Sub-micron Patterning on Polymer Films for Protein Arrays

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0900-O09-35.1

Sub-micron Patterning on Polymer Films for Protein Arrays Karen L. Christman1,2, Michael V. Requa3,4, Vanessa D. Enriquez-Rios1,2, Paula Mendes1,2, J. Fraser Stoddart1,2, Kimberly L. Turner 3,4, and Heather D. Maynard1,2*. 1 Department of Chemistry and Biochemistry and 2California NanoSystems Institute, University of California Los Angeles, 607 Charles E. Young Dr. East, Los Angeles, CA 90095-1569, U.S.A. 3 Mechanical Engineering and Environmental Engineering and 4California NanoSystems Institute, University of California Santa Barbara, Santa Barbara, CA 93106-5070, U.S.A. ABSTRACT Patterning proteins at the sub-micron and nanoscale has many uses, including fabrication of protein arrays for diagnostic and sensor applications. Many groups have reported micron scale protein patterns using photolithography; however, smaller scales have not been realized. In this study, we demonstrate sub-micron protein patterns using photolithography. Patterning is achieved by chemical transformation of pH-reactive polymer films. Site-specific immobilization of streptavidin within a protein resistant background is demonstrated. This methodology could be utilized for the development of high density proteins arrays for biotechnology applications.

INTRODUCTION The emerging technology of protein micro and nanoarrays offers exciting possibilities for biosensor applications [1, 2]. The resolution of commercially available arrays is limited due to the robotic printing techniques used in fabrication [3]. As an alternative approach, we have recently developed a methodology for protein patterning using pH-responsive polymer films and photolithography. This technique uses poly(3,3'-diethoxypropyl methacrylate) (PDEPMA), which contains reactive acetal groups that hydrolyze to aldehydes in the presence of acid (Figure 1). Aldehydes readily react with aminooxy-functionalized compounds [4] without the addition of any other reagent and can be reacted with amines via reductive amination [5]. We first demonstrated micron scale protein patterning (18 x 18 micron features) using PDEPMA, the photoacid generator (PAG) triphenylsulfonium triflate, and deep ultraviolet light (λmax=248 nm). In the current study, we examine the utility of PDEPMA for protein patterning at the sub-micron scale.

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Figure 1. Poly(3,3’-diethoxypropyl methacrylate). Upon exposure to acid, acetal side chains are converted to aldehydes.

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EXPERIMENTAL DETAILS 3,3’-diethoxypropyl methacrylate was synthesized and polymerized according to previously described procedures [6, 7]. Silicon wafers were coated using C4F8 plasma deposition (C4F8 flow rate: 100 sccm; argon flow rate: 10 sccm; pressure: 15 mT; inductively coupled plasma power source: 300 W at 13.56 MHz; process time: 10 sec; wafer temp: 30 ºC). PDEPMA was then spin-coated onto the substrates using a 2 % w/w solution in chloroform containing diphenyliodonium-9,10-dimethoxyanthracene-2-sulfonate (DIAS; 5 wt % PAG/polymer; Aldrich). Films were exposed to i-line light throug