Immobilization of single‐stranded DNA by self‐assembled polymer on gold substrate for a DNA chip

We developed a self‐assembling polymer based on polyallylamine (PAH) for use in DNA chips. Thioctic acid (TA) was covalently attached to PAH in sidechains to immobilize the polymer on a gold surface by self‐assembly. N ‐hydroxysuccinimide‐ester terminated probe single‐stranded (ss) DNA is easily covalently immobilized onto a TA‐PAH‐coated gold surface. Finally, the surface was covered with polyacrylic acid, which formed ion complexes with the TA‐PAH, to reduce the cationic charge. This ssDNA on a polymer‐coated surface recognized a fully matched DNA sequence and restrained nonspecific adsorption of target DNA. The selectivity and efficiency of hybridization was affected by adjusting the ionic strength of sodium chloride. © 2005 Wiley Periodicals, Inc.