The unique practical properties of adsorption have promoted its extensive use in genetic analysis. The disadvantages of adsorption with respect to covalent immobilization are mainly that (1) nucleic acids may be readily desorbed from the substrate, and (2) base moieties may be unavailable for hybridization if they are bonded to the substrate in multiple sites [34]. However, the electrochemical detection strategy based on the intrinsic oxidation of DNA requires the DNA to be adsorbed in close contact with the electrochemical substrate by multi-point attachment. This multi-site attachment of DNA can be thus detrimental for its hybridization but is crucial for the detection based on its oxidation signals
