One-step label-free optical genosensing system for sequence-specific DNA related to the human immunodeficiency virus based on the measurements of light scattering signals of gold nanorods.

A one-step label-free optical genosensing method has been developed in this contribution by taking short DNA target with its sequence related to the human immunodeficiency virus type 1 (HIV-1) as an example. By employing anisotropic nonspherical and positively charged gold nanorods (Au-NRs) as the recognition platform, which show high stability against aggregation under high ionic strength conditions without any additional stable reagent, we found that the addition of target DNA to the mixture of nonmodified Au-NRs suspension and label-free probe DNA in high ionic strength buffer leads to a color change from red to light purple in less than 5 min, displaying strong plasmon resonance light scattering (PRLS) signals. Mechanism investigations showed that the strong PRLS signals should be ascribed to the aggregation of Au-NRs induced by the formed double-stranded oligonucleotides (dsDNA) from the hybridization of target DNA with probe DNA. With the PRLS signals, we monitored the hybridization process of a 21-mer single-stranded oligonucleotide (ssDNA) from the HIV-1 U5 long terminal repeat (LTR) sequence with its complementary oligonucleotide and detected the effect of single-base-pair mismatches. Two polymerase chain reaction (PCR) amplicon artificial samples derived from Mycobacterium tuberculosis glmS and genes encoding for Bacillus glucanase and an HIV-1 LTR sample isolated from HIV-1-positive blood were detected with satisfactory results, showing that the present method has simplicity, sensitivity, specificity, and reliability for sequence-specific DNA detection related to the HIV gene.