We developed a self-assembling polymer based on polyallylamine (PAN) 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. (C) 2005 Wiley Periodicals, Inc.