A flexible gradient lateral flow immunochromatographic assay for qualitative, semi-quantitative, and quantitative determination of serum amyloid A.

Serum amyloid A (SAA) is an acute-phase protein produced in response to inflammatory proteins during infections, inflammation, trauma, surgery, cancer, and other conditions. Early and accurate detection of SAA is necessary for diagnosis and monitoring of disease progression. To meet this need, we developed a gradient lateral flow immunoassay test strip using Au nanoparticles as signal reporters. The test strip has three test (T1, T2, and T3) lines with progressively decreasing concentrations of SAA antibody, enabling the determination of high, medium, and low concentrations of SAA in serum. The test strip results were analyzed using three distinct readout methods, each with different sensitivity, accuracy, and precision for SAA concentration measurements. Qualitative judgment is based on the color of the T1 line. Semi-quantitative assessment of SAA concentration is determined by the number of colored T-lines. Specifically, color development in T1 line alone indicates a concentration range of 10-50 µg/mL, while T1 and T2 lines together indicate a range of 50-100 µg/mL, and development in all three lines (T1, T2, and T3) indicates a concentration of >100 µg/mL. Quantitative analysis was performed using either smartphone imaging or image scanning with ImageJ software. By using a five-parameter logistic function, we found a strong correlation (R2 = 0.998) between the ratio of signal intensities of (T1 + T2 + T3) to the control (C) line and SAA concentrations ranging from 5 to 1000 µg/mL. At lower concentrations (0-100 µg/mL), we observed a proportional relationship between the value of (T1 + T2 + T3)/C and SAA concentration. The limit of detection for SAA was 9.33 ng/mL (or 6.53 µg/mL of SAA in undiluted serum samples) for the smartphone method and 3.06 ng/mL (or 2.14 µg/mL of SAA in undiluted serum samples) for the scanner method. The gradient test strip was highly consistent with a commercially available SAA immunochromatographic test strip when tested with real human serum samples. Passing-Bablok regression indicated that results obtained using the smartphone app and scanner methods of the gradient test strip were comparable to those obtained using the commercial test strip. The gradient test strip is flexible and adaptable, providing solutions for qualitative, semi-quantitative, and quantitative SAA measurements.

Development of Levo-Lansoprazole Chiral Molecularly Imprinted Polymer Sensor Based on the Polylysine-Phenylalanine Complex Framework Conformational Separation.

The efficacies and toxicities of chiral drug enantiomers are often dissimilar, necessitating chiral recognition methods. Herein, a polylysine-phenylalanine complex framework was used to prepare molecularly imprinted polymers (MIPs) as sensors with enhanced specific recognition capabilities for levo-lansoprazole. The properties of the MIP sensor were investigated using Fourier-transform infrared spectroscopy and electrochemical methods. The optimal sensor performance was achieved by applying self-assembly times of 30.0 and 25.0 min for the complex framework and levo-lansoprazole, respectively, eight electropolymerization cycles with o-phenylenediamine as the functional monomer, an elution time of 5.0 min using an ethanol/acetic acid/H2O mixture (2/3/8, V/V/V) as the eluent, and a rebound time of 10.0 min. A linear relationship was observed between the sensor response intensity (ΔI) and logarithm of the levo-lansoprazole concentration (l-g C) in the range of 1.0 × 10-13-3.0 × 10-11 mol/L. Compared with a conventional MIP sensor, the proposed sensor showed more efficient enantiomeric recognition, with high selectivity and specificity for levo-lansoprazole. The sensor was successfully applied to levo-lansoprazole detection in enteric-coated lansoprazole tablets, thus demonstrating its suitability for practical applications.

Aptamer-Adjusted Carbon Dot Catalysis-Silver Nanosol SERS Spectrometry for Bisphenol A Detection.

Carbon dots (CDs) can be prepared from various organic (abundant) compounds that are rich in surfaces with -OH, -COOH, and -NH2 groups. Therefore, CDs exhibit good biocompatibility and electron transfer ability, allowing flexible surface modification and accelerated electron transfer during catalysis. Herein, CDs were prepared using a hydrothermal method with fructose, saccharose, and citric acid as C sources and urea as an N dopant. The as-prepared CDs were used to catalyze AgNO3-trisodium citrate (TSC) to produce Ag nanoparticles (AgNPs). The surface-enhanced Raman scattering (SERS) intensity increased with the increasing CDs concentration with Victoria blue B (VBB) as a signal molecule. The CDs exhibited a strong catalytic activity, with the highest activity shown by fructose-based CDs. After N doping, catalytic performance improved; with the passivation of a wrapped aptamer, the electron transfer was effectively disrupted (retarded). This resulted in the inhibition of the reaction and a decrease in the SERS intensity. When bisphenol A (BPA) was added, it specifically bound to the aptamer and CDs were released, recovering catalytical activity. The SERS intensity increased with BPA over the concentration range of 0.33-66.67 nmol/L. Thus, the aptamer-adjusted nanocatalytic SERS method can be applied for BPA detection.

Facile preparation of Cu-doped carbon dots for naked-eye discrimination of phenylenediamine isomers and highly sensitive ratiometric fluorescent detection of H2O2.

Changing a detection analyte into a colored material is a key challenge for visual discrimination of isomers. In this work, a novel fluorescent probe incorporating Cu-doped carbon dots (Cu-CDs), for the first time, was developed for naked-eye discrimination of phenylenediamine isomers and highly sensitive ratiometric fluorescence detection of H2O2. In this strategy, Cu-CDs were synthesized by a facile hydrothermal approach using citric acid, formamide, and CuCl2 as reactants. The prepared Cu-CDs exhibited outstanding peroxidase-like activity and stability. Consequently, a chemosensor platform based on Cu-CDs was constructed to enable naked-eye discrimination of phenylenediamine isomers through the H2O2-mediated oxidation reaction. Moreover, a Cu-CDs-based ratiometric fluorescence sensor was proposed as a means to sensitively detect H2O2 with a detection limit of 5.0 nM. The sensor was further employed for monitoring H2O2 in human serum, indicating its potential applications in other biologically related study.

Fullerol Nanocatalysis and Trimodal Surface Plasmon Resonance for the Determination of Isocarbophos.

Fullerol (C60OH) has been shown to catalyze the trisodium citrate (TSC)-silver nitrate reaction to generate Ag nanoparticles (AgNPs). These AgNPs exhibit significant nanoplasmic surface-enhanced Raman scattering (SERS), resonance Rayleigh scattering (RRS), and absorption (Abs). When an aptamer (Apt) adsorbs on the C60OH surface, catalysis is inhibited, and the intensities of SERS, RRS, and Abs decrease. In the presence of isocarbophos (IPS), Apt forms a stable complex (Apt-IPS) and releases C60OH. As a result, SERS, RRS, and Abs intensities increase with increasing IPS concentration. Accordingly, a new SERS, RRS, and Abs trimodal method using Apt-labeled fullerol was established for the determination of IPS. Of the three spectral methods, SERS was the most sensitive, while the Abs method was the most cost-effective.

A simple and selective resonance Rayleigh scattering-energy transfer spectral method for determination of trace neomycin sulfate using Cu2O particle as probe.

The stable Cu2O nanocubic (Cu2ONC) sol was prepared, based on graphene oxide (GO) catalysis of glucose-Fehling's reagent reaction, and its absorption and resonance Rayleigh scattering (RRS) spectra, transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) were examined. Using the as-prepared Cu2ONC as RRS probe, and coupling with the neomycin sulfate (NEO) complex reaction, a new, simple, sensitive and selective RRS-energy transfer (RRS-ET) method was established for detection of neomycin sulfate, with a linear range of 1.4-112µM and a detection limit of 0.4µM. The method has been applied to the detection of neomycin sulfate in samples with satisfactory results.

Resonance Rayleigh Scattering and SERS Spectral Detection of Trace Hg(II) Based on the Gold Nanocatalysis.

Mercury (Hg) is a heavy metal pollutant, there is an urgent need to develop simple and sensitive methods for Hg(II) in water. In this article, a simple and sensitive resonance Rayleigh scattering (RRS) method was developed for determination of 0.008-1.33 µmol/L Hg, with a detection limit of 0.003 µmol/L, based on the Hg(II) regulation of gold nanoenzyme catalysis on the HAuCl4-H2O2 to form gold nanoparticles (AuNPs) with an RRS peak at 370 nm. Upon addition of molecular probes of Victoria blue B (VBB), the surface-enhanced Raman scattering (SERS) peak linearly decreased at 1612 cm-1 with the Hg(II) concentration increasing in the range of 0.013-0.5 µmol/L. With its good selectivity and good accuracy, the RRS method is expected to be a promising candidate for determining mercury ions in water samples.

A surface enhanced Raman scattering quantitative analytical platform for detection of trace Cu coupled the catalytic reaction and gold nanoparticle aggregation with label-free Victoria blue B molecular probe.

With development of economy and society, there is an urgent need to develop convenient and sensitive methods for detection of Cu2+ pollution in water. In this article, a simple and sensitive SERS sensor was proposed to quantitative analysis of trace Cu2+ in water. The SERS sensor platform was prepared a common gold nanoparticle (AuNP)-SiO2 sol substrate platform by adsorbing HSA, coupling with the catalytic reaction of Cu2+-ascorbic acid (H2A)-dissolved oxygen, and using label-free Victoria blue B (VBB) as SERS molecular probes. The SERS sensor platform response to the AuNP aggregations by hydroxyl radicals (•OH) oxidizing from the Cu2+ catalytic reaction, which caused the SERS signal enhancement. Therefore, by monitoring the increase of SERS signal, Cu2+ in water can be determined accurately. The results show that the SERS sensor platforms owns a linear response with a range from 0.025 to 25µmol/L Cu2+, and with a detection limit of 0.008µmol/L. In addition, the SERS method demonstrated good specificity for Cu2+, which can determined accurately trace Cu2+ in water samples, and good recovery and accuracy are obtained for the water samples. With its high selectivity and good accuracy, the sensitive SERS quantitative analysis method is expected to be a promising candidate for determining copper ions in environmental monitoring and food safety.

A novel and highly sensitive nanocatalytic surface plasmon resonance-scattering analytical platform for detection of trace Pb ions.

Gold nanoparticles (AuNP) have catalysis on the reaction of HAuCl4-H2O2. The produced AuNP have strong resonance Rayleigh scattering (RRS) effect and surface-enhanced resonance Raman scattering (SERS) effect when Victoria blue B (VBB) and rhodamine S (RhS) were used as probes. The increased RRS/SERS intensity respond linearly with the concentration of gold nanoparticles (AuNPB) which synthesized by NaBH4 over 0.038-76 ng/mL, 19-285 ng/mL, 3.8-456 ng/mL respectively. Four kinds of tested nanoparticles have catalysis on the HAuCl4-H2O2 particles reaction. Thus, a novel nanocatalysis surface plasmon resonance-scattering (SPR-S) analytical platform was developed for AuNP. The DNAzyme strand hybridized with the substrate strand to form double-stranded DNA (dsDNA) which couldn't protect AuNPc to aggregate to AuNPc aggregations, having strong RRS effect. Upon addition of Pb(2+), dsDNA could be cracked by Pb(2+) to produce single-stranded DNA (ssDNA) that adsorbed on the AuNPc surface to form AuNPc-ssDNA conjugates. The conjugates have strong catalysis on HAuCl4-H2O2 reaction. With increased Pb(2+) concentration, the concentration of AuNPc-ssDNA increased and lead to the catalytic activity stronger. The increased RRS intensity responds linearly with Pb(2+) concentration over 16.7-666.7 nmol/L. The SERS intensity responded linearly with the concentration of Pb(2+) over 50-500 nmol/L.

Distribution and source apportionment of polycyclic aromatic hydrocarbons in the surface soil of Baise, China.

To estimate the distribution and sources of polycyclic aromatic hydrocarbons (PAHs) in the soils of Baise, in southwest China, soil sampling sites were selected from industry, traffic, rubbish, gas station, residential, and suburban areas for analysis of PAHs. The average concentrations of ∑16PAHs in the present study varied significantly, depending on the sampling location, and ranged from 16.8 to 6,437.0 µg/kg (dry weight basis), with a mean value of 565.8 µg/kg. PAH concentrations decreased significantly along the industry-traffic-rubbish-gas station-residential-suburban transect. The PAH profiles in the surface soil of the different areas imply that either source proximity to the sampling sites, or transport and deposition effects influenced PAH distributions. Two diagnostic ratios were selected and used to apportion PAH sources in the surface soil, and bivariate plots show general trends of covariation. Principal component analysis and multivariate linear regression were used to determine the primary sources and their contributions of PAHs to the soils. The model showed that factors 1 (coal and wood combustion) and 2 (petroleum combustion) contributed over 52.1 and 32.5% of the total source of soil PAHs, respectively. The remaining 15.4% came from evaporative and uncombusted petroleum.

Distribution and source apportionment of polycyclic aromatic hydrocarbons in soils and leaves from high-altitude mountains in southwestern china.

Several studies have investigated the distribution patterns and geographic sources of polycyclic aromatic hydrocarbons (PAHs) in mountainous areas. Little is known about how different sources contribute to PAH concentrations at different elevations along mountain slopes. To estimate the distribution and sources of PAHs at different altitudes in mountainous areas of southwestern China, samples of soils and leaves from trees were collected from 1000 to 1500 m asl in the Dawangling forest and analyzed for PAHs. Total PAH concentrations ranged from 93.9 to 802.3 ng g (average, 252.3 ng g) in soils and from 4.1 to 100.9 ng g (average, 23.1 ng g) in leaves. Our results suggest that soil PAH levels in the study area could be classified as "weakly contaminated." The PAH levels in leaves from the Dawangling forest were lower than those found in Himalayan spruce needles from the central Himalayas in China and from an agricultural station in southern England. Total PAHs in the Dawangling forest soils increased with elevation, primarily due to the low-molecular-weight PAHs, which accumulated in samples from higher altitudes. In contrast, high-molecular-weight PAHs were inversely related to or unrelated to elevation. The PAH profiles were similar in soils and leaves from all mountainous regions. Diagnostic ratios showed that the PAHs in soils at different altitudes were from different pollution emission sources; therefore, PAHs in the entire study area were probably derived from mixed sources. Cluster analyses confirmed that liquefied petroleum gas, coal/wood combustion, and petroleum combustion were likely the predominant PAH sources in this region.

Resonance scattering spectral detection of trace ATP based on label-free aptamer reaction and nanogold catalysis.

Double-stranded DNA (dsDNA) cannot protect gold nanoparticles (AuNPs) in the presence of NaCl, and dsDNA interacted with adenosine triphosphate (ATP) to form stable G-quartet and a single-stranded DNA (DNA 2) that can protect AuNPs. The unprotected AuNPs were aggregated to AuNP aggregations (AuNPA) that exhibited a resonance scattering (RS) peak at 590 nm. The RS intensity at 590 nm decreased linearly when the ATP concentration increased in the range of 6.6-110 nM. The catalysis of AuNP-DNA 2 was stronger than that of the AuNPA on the glucose-Cu(II) particle reaction, and the product appeared as an RS peak at 620 nm. When the ATP concentration was increased, the AuNP-DNA 2 increased, and the RS intensity at 620 nm increased linearly. The increased RS intensity (ΔI(620 nm)) was linear to ATP concentration in the range of 2.2-220 nM, with a regression equation of ΔI(620 nm) = 0.709C + 7.7, and a detection limit of 0.5 nM. Hereby, a new RS method of ATP detection was set up with high sensitivity and selectivity.

[Resonance scattering detection of trace Hg2+ using aptamer modified AuSe nanoalloy].

Under the condition of sodium citrate as stabilizer, the gold-selenium (AuSe) nano-alloy was prepared by sodium borohydride reduction procedure, and was modified by single-strand aptamer to obtain an aptamer nano-alloy probe (apta-AuSe) for Hg(II). In pH 6.8 Na2HPO4-NaH2PO4 buffer solution and in the presence of NaCl of 33 mmol L(-1), the Apta-AuSe probe is not aggregation. The apta-AuSe interacts with Hg2+ to form stable double-strand T-Hg(II)-T mismatches and to release AuSe nano-alloy particles from the probe. The released AuSe nano-alloy particles (20:1) aggregated to form bigger clusters that resulted in the resonance scattering (RS) intensity (I590 nm) increasing at 590 nm. The increased intensity delta I590 nm was proportional to the Hg2+ concentration from 1.3 to 1466 nmol L(-1), with a detection limit of 0.74 nmol L(-1). The regress equation was delta I590 nm = 0.603c + 2.0. Thus, a new resonance scattering (RS) spectroscopy of apta-AuSe was applied to the analysis of trace mercury ion. This simple, rapid, selective and sensitive aptamer AuSe nano-alloy RS assay was applied to the determination of Hg2+ in wastewater, with satisfactory results.

A simple and sensitive fluorescence quenching method for the determination of H(2)O(2) using Rhodamine B and FE(3)O(4) nanocatalyst.

In pH 1.99 sodium acetate-HCl buffer solutions at 60 °C, Rhodamine B exhibited a strong fluorescence peak at 584 nm using an excitation wavelength of 548 nm. The fluorescence quenching occurred when Fe(3)O(4) nanoparticles catalyzed H(2)O(2) oxidation of Rhodamine B. Under the chosen conditions, the fluorescence intensity at 584 nm decreased when the concentration of H(2)O(2) increased. The fluorescence quenching intensity is linear with the concentration of H(2)O(2) in the range of 10-200 nmol/L. Thus, a new and simple and sensitive nanocatalytic fluorescence method was proposed for the determination of H(2)O(2) in synthetic sample, with satisfactory results.

A highly sensitive aptamer-nanogold catalytic resonance scattering spectral assay for melamine.

The aptamer (ssDNA) was used to label nanogold (NG) particle to fabricate an aptamer-nanogold (NGssDNA) probe for melamine. The probe was stabile in pH 6.6 Na(2)HPO(4)-NaH(2)PO(4) buffer solutions and in the presence of high concentration of electrolyte. Upon addition of melamine, it interacted with the probe to form big NGssDNA-melamine aggregations that led to the resonance Rayleigh scattering (RRS) intensity at 566 nm increased greatly. The increased RRS intensity (ΔI) is linear to melamine concentration in the range of 1.89-81.98 µg/L, with a detection limit of 0.98 µg/L melamine. The unreacted probe in the aptamer reaction solution exhibited strong catalytic effect on the slow Cu(2)O particle reaction between glucose and Fehling reagent, but the catalytic activity of NG aggregations is very weak. When melamine concentration increased, the unreacted probe decreased, the RRS peak intensity at 614 nm decreased. The decreased RS intensity is linear to melamine concentration in the range of 0.63-47.30 ng/L melamine, with a detection limit of 0.38 ng/L. The aptamer-modified nanogold catalytic RRS assay was applied to determination of melamine in milk, with high sensitivity and selectivity, simplicity and rapidity.

A novel and sensitive resonance scattering assay for detection of urea in serum coupled urease catalytic reaction and NH4+ associated particle reaction.

In the pH 6.6 Na2HPO4-NaH2PO4 buffer solutions and in the presence of urease catalyst, urea can be decomposed to form NH4+. The NH4+ reacted with sodium tetraphenyl boron (NaTPB) to form the association particles that exhibited a resonance scattering (RS) peak at 474 nm. When the urea concentration increased, NH4+ increased, and RS intensity at 474 nm enhanced linearly. Under the chosen conditions, the increased RS intensity (ΔI (474 nm)) had a linear response to the urea concentration in the range of 0.125-15 µM, with a detection limit of 0.058 µM urea, and a regression equation of ΔI (474 nm) = 31.6C + 2.1, a correlation coefficient of 0.9986. This catalytic RS method was applied for the detection of urea in human serum sample, with good selectivity and sensitivity, and the results were consistent with the reference method.