Applied Surface Science 258 (2012) 3750–3756 Contents lists available at SciVerse ScienceDirect Applied Surface Science jou rn al h om epa g e: www.elsevier.com/locate/apsusc Synthesis and conformational characterization of functional di-block copolymer brushes for microarray technology Gabriele Di Carlo a , Francesco Damin a , Lidia Armelao b , Chiara Maccato c , Selim Unlu d,e , Philipp S. Spuhler e , Marcella Chiari a,∗ a Institute of Chemistry of Molecular Recognition, National Research Council of Italy, Via M. Bianco 9, 20131 Milano, Italy b ISTM-CNR and INSTM, Department of Chemistry, University of Padova, Via F. Marzolo 1, 35131 Padova, Italy c Department of Chemistry and INSTM, University of Padova, Via F. Marzolo 1, 35131 Padova, Italy d Department of Electrical and Computer Engineering, Boston University, St. Mary Street 8, Boston, MA 02215, United States e Department of Biomedical Engineering, Boston University, St. Mary Street 8, Boston, MA 02215, United States a r t i c l e i n f o Article history: Received 16 June 2011 Received in revised form 20 September 2011 Accepted 3 December 2011 Available online 13 December 2011 Keywords: Surface initiated polymerization Reversible addition–fragmentation chain transfer polymerization (RAFT) Block copolymers Polymer brushes DNA microarray a b s t r a c t Surface initiated polymerization (SIP) coupled with reversible addition-fragmentation chain transfer polymerization (RAFT) was used to functionalize microarray glass slides with block polymer brushes. N,N- dimethylacrylamide (DMA) and N-acryloyloxysuccinimide (NAS) (graft-poly[DMA-b-(DMA-co-NAS)]) brushes, with di-block architecture, were prepared from a novel RAFT chain transfer agent bearing a silanating moiety (RAFT silane) directly anchored onto the glass surfaces. Conformational characteriza- tion of the coatings was performed by Self Spectral Interference Fluorescence Microscopy (SSFM), an innovative technique that describes the location of a fluorescent DNA molecule relative to a surface with sub-nanometer accuracy. X-ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscopy (SEM) were used to characterize the coatings composition and morphology. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Many of the methods used in genomics or proteomics are based on solid phase hybridization or complexation reactions between surface immobilized probes and free solution targets. Protein and DNA microarrays are examples of technologies for the simultaneous detection and quantification of a large number of biomolecules based on this principle. Chemical or biochem- ical reactions between free fluid components and immobilized probes require that an adequate number of molecules, with appro- priate conformation, are immobilized on the surface. The most commonly used immobilization methods on glass surfaces involve the deposition of reactive silane films with terminal functional groups that react with biomolecules, either directly or through a subsequent modification. However, steric hindrance may sig- nificantly reduce the reaction between surface functional groups and probe molecules on these types of monodimensional coatings, leading to poor grafting density. A more advantageous method of immobilization implies the formation of a chemically reactive ∗ Corresponding author. Tel.: +39 02 28500035. E-mail address: marcella.chiari@icrm.cnr.it (M. Chiari). polymer film on the glass surface [1–5]. A polymeric coating is needed to control the local chemical environment so as to retain the native conformation of proteins [6]. In addition, poly- mer coatings provide a three dimensional binding scaffold, which leads to a substantial increase in the density of probes per unit area. Homo- and block-copolymers brushes bearing chemical func- tionalities for the covalent attachment of biomolecules can be obtained by “grafting-onto” or “grafting-from” methods [7–13]. In this work, by using a “grafting from” approach we have functionalized glass substrates with brushes obtained by surface initiated (SI) controlled radical polymerization (CRP) [14]. CRP techniques, including nitroxide-mediated radical polymerization (NMP) [15], atom transfer radical polymerization (ATRP) [16] and reversible addition–fragmentation chain transfer polymerization (RAFT) [17], are excellent methods for the preparation of well- defined polymer structures such as block copolymers, star shape polymers, and interpenetrating polymer networks [18]. In partic- ular, RAFT has recently emerged as a promising controlled radical polymerization technique due to its versatility and simplicity. A major advantage of RAFT polymerization over other processes for living/controlled free-radical polymerization is its compatibility with a wide range of monomers including functional monomers. 0169-4332/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2011.12.019