Highly sensitive gold nanoparticles-based optical sensing of DNA hybridization using bis(8-hydroxyquinoline-5-solphonate)cerium(III) chloride as a novel fluorescence probe

• Preparation of a novel fluorescent sensor for sensitive detection of DNA hybridization.
• Derivatizing of colloidal gold nanoparticles with 3-thiolated 16-base oligonucleotides.
• Use of bis(8-hydroxy quinoline-5-solphonate)cerium(III) chloride as a fluorescence probe.
• Highly sensitive and fast quenching of probe fluorescence due to DNA hybridization at the modified GNPs.
• Linear dynamic range of 1.0 × 10−10−3.0 × 10−8 M for target DNA, with a limit of detection of 7.0 × 10−11 M.

A simple and sensitive method for the detection of DNA hybridization in a homogeneous format was developed, using bis(8-hydroxyquinoline-5-solphonate)cerium(III) chloride (Ce(QS)2Cl) as a novel fluorescent probe. The method is based on fluorescence quenching by gold nanoparticles used as both nanoscafolds for the immobilization of the probe DNA sequence, which is related to Alicyclobacillus acidophilus strain TA-67 16S ribosomal RNA, and nanoquenchers of the Ce(QS)2Cl probe. The probe DNA-functionalized GNPs were synthesized by derivatizing the colloidal gold nanoparticles solution with 3-thiolated 16-base oligonucleotides. Addition of sequence-specific target DNAs (16 bases) into the mixture containing probe DNA-functionalized GNPs and fluorescent probe lead to the quenching of Ce(QS)2Cl fluorescence at 360 nm (λex = 270  nm), due to DNA hybridization, the resulting quenched intensity being proportional to the concentration of target DNA. Under optimal conditions of pH 7.4 and Ce(QS)2Cl concentration of 1.0 × 10−7 M, the linear dynamic range found to be 1.0 × 10−10−3.0 × 10−8 M DNA, with a limit of detection of 7.0 × 10−11 M. The interaction mechanism for the binding of Ce(QS)2Cl to DNA was studied in detail, and results proved that the interaction mode between Ce(QS)2Cl and DNA is groove binding, with a binding constant of 1.0 × 105 M−1.

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