Nanoparticle-enhanced Fluorescence Research Articles

Enhancing the Luminescence Efficiency of Triphenylamine–Thiophene Aggregation-Induced Emission Luminogens Using Shell-Isolated Nanoparticle-Enhanced Fluorescence (SHINEF)

Enhancing the Luminescence Efficiency of Triphenylamine–Thiophene Aggregation-Induced Emission Luminogens Using Shell-Isolated Nanoparticle-Enhanced Fluorescence (SHINEF)

Microscopic Perspective of Synergy between Localized Surface Plasmon Resonance and Disruption of Dye Aggregates in Metal Nanoparticle-Enhanced Fluorescence

Microscopic Perspective of Synergy between Localized Surface Plasmon Resonance and Disruption of Dye Aggregates in Metal Nanoparticle-Enhanced Fluorescence

Improved imaging and preservation of lysosome dynamics using silver nanoparticle-enhanced fluorescence.

The dynamics of living cells can be studied by live-cell fluorescence microscopy. However, this requires the use of excessive light energy to obtain good signal-to-noise ratio, which can then photobleach fluorochromes, and more worrisomely, lead to phototoxicity. Upon light excitation, noble metal nanoparticles such as silver nanoparticles (AgNPs) generate plasmons, which can then amplify excitation in direct proximity of the nanoparticle's surface and couple to the oscillating dipole of nearby radiating fluorophores, modifying their rate of emission and thus, enhancing their fluorescence. Here, we show that AgNPs fed to cells to accumulate within lysosomes enhanced the fluorescence of lysosome-targeted Alexa488-conjugated dextran, BODIPY-cholesterol, and DQ-BSA. Moreover, AgNP increased the fluorescence of GFP fused to the cytosolic tail of LAMP1, showing that metal enhanced fluorescence can occur across the lysosomal membrane. The inclusion of AgNPs in lysosomes did not disturb lysosomal properties such as lysosomal pH, degradative capacity, autophagy and autophagic flux, and membrane integrity, though AgNP seemed to increase basal lysosome tubulation. Importantly, by using AgNP, we could track lysosome motility with reduced laser power without damaging and altering lysosome dynamics. Overall, AgNP-enhanced fluorescence may be a useful tool to study the dynamics of the endo-lysosomal pathway while minimizing phototoxicity.

Role of emitter position and orientation on silicon nanoparticle-enhanced fluorescence

High-index spherical dielectric nanoparticles are explored as templates for tailoring the fluorescence of nearby electric point-dipole-like emitters. The role of emitter orientation and position around the nanosphere on the modification of both its excitation and its emission rate is studied rigorously through derivation of appropriate analytic solutions. It is shown that dielectric nanoparticles, which support a richness of optical modes of electric or magnetic character and thus a variety of mechanisms for near-field enhancement, provide moderate fluorescence enhancement factors—as compared, e.g., to their plasmonic counterparts—which survive, however, for a wide range of emitter positions and orientations. Understanding the physical mechanisms governing this behaviour, which offers a promising route towards efficient control of the emission properties of randomly arranged emitters, is widely facilitated by the existence of analytic expressions such as the ones derived here. Further enhancement can be achieved by designing nanoparticle-aggregate antennas, or by combining dielectric and plasmonic components.

Silica-Coated Silver Nanoparticles Decorated with Fluorescent CdTe Quantum Dots and DNA Aptamers for Detection of Tetracycline

An aptamer-labelled fluorescent nanoprobe-integrated shell-isolated nanoparticle-enhanced fluorescence spectroscopy (SHINEFs) had been proposed for selective and sensitive detection of Tc. In the s...

Optical writing and single molecule reading of photoactivatable and silver nanoparticle-enhanced fluorescence.

We designed a hybrid nanoparticle–molecular system composed of silver nanostructures (AgNP) and a fluorogenic boron dipyrromethene (BODIPY) that can be selectively activated by UVA or UVC light in the presence of an appropriate photoacid generator (PAG). Light irradiation of the PAG encourages the release of p-toluenesulfonic, triflic or hydrobromic acid, any of which facilitate optical ‘writing’ by promoting the formation of a fluorescent species. Metal-enhanced fluorescence (MEF) by AgNP was achieved through rational design of the nano–molecular system in accordance with the principles of radiative decay engineering. In addition to increasing signal to noise, AgNP permitted shorter reaction times and low irradiance – all of which have important implications for applications of fluorescence activation in portable fluorescence patterning, bioimaging and super-resolution microscopy. Single molecule fluorescence microscopy provided unique insights into the MEF mechanism which were hidden by ensemble-averaged measurements, demonstrating that single molecule ‘reading’ is a valuable tool for characterizing particle–molecule interactions such as those responsible for the relative contributions of increased excitation and plasmophoric emission toward overall MEF. This work represents a step forward in the contemporary design of synergistic nano–molecular systems, and showcases the advantage of fusion between classic spectroscopic techniques and single molecule methods in terms of improved quantitative understanding of fluorophore–nanoparticle interactions, and how these interactions can be exploited to the fullest extent possible.

Ultrasensitive detection of heparin by exploiting the silver nanoparticle-enhanced fluorescence of graphitic carbon nitride (g-C3N4) quantum dots.

A composite (Ag-g-CNQDs) was prepared from graphitic carbon nitride quantum dots and silver nanoparticles by water phase synthesis. Aided by metal-enhanced fluorescence, the composite exhibits excitation-dependent red emission with a peak at 600nm with a quantum yield of 21%. If the composite is coated with polyethylenimine (PEI) to form the Ag-g-CNQD/PEI complexe, fluorescence is strongly reduced. Upon addition of heparin, the fluorescence of the system is enhanced because PEI has a higher affinity for heparin than Ag-g-CNQDs. The effect was used to design a fluorometric assay for heparin.The emission at 600nm increases linearly in the 0.025 to 2.5μM heparin concentration range, with a 8.2nM limit of detection. Graphical abstract Schematic illustration for fabricating a composite consisting of silver nanoparticles and graphitic carbon nitride quantum dots (Ag-g-CNQDs). Its redfluorescence is weak in presence of polyethyleneimine but restored on addition of heparin. This forms the basis for anew method for heparin detection.

Novel metal nanoparticle-enhanced fluorescence for determination of trace amounts of fluoroquinolone in aqueous solutions

Metal-enhanced fluorescence of fluoroquinolones (FQs) was first observed in aqueous solutions. In addition, a new type of silver nanoparticles (AgNP) was synthesized with simple and easy synthetic processes and environmentally friendly compounds. The effects of different concentrations of AgNPs on the fluorescence behaviours of ciprofloxacin (CIP), enrofloxacin (ENR) and lomefloxacin (LMF) in aqueous solutions were investigated, respectively. The experimental results demonstrated that the fluorescence peak shapes and the locations of the features in the excitation and emission spectra for each FQ that was mixed with AgNPs were almost the same as those of the standard FQs. An enhancement or quenching of the fluorescence can also be observed, depending on the exact conditions. Compared with the identical control samples that lack AgNPs, the fluorescence of each FQ in aqueous solutions was greatly enhanced by AgNPs with concentrations at a volume ratio of 5%. Moreover, at the optimum AgNP concentration, novel sensitive fluorometric methods for the separate determination of trace amounts of CIP, ENR and LMF in aqueous solutions were established. Under optimal experimental conditions, the linear dynamic ranges for the determination of CIP, ENR and LMF concentrations varied from 0.025 to 1.0mgL−1, 5.0 to 160ngL−1 and 0.01 to 0.8mgL−1, and the limits of detection were 90, 5 and 6ngL−1, respectively; the relative standard deviation was less than 1.2% (n = 9). The experimental recovery results for the determination of CIP, ENR and LMF in aqueous solutions ranged from 99% to 102%, 90% to 103% and 92% to 107%, respectively. Compared with the established method in which no AgNPs were added, the quantitation limits of the silver nanoparticle-enhanced fluorometric methods were approximately 2-fold lower for CIP, 2.6-fold lower for ENR and 4-fold lower for LMF. Significantly, the novel silver nanoparticle-enhanced fluorometric methods were successfully applied to directly determine CIP, ENR and LMF concentrations in pharmaceutical preparations, demonstrating the methods’ advantages of simplicity, sensitivity and low cost.

Shell-isolated nanoparticle-enhanced fluorescence (SHINEF) of CdTe quantum dots

We report shell-isolated nanoparticle-enhanced fluorescence (SHINEF) of CdTe quantum dots. Enhanced spectra are obtained after Ag SHINs were spread onto homogenous CdTe quantum dot/polyelectrolyte layer-by-layer (LbL) films on quartz. The thin silica shell of the SHINs effectively isolates the Ag cores, preventing short-range quenching to the metal and enabling plasmon enhancement of the quantum dot fluorescence (ca. 35 fold).

Optical properties of Ag nanoparticle-polymer composite film based on two-dimensional Au nanoparticle array film

The nanocomposite polyvinyl pyrrolidone (PVP) films containing Ag nanoparticles and Rhodamine 6G are prepared on the two-dimensional distinctive continuous ultrathin gold nanofilms. We investigate the optical properties and the fluorescence properties of silver nanoparticles-PVP polymer composite films influenced by Ag nanoparticles and Au nanoparticles. Absorption spectral analysis suggests that the prominently light absorption in Ag nanowire/PVP and Ag nanowire/PVP/Au film arises from the localized surface plasmon resonance of Ag nanowire and Au nanofilm. The enhanced fluorescence is observed in the presence of Ag nanowire and Au nanofilm, which is attributed to the excitation of surface plasmon polariton resonance of Ag nanowire and Au nanofilm. The gold nanofilm is proven to be very effective fluorescence resonance energy transfer donors. The fabricated novel structure, gold ultrathin continuous nanofilm, possesses high surface plasmon resonance properties and prominent fluorescence enhancement effect. Therefore, the ultrathin continuous gold nanofilm is an active substrate on nanoparticle-enhanced fluorescence.

A gold nanoparticle-enhanced fluorescence polarization biosensor for amplified detection of T4 polynucleotide kinase activity and inhibition.

A novel fluorescence polarization (FP) nanosensor based on λ exonuclease cleavage reaction and FP enhancement effect of gold nanoparticles (AuNPs) has been developed for the detection of T4 polynucleotide kinase activity and inhibition. This FP sensor exhibits higher detection sensitivity over traditional fluorescence sensors by two orders of magnitude.

Determination of catecholamines based on the measurement of the metal nanoparticle-enhanced fluorescence of their terbium complexes

We have developed a method for the determination of the three catecholamines (CAs) epinephrine (EP), norepinephrine (NE), and dopamine (DA) at sub-nanomolar levels. It is found that the luminescence of the complexes formed between the CAs and Tb3+ ion is strongly enhanced in the presence of colloidal silver nanoparticles (Ag-NPs). The Ag-NPs cause a transfer of the resonance energy to the fluorophores through the interaction of the excited-state fluorophores and surface plasmon electrons in the Ag-NPs. Under the optimized condition, the luminescence intensity of the system is linearly related to the concentration of the CAs. Linearity is observed in the concentration ranges of 2.5–110 nM for EP, 2.8–240 nM for NE, and 2.4–140 nM for DA, with limits of detection as low as 0.25 nM, 0.64 nM and 0.42 nM, respectively. Relative standard deviations were determined at 10 nM concentrations (for n = 10) and gave values of 0.98%, 1.05% and 0.96% for EP, NE and DA, respectively. Catecholamines were successfully determined in pharmaceutical preparations, and successful recovery experiments are demonstrated for urine and serum samples.

Ultrasensitive endonuclease activity and inhibition detection using gold nanoparticle-enhanced fluorescence polarization

We have developed a highly sensitive and selective fluorescence polarization assay method based on the specificity of the DNA cleavage reaction with the enhancement of gold nanoparticles (AuNPs) for assaying endonuclease activity and inhibition. This assay can detect EcoRI endonuclease down to 5.0×10(-4) U mL(-1) with a detection range from 5.0×10(-4) to 10 U mL(-1).

Silver nanoparticle-enhanced fluorescence in microtransponder-based immuno- and DNAhybridization assays

The aim of this study is to improve assay sensitivity in common solid-phase bioassay configurations as the result of using silver nanoparticles. The solid phase was provided by numerically indexed, silicon-based electronic chips, microtransponders (p-Chips) that have previously been used in multiplexed assays. Assay configurations investigated included an ELISA-type immunoassay and a DNA hybridization assay. The surface of p-Chips was derivatized with the silver island film (SIF) and a polymer, and then characterized with AFM and SEM. Silver nanoparticle sizes were in the range of 100 to 200 nm. Four fluorophores were tested for fluorescence enhancement; namely, green fluorescent protein, phycoerythrin, Cy3 and Alexa Fluor 555. We consistently observed significant fluorescence enhancement and sensitivity improvement in the p-Chip-based assays: the sensitivity in the cytokine IL-6 immunoassay was 4.3 pg/ml, which represented a 25-fold increase over the method not involving a SIF; and 50 pM in the hybridization assay, a 38-fold increase. The greatest enhancement was obtained for p-Chip surfaces derivatized first with the polymer and then coated with SIF. In conclusion, we show that the SIF-p-Chip-based platform is a highly sensitive method to quantify low-abundance biomolecules in nucleic acid-based assays and immunoassays.

The Effect of an Active Substrate on Nanoparticle‐Enhanced Fluorescence

The Effect of an Active Substrate on Nanoparticle‐Enhanced Fluorescence

Decreasing photobleaching by silver nanoparticles on metal surfaces: application to muscle myofibrils

Recently it has become possible to study single protein molecules in a cell. However, such experiments are plagued by rapid photobleaching. We recently showed that the interaction of fluorophores with localized surface plasmon polaritons (LSPs) induced in the metallic nanoparticles led to a substantial reduction of photobleaching. We now investigate whether the photobleaching could be further reduced when the excited fluorophore interacts with the LSP excited in the metallic nanoparticles resident on mirrored surface. As an example we use myofibrils, subcellular structures within skeletal muscle. We compare nanoparticle-enhanced fluorescence of myofibrils in the presence and in the absence of a mirrored surface. The proximity of the mirrored surface led to enhancement of fluorescence and to a decrease in fluorescent lifetime, much greater than that observed in the presence of nanoparticles alone. We think that the effect is caused by the near-field interactions between fluorophores and LSP, and between fluorophores and propagating surface plasmons (PSPs) produced in the metallic surface by the nanoparticles. Photobleaching is decreased because fluorescence enhancement enables illumination with a weaker laser beam and because the decrease in fluorescence lifetime minimizes the probability of oxygen attack during the time a molecule is in the exited state.