Target-triggered signal turn-on detection of prostate specific antigen based on metal-enhanced fluorescence of Ag@SiO₂@SiO₂-RuBpy composite nanoparticles

Abstract

A three-layer core-shell nanostructure consisting of a silver core, a silica spacer, and a fluorescent dye RuBpy-doped outer silica layer was fabricated, and the optimal metal-enhanced fluorescence (MEF) distance was explored through adjusting the thickness of the silica spacer. The results show that the optimal distance is ∼10.4 nm with the maximum fluorescence enhancement factor 2.12. Then a new target-triggered MEF 'turn-on' strategy based on the optimized composite nanoparticles was successfully constructed for quantitative detection of prostate specific antigen (PSA), by using RuBpy as the energy donor and BHQ-2 as the acceptor. The hybridization of the complementary DNA of PSA-aptamer immobilized on the surface of the MEF nanoparticles with PSA-aptamer modified with BHQ-2, brought BHQ-2 in close proximity to RuBpy-doped silica shell and resulted in the decrease of fluorescence. In the presence of target PSA molecules, the BHQ-PSA aptamer is dissociated from the surface of the nanoparticles with the fluorescence switched on. Therefore, the assay of PSA was achieved by measuring the varying fluorescence intensity. The results show that PSA can be detected in the range of 1-100 ng ml with a detection limit of 0.20 ng ml (6.1 pM), which is 6.7-fold increase of that using hollow RuBpy-doped silica nanoparticles. Moreover, satisfactory results were obtained when PSA was detected in 1% serum.

Recent progress in sensing application of metal nanoarchitecture-enhanced fluorescence

“…So far, LSPs have been used to enhance the emission of dyes, 17,19,21,22 rare earth elements, 23–28 quantum dots (QDs), 14,29–43 carbon dots, 36,38 carbon nanotubes, 44 gold nanoclusters 45,46 and even upconversion fluorophores. 33,47,48 And this enhanced fluorescence has already been extensively applied in environmental analysis, 45,48–64 tip-enhanced fluorescence spectroscopy, 65 biotechnology 66 (including fluorescence imaging, 67–71 DNA mismatch investigation, 72,73 immunoassays, 26,74–80 bioassays, 28,38,42,81–100 and investigation of biological mechanisms 67,101–103 ), biomedical analysis (virus and bacteria detection 43,104 and clinical diagnosis 105,106 ) and so on. Characteristics and applications of MEF have been summarized in Table 1 .…”

Recent Developments in Plasmonic Nanostructures for Metal Enhanced Fluorescence-Based Biosensing

“…Combining the plasmonic nanostructures with immunoassays or microarrays offers the unique advantages of detectability, and introduces a wide range of fluorescence-based applications with a large variety of commercially available analytes, as summarized in Table 5. Various detection analytes, including biomarkers, pathogens, and toxins, have been reported in the literature with new detection methodologies and enhanced detection limits to provide a valuable tool for early diagnosis [131,132], point-of-care (POC) diagnosis [133,134], and forensic applications [122,135]. Metallic nanoparticles with a silica spacer and a silica core were reported for quantitative detection of the prostate-specific antigen (PSA) with high sensitivity [133].…”

“…Various detection analytes, including biomarkers, pathogens, and toxins, have been reported in the literature with new detection methodologies and enhanced detection limits to provide a valuable tool for early diagnosis [131,132], point-of-care (POC) diagnosis [133,134], and forensic applications [122,135]. Metallic nanoparticles with a silica spacer and a silica core were reported for quantitative detection of the prostate-specific antigen (PSA) with high sensitivity [133]. The detection antibody was attached to a 50 nm Ag particle labeled with RuBpy dye to monitor the fluorescence intensity associated with the binding event.…”

“…The detection antibody was attached to a 50 nm Ag particle labeled with RuBpy dye to monitor the fluorescence intensity associated with the binding event. The reported detection time was 30 min for the binding event with a detection limit of 0.20 ng/mL [133]. In another study, the metallic vertical nanorods were used for the quantitative detection of human semen and vaginal fluids [135].…”

Dual Amplification Fluorescence Assay for Alpha Fetal Protein Utilizing Immunohybridization Chain Reaction and Metal-Enhanced Fluorescence of Carbon Nanodots

“…In recent years, the use of metallic surface plasmon on metal nanostructures to enhance the brightness and photostability of fluorophores in the near field is offering some opportunities to increase the classical photophysical properties of the known fluorophores. Many reports have shown that surface plasmons affect emission of the near-field fluorophores and increase their quantum yield by raising the radiative decay rate of the excited fluorophores, thus more or less enhancing their fluorescence emission. − This is known as metal-enhanced fluorescence (MEF) and has been reported for various fluorophores − and quantum dots − that are in close proximity to the nanostructures of some noble metals.…”