(563e) Heavy Metal Ion Detection Using Peptide-Modified Hydrogel Layers on a Quartz Crystal Microbalance

Current technology using spectroscopic analytical techniques such as atomic absorption or fluorimetry does not permit the portability of detection equipment for heavy metal ion sensing applications. Developing and fabricating a multiplexed, ultra-sensitive, inexpensive, portable sensor will benefit potable water testing. We propose that nanoscale changes can be amplified into a readable and reliable signal via ion-specific polymer membranes supported by a quartz crystal microbalance (QCM). Detection can be accomplished by changes in resonant frequency. Synthesis of peptide-embedded hydrogel layers using poly(N-isopropylacrylamide) (NIPAAm) on a QCM as the sensing platform for the detection of specific heavy metal ions in aqueous media is demonstrated. The QCM is a versatile sensor, commonly used in vapor, liquid, and biological detection applications. NIPAAm is a thermoresponsive material that exhibits a well-defined lower critical solution temperature (LCST) which is affected by chemical interactions within the hydrogel structure. Metallopeptide motifs embedded within the NIPAAm network create the high degree of selectivity for metal ions. A binding event of the target analyte causes the formation of a chelate complex, which changes the chemical interactions within the hydrogel network. Consequently, a shift in the LCST is experienced. Thus, detection can be accomplished by monitoring macroscopic viscoelastic changes (via frequency shifts) in conjunction with shifts in the LCST. Dissipation in the sensing layers will also be monitored via impedance measurements and/or the QCM-D technique, and results will be presented. These additional measurements will help better characterize the sensing layer, allowing for better design.