Immobilization of Amine-modified Oligonucleotides on Bifunctional Polymer Brushes Synthesized by Surface-initiated Polymerization

Jung-Hwa Lee, Jun-Myung Kim, Jung-Ahn Kim, Joo-Hoon Kim
2012 Bulletin of the Korean Chemical Society (Print)  
Polymer brushes on solid substrates formed by surfaceinitiated polymerization can tailor the substrates' surface properties, 1 allowing for example, the functionalization of glass surfaces for the construction of DNA microarrays used in the diagnosis of diseases and the study of genomics. 2 Glass surfaces are often functionalized by the formation of self-assembled monolayers (SAMs) of silanes containing functional groups, such as amine, alcohol, or carboxylic acid, at their terminal ends. 3
more » ... erminal ends. 3 However, silanization is difficult to control for the formation of high-quality SAMs, resulting in poorly reproducible surface functionalization. 4 Therefore polymer brushes, which can be grown as highdensity brushes in a controllable manner, have been studied for the surface functionalization of glass substrates. For example, polymer brushes based on polyethylene glycol methacrylate (PEGMA) have been used for surface coatings because they can limit the nonspecific adsorption of biomolecules onto the surfaces. 5 Here, we report the synthesis of a bifunctional polymer brush by surface-initiated polymerization and its application in the immobilization of oligonucleotides. The polymer brush possessed two functional moieties, bio-inert polyethylene glycol (PEG) and bio-reactive aldehyde groups, which respectively provided effective resistance to biofouling and high binding ability for the specific immobilization of amine-modified oligonucleotides. The surface-initiated polymerization of the bifunctional polymer brush is outlined in Scheme 1. 2-Bromo-2-methyl-N-(3-triethoxysilylpropyl)-propionamide (BTPAm) was synthesized by a synthetic procedure reported previously 6 (Supporting Information, Figure S1 ) and a SAM of BTPAm was formed by immersing a freshly cleaned and O 2 plasmatreated glass substrate in a toluene solution of BTPAm (0.3 w/v %) with subsequent curing at different temperatures. The resulting SAM was confirmed by the appearance of peaks characteristic of NH-CO at 1650 cm −1 , N-H bending at 1530 cm −1 , and Si-O stretching at 1112-1026 cm −1 in the ATR-FTIR spectrum of the BTPAm initiator film (Figure 1 , spectrum b) compared with the spectrum of bare surface (Figure 1, spectrum a) . 6b The surface-tethered BTPAm presented a terminal bromoisobutyrate moiety, which allowed surface-initiated atom transfer radical polymerization (SI-ATRP) on the glass substrates. 7 SI-ATRP can provide control over chain length and surface density of polymers under ambient conditions. 8 The surface-initiated polymerization was then conducted in an oxygen-free environment using CuBr/Tris[2-(dimethylamino)ethyl]amine (Me 6 TREN) cata-Figure 1. ATR-FTIR spectra of (a) bare, (b) BTPAm-coated, and (c) poly(PEGMA-FPMA-MMA)-coated surfaces. Scheme 1. Surface-initiated polymerization of poly(PEGMA-FPMA-MMA).
doi:10.5012/bkcs.2012.33.6.2043 fatcat:4aopvkaxqrhpzhqj2ks5s6543m