A novel optical biosensor for detecting target DNA, utilizing gold nanorods (GNRs) as molecular probes
is demonstrated. This sensor is based on simultaneous biorecognition-mediated hybridization of target
DNA in a sandwich type manner with two different capture probe DNA sequences modified separately
with identical sets of GNRs, which leads to aggregation of GNRs. The hybridization induced aggregation
as revealed by TEM analysis, promotes the modulation of surface plasmon resonance of GNRs, which
forms the basis of complementary target DNA detection from the Chlamydia trachomatis pathogen. Thermally
induced reversible dissociation of hybridizedDNAis demonstrated by melting analysis. The present
sensing strategy is successfully demonstrated by detecting PCR amplified C. trachomatis pathogen gene
isolated from human urine sample in a concentration range of 0.25–20 nM. Furthermore, this sensor displays
excellent specificity by discriminating the target DNA versus other non-specific pathogenic genes.