A distance-dependent metal-enhanced fluorescence sensing platform based on molecular beacon design.
A new metal-enhanced fluorescence (MEF) based platform was developed on the basis of distance-dependent fluorescence quenching-enhancement effect, which combined the easiness of Ag-thiol chemistry with the MEF property of noble-metal structures as well as the molecular beacon design. For the given sized AgNPs, the fluorescence enhancement factor was found to increase with a d(6) dependency in agreement with fluorescence resonance energy transfer mechanism at shorter distance and decrease with a d(-3) dependency in agreement with plasmonic enhancement mechanism at longer distance between the fluorophore and the AgNP surface. As a proof of concept, the platform was demonstrated by a sensitive detection of mercuric ions, using thymine-containing molecular beacon to tune silver nanoparticle (AgNP)-enhanced fluorescence. Mercuric ions were detected via formation of a thymine-mercuric-thymine structure to open the hairpin, facilitating fluorescence recovery and AgNP enhancement to yield a limit of detection of 1 nM, which is well below the U.S. Environmental Protection Agency regulation of the Maximum Contaminant Level Goal (10nM) in drinking water. Since the AgNP functioned as not only a quencher to reduce the reagent blank signal but also an enhancement substrate to increase fluorescence of the open hairpin when target mercuric ions were present, the quenching-enhancement strategy can greatly improve the detection sensitivity and can in principle be a universal approach for various targets when combined with molecular beacon design.
Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, Institute of Analytical Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
Zhenpeng
Z
Zhou
Hongduan
H
Huang
Yang
Y
Chen
Feng
F
Liu
Cheng Zhi
CZ
Huang
Na
N
Li
D015374:Biosensing Techniques; D060766:Drinking Water / Q000737:chemistry; D005453:Fluorescence; D006801:Humans; D007477:Ions / Q000302:isolation & purification; D008628:Mercury / Q000302:isolation & purification*; D053768:Metal Nanoparticles / Q000737:chemistry; D008670:Metals / Q000737:chemistry*; D012834:Silver / Q000737:chemistry
D060766:Drinking Water; D007477:Ions; D008670:Metals; D012834:Silver; D008628:Mercury
Distance-dependence; Mercuric ion; Metal-enhanced fluorescence; Molecular beacon