Colloid Au-enhanced DNA immobilization for the electrochemical detection of sequence-specific DNA

We use colloidal An to enhance the DNA immobilization amount on a g-Old ele ctrode and ultimately lower the detection limit of our electrochemical DNA biosensor. Self-assembly of approximately 16-nm diameter colloidal Au onto a cysteamine modified gold electrode resulted in an easier attachment of an oligonucleotide with a mercaptohexyl group at the 5 ' -phosphate end, and therefore an increased capacity for nucleic acid detection. Quantitative re sults showed that the surface densities of oligonucleotides on the Au collo id modified gold electrode were approximately (1-4) x 10(14) molecules cm(- 2). Hybridization was induced by exposure of the ssDNA-containing gold elec trode to ferrocenecarboxaldehyde labeled complementary ssDNA in solution. T he detection limit is 5 x 10(-10) mol 1(-1) of complementary ssDNA, which i s much lower than our previous electrochemical DNA biosensors. The Au nanop article films on the An electrode provide a novel means for ssDNA immobiliz ation and sequence-specific DNA detection. (C) 2001 Elsevier Science B.V. A ll rights reserved.