Filter Effect Of Gold Nanoparticles Research Articles

Ratiometric Fluorescent Lateral Flow Immunoassay for Point‐of‐Care Testing of Acute Myocardial Infarction

AbstractWe report the development of a highly sensitive ratiometric fluorescent lateral flow immunoassay (RFLFIA) strip for rapid and accurate detection of acute myocardial infarction biomarker, namely heart‐type fatty acid binding protein (H‐FABP). The RFLFIA strip works in terms of ratiometric change of fluorescence signal, arising from blending of fluorescence emitted by two composite nanostructures conjugated to capture and probe antibodies and inner filter effect of gold nanoparticles. In conjunction with using custom smartphone‐based analytical device and tonality analysis, quantitative detection of H‐FABP was achieved with a low limit of detection at 0.21 ng mL−1. The RFLFIA strip can generate a visually distinguishable green‐to‐red color change around the threshold concentration of H‐FABP (6.2 ng mL−1), thus allowing the semi‐quantitative diagnosis by the naked eye.

Ratiometric Fluorescent Lateral Flow Immunoassay for Point-of-Care Testing of Acute Myocardial Infarction.

We report the development of a highly sensitive ratiometric fluorescent lateral flow immunoassay (RFLFIA) strip for rapid and accurate detection of acute myocardial infarction biomarker, namely heart-type fatty acid binding protein (H-FABP). The RFLFIA strip works in terms of ratiometric change of fluorescence signal, arising from blending of fluorescence emitted by two composite nanostructures conjugated to capture and probe antibodies and inner filter effect of gold nanoparticles. In conjunction with using custom smartphone-based analytical device and tonality analysis, quantitative detection of H-FABP was achieved with a low limit of detection at 0.21 ng mL-1 . The RFLFIA strip can generate a visually distinguishable green-to-red color change around the threshold concentration of H-FABP (6.2 ng mL-1 ), thus allowing the semi-quantitative diagnosis by the naked eye.

Perovskite nanocrystals fluorescence nanosensor for ultrasensitive detection of trace melamine in dairy products by the manipulation of inner filter effect of gold nanoparticles

Barium sulfate-coated CsPbBr3 perovskite nanocrystals (CsPbBr3 NCs@BaSO4) was successfully synthesized that exhibited stable and intense fluorescence property in aqueous buffer. With the CsPbBr3 NCs@BaSO4 as signal readout, an ultrasensitive fluorescence nanosensor was developed for turn-on determination of melamine by the manipulation of inner filter effect of citrate-protected gold nanoparticles (AuNPs). The fluorescence of the CsPbBr3 NCs@BaSO4 was remarkably quenched by the AuNPs due to inner filter effect. This inner filter effect could be weakened by the addition of melamine as a result of melamine-triggering aggregation of the AuNPs and subsequently led to a recovery in the fluorescence of the CsPbBr3 NCs@BaSO4. The recovery ratio was proportional to the concentration of melamine in the range of 5.0–500.0 nmol/L. The limit of detection was 0.42 nmol/L and the relative standard deviation was 4.0% for the repetitive determination of 500.0 nmol/L melamine solution (n = 11). The nanosensor was successfully applied to analysis of melamine in dairy product samples.

Rhodamine-assisted fluorescent detection for lysozyme based on the inner filter effect of gold nanoparticles

This work proposed a rapid, sensitive and low-cost fluorescent assay to achieve lysozyme detection in the presence of gold nanoparticles (AuNPs) and rhodamine 6G (R6G). When R6G and AuNPs aqueous solutions were mixed, fluorescence of R6G was quenched via the inner filter effect (IFE). Whereas, upon addition of lysozyme into AuNPs solution, lysozyme with positive charge bound to the negatively-charged AuNPs, leading to the aggregation of AuNPs. After that, R6G as a fluorescence indicator was introduced into the above-mentioned mixture. In this case, weakened IFE occurred between AuNPs and R6G. It is found that the fluorescent intensity of R6G enhanced as the concentration of lysozyme increased. The optimum concentrations of R6G and AuNPs were studied by fluorescence spectrophotometer. Based on the above, lysozyme could be detected and its detection limit is about 1 ng/mL. Quantitative evaluation of lysozyme could be performed within a concentration range of 0.1–10 μg/mL. This strategy was also applied to monitor lysozyme in urine samples with a pleased result. It provides a great promise for the diagnosis and prognosis by fluorescence for lysozyme-related diseases.

A fluorometric aptasensor for bisphenol a based on the inner filter effect of gold nanoparticles on the fluorescence of nitrogen-doped carbon dots.

An aptamer-based fluorometric assay is described for the determination of bisphenol A (BPA). The aptamer against BPA is first attached to the surface of the red AuNPs, and this prevents the AuNPs from salt-induced formation of a blue-colored aggregate. Hence, the blue fluorescence of added nitrogen-doped carbon dots (NCDots) is quenched via an inner filter effect (IFE) caused by the red AuNPs. After addition of BPA, the BPA/aptamer complex is formed, and the AuNPs are no longer stabilized agains aggregation. This weakens the IFE and results in the recovery of the fluorescence of the NCDots which is measured best at excitation/emission wavelengths of 300/420nm. The recovered fluorescence increases linearly in the 10 to 250nM and 250 to 900nM BPA concentration ranges, and the detection limit is 3.3nM. The method was successfully applied to the determination of BPA in spiked environmental tap water samples. Graphical abstract Schematic presentation of a fluorometric aptamer based assay for bisphenol A (BPA). It is based on the inner filter effect of gold nanoparticles (AuNPs) on the fluorescence of nitrogen-doped carbon dots (NCDots).

Dual mode detection of amifostine based on gold nanoparticles and sulfanilic acid functionalized graphene quantum dots

Visual and fluorescence detection of amifostine based on the inner filter effect of gold nanoparticles on sulfanilic acid functionalized graphene quantum dots.

A boronic acid based glucose assay based on the suppression of the inner filter effect of gold nanoparticles on the orange fluorescence of graphene oxide quantum dots

The authors describe a non-enzymatioc glucose assay that has three features: (a) The use of a boronic acid as the recognition element; (b) the aggregation of gold nanoparticles (AuNPs), and (c) the use of graphene oxide quantum dots (GOQD) whose fluorescence matches the absorption of the AuNPs and thereby results in an inner filter effect (IFE). The GOQD display an orange colored fluorescence that is filtered off by the AuNPs due to an IFE. In the presence of 3-aminobenzeneboronic acid, glucose is bound to form a cationic species that causes the aggregation of AuNPs to form large assemblies. This is accompanied by a color change from red to blue, and the IFE no longer does occur so that the orange fluorescence of the GOQD pops up again. These findings were used to design an assay witha linear response in the 2.5 to 75 μmol L−1 glucose concentration range, with a detection limit of 0.65 μmol L−1. The method was applied to the determination of glucose in spiked diluted serum and gave satisfactory results.

Sensitive fluorescent detection of fibrin based on the inner filter effect of gold nanoparticles

A simple, rapid and sensitive fluorescent assay for determination of fibrin has been developed based on the inner filter effect (IFE) of gold nanoparticles (AuNPs).

A dual-mode nanosensor based on the inner filter effect of gold nanoparticles on the fluorescence of CdS quantum dots for sensitive detection of arginine

Fluorescent detection of arginine based on the inner filter effect of AuNPs on l-Cys-capped CdS QDs.

Aptasensor for visual and fluorometric determination of lysozyme based on the inner filter effect of gold nanoparticles on CdTe quantum dots

The authors describe an aptasensor for visual and fluorescent detection of lysozyme via an inner filter effect (IFE). The assay is based on the fact that red gold nanoparticles (AuNPs) act as powerful absorbers of the green fluorescence of CdTe because of spectral overlap. If the lysozyme-binding aptamer is adsorbed onto the surface of the AuNPs, the salt-induced aggregation of AuNPs (that leads to a color change from red to blue) does not occur and the IFE remains efficient. If lysozyme is present, it will bind the aptamer and thereby prevent its adsorption on the AuNPs. As a result, the salt-triggered aggregation of the AuNPs will occur. Consequently, color will change from red to blue, and green fluorescence will pop up because the IFE is suppressed. Under optimum conditions, fluorescence is linearly related to lysozyme concentration in the 1.0 nM to 20 nM concentration range, with a 0.55 nM limit of detection. The method is perceived to be of wider applicability in that it may be used to design other visual and fluorescent assays if appropriate aptamers are available.

Highly sensitive colorimetric and fluorescent sensor for cyanazine based on the inner filter effect of gold nanoparticles

Cyanazine residue poses a great threat to human health and its derivatives would remain in soils, natural waters, and other environmental domains for a long time. Herein, a simple, rapid, and ultra-sensitive analytical method for the determination of cyanazine (CZ) based on inner filter effect (IFE) of Au nanoparticles (AuNPs) on the fluorescence of CdTe quantum dots (QDs) is first described in this study. With the presence of citrate-stabilized AuNPs, the fluorescence of GSH-capped CdTe QDs was remarkably quenched by AuNPs via IFE. The fluorescence of the AuNP–CdTe QD system was recovered upon addition of CZ. CZ can adsorb on to the surface of AuNPs due to its cyano group that has good affinity with gold, which could induce the aggregation of AuNPs accompanying color change from red to blue. Thus, the IFE of AuNPs on CdTe QDs was weakened, and the fluorescence intensity of CdTe QDs was recovered accordingly. A good linear correlation for detection of CZ was exhibited from 0.05 to 9 μM, and the detection limit reached 0.1568 μM, which was much lower than the safety limit required by the USA, the UK, and China. In order to probe into the selectivity of AuNPs towards CZ over other pesticides, various frequently used pesticides were mixed with AuNPs. AuNP composite solution shows good selectivity towards CZ among other pesticides. This method was successfully carried out for the assessment of CZ in real samples with satisfactory results, which revealed many advantages such as high sensitivity, low cost, and non-time-consuming compared with traditional methods.

Dopamine assay based on an aggregation-induced reversed inner filter effect of gold nanoparticles on the fluorescence of graphene quantum dots

We describe a fluorescent dopamine assay that is based on the inner filter effect (IFE) of gold nanoparticles (AuNPs) on the fluorescence of graphene quantum dots (GQDs). The green fluorescence of GQDs is remarkably inhibited in the presence of citrate-stabilized AuNPs via IFE. Upon the addition of dopamine (DA), aggregation of the AuNPs occurs which is associated with a color change from red to blue. The IFE can no longer occur and the fluorescence of GQDs is recovered. Under the optimum conditions, a linear correlation exists between fluorescence intensity and the concentration of DA in the range from 20nM to 200nM with a detection limit of 15nM (at 3σ/s). The assay is rapid, inexpensive and highly sensitive.

Visual and fluorescent assays for selective detection of beta-amyloid oligomers based on the inner filter effect of gold nanoparticles on the fluorescence of CdTe quantum dots

Beta-amyloid (Aβ) peptides are the major constituents of senile plaques in the brains of Alzheimer’s disease (AD) patients. Aβ monomers (AβMs) can coalesce to form small, soluble oligomers (AβOs), followed by reorganization and assembly into long, thread-like fibrils (AβFs). Recently, soluble AβOs have been regarded as reliable molecular biomarkers for the diagnosis of AD because of their high toxicity for neuronal synapse and high concentration levels in the brains of AD patients. In this work, we reported a label-free, sensitive and selective method for visual and fluorescent detection of AβOs based on the inner filter effect (IFE) of gold nanoparticles (AuNPs) on the fluorescence of CdTe quantum dots (QDs). Specifically, the fluorescence of CdTe QDs was quenched significantly by AuNPs through the IFE. PrP(95–110), an AβOs-specific binding peptide from cellular prion protein, triggered the aggregation and color change of AuNPs suspension; thus, the IFE of AuNPs on the fluorescence of CdTe QDs was weakened and the fluorescence intensity was recovered. However, in the presence of AβOs, the specific interaction of AβOs and PrP(95–110) prevented the absorption of PrP(95–110) onto the surface of AuNPs. As a result, the aggregation of AuNPs was inhibited and the fluorescence intensity of CdTe QDs was quenched again. This label-free method is specific for detection of AβOs but not for AβMs and AβFs. The detection limits were found to be 0.5nM for the visual assay and 0.2nM for the fluorescent detection. We believe that this work would be valuable for many investigations related to AD diagnosis and drug discovery.

Gold Nanocluster-Assisted Fluorescent Detection for Hydrogen Peroxide and Cholesterol Based on the Inner Filter Effect of Gold Nanoparticles

We developed a simple, sensitive inner filter effect (IFE)-based fluorescent assay for sensing H2O2 and cholesterol. In the process, poly(vinylpyrrolidone)-protected gold nanoparticles (PVP-AuNPs) and fluorescent BSA-protected gold nanoclusters (BSA-AuNCs) were used as an IFE absorber/fluorophore pair. PVP-AuNPs can be a powerful absorber to influence the emission of the fluorophore, BSA-AuNCs, in the IFE-based fluorescent assays. That is due to the high extinction coefficient of AuNPs and the complementary overlap between the surface plasmon resonance (SPR) absorption of PVP-AuNPs and the excitation of BSA-AuNCs. The PVP-Au seeds, produced by directly mixing PVP with HAuCl4, were able to catalyze H2O2 to enlarge AuNPs. The SPR absorption of PVP-AuNPs was enhanced with an increased concentration of H2O2 and, subsequently, induced significant fluorescence quenching of BSA-AuNCs. The IFE-based fluorescent assay enabled the detection of H2O2 and generation of H2O2 in the presence of O2/cholesterol and cholesterol oxidase (ChOx) by the fluorescence response of BSA-AuNCs. The present IFE-based approach can detect H2O2 ranging from 1 to 100 μM with a detection limit of 0.8 μM and cholesterol ranging from 1 to 100 μM with a detection limit of 1.4 μM.

Visual and fluorescent detection of acetamiprid based on the inner filter effect of gold nanoparticles on ratiometric fluorescence quantum dots

In this work, we develop a simple and rapid sensing method for the visual and fluorescent detection of acetamiprid (AC) based on the inner-filter effect (IFE) of gold nanoparticles (AuNPs) on ratiometric fluorescent quantum dots (RF-QDs). The RF-QDs based dual-emission nanosensor was fabricated by assembling green emissive QDs (QDs539nm, λem=539nm) on the surface of red emissive QDs (QDs661nm, λem=661nm)-doped silica microspheres. The photoluminescence (PL) intensity of RF-QDs could be quenched by AuNPs based on IFE. Acetamiprid can adsorb on the surface of AuNPs due to its cyano group that has good affinity with gold, which could induce the aggregation of AuNPs accompanying color change from red to blue. Thus, the IFE of AuNPs on RF-QDs was weakened and the PL intensity of RF-QDs was recovered accordingly. Under the optimized conditions, the PL intensity of the RF-QDs/AuNPs system was proportional to the concentration of AC in the range of 0.025–5.0μgmL−1, with a detection limit of 16.8μgL−1. The established method had been used for AC detection in environmental and agricultural samples with satisfactory results.

Efficient inner filter effect of gold nanoparticles on the fluorescence of CdS quantum dots for sensitive detection of melamine in raw milk

A simple, rapid and ultra-sensitive analytical method for the determination of melamine in raw milk based on inner filter effect (IFE) of Au nanoparticles (AuNPs) on the fluorescence of CdS quantum dots (QDs) is described in this study. With the presence of citrate-stabilized AuNPs, the fluorescence of l-cysteine (l-Cys)-capped CdS QDs was remarkably quenched by AuNPs via IFE. The fluorescence of the AuNPs-CdS QDs system was recovered upon addition of melamine, since melamine could induce the aggregation of AuNPs accompanying the reduction of their characteristic plasmon absorption at ∼522 nm, which resulted in “turn-on” of the IFE-decreased fluorescence of CdS QDs. Under the optimum conditions, a good linear correlation for detection of melamine in raw milk was exhibited from 0.05 mg·L−1 to 0.35 mg·L−1, and the detection limit was 0.017 mg·L−1, which was much lower than the detection limit of HPLC coupled with UV detector and the safety limit required by USA, UK and China. This method was successfully carried out for the assessment of melamine in raw milk samples, which revealed many advantages such as high sensitivity, low cost and non-time-consuming compared with traditional methods.

Inner filter effect of gold nanoparticles on the fluorescence of rare-earth phosphate nanocrystals and its application for determination of biological aminothiols

A simple, sensitive fluorescent method for detecting biological aminothiols has been developed based on the inner filter effect principle that utilizes CePO4:Tb3+ luminescent nanoparticles as the donor and gold nanoparticles (AuNPs) as the energy receptor. Stable, water-soluble and well-dispersible CePO4:Tb3+ nanoparticles with low photobleaching features were synthesized conveniently by a facile solvothermal method. At the same time, AuNPs with a high extinction coefficient are expected to be capable of functioning as powerful receptor. Based on the complementary overlap between the emission spectrum of CePO4:Tb3+ nanoparticles and the absorption spectrum of Au NPs, an inner filter effect system was constructed. In the presence of aminothiols (such as cysteine), AuNPs interacted with the aminothiols, thereby inducing the aggregation of AuNPs, which induced the fluorescence recovery. In the present work, we developed a turn-on fluorescent assay for the determination of biological aminothiols. Under the optimum conditions, the linear concentration ranges were 1.0×10−7–2.0×10−6M for cysteine, 5.0×10−8–5.0×10−7M for glutathione and 8.0×10−8–1.0×10−6M for homocysteine, respectively. The method is successfully applied to the quantification of biological aminothiols in synthetic samples.

Homogeneous fluorescence-based immunoassay via inner filter effect of gold nanoparticles on fluorescence of CdTe quantum dots

Homogeneous immunoassays are becoming more and more attractive for modern medical diagnosis because they are superior to heterogeneous immunoassays in sample and reagent consumption, analysis time, portability and disposability. Herein, a universal platform for homogeneous immunoassay, using human immunoglobulin (IgG) as a model analyte, has been developed. This assay relies upon the inner filter effect (IFE) of gold nanoparticles (AuNPs) on CdTe QDs fluorescence. The immunoreaction of antigen and antibody can induce the aggregation of antibody-functionalized AuNPs, and after aggregation the IFE of AuNPs on CdTe QDs fluorescence is greatly enhanced, resulting in a decrease of fluorescence intensity in the system. Based on this phenomenon, a wide dynamic range of 1-100 pg mL(-1) for determination of IgG can be obtained. The proposed method shows a detection limit of 0.3 pg mL(-1) for human IgG, which is much lower than the corresponding absorbance-based approach and compares favorably with other reported fluorescent methods. This immunoassay method is simple, rapid, cheap, and sensitive. The proposed method has been successfully applied to measuring IgG in serum samples, and the obtained results agreed well with those of the enzyme-linked immunosorbent assay (ELISA).

Inner filter effect of gold nanoparticles on the fluorescence of quantum dots and its application to biological aminothiols detection

We have demonstrated the design of a new type fluorescence assay based on the inner filter effect (IFE) of gold nanoparticles (AuNPs) on the fluorescence of quantum dots (QDs). With a high extinction coefficient, AuNPs are expected to be capable of functioning as powerful absorbers. QDs with tunable emission wavelength are ideal fluorophores because the emission spectra of the rationally synthesized QDs can perfectly overlap with the absorption band of the absorber. Aminothiols are chosen as the model analytes, and the IFE-based fluorescent method for detection of aminothiols was suggested. Under the optimum conditions, the response is linearly proportional to the concentration of cysteine in the range of 0.05–0.9μgmL−1. The present IFE-based fluorescent strategy could be also used to detect glutathione and homocysteine. The linear concentration ranges were 0.05–1.0μgmL−1 for glutathione and 0.01–1.0μgmL−1 for homocysteine.