ABSTRACT
A simple and sensitive fluorometric method is developed utilizing aggregation-induced emission probe based silica nanoparticles for the detection of nitroaromatic explosives. A positively charged tetraphenylethene based probe (TPE-C2-2+) is doped into silica nanoparticles exploiting electrostatic interactions to produce TPE-SiO2 nanoparticles with a uniform particle size. The TPE-SiO2 nanoparticles exhibit strong fluorescence emission due to the aggregation-induced emission (AIE) effect of the doped TPE probe. The fluorescence emission of TPE-SiO2 offers quantitative and sensitive response to picric acid (PA), 2,4-dinitrotoluene (DNT) and 2,4,6-trinitrotoluene (TNT) which are used as model examples of nitroaromatic compounds. The fluorescence spectroscopy results show that the fluorescence emission of TPE-SiO2 was greatly quenched in the presence of the electron-poor nitroaromatic compounds due to the inner filter effect (IFE) and possibly the contact quenching mechanism. TPE-SiO2 nanoparticles show better sensitivity towards PA and could detect PA down to 0.01 µM with a linear detection range of 0.1-50 µM. The increased chemical stability, efficient high sensitivity and simple synthesis of the TPE-SiO2 nanoparticles demonstrate that they can be used as an excellent fluorescent probe for a wide range of electron-poor compounds, i.e. nitroaromatic compounds. Interference studies show that common interfering species with nitroexplosives such as acids, bases, volatile organic compounds, and salt solutions have a negligible effect during the sensing process.
ABSTRACT
A sensitive sandwich immunoassay for the sensing of human epididymis protein 4 (HE4) is developed based on aggregation-induced emission probe doped silica nanoparticles. Fluorescent silica nanoparticles (TSiO2) with excellent performance were prepared using a tetraphenylethylene based probe (TPE-C4-4) to produce a controlled aggregation effect, and HE4 was detected using antibody-functionalized fluorescent silica nanoparticles. The fluorescent silica nanoparticles possess good photophysical properties. The TSiO2 NPs were surface modified with carboxyl groups, and the antibody was covalently attached onto the surface of the nanoparticles. In addition, magnetic beads were modified with N-hydroxysulfosuccinimide sodium salt (NHS) on their surface, capable of forming stable peptide bonds with the antibody. TSiO2 NPs modified by an antibody and the magnetic beads modified by an antibody were used for the sandwich immunoassay for HE4 protein. The assay is quite sensitive and selective. The detection limit of HE4 is estimated to be 40 pM. The assay shows promising applications for the early diagnosis of ovarian cancer and the development of ovarian cancer-related drugs.
Subject(s)
Fluorescent Dyes/chemistry , Immunoassay/methods , Nanoparticles/chemistry , Silicon Dioxide/chemistry , WAP Four-Disulfide Core Domain Protein 2/analysis , Biosensing Techniques/methods , Humans , Limit of Detection , Male , Sensitivity and Specificity , Stilbenes/chemistryABSTRACT
A novel sensing strategy for acetylcholinesterase (AChE) and alpha-fetoprotein (AFP) is developed, based on the perylene probe monomer to excimer fluorescence transformation induced by the in situ generation of a metal coordination polymer. In the presence of AChE, acetylthiocholine chloride was hydrolyzed to thiocholine. Ag+ and the produced thiocholine formed a positively charged metal coordination polymer, which induced the aggregation of a negatively charged perylene probe and the formation of probe excimer emission. The intensity ratio of excimer to monomer emission was proportional to the AChE concentration. A sensing method for AChE was thus established with a detection limit of 0.02 mU mL-1. The excimer emission with a large Stokes shift could avoid the interference of background fluorescence from complex biological samples, and thus achieved selective and sensitive detection of AChE. In addition, a fluorescence immunoassay strategy for AFP was then developed. Gold nanoparticles (AuNPs) co-immobilized with acetylcholinesterase and the AFP antibody as the capture and amplification probe were first prepared. In the presence of AFP, the sandwich structure was formed by immunological recognition. The hydrolysis of acetylthiocholine was catalyzed by AChE on the AuNPs, and the metal coordination polymer was then formed which resulted in the aggregation of the perylene probe and the formation of the excimer emission. The proposed sensing method offers a new strategy for the detection of other biomarkers.
Subject(s)
Acetylcholinesterase/urine , Coordination Complexes/chemistry , Gold/chemistry , Metal Nanoparticles/chemistry , Perylene/chemistry , Polymers/chemistry , alpha-Fetoproteins/analysis , Biosensing Techniques , Fluorescence , Humans , Immunoassay , Limit of DetectionABSTRACT
In this work, we report a novel sensor for colorimetric and fluorometric H2O2 sensing which is based on silver nanoparticles decorated and tetraphenylethene probe doped silica nanoparticles (Ag@TPE-SiO2 NPs). A positively charged tetraphenylethene (TPE) probe is doped into silica nanoparticles, and the nanoparticles exhibit strong fluorescence emission due to aggregation-induced emission (AIE) of the TPE probe. Ag nanoparticles (AgNPs) are prepared in situ on the surface of the silica nanoparticles. AgNPs serve as a nanoquencher which can quench the AIE emission of the TPE-SiO2 NPs efficiently. However, AgNPs can be oxidized to Ag+ by H2O2, which leads to fluorescence recovery and color fading of the Ag@TPE-SiO2 NPs. The dual-readout strategy allows sensitive analysis of H2O2. The detection limit of the fluorometric and colorimetric assay is 0.28 and 2.1⯵M, respectively. And the nanosensor also shows good selectivity. In addition, analysis of H2O2 in human serum and intracellular imaging of H2O2 are both demonstrated. With the good analytical properties of merit, the proposed nanoprobe has a promising potential for H2O2 related bioanalysis and biomedical applications.
Subject(s)
Biosensing Techniques/methods , Blood Chemical Analysis/methods , Hydrogen Peroxide/analysis , Nanoparticles/chemistry , Silicon Dioxide/chemistry , Silver/chemistry , Stilbenes/chemistry , Biosensing Techniques/instrumentation , Colorimetry , Fluorometry , Humans , Hydrogen Peroxide/blood , Intracellular Space/chemistry , Limit of Detection , Metal Nanoparticles/chemistry , Molecular ImagingABSTRACT
Metal ions sensing play critical roles in environmental monitoring and in biology. In this assay, we report the development of a facile fluorometric method for the sensing of Ag+ ions via the in situ formation of metal coordination polymer, based on the selective interactions of GSH with Ag+. The formation of coordination polymer with net multiple negative charges in an aqueous buffer solution (Tris-HAc, pH 9.0) resulted in aggregation and fluorescence quenching of a cationic perylene probe. The difference in emission intensity spurred us to develop a new strategy for sensing Ag+ ions. The proposed Ag+ detection method is simple, convenient, selective and sensitive, and can be used for Ag+ detection in lake water samples.
