Project Objectives/Hypotheses
There is an urgent need to develop chemical and biological sensors for water quality monitoring that rapidly detect chemicals or environmental conditions that can be hazardous to the health of the environment and affected public. The overall goal of this proposal is to develop a low cost, robust biosensor design concept that can be broadly applied for water quality monitoring. This biosensor project will encompass novel aspects of materials science, optical engineering and nanotechnology to construct a prototype, which will include an optical detection (optode) scheme integrated within a microfluidic device that contains whole bacterial cells, which elicit a stress response in the presence of electrophilic (oxidative) toxins. The stress response yields a detectable signal that is correlated with the concentration of toxins in the sample. The specific objectives of this project are to: (i) evaluate an alternative containment polymer for the optode to enhance its structural (and some functional) properties, (ii) construct and characterize optodes into which gold nanoparticles are encapsulated that will enhance its functional properties, (iii) design and construct a microfluidic base unit that will be part of the prototype biosensor, and (iv) perform tests on prototype function using waters collected from various environments that are spiked with toxic chemicals.

Project Approach
A multidisciplinary approach is proposed to develop a microfluidic-based sensor design concept that can be translated into a broad range of applications. The unique aspects of the design concept include development of environmentally robust optode films that are integrated with microfluidic assemblies that are constructed completely of polymers (plastic materials). This plastic assembly will be integrated with light emitting diodes (LED) and fluorescence-enhancing nanoparticles to yield a low-cost, hybrid sensor design. For this proposal, we focus on a biosensor application that will include whole cell biological elements that detect the presence of electrophilic (oxidative, or thiol-reactive) chemicals through activation of the glutathione-gated K+ efflux (GGKE) bacterial stress response. Electrophiles can cause significant damage to both prokaryotic and eukaryotic cells and are a public health risk. Electrophiles such as heavy metals, chloro- and nitro- substituted organic compounds will be detected with this sensor. Dr. Laurie Locascio, a leading expert in the design and construction of plastic microfluidic devices, has offered the assistance of her lab, located at the National Institute of Standards and Technology in Gaithersburg, MD, for design and construction of the microfluidic base to the biosensor. We will also collaborate with Dr. Locascio's group, who are investigating additional strategies for optimizing optode function in a microfluidic setting. This will ensure the best optode design is implemented in the prototype device that is tested in year 3.

Expected Results
Preliminary work on a GGKE biosensor has started; therefore, this proposal will support research that will help us improve on the integrity, reliability and robustness of key elements, and we expect to have a functional prototype biosensor by the end of the study. Companies have already indicated their interest in the concept. The diverse team assembled for this project can deliver on the promise to complete a functional prototype; shortly thereafter, one of these companies will be able to move the idea to field deployment and commercialization.