Surface techniques for an electrochemical DNA biosensor

The surface of platinum electrodes was modified by a technique that provides binding sites for covalent site-specific immobilization of DNA. In the course of immobilization certain substances such as thiols, iodine and iodide were brought in contact with the metal. The effect on the electrochemical characteristics of thin film platinum electrodes caused by chemisorption of these substances was investigated. Voltage pulsing was very effective in restoring the electrocatalytical properties of the electrodes. A 20 bp oligonucleotide was immobilized via primary amino groups or terminal phosphate and immobilization efficiency of the different immobilized strands was determined. Mercapto-silane coatings and controlled introduction of charged groups in the course of immobilization prevented unspecific DNA binding caused by adsorption. (C) 1997 Elsevier Science Limited.