Electrochemical characterization and quantitation of dna immoblized on gold

摘要

Electrochemical techniques were used to characterize the interaction of DNA with gold and to quantitate the surface density of DNA on an electrode. Oligonucleotides were immobilized on gold by forming mixed monolayers of thiol-derivitized, single-stranded oligonucleotide and 6mercapto-l-hexanol. Accumulation of charge-compensating redox marker in the DNA monolayer under appropriate conditions was used to determine the surface density of DNA. Surface densities of singlestranded DNA were precisely varied in the range of 1-16 x 10~(12) molecules/cm~2 using mixed monolayers. Nucleic acid segments of different lengths were found to pack on the surface to the extent that the limiting surface density is proportional to the square root of the number of bases in the segment. The hybridization efficiency of immobilized singlestranded DNA to complementary strands was measured as a function of the surface density. Complete pairing of the immobilized DNA with complementary nucleic acid was observed for surface densities below 4 x 10~(12) molecules/cm~2; above this value the hybridization efficiency decreases steadily with increasing surface density.