen micron‐high micropost topography, which blocks migration, concentrates PIP2 near to the post. Actin dynamics within stress fibers, measured by fluorescence recovery after photobleaching, was not significantly different with stiffness, microtopography, nor with drug treatment. PIP2‐modulating drugs delivered from microrod structures also affected migration velocity. Thus, manipulation of the microenvironment and lipid signaling regulatory drugs might be beneficial in improving therapeutics geared toward wound healing.

Here, efforts toward the development of a microneedle-based glucose sensor or “smart patch” for intradermal glucose sensing are described. Metallic microneedle array electrodes, conducting polymers, and glucose oxidase form the sensor platform. This work represents the first steps toward the development of painless, transdermal-sensing devices for continuous glucose monitoring