Molecularly Imprinted Polymers Used as Optical Waveguides for the Detection of Fluorescent Analytes
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Molecularly Imprinted Polymers Used as Optical Waveguides for the Detection of Fluorescent Analytes Jennifer J. Brazier, Mingdi Yan, Scott Prahl, and Yin-Chu Chen Chemistry Department, Portland State University, Portland, OR 97207- 0751, U.S.A. ABSTRACT This article demonstrates the novel approach of fabricating molecularly imprinted polymers (MIPs) as fiber optic waveguides for the detection of fluorescent analytes. Combining a polyurethane system and the soft lithography technique of micromolding in capillaries (MIMIC), polymer waveguides of 50 µm and 100 µm dimensions were patterned onto a silicon substrate. Laser coupling into small waveguide segments has been verified visually. Binding experiments using the waveguides are currently being explored. Some preliminary binding studies have been performed, however, for smaller, freestanding filaments of sizes consistent with conventionally prepared MIP particles. Using fluorimetry measurements, templated fibers of 20 µm dimension preferentially bound the analyte molecules by a factor of 1.5 as compared to control polymers. INTRODUCTION Molecularly imprinted polymers are biomimetic materials used for the sensitive and selective detection of small organic molecules. Through host-guest interactions, imprinted polymers often display recognition capabilities comparable to those of antibody-antigen systems.1 The imprinted polymers, however, are much more stable to organic solvents, pH, and temperature than their biological counterparts. With such benefits, this technology has found a niche in various separation techniques such as HPLC, CEC, TLC,2-4 and in many sensor applications.5-6 Traditionally, molecularly imprinted polymers are synthesized in bulk and then subjected to a grinding and sieving process that results in particles of 25 µm or larger dimension. This process, however, is tedious and often creates particles of irregular shape and size. Furthermore, many of the imprinted sites are destroyed during the grinding procedure. Because of these drawbacks, various other synthetic techniques have been employed to create polymers ranging from thin films to small beads.7-8 This article demonstrates the novel approach of fabricating imprinted polymers in the form of fiber optic filaments for the detection of fluorescent polyaromatic hydrocarbons. EXPERIMENTAL DETAILS Materials PDMS (Sylgard 184 elastomer, Dow Corning) and its corresponding curing agent were purchased from K.R. Anderson, Inc. (Kent, WA). A silicon master was patterned via conventional photolithography using SU-8 photoresist (Microchem Corporation, Newton, MA). Bisphenol A, phlorglucinol, and anthracene were purchased from Aldrich and were used as M6.4.1 Downloaded from https://www.cambridge.org/core. University of Alberta Libraries, on 15 Aug 2017 at 11:51:02, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1557/PROC-723-M6.4
Silicon Master
Pour PDMS and cure at 70oC, 4h
Remove stamp and place on substrate
Fill capillaries and cure polym
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