Kristen Helton

University of Washington Seattle | UW · Department of Bioengineering

We describe a simple method of tracking oxygen in real-time with injectable, tissue-integrating microsensors. The sensors are small (500 μm × 500 μm × 5 mm), soft, flexible, tissue-like, biocompatible hydrogels that have been shown to overcome the foreign body response for long-term sensing. The sensors are engineered to change luminescence in the...

Patients with limb-threatening ischemia exhibit uneven patterns of perfusion in the foot, which makes it challenging to determine adequate topographic perfusion by angiography alone. This study assessed the feasibility of reporting dynamic relative oxygen indices and tissue oxygen concentration from multiple locations on the foot during endovascula...

Purpose: To maximize mass transport into biomaterial scaffolds for regenerative medicine, in vivo diagnostics, therapeutics, and cell delivery. We utilized matrix morphology to encourage long-term tissue integration. Methods: We implanted 1cm-diameter poly-hydroxyethylmethacrylate (pHEMA) disks with 40 and 80µm nominal interconnected pores into ra...

Biomaterials elicit foreign body responses when implanted into living tissue. While biocompatibility has been improved, the fundamental aspects of tissue responses to biomaterials and their in vivo evaluation remain poorly appreciated. Here, we quantified vascularization of porous poly2-hydroxyethylmethacrylate (polyHEMA) with 40 and 80 μm nominal...

Background: Continuous glucose monitoring is crucial to developing a successful artificial pancreas. However, biofouling and host response make in vivo sensor performance difficult to predict. We investigated changes in glucose diffusivity and sensor response of optical enzymatic glucose sensors due to biological exposure. Method: Three hydrogel...

Implantable devices induce inflammation and collagen formation, which perturb the metabolic microenvironment and reduce mass transport. This study tested whether novel porous biomaterials improve tissue integration and normalize the glucose gradients. Five materials 700μm thick were implanted into rat dorsal subcutis: cotton cloth, solid silicone e...

The importance of biomechanics in glucose sensor function has been largely overlooked. This article is the first part of a two-part review in which we look beyond commonly recognized chemical biocompatibility to explore the biomechanics of the sensor-tissue interface as an important aspect of continuous glucose sensor biocompatibility. Part I provi...

This article is the second part of a two-part review in which we explore the biomechanics of the sensor-tissue interface as an important aspect of continuous glucose sensor biocompatibility. Part I, featured in this issue of Journal of Diabetes Science and Technology, describes a theoretical framework of how biomechanical factors such as motion and...

We present a fractional sensitivity analysis of a competitive microfluidic heterogeneous immunoassay for a small molecule analyte. A simple two-dimensional finite element model is used to determine the fractional sensitivity of the assay signal with respect to analyte concentration, flow rate, initial surface density of binding sites, and antibody...

This report details an approach to saliva conditioning for compatibility of raw patient samples with microfluidic immunoassay components, principally biosensor surfaces susceptible to fouling. Stimulated whole human saliva spiked with a small molecule analyte (phenytoin, 252 Da) was first depleted of cells, debris and high molecular weight glycopro...

As part of a project to develop an integrated microfluidic biosensor for the detection of small molecules in saliva, practical issues of extraction of analytes from non-Newtonian samples using an H-filter were explored. The H-filter can be used to rapidly and efficiently extract small molecules from a complex sample into a simpler buffer. The locat...

Saliva is an underused fluid with considerable promise for biomedical testing. Its potential is particularly great for monitoring small-molecule analytes since these are often present in saliva at concentrations that correlate well with their free levels in blood. We describe the development of a prototype diagnostic device for the rapid detection...

The developing world does not have access to many of the best medical diagnostic technologies; they were designed for air-conditioned laboratories, refrigerated storage of chemicals, a constant supply of calibrators and reagents, stable electrical power, highly trained personnel and rapid transportation of samples. Microfluidic systems allow miniat...

Thesis (Ph. D.)--University of Washington, 2007. A promising application of microfluidic technology is the realization of fully-automated and miniaturized lab-on-a-chip (LOC) systems. The benefits of performing assays at the microscale include smaller reagent volumes, rapid analysis times, multiplexed assays and the ability to test at the point of...