Aminosilanes are widely used for covalent linkage of biomolecules to glass in biosensor and DNA chip fabrication. First introduced by Lyubchenko et al [1], silanization of mica and other substrates with trialkoxyaminoalkylsilanes has become a common technique in AFM studies of immobilised biological species. As a drawback of this relatively simple method, it has been pointed to the poor reproducibility in formation of uniform siloxane layer [2]. The formation of homogeneous siloxane (mono)layer of trialkoxysilanes is extremely sensitive to the presence of surface silanols on the substrate as well as to the quantity of pre-adsorbed water on the substrate and in silanizing environment [3]. In this work we present further developments of the approach reported previously [4] on the preparation of uniform aminofunctionalized siloxane films using sol-gel technique. We show that these films can be used in SPM studies of covalently immobilized biological species as well as supports in DNA chip fabrication.

In our experiments 3-aminopropyltrimethoxysilane and tetramethoxysilane were co-polymerised linearly, followed by deposition onto glass substrate from methanol solution and subsequent gelation to three-dimensional siloxane layer. FTIR and ¹³C NMR spectroscopy and MALDI-TOF mass spectrometry were applied to unveil chemical characteristics of linearly polymerised siloxane chains. AFM was used to probe the topographic features of the films. High-resolution phase contrast imaging revealed molecular sub-structure of the film, showing clearly densely packed linear siloxane chains. Spectroscopic analysis of the samples confirmed the presence of aminopropyl groups, pointing to their ability for covalent coupling of biomolecules.


1) Y.L. Lyubchenko et al, J. Biom. Struc. Dyn. 10, 589 (1992).
2) H.X. You, C.R. Lowe, J. Colloid. Interface Sci. 182, 586 (1996).
3) C.R. Kessel, S. Granick, Langmuir, 7, 532 (1991).
4) T.Tätte et al, Surface Science, in press.

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