A new DNA detection method based on fluorescent gold nanoparticle (AuNP) probes and DNA chips was introduced here. Firstly, chips were modified with amine-oligonucleotide probe complementary to target DNA (capture probe). Gold nanoparticles were modified with two types of probes, one was another thiolated-oligonucleotide probe complementary to target DNA (detecting probe) and the other was thiolated-oligonucleotide probe without homologous sequence to detected samples (signal probe). The end of signal probe opposite the gold nanoparticles was modified with Cy5. The ratio of them is 1∶5. Through hybridization, the sandwich structures (DNA chip-target DNA-AuNP probes) were formed. Excess samples and AuNP probes were removed by washing for several times. And the amount of target DNA was determined by detecting the fluorescent signal of the AuNP probes. Low to 1 pmol/L target DNA could be detected with this method. Because the signal DNA probe with fluorescence rather than the target DNA was identified in this approach, the different proportions of detecting probe and signal probe could affect the detection signal significantly. Effect of different proportions of probes on detecting signal would be studied at a ratio of 1∶30, 1∶60, 1∶100 and higher sensitivity would be achieved. So, this will be one of the most important DNA detection methods.

Key words: gold nanoparticle probe, fluorescent probe, DNA chip, hybridization, DNA detection