Indoor window film samples were collected in buildings during 2014-2015 for the determination of six phthalate diesters (PAEs). Linear regression analysis suggested that the film mass was positively and significantly correlated with the duration of film growth (from 7 to 77 days). PAEs were detected in all window film samples (n = 64). For all the samples with growth days ranged from 7 to 77 days, the median concentrations of total six PAEs (∑6PAEs) in winter and summer window film samples were 9900 ng/m(2) film (2000 μg/g film) and 4700 ng/m(2) film (650 μg/g film), respectively. Among PAEs analyzed, di-2-ethyl-hexyl phthalate (DEHP) was the major compound (71 ± 9.7%), followed by di-n-butyl phthalate (DBP; 20 ± 7.4%) and diisobutyl phthalate (DiBP; 5.1 ± 2.2%). Positive correlations among PAEs suggested their common sources in the window film samples. Room temperature and relative humidity were negatively and significantly correlated with PAEs concentations (in ng/m(2)). Poor ventilation in cold winter in Noreastern China significantly influenced the concentrations of PAEs in window film which suggested higher inhalation exposure dose in winter. The median hazard quotient (HQ) values from PAEs exposure were below 1, suggesting that the intake of PAEs via three exposure pathways was considered as acceptable.
In a clinical assay, enzymes are essential biomarkers for human disease diagnosis. In this work, a spectral-resolved singleparticle detection (SPD) method is introduced to quantify alkaline phosphatase (ALP) activity in human serum with a supraparticle (SP) based on MnO 2 -modified gold nanoparticle (denoted as GNP@ MnO 2 SP) as the probe. In the presence of ALP, 2-phospho-Lascorbic acid trisodium salt can be hydrolyzed into L-ascorbic acid, which serves as a good reduction agent to trigger the decomposition of the MnO 2 shell on the GNP surface. Given that a trace amount of ALP exists, noticeable scattering color change can be detected at the single-particle level due to the sensitive localized surface plasmon resonance (LSPR) effect from GNPs. With spectral-resolved darkfield optical microscopy, a linear dynamic range of 0.06 to 2.48 mU/ mL (R 2 = 0.99) and a very low limit of detection of 5.8 μU/mL for the ALP assay are readily achieved, which is more sensitive over the methods based on ensemble sample measurement. As a consequence, this strategy opens a new avenue for the design of an ultrasensitive detection method for disease-correlated biomarker diagnosis in the future.
In this work, we demonstrate a convenient yet sensitive color-coded single-particle detection method for the quantification of pyrophosphate (PPi) by using single gold nanoparticle (GNP) as the probe. The design is based on GNP-dependent catalytic deposition of Cu onto the surface of GNPs with reduced nicotinamide adenine dinucleotide (NADH). Without PPi, Cu can be directly reduced to Cu through the gold-catalyzed oxidization of NADH. In the presence of PPi, the coating process is impeded due to the strong coordination capability of PPi with Cu. The selective coating of Cu shell onto the GNPs surface results in the extraordinary red-shift of localized surface plasmon resonance from individual GNPs. By quantitatively counting the fraction of yellow particles with color-coded dark-field optical microscopy, the trace amounts of PPi in solution can be accurately quantified. The limit-of-detection is as low as 1.49 nM with a linear dynamic range of 0-4.29 μM, which is much lower than the spectroscopic measurements in bulk solution. In artificial urine sample, good recovery efficiency was achieved. As a consequence, the method demonstrated herein will find promising applications for the ultrasensitive detection of target biomolecules under biological milieu in the future.
Glutathione S-transferase (GST) is a group of multifunctional enzyme and participates in many physiological processes, such as xenobiotic biotransformation, drug metabolism, and degradation of toxic products. Herein, we demonstrate a label-free fluorescent conjugated polymer nanoparticle (FCPNPs)-based single-particle enumeration (SPE) method for the sensitive GST assay. Fluorescence resonance energy transfer (FRET) is formed between the glutathione-modified FCPNPs (FCPNPs-GSH) and polyethyleniminecapped gold nanoparticles (GNPs@PEI). Therefore, the fluorescence of FCPNPs-GSH is quenched remarkably. In the presence of GST, GNPs@PEI stay away from FCPNPs-GSH due to the specific interaction between FCPNPs-GSH and GST, leading to the inhibition of FRET. As a result, the fluorescence emission of FCPNPs-GSH is restored, which is reflected as the increase of the number of fluorescent particles in the microscopic image. By statistically counting the target concentration-dependent fluorescent particle number, accurate quantification of GST is achieved. The linear range from 0.01 to 6 μg/mL is obtained for GST assay and the limit-of-detection (LOD) is 1.03 ng/mL, which is much lower than the ensemble fluorescence spectra measurements in bulk solution. In urine sample assay, satisfactory recoveries in the range of 97.5−106.5.0% are achieved. Because of the high sensitivity and excellent specificity, this method can be extended to the detection of other disease-related biomolecules in the future.
Contamination of foods and feeds by aflatoxins is a universal yet serious problem all over the world. Particularly, aflatoxin B 1 (AFB1) is the most primary form and readily leads to terrible damages to human health. In this work, we construct a sensitive aptasensor based on singleparticle detection (SPD) to analyze AFB1 in peanut samples with luminescence resonance energy transfer (LRET) between the aptamermodified upconversion nanoparticles (UCNPs-aptamer) and gold nanoparticles (GNPs). The UCNP-aptamer plays as the luminescence donor, while GNP acts as the energy acceptor. In the absence of AFB1, GNPs would adsorb onto the surface of UCNPs-aptamer because of the association between aptamers and GNPs, leading to luminescence quenching. However, the luminescence of UCNPs-aptamer is recovered gradually in the presence of AFB1, because the aptamers possess stronger affinity toward AFB1 than GNPs. Through statistically counting the number of luminescent particles on the glass slide surface, the concentration of AFB1 in solution is accurately determined. The linear dynamic range for AFB1 detection is from 3.13 to 125.00 ng/mL. The limit-of-detection (LOD) is 0.17 ng/mL, which is much lower than the allowable concentration in foods. As a result, this method would provide promising application for the sensitive detection of AFB1 in foods and feeds, which might make a meaningful contribution to food safety and public health in the future.
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