Nanoparticle-based Biosensors for Rapid and Sensitive Detection of Contaminants in Food and Water

<p>NON-TECHNICAL SUMMARY: Medical costs and productivity losses associated with food and water contamination is estimated to amount to more than $6 billion annually. This project seeks to develop technologies to incorporate nanomaterials with unique electronic and optical properties into existing biodetection systems. Functionalization and assembly of nanoparticles and nanotubes will be investigated aiming to improve the detection sensitivity. The expected outcomes from this project include: 1) creation of novel nanomaterial-based biosensors for the detection of bacteria and pesticides; and 2) understanding of the potential of nanomaterials in improving the detection limit and response time of biosensors.</p>

<p>APPROACH: Oxide nanoparticles and aligned carbon nanotubes will be tested as the platforms for biosensor fabrication. The oxide nanoparticles will be surface functionalized and coupled with the probe DNA molecules, which hybridize with the target DNA sequences of E. coli. O157: H7. The fluorescence enhancement effect of the oxide nanoparticles allows amplification of the fluorescence intensity of the hybridized DNAs, thus contributing to the detection of trace amount of target DNA. The detection limit will be determined at a signal-to-noise ratio ≥ 3. The effects of nanoparticle size, surface chemistry, and immobilization chemistry on the detection sensitivity will be investigated. The aligned carbon nanotubes will be transferred to an electrochemical working electrode with the alignment retained. Each nanotube will be encapsulated by hydrogels with enzymes embedded. The hydrogel network provides an environment favorable for the activity of enzymes and also prevents the "leaking" of enzymes. Acetylcholinesterase will be used as the enzyme for the detection of organophosphate pesticides. The aligned carbon nanotubes play a dual role as both the substrate for enzyme immobilization and the transducer for amplification of the electrochemical signal generated from the enzymatic reaction. The amplification arises from two perspectives: 1) the strong catalytic effect of nanotubes to generate higher amount of current flow at the same potential; 2) the high density of nanotubes in the array that collects current flow from millions of carbon nanotubes. It is expected that this amplification effect will greatly improve the detection sensitivity of the electrochemical sensor towards organophosphate pesticides./</p>

<p>&nbsp;</p>

<p>PROGRESS: 2011/10 TO 2012/09 OUTPUTS: Assembled carbon nanotube arrays offer an ideal platform for miniaturized sensor devices, owing to the exceptional electrical properties and the ordered structure. For sensing applications, surface functionalization is critical, as it not only provides the functionality needed for detecting analytes such as pesticides and nerve agents, but also improves the surface biocompatibility. Most solution-based functionalization resulted in the collapse of nanotube alignment during the wetting and drying processes. We worked on vapor-based functionalization of assembled carbon nanotubes without altering the original nanotube alignment. We functionalized carbon nanotubes with intelligent hydrogels that respond to the change of pH in the surroundings. The vapor deposition method allowed excellent preservation of the hydrogel functionality and control of the hydrogel thickness at sub-100 nm level. The ultrathin hydrogel coatings imparted pH-responsiveness to the nanotubes and significantly enhanced the surface wettability. To the best of our knowledge to date, our work is the first to use vapor deposition for functionalization of carbon nanotube arrays with pH-responsive hydrogels. PARTICIPANTS: Principal Investigator: Yu (Jessie) Mao Graduate Research Assistant: Qing Song Graduate Research Assistant: Bin Zhi TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.</p>

<p>IMPACT: 2011/10 TO 2012/09 Rapid detection of chemicals and pathogens is urgently needed to ensure food and agriculture biosecurity. Using carbon nanotubes as the sensor substrates can advance our capability in fabricating novel biosensors with rapid response time and enhanced sensitivity. Our study on fabricating hydrogel-carbon nanotube arrays can significantly impact the device development of aligned carbon nanotubes and contribute to carbon nanotube-based biosensing. In addition, our work on studying nanomaterial-based biosensing will directly contribute to signal enhancement and device miniaturization of biosensors</p>