Re ECF Project: 2010-03

Project Title: A selective oligonucleotide-based luminescent switch-on probe for the detection of nanomolar mercury (II) ion in aqueous solution

Applicant: Dr. Edmond Dik-lung MA of Hong Kong Baptist University

Total Approved Grant: $416,000 (ECF & WWGF: 50/50)

Duration: 1/5/2011 to 30/11/2012

Project Status/Remarks: Completed

The project aims to develop a rapid and sensitive detection method for mercury(II) ion in aqueous solution based on DNA oligonucleotide and luminescent transition metal complexes in polluted water samples.

Summary of the Findings/Outcomes:
The team had successfully synthesized and characterized several cyclometalated metal complexes as novel luminescent probes targeting various DNA structures such as G-quadruplex and double stranded DNA. They found most iridium(III) complexes are selective towards G-quadruplex DNA over other forms of DNAs such as single stranded DNA and double stranded DNA. They envisaged that the strong luminescence enhancement of these complexes in the presence of specific form of DNAs could be attributed to the specific interactions between the metal complexes and DNA structures. For example, some iridium(III) complexes could interact with G-quadruplex DNA via end-stacking interaction. These specific interactions between DNA and metal complexes could protect the metal complex from the aqueous buffer environment and non-radiative decay, leading to an enhancement of 3MLCT luminescence.

The original platinum(II) complex was chosen for further investigation because of its significant signal enhancement in the presence of double-stranded DNA, the assay conditions were fully optimized and the proposed methodology. The proposed strategy could discriminate Hg2+ ions from at least 100 fold excess of other interfering metal ions. The optimized assay was applied thoroughly in real water sample analyses. The results had shown the proposed methodology is able to quantitatively detect Hg2+ in the water samples collected from different areas in Hong Kong. Overall, the assay exhibited the good analytic performance in the these water samples with acceptable percentage recovery values compared to buffer solution and with a detection limit in nanomolar range.