Fabrication of DNA Microarrays with Poly(<scp>l</scp>-glutamic acid) Monolayers on Gold Substrates for SPR Imaging Measurements

Abstract

Robust single-stranded DNA (ssDNA) microarrays are created by attaching amine-modified oligonucleotides to a monolayer of poly(L-glutamic acid) (pGlu) that is electrostatically adsorbed onto a chemically modified gold thin film. This surface attachment chemistry methodology is first characterized with a combination of polarization-modulation Fourier transform infrared (PM-FTIR) spectroscopy and surface plasmon resonance (SPR) angle shift measurements. SPR imaging (SPRI) measurements of these ssDNA microarrays are then used to study two surface bioaffinity interactions: (i) the quantitative hybridization adsorption of complementary ssDNA onto mixed ssDNA microarray elements and (ii) the adsorption of single-stranded binding protein (SSB) onto fully and partially hybridized DNA microarray elements. The Langmuir adsorption coefficient (K(Ads)) of SSB binding to ssDNA was determined to be (5.5 +/- 0.4) x 10(9) M(-1).