Covalent Binding to Activated Nonactivated Surfaces

DNA was first bound to a pretreated electrode via covalent attachment using carbodiimide molecules by Millan et al [20] in 1992. After the carbodiimide reaction, DNA was bound to the surface from its guanine bases. This method was later improved 

Single-stranded amino-linked DNA or label-free short DNA sequences are bound to these groups by their amino tags [21] and deoxyguanosine residues, respectively [20]. 

On the other hand, covalent agents can also be applied to the unpreated carbon surface directly before DNA immobilization onto activated sites of carbodiimide compounds [21]. 

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