Achieving differentiation of single-base mutations through hairpin oligonucleotide and electric potential control.

A novel assay for surface DNA hybridization, which is free of sample and probe labeling, convenient and of low cost, sensitive and capable of differentiation of single-base mutations, is reported. Hairpin oligonucleotides are carefully designed as probes and are covalently attached to Si chips. Segments of the human p53 gene are chosen to demonstrate the major features of the novel technique. Impedance measurement is used to detect the hybridization. To further optimize the performance, electric potential is applied on the chip. The apparently different responses of the chip to the complementary strand and the single-base mutant are shown under electric potential control. The criteria on the design of the hairpin oligonucleotides are discussed.