Chitosan Biotinylation and Electrodeposition for Selective Protein Assembly Xiao-Wen Shi, Yi Liu, Angela T. Lewandowski, Li-Qun Wu, Hsuan-Chen Wu, Reza Ghodssi, Gary W. Rubloff, William E. Bentley, Gregory F. Payne * Introduction The interfacing of proteins to devices is important for applications that range from point-of-care diagnostics to high-throughput drug screening. For many applications, protein assembly must be spatially controllable so individual proteins in an array can be assembled at a specific device address. Spatial control of protein assembly is often achieved using printing or photolithographic approaches. An emerging alternative approach for spatially- controlled assembly is to use the pH-responsive amino- polysaccharide chitosan to guide protein assembly. [1–3] Scheme 1a illustrates that chitosan can be induced to undergo a localized sol-gel transition in response to the localized pH gradient created by electrochemical proton consumption at a cathode surface. [4–9] Once electrodepos- ited, the chitosan film is stable and adheres to the electrode surface without the need for an applied voltage, provided Full Paper An alternative route to protein assembly at surfaces based on using the unique capabilities of biological materials for the spatially selective assembly of proteins is described. Specifically, the stimuli-responsive properties of aminopolysaccharide chitosan are combined with the molecular-recognition capabilities of biotin- streptavidin binding. Biotinylated chitosan retains its stimuli-responsive properties and is capable of electrodepositing at specific electrode addresses. Once deposited, it is capable of binding streptavidin, which can mediate the subsequent assembly of biotinylated proteins. Spatially selective protein assembly using biotinylated Protein A and fluorescently-labeled anti- bodies is demonstrated. X.-W. Shi, A. T. Lewandowski, L.-Q. Wu, H.-C. Wu, W. E. Bentley, G. F. Payne Center for Biosystems Research, University of Maryland Bio- technology Institute, 5115 Plant Sciences Building, College Park, MD 20742, USA Fax: þ1 301 314 9075; E-mail: payne@umbi.umd.edu A. T. Lewandowski, W. E. Bentley Department of Chemical and Biomolecular Engineering, Univer- sity of Maryland at College Park, College Park, MD 20742, USA H.-C. Wu, W. E. Bentley Fischell Department of Bioengineering, University of Maryland at College Park, College Park, MD 20742, USA R. Ghodssi Department of Electrical and Computer Engineering, University of Maryland at College Park, College Park, MD 20742, USA R. Ghodssi, G. W. Rubloff The Institute for Systems Research, University of Maryland at College Park, College Park, MD 20742, USA G. W. Rubloff Department of Materials Science and Engineering, University of Maryland at College Park, College Park, MD 20742, USA Macromol. Biosci. 2008, 8, 000–000 ß 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim DOI: 10.1002/mabi.200700220 1 Early View Publication; these are NOT the final page numbers, use DOI for citation !! R