Lysosomes Initiating and DNAzyme-Assisted Intracellular Signal Amplification Strategy for Quantification of Alpha-Fetoprotein in a Single Cell.

Cellular trace proteins are critical for maintaining normal cell functions, with their quantitative analysis in individual cells aiding our understanding of the role of cell proteins in biological processes. This study proposes a strategy for the quantitative analysis of alpha-fetoprotein in single cells, utilizing a lysosome microenvironment initiation and a DNAzyme-assisted intracellular signal amplification technique based on electrophoretic separation. A nanoprobe targeting lysosomes was prepared, facilitating the intracellular signal amplification of alpha-fetoprotein. Following intracellular signal amplification, the levels of alpha-fetoprotein (AFP) in 20 HepG2 hepatoma cells and 20 normal HL-7702 hepatocytes were individually evaluated using microchip electrophoresis with laser-induced fluorescence detection (MCE-LIF). Results demonstrated overexpression of alpha-fetoprotein in hepatocellular carcinoma cells. This strategy represents a novel technique for single-cell protein analysis and holds significant potential as a powerful tool for such analyses.

Intracellular Multicomponent Synchronous DNA-Walking Strategy for the Simultaneous Quantification of Tumor-Associated Proteins in a Single Cell.

Single-cell protein analysis is very important for understanding cellular heterogeneity and single-cell biology. However, owing to the extremely low levels of some tumor-associated proteins in individual cells, the absolute quantification of such tumor-associated proteins in a single cell remains a challenge. Herein, an intracellular multicomponent synchronous DNA-walking strategy is proposed for the simultaneous quantification of multiple tumor-associated proteins in a single cell. In this strategy, a nanoprobe based on a DNA walker was designed for the simultaneous signal amplification of nucleolin (NCL) and thymidine kinase 1 (TK1) in a single cell. NCL and TK1 in single cells were simultaneously detected on a microchip platform with detection limits of 1.0 and 0.8 pM, respectively. The results obtained from 20 liver cancer cells (HepG2) and 20 normal hepatocytes (HL-7702) indicated that NCL and TK1 were overexpressed in liver cancer cells. However, the levels of NCL and TK1 in normal hepatocytes are only about one-tenth to one-sixth of those in hepatic carcinoma. Using different nucleic acid aptamers, the proposed strategy can be applied for the analysis of other single-cell proteins and in the early diagnosis of cancer.

Nitrogen and sulfur co-doped carbon dot-based ratiometric fluorescent probe for Zn2+ sensing and imaging in living cells.

A near-infrared nitrogen and sulfur co-doped carbon dot (N,S-CD)-based ratiometric fluorescent probe is proposed that is synthesized via hydrothermal approach using glutathione and formamide as precursor for sensing and imaging of Zn2+. The prepared N,S-CDs facilitate binding with Zn2+ owing to N and S atom doping. The ratio (I650/I680) of fluorescence intensity at 650 nm and 680 nm increased with the concentrations of Zn2+ when the excitation wavelength was 415 nm. The linearity range was 0.01 to 1.0 µM Zn2+with a detection limit of 5.0 nM Zn2+. The proposed probe was applied to label-free monitoring of Zn2+ in real samples and fluorescent imaging of Zn2+ in living cells, which confirmed its promising applications.

A nanocomposite prepared from copper(II) and nitrogen-doped graphene quantum dots with peroxidase mimicking properties for chemiluminescent determination of uric acid.

Nitrogen-doped graphene quantum dots (N-GQD) were employed along with Cu(II) ions under alkaline conditions and room temperature to synthesize nanocomposites of type Cu(II)/Cu2O/N-GQDs. These nanocomposites exhibit excellent stability and dispersity, and also display a peroxidase-like activity that is superior to pure Cu2O nanoparticles and natural peroxidase (POx). A chemiluminescence (CL) method was designed that is based on the use of uricase which oxidizes uric acid under formation of H2O2. The nanocomposites were used as a POx mimic in the luminol-H2O2 CL system. Under optimized conditions, a linear relationship between CL intensity and the uric acid (UA) concentration in the range of 0.16-4.0 µM, and a detection limit of 0.041 µM (at S/N = 3) were obtained. The CL method was applied to the determination of UA in spiked serum and urine, and recoveries ranged from 85.0 to 121.3%. Graphical abstract Schematic presentation of synthesis strategy of Cu(II)/Cu2O/N-GQDs and the CL method based Cu(II)/Cu2O/N-GQDs for H2O2-meidated uric acid detection. The method can be used for the determination of uric acid (UA) with the detection limit of 0.041 µM.

Removal of Lead(II) Ions from Aqueous Solution Using L. Seed Husk Ash as a Biosorbent.

The removal of heavy metals, especially from wastewater, has attracted significant interest because of their toxicity, tendency to bioaccumulate, and the threat they pose to human life and the environment. Many low-cost sorbents have been investigated for their biosorption capacity toward heavy metals. However, there are no reports available on the removal of Pb(II) from aqueous solution by of L. seed husk ash. In this work, use of seed husk ash for the removal of Pb(II) from wastewater was investigated as a function of contact time and the initial pH of the solution. Kinetics and equilibrium constants were obtained from batch experiments. Our study shows that the adsorption process follows pseudo-second-order kinetics. Moreover, the Langmuir absorption model gave a better fit to the experimental data than the Freundlich equation. The maximum adsorption capacity of the husk ash was 263.10 mg g at 298 K and pH 5.0, and this is higher than the previously reported data obtained using other sorbents. The results obtained confirm that seed husk ash is an effective sorbent for the removal of Pb(II) from aqueous solution. Analysis of infrared spectra of the husk ash after absorption of Pb(II) suggested that OH, C=O, C-O, Si-O-Si, and O-Si-O groups were important for the Pb(II) ion removal. Moreover, practical tests on this biosorbent for Pb(II) removal in real wastewater samples successfully demonstrated that seed husk ash constitutes an efficient and cost-effective technology for the elimination of heavy metals from industrial effluent.

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.

Effects of different oxidants on the behaviour of microplastic hetero-aggregates.

Microplastic hetero-aggregates are stable forms of microplastics in the aqueous environment. However, when disinfecting water containing microplastic hetero-aggregates, the response of them in water to different oxidizing agents and the effect on water quality have not been reported. Our results showed that Ca(ClO)2, K2S2O8, and sodium percarbonate (SPC) treatment could lead to the disaggregation of microplastic hetero-aggregates as well as a rise in cell membrane permeability, which caused a large amount of organic matter to be released. When the amount of oxidant dosing is insufficient, the oxidant cannot completely degrade the released organic matter, resulting in DOC, DTN, DTP and other indicators being higher than before oxidation, thus causing secondary pollution of the water body. In comparison, K2FeO4 can purify the water body stably without destroying the microplastic hetero-aggregates, but it only weakly inhibits the toxic cyanobacteria Microcystis and Pseudanabaena, which may cause cyanobacterial bloom as well as algal toxin and odorant contamination in practical application. Compared with the other oxidizers, K2S2O8 provides better inhibition of toxic cyanobacteria and has better ecological safety. Therefore, when treating microplastic-containing water bodies, we should consider both water purification and ecological safety, and select appropriate oxidant types and dosages to optimize the water treatment.

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.

An ultrasensitive chemiluminescence strategy based on a microchip platform for telomerase detection at a single-cell level.

An ultrasensitive chemiluminescence strategy based on signal amplification with a microchip platform was proposed to detect telomerase. This strategy was successfully applied to the determination of lysate samples from HL-7702, HeLa, A549 and MCF-7 cell lines with the detection limit lower than 1 HeLa cell.

Facile synthesis of a direct Z-scheme BiOCl-phosphotungstic acid heterojunction for the improved photodegradation of tetracycline.

The fabrication of a Z-scheme heterojunction photocatalyst can effectively modulate the electron transfer and separation of photoinduced charge carriers to enhance photocatalytic performance. Here, we demonstrate a direct Z-scheme BiOCl-phosphotungstic acid (BiOCl-HPW) heterojunction, fabricated via a one-step hydrothermal synthesis, as a highly active and stable photocatalyst for the photodegradation of tetracycline. BiOCl-HPWs result in a dramatic improvement in visible-light utilization and photogenerated e- and h+ separation, as well as a decrease in the electrical resistance by the addition of HPW. Notably, the BiOCl-HPW heterojunction with optimized phosphotungstic acid (HPW) content achieved an outstanding photodegradation rate of tetracycline (0.0195 min-1). A reasonable Z-scheme photocatalytic mechanism based on the analysis of band structure and monitoring of active radicals is proposed. This study highlights the potential implications of the BiOCl-HPW heterojunctions in the photodegradation of other toxic chemicals and photocatalytic studies.

Cu-Doped Carbon Dots as Catalysts for the Chemiluminescence Detection of Glucose.

Development of metal-doped carbon dots (CDs) to effectively modulate their electronic properties and surface chemical reactivities is still in its early stage. In this paper, a facile solid-phase synthesis strategy was developed to synthesize Cu-doped CDs (Cu-CDs) using citric acid as the carbon source and Cu(NO3)2·3H2O as the dopant, respectively. The as-prepared Cu-CDs exhibited superior peroxidase-like activity to horseradish peroxidase and were stable under a wide range of pH and temperatures. Consequently, the Cu-CD-based chemiluminescence sensing was applied to sensitively detect glucose with a low detection limit of 0.32 µM, and the recoveries and the relative standard deviation of the serum sample are 87.2-112.2 and 8.16% (n = 6), respectively. Notably, the proposed chemiluminescence sensing was also successfully applied for label-free detection of glucose in complex biological samples, which envisioned its potential applications in clinical diagnosis and other analytical assays.

Identification of polycyclic aromatic hydrocarbons (PAHs) in soil by constant energy synchronous fluorescence detection.

In this paper, a novel method of constant energy synchronous fluorescence (CESF) was proposed to the simultaneous determination of different polycyclic aromatic hydrocarbons (PAHs) in a mixture of 16 components. When different appropriate intervals of the constant energy (Deltanu=1400 or 4800cm(-1)) were chosen during constant energy synchronous scanning, 13 PAHs could be identified and quantified by the corresponding synchronous spectra. Results show that their linear relations are fine and the limits of detection (LODs) were between 0.2 and 7.6ngml(-1). Then the application of CESF method proposed in the analysis of the real soil samples under the optimum conditions indicated that 11 PAHs could be identified and the total concentration of PAHs in a real soil sample is 5.1microg g(-1), most of PAHs in the soil samples had three or four rings. Recoveries of these PAHs were from 70.9 to 121.4% in most cases. This CESF method is a simple, rapid, sensitive method with high resolution and also suitable to analyze the complex mixtures of PAHs in other environmental samples.

Fluorescent carbon dots with tunable emission by dopamine for sensing of intracellular pH, elementary arithmetic operations and a living cell imaging based INHIBIT logic gate.

Fluorescent carbon dots (C-dots) have drawn great attention in recent years, and many researchers have focused on developing preparation routes and broadening the applications of C-dots. In this work, novel luminescent C-dots with tunable emission were prepared by the pyrolysis of citric acid (CA) and dopamine (DA). By adjusting the molar ratio of CA and DA in the precursor from 2 : 1 to 2 : 3, the maximum fluorescence emission of the obtained C-dots is at 510 nm in acid solution, while it shifts to 450 nm under neutral conditions, and the fluorescence is quenched in a basic solution. By controlling the unique fluorescence emission at different pH values, a three-state switch is achieved. Half-addition and half-subtraction were performed at 525 nm and 450 nm emissions as outputs. And a living cell imaging based INHIBIT logic gate operation was achieved by imaging the channel ratio of the cells.

Nitrogen and Phosphorus Co-Doped Carbon Nanodots as a Novel Fluorescent Probe for Highly Sensitive Detection of Fe(3+) in Human Serum and Living Cells.

Chemical doping with heteroatoms can effectively modulate physicochemical and photochemical properties of carbon dots (CDs). However, the development of multi heteroatoms codoped carbon nanodots is still in its early stage. In this work, a facile hydrothermal synthesis strategy was applied to synthesize multi heteroatoms (nitrogen and phosphorus) codoped carbon nanodots (N,P-CDs) using glucose as carbon source, and ammonia, phosphoric acid as dopant, respectively. Compared with CDs, the multi heteroatoms doped CDs resulted in dramatic improvement in the electronic characteristics and surface chemical activities. Therefore, the N,P-CDs prepared as described above exhibited a strong blue emission and a sensitive response to Fe(3+). The N,P-CDs based fluorescent sensor was then applied to sensitively determine Fe(3+) with a detection limit of 1.8 nM. Notably, the prepared N,P-CDs possessed negligible cytotoxicity, excellent biocompatibility, and high photostability. It was also applied for label-free detection of Fe(3+) in complex biological samples and the fluorescence imaging of intracellular Fe(3+), which indicated its potential applications in clinical diagnosis and other biologically related study.

Nitrogen-rich functional groups carbon nanoparticles based fluorescent pH sensor with broad-range responding for environmental and live cells applications.

A nitrogen-rich functional groups carbon nanoparticles (N-CNs) based fluorescent pH sensor with a broad-range responding was prepared by one-pot hydrothermal treatment of melamine and triethanolamine. The as-prepared N-CNs exhibited excellent photoluminesence properties with an absolute quantum yield (QY) of 11.0%. Furthermore, the N-CNs possessed a broad-range pH response. The linear pH response range was 3.0 to 12.0, which is much wider than that of previously reported fluorescent pH sensors. The possible mechanism for the pH-sensitive response of the N-CNs was ascribed to photoinduced electron transfer (PET). Cell toxicity experiment showed that the as-prepared N-CNs exhibited low cytotoxicity and excellent biocompatibility with the cell viabilities of more than 87%. The proposed N-CNs-based pH sensor was used for pH monitoring of environmental water samples, and pH fluorescence imaging of live T24 cells. The N-CNs is promising as a convenient and general fluorescent pH sensor for environmental monitoring and bioimaging applications.

Facilely prepared Fe3O4/nitrogen-doped graphene quantum dot hybrids as a robust nonenzymatic catalyst for visual discrimination of phenylenediamine isomers.

In this work, we report a reducing agent-free strategy for the synthesis of Fe3O4 nanoparticle/nitrogen-doped graphene quantum dot (Fe3O4/N-GQD) hybrids, and constructed a sensing platform based on Fe3O4/N-GQDs for the visual discrimination of phenylenediamine isomers. Fe3O4/N-GQDs were facilely prepared by hydrothermal treatment of Fe(3+)/N-GQD solutions under alkaline conditions without other reagents. The prepared Fe3O4/N-GQDs exhibited outstanding peroxidase-like activity and were stable under a wide range of pH values and temperatures. The phenylenediamine isomers (o-phenylenediamine, m-phenylenediamine, and p-phenylenediamine) were discriminated through the H2O2-mediated oxidation reaction using Fe3O4/N-GQDs as novel peroxidase mimics, which resulted in appreciable color changes. The proposed method is simple, economical, and effective for discrimination of isomers, and can be used for sensitive and selective quantitative analysis of o-phenylenediamine and p-phenylenediamine. A good linear relationship from 1 to 90 µM and a detection limit of 230 nM for o-phenylenediamine were achieved, and the linear relationship for p-phenylenediamine was from 2 to 70 µM with a detection limit of 530 nM. The proposed method may open new applications of Fe3O4/N-GQDs in biomedicine and environmental chemistry.

Visual discrimination of dihydroxybenzene isomers based on a nitrogen-doped graphene quantum dot-silver nanoparticle hybrid.

A room temperature reducing agent-free strategy for the synthesis of a nitrogen-doped graphene quantum dot-silver nanoparticle (N-GQD/AgNP) hybrid was presented. In this strategy, N-GQDs were used as a reducing agent and stabilizer for the formation of the N-GQD/AgNP hybrid, and the formation of the N-GQD/AgNP hybrid may result from the extraordinary reduction properties of N-GQDs, which are attributed to the nature of the surface oxygen-containing functional groups. The N-GQD/AgNP hybrid exhibits good dispersity and outstanding catalytic ability toward the oxidation of catechol (CC) and hydroquinone (HQ) by Ag(+). In the presence of the N-GQD/AgNP hybrid, the reduction of Ag(+) by CC and HQ was improved. CC enhanced the absorbance of the N-GQD/AgNP-Ag(+) system the most, and HQ followed, while resorcinol (RC) had only a little effect on the absorption intensity of the system. Thus, a sensitive and selective colorimetric sensing method based on the N-GQD/AgNP-Ag(+) system was developed for the discrimination of CC, HQ and RC. A good linear relationship was obtained from 0.1 to 15.0 µM for CC and from 0.3 to 20.0 µM for HQ. The detection limits of CC and HQ were 0.03 and 0.1 µM, respectively. In addition, the proposed method also shows a high selectivity for the detection of CC and HQ, and appreciable changes in color of the N-GQD/AgNP-Ag(+) system toward CC, RC and HQ were observed.

One-pot green synthesis of oxygen-rich nitrogen-doped graphene quantum dots and their potential application in pH-sensitive photoluminescence and detection of mercury(II) ions.

Nitrogen doping has been a powerful method to modulate the properties of carbon materials for various applications, and N-doped graphene quantum dots (GQDs) have gained remarkable interest because of their unique chemical, electronic, and optical properties. Herein, we introduce a facile one-pot solid-phase synthesis strategy for N-doped GQDs using citric acid (CA) as the carbon source and 3,4-dihydroxy-L-phenylalanine (L-DOPA) as the N source. The as-prepared N-GQDs with oxygen-rich functional groups are uniform with an average diameter of 12.5 nm. Because of the introduction of nitrogen atoms, N-GQDs exhibit excitation-wavelength-independent fluorescence with the maximum emission at 445 nm, and a high quantum yield of 18% is achieved at an excitation wavelength of 346 nm. Furthermore, a highly efficient fluorosensor based on the as-prepared N-GQDs was developed for the detection of Hg(2+) because of the effective quenching effect of metal ions via nonradiative electron transfer. This fluorosensor exhibits high sensitivity toward Hg(2+) with a detection limit of 8.6 nM. The selectivity experiments reveal that the fluorescent sensor is specific for Hg(2+). Most importantly, the practical use of the sensor based on N-GQDs for Hg(2+) detection was successfully demonstrated in river-water samples.