Wide temperature adaptive oxidase-like based on mesoporous manganese based metal-organic framework for detecting total antioxidant capacity.

Overcoming the intense variation of enzymatic activity among different temperatures is very critical in catalytic medicine and catalytic biology. Here, Mn-based metal-organic framework-based wide-temperature-adaptive mesoporous artificial enzymes (Mn-TMA-MOF) were designed and synthesized. The oxidase-like Mn-TMA-MOF showed excellent catalytic activity at 0-50 °C and avoided the activity loss and instability due to temperature variation that occurred. The excellent oxidase-like properties of Mn-TMA-MOF with wide temperature adaptativeness are mainly ascribed to the mixed oxidized state (Mn3+/Mn2+) and high substrate affinity (Km = 0.034 mM) of Mn. Moreover, the mesopore-micropores two-level structure of Mn-TMA-MOF provides a large space and surface area for enzyme catalysis. Based on the stability of Mn-TMA-MOF, we developed a colorimetric sensor that can detect total antioxidant capacity in fruits with a limit of detection up to 0.59 µM.

Preparation and Biotoxicity of Coal-Based Carbon Dot Nanomaterials.

Coal-based Carbon Dots (C-CDs) have gradually become a research focus due to the abundant raw materials and low preparation cost. Still, before coal-based carbon dots are widely used, a systematic biological toxicity study is the basis for the safe utilization of C-CDs. However, the level of toxicity and the mechanism of toxicity of C-CDs for organisms are still unclear. To ensure the safe utilization of C-CDs, the present study investigated C-CD nanomaterials as stressors to probe their biotoxic effects on plant, bacterial, and animal cells as well as the photocatalytic oxidative properties of C-CDs. The results showed that low concentrations of C-CDs could promote various growth indicators of wheat, and high concentrations of C-CDs had significant inhibitory effects on wheat growth; C-CDs had significant toxic effects on (S. aureus) at specific concentrations and were light-related; meanwhile, at concentrations of 1-5000 µg/mL, C-CDs were almost not toxic to HeLa cells; however, when irradiated at 365 nm, even low concentrations of C-CDs were toxic to cells by the mechanism that C-CDs could generate singlet oxygen (1O2) by photocatalytic oxidation under 365 nm excitation light, resulting in enhanced toxicity of C-CDs to cells.

Preparation of N-doped carbon dots and application to enhanced photosynthesis.

Regulation of photosynthesis rates is one of the key ways to increase crop yields. Carbon dots (CDs), which are low-toxity and biocompatible optical nanomaterials, can be easily prepared and are ideal for improving photosynthesis efficiency. In this study, nitrogen-doped CDs (CNDs) with a fluorescent quantum yield of 0.36 were synthesized via a one-step hydrothermal method. These CNDs can convert a part of ultraviolet light in solar energy to blue light (emission peak at 410 nm) that can be utilized in photosynthesis and that overlaps with the optical absorption spectrum of chloroplasts in the blue light zone. Consequently, chloroplasts can pick up photons excited by the CNDs and transfer them to the photosynthetic system in the form of electrons, thereby accelerating the photoelectron transport rate. These behaviors can reduce ultraviolet light stress on wheat seedlings and improve the efficiency of electron capture and transfer from chloroplasts through optical energy conversion. As a result, various photosynthetic indices and biomass of wheat seedlings are improved. Cytotoxicity experiments have showed that CNDs within a certain concentration range almost do not affect cell survival.

Preparation and photodynamic antibacterial/anticancer effects of ultralong-lifetime room-temperature phosphorescent N-doped carbon dots.

Room-temperature phosphorescent (RTP) N-doped carbon-dots (CNDs) featuring eco-friendliness, low cost and high biocompatibility, are ideal photodynamic antibacterial and anticancer nanomaterials. However, the existing CNDs are limited by low singlet oxygen (1O2) quantum yield, which has become a bottleneck in the development of CNDs. One basic reason is the short T1-state exciton lifetime of CNDs. Herein, triethylenetetramine hexaacetic acid was used to synthesize CNDs via a one-step hydrothermal method. CNDs are characterized with low toxicity, high biocompatibility and ultralong-lifetime RTP (URTP). In addition to the URTP (average lifetime 414 ms) under solid conditions, CNDs even had URTP (average lifetime 320 ms) in a water environment. The ultralong T1 exciton lifetime largely extends the collision time between T1 state excitons and O2 and prolongs the energy transfer time, not only improving the quantum yield (0.63) of singlet oxygen (1O2) in solution, but also facilitating the photodynamic antibacterial and anticancer effects.

Ultralong and Color-Tunable Room-Temperature Phosphorescence Based on Commercial Melamine for Anticounterfeiting and Information Recognition.

Advances have been made in the research on color-tunable organic ultralong room-temperature phosphorescence (OURTP) materials. Due to the high cost of raw materials, complex and strict synthesis conditions, and low yields, it is hard to obtain cheap commercial OURTP materials within a short time. Therefore, it is of practical significance to research and develop new OURTP functions based on commercialized organic materials. In this study, the OURTP characteristics of melamine (MEL), a kind of commercially available, cheap, and pure organic material, were investigated and explored. MEL was found with color-tunable and excellent OURTP, the average lifetime can reach 0.74 s, and the phosphorescence quantum yield can reach 17%. Since the ratio of molecular phosphorescence of MEL to the ultralong phosphorescence mediated by H-aggregation differs with the excitation wavelength and their luminescence life spans are also different, the color of OURTP materials is dependent on both excitation wavelength and time. Moreover, the OURTP characteristics of MEL can be utilized in anticounterfeiting and information identification.

Synthesis of biological quantum dots based on single-strand DNA and its application in melamine detection.

By taking TC base-rich single-stranded DNA (ssDNA) as the raw material, a fluorescent biological quantum dots (Bio-dots) probe was prepared in one step through hydrothermal method, where its lifetime was greatly extended in comparison with Carbon quantum dots (CQDs), reaching 10.7 ns. The fluorescent detection of melamine in milk samples was realized by using the base pairing principle. Under the optimal conditions, the linear range of Bio-dots probe fluorescence sensor for melamine detection is 5-600 µM, and the detection limit is (3σ) 1.4 µM. Bio-dots can not only emit photoluminescence, but also detect target molecules as a functional recognition group. As the raw material ssDNA was basically non-toxic and there was no toxic substances participated in its synmanuscript process, this Bio-dots probe was a kind of green and environmentally-friendly photoluminescent functional material.

Preparation of galactose oxidase functional phosphorescent quantum dots and detection of D-galactose.

Environmental friendly nano biosensor can improve the detection performance of traditional biomolecular sensors and have important application value in practical applications. In this study, a kind of room temperature phosphorescence (RTP) quantum dots (QDs) (GOX RTP QDs) nanobiosensor was prepared by mineralization at room temperature (25 °C), using galactose oxidase (GOX) as template, which improved the catalytic ability of traditional GOx to D-Galactose. The specific enzyme substrate reaction between GOx and D-Galactose and photoinduced electron transfer (Piet) were used to detect the RTP of D-galactose. The linear range of D-galactose detection is 0.02-0.8 mM, and the detection limit of the method is 0.008 mM. This method is based on the RTP property of QDs, which can effectively avoid the interference of background fluorescence of biological samples, and does not need complex sample pretreatment process. Therefore, this method is more suitable for the quantitative detection of D-Galactose in biological samples.

Detection of biological mercaptan by DNA functionalized room temperature phosphorescent quantum dot nanocomposites.

In this study, green low-toxicity Mn-doped Zns (Mn-Zns) room-temperature phosphorescent (RTP) quantum dots (QDs) (PQDs) nanocomposites (DNA-PQDs) were prepared under the optimal conditions by using single-stranded DNA (PS-C-ssDNA) rich of cytosine C and Thioguanine G (PS) as the template. DNA-PQDs interact with Ag+ to form AgN bonds and further produce C-Ag+-C conjugates. As a result, DNA-PQDs cluster together and induce the phosphorescent exciton energy transfer (PEET), resulting in quenching of room-temperature phosphorescent of DNA-PQDs. Nevertheless, Ag+ tends to form AgS bonds with biological mercaptan when it is added in, so that Ag+ falls from C-Ag+-C. DNA-PQDs changed from aggregation to looseness and RTP is recovered accordingly. On this basis, RTP detection of biological mercaptan is realized. Since this sensor system has RTP properties based on DNA-PQDs, it is very applicable to detection of mercaptan compounds in biological fluids.

A simple and rapid LC-MS/MS method for the simultaneous determination of eight antipsychotics in human serum, and its application to therapeutic drug monitoring.

A simple and rapid liquid chromatography/tandem mass spectrometry (LC-MS/MS) method was developed and used to determine eight antipsychotics (aripiprazole, clozapine, haloperidol, olanzapine, paliperidone, quetiapine, risperidone, and ziprasidone) in human serum for practical clinical usage. Stable isotope-labeled internal standards were used for all drugs to compensate for method variability, including matrix effects, ion extraction and ionization variations. Samples were prepared by simple protein precipitation with methanol. Chromatographic separation was accomplished in less than 3.3 min on a KINTEX C18 column (50 mm × 3.0 mm, 5 µm) using a gradient elution of 2 mM aqueous ammonium formate and methanol at a flow rate of 0.5 mL/min. Quantification was performed by multiple reaction monitoring (MRM) in the positive mode. The method was fully validated according to the latest recommendations of international guidelines. The correlation coefficients of calibration curves were all greater than 0.9945. Internal standard-normalized matrix effects ranged from 96.3% to 115%, and extraction recoveries were between 88.1% and 107%. Coefficients of variation ranged from 1.82 - 13.5% for intra-day precision, 5.69-14.7% for inter-day precision, and the relative error for accuracy did not exceed ±â€¯13.5% for any analyte. The method was successfully applied to routine clinical therapeutic drug monitoring for 2,173 samples.

Fluorescence detection of fluorine ions in biological fluids based on aggregation-induced emission.

Traditional chemical and biological sensors developed through aggregation-induced emission (AIE) are mainly based on "Turning on" pattern of fluorescence enhancement, which often has poor selectivity and can be easily interfered with by other substances. On this basis, an AIE-based tetraphenyl ethylene (TPE) derivative (TPE-COOH) was prepared in this study and aggregated by adding Al3+, so as to form the TPE-COOH/Al3+ polymer. TPE-COOH fluorescence was enhanced through AIE principle, thus realizing the "Turning on" state. F- could bind to Al3+ after the addition of F- ions which would result in the decomposition of TPE-COOH/Al3+ aggregate, dissolved state of TPE-COOH and gradual reduction of fluorescence intensity of the system, thus realizing "Turning off" state. Moreover, F- ions in biological fluid were analyzed and detected through such AIE-based "Turning on-off" pattern. The linear range of this method for F- detection was 3-12 µM and the detection limit was 0.9 µM.

Preparation of graphene oxide quantum dots from waste toner, and their application to a fluorometric DNA hybridization assay.

A one-pot hydrothermal method was developed for the synthesis of graphene oxide quantum dots (GOQDs). It is making use of toner waste as the precursor and H2O2 as the oxidant. Synthesis takes 4 h and does not require strong acids or complex purification steps and does not produce environmentally harmful metal ions. The GOQDs display blue fluorescence with excitation/emission maxima at 340/445 nm. The feasibility of detecting specific DNA sequence was promoted using polyethyleneimine to modify the GOQDs surface. A method was developed to recognized a specific DNA sequence. This is based on electrostatic aggregation of GOQDs and ssDNA labeled with Dabcyl at the 3' end, which promotes fluorescence quenching of GOQDs. The possible fluorescence quenching mechanism (which is mainly dynamic) was investigated using the Stern-Volmer equation. When a target sequence was added, which is complementary to the ssDNA, the dabcyl-labeled ssDNA is released due to strict complementary base pairing. This promotes fluorescence recovery of GOQDs. The assay has a 0.17 nM detection limit and a linear range of 0.5-30 nM. The method was used to quantify specific DNA sequences from extracts of genetically modified plant tissues. Graphical abstract Graphene oxide quantum dots (GOQDs) were synthesized by one-pot hydrothermal method using waste toner, and the surface was modified by polyethyleneimine (PEI). Through the interaction of PEI-GOQDs with Dabcyl-DNA single strands to dynamically quench the fluorescence of GOQDs. Based on DNA hybridization technology, we established specific DNA sequence detection nanoprobe.

Phosphorimetric determination of 4-nitrophenol using mesoporous molecular imprinting polymers containing manganese(II)-doped ZnS quantum dots.

Mesoporous molecularly imprinted polymers (MIPs) containing mangnanese-doped ZnS quantum dots (Mn-ZnS QDs) were prepared for specific recognition and detection of 4-nitrophenol (4-NP). The Mn-ZnS QDs display orange room-temperature phosphorescence with excitation/emission peaks at 295/590 nm and a decay time of 2.0 ms. In the presence of 4-NP, the orange phosphorescence is strongly reduced. Phosphorescence drops linearly in the 0.1-100 µM 4-NP concentration range, and the detection limit is 60 nM. The detection limit is far lower than the maximally allowed 4-NP concentrations in surface water and drinking water as specified by the U.S. Environmental Protection Agency. The intraday (n = 5) and interday (n = 6) spiked recovery rates were 96.0-104.5% and 97.9-107.9%, respectively, with relative standard deviations of 0.7-4.8% and 1.8-7.5% respectively. These MIPs integrated the characteristic features of phosphorimetry and molecular imprinting. Potential interference by competitive substances, background fluorescence or scattered light are widely reduced. Graphical abstract Schematic presentation of the synthesis of phosphorescent molecularly-imprinted polymers. A novel probe with manganese-doped ZnS quantum dots (Mn-ZnS QDs) and 3-aminopropyl-triethoxysilane (APTES) as functional monomers and tetraethoxysilane (TEOS) as crosslinking agent was prepared for selective phosphorescence detection of 4-nitrophenol (4-NP).

Preparation of Single-Stranded DNA-Templated Room-Temperature Phosphorescent Quantum Dots and Their Application for Mercury(II) Detection in Environmental and Biological Fluids.

The direction synthesis of biofunctional nanomaterials with DNA as the template is of high application value. By using phosphorothioate-thymine single-stranded DNA (PS-T-ssDNA) as the template and through synthetic conditions optimization, novel low-toxicity and environment-friendly ssDNA-functionalized room-temperature phosphorescent quantum dots (PS-T-ssDNA RTP QDs) were prepared at low temperature (37 °C). Then, the quantitative RTP-based mercury(II) (Hg2+) detection was achieved by utilizing the specific identifying ability of T-base-pair Hg2+ (T-Hg2+-T) and its photoinduced electron transfer. This RTP sensor in Hg2+ detection had a linear range of 0.02 to 0.8 µM and a detection limit of 4.8 nM. The dependence on RTP of QDs effectively avoids interference from background fluorescence and scattering light in the environment or biological samples. This sensor also possessed an RTP stability and a long service life and did not require sample pretreatment. Thus this sensor is suitable for environmental and quantitative Hg2+ detection in biological samples.

Preparation of DNA functional phosphorescent quantum dots and application in melamine detection in milk.

Bio-functionalization of quantum dots (QDs) is of important value in practical applications. With single-stranded DNA (ssDNA) rich in thymine T and thioguanine G taken as the template, a new-type nanocomposite material (ssDNA-PQDs) synthesized from low-toxicity T-ssDNA functionalized Mn-ZnS and room-temperature phosphorescent (RTP) QDs (PQDs) was prepared in this paper by optimizing synthesis conditions, and these ssDNA-PQDs could emit orange RTP signals at 590 nm. As these ssDNA-PQDs are rich in T sequences and T sequences can bond with melamine through the hydrogen-bond interaction, ssDNA-PQDs experience aggregation, thus causing phosphorescent exciton energy transfer (PEET) between ssDNA-PQDs of different particle sizes and their RTP quenching. Based on this principle, an RTP detection method for melamine was established. The linear range and detection limit of the detection method are 0.005-6 mM and 0.0016 mM respectively. As this method is based on the RTP nature of ssDNA-PQDs, it can avoid disturbance from background fluorescence and scattered light of the biological fluid, and it is very suitable for melamine detection in the biological fluid milk.

-Phosphorescent Mesoporous Surface Imprinting Microspheres: Preparation and Application for Transferrin Recognition from Biological Fluids.

The relationship between the thickness of surface molecularly imprinted polymers (MIPs) and specific recognition performance of transferrin (Trf) as well as the quantitative relation between the grafting amount of Mn-ZnS room-temperature phosphorescence (RTP) quantum dots (QDs) (short for PQDs) and RTP signals for recognition of Trf was analyzed in this study. Based on analysis results, RTP protein mesoporous imprinting microspheres (SiO2-PQDs-MIPs) with high specificity and strong interference resistance were developed using a mesoporous SiO2 nanomaterial that can create more three-dimensional precise recognition sites as the matrix and using PQDs with strong resistance to background fluorescence interference as the luminescent materials. A discriminatory analysis of Trf was realized by the phosphorescence quenching principle based on light quenching caused by the photoinduced electron transfer. The concentration range, limit of detection, relative standard deviation, and imprinting factor of Trf detection under pH 7.4 are 0.05-1.0 µM, 0.014 µM, 3.23%, and 3.09, respectively. Although the sensing signals of SiO2-PQDs-MIPs for proteins are based on the phosphorescence of PQDs, they are particularly suitable for specific recognition and accurate quantitative detection of proteins in biological fluids. Research conclusions are expected to realize high-efficiency recognition of target proteins in actual biological samples.

Hybrid detection of target sequence DNA based on phosphorescence resonance energy transfer.

The severe background fluorescence and scattering light of real biological samples or environmental samples largely reduce the sensitivity and accuracy of fluorescence resonance energy transfer sensors based on fluorescent quantum dots (QDs). To solve this problem, we designed a novel target sequence DNA biosensor based on phosphorescent resonance energy transfer (PRET). This sensor relied on Mn-doped ZnS (Mn-ZnS) room-temperature phosphorescence (RTP) QDs/poly-(diallyldimethylammonium chloride) (PDADMAC) nanocomposite (QDs+) as the energy donor and the single-strand DNA-ROX as the energy receptor. Thereby, an RTP biosensor was built and used to quantitatively detect target sequence DNA. This biosensor had a detection limit of 0.16nM and a linear range of 0.5-20nM for target sequence DNA. The dependence on RTP of QDs effectively avoided the interference from background fluorescence and scattering light in biological samples. Moreover, this sensor did not need sample pretreatment. Thus, this sensor compared with FRET is more feasible for quantitative detection of target sequence DNA in biological samples. Interestingly, the QDs+ nanocomposite prolonged the phosphorescence lifetime of Mn-ZnS QDs by 2.6 times to 4.94ms, which was 5-6 magnitude-order larger than that of fluorescent QDs. Thus, this sensor largely improves the optical properties of QDs and permits chemical reactions at a long enough time scale.

A DNA probe based on phosphorescent resonance energy transfer for detection of transgenic 35S promoter DNA.

A QDs-DNA nano-probe was made by combining Mn-doped ZnS room-temperature phosphorescence (RTP) quantum dots (QDs) and DNA. Then an RTP sensor for quantitative detection of genetically-modified mark sequence cauliflower mosaic virus 35S promoter (Ca MV 35S) DNA was built on basis of phosphorescent resonance energy transfer (PRET). The underlying principles were that a QDs-DNA water-soluble nano-probe was built by connecting single-strand DNA to the surfaces of QDs via a ligand exchange method. This probe had good RTP performance and could well identify Ca MV 35S. Thereby, the simple, rapid and efficient detection of genetically-modified organisms was realized. With the increase of target DNA sequence, the phosphorescent intensity of QDs was gradually reduced due to the energy transfer between QDs and the organic quencher BHQ2. This sensor had a detection limit of 4.03nM and a detection range of 12-300nM. Moreover, this sensor had high selectivity. This sensor could effectively detect the target DNA compared with mismatched and random sequences. Thus, this method is very promising for biological analysis.

A comparative analysis of ESM-1 and vascular endothelial cell marker (CD34/CD105) expression on pituitary adenoma invasion.

OBJECTIVE: Pituitary adenomas are benign neoplasms that display invasive behavior-a characteristic traditionally associated with malignancy-through an ill-defined mechanism. The role of angiogenesis-related molecules in this pathological condition remains perplexing. Our purpose is to assess the impact of endocan (endothelial cell specific molecule-1, ESM-1), CD34 and CD105 on pituitary adenoma invasion. METHODS: In this study, immunohistochemical analyses for endocan, CD34 and CD105 were performed on paraffin-embedded samples of 66 pituitary adenomas, five normal pituitaries, and five primary hepatic carcinomas. Knosp tumor grades based on magnetic resonance imaging coronal scanning were used to assess the invasiveness of each sample. The associations between endocan expression, CD34/CD105-positive microvessel densities (MVDs), and Knosp tumor invasion grades were evaluated. RESULTS: These results showed that endocan protein expression in tumor cells (TCs) was higher than that in endothelial cells (ECs) and strongly correlated with Knosp grades (P < 0.001, Spearman's r = 0.616). Moreover, while endocan-positive TCs localized around the blood vessels in adenomas with higher Knosp grades, no significant association was found between CD34/CD105-MVDs and Knosp grades (CD34: P = 0.256, r = 0.142; CD105: P = 0.183, r = 0.166). Normal pituitary seemed to exhibit lower endocan expression and contained more CD34/CD105-MVDs than pituitary adenomas. CONCLUSION: Endocan expresses in both TCs and ECs of pituitary adenoma. Endocan overexpression in TCs more accurately reflects invasiveness compared to that of CD34/CD105-MVDs and that angiogenesis may not be the primary driver of endocan-medicated pituitary adenoma invasion.

Detection of quercetin based on Al(3+)-amplified phosphorescence signals of manganese-doped ZnS quantum dots.

A simple phosphorescence method is proposed for quercetin detection based on Al(3+)-amplified room-temperature phosphorescence (RTP) signals of 3-mercaptopropionic acid (MPA)-capped Mn-doped ZnS quantum dots (QDs). The sensor was established based on some properties as follows. Al(3+) can interact with carboxyl groups on the surface of MPA-capped Mn-doped ZnS QDs via chelation, which will lead to the aggregation of QDs and amplification of RTP signals, After the addition of quercetin, it can form more stable complex with Al(3+) in alkaline aqueous solution and dissociate Al(3+) from the surface of Mn-doped ZnS QDs, which will result in significant recovery of RTP intensity of the MPA-capped Mn-doped ZnS-Al(3+) system. Under the optimized conditions, the change of RTP intensity was proportional to the concentration of quercetin in the range from 0.1 to 6.0 mg L(-1), with a high correlation coefficient of 0.996 and a detection limit of 0.047 mg L(-1). The proposed method is potentially suitable for detection of quercetin in real samples without complicated pretreatment.

Facile and sensitive detection of protamine by enhanced room-temperature phosphorescence of Mn-doped ZnS quantum dots.

Quantum dot (QD) nanohybrids provide an effective route to explore the new properties of materials and are increasingly used as highly valuable sensitive (bio) chemical probes. Interestingly, the room-temperature phosphorescence (RTP) of 3-mercaptopropionic acid (MPA)-capped Mn-doped ZnS QDs could be remarkably enhanced by the addition of protamine. Based on the above finding, a simple, sensitive, and selective method for rapid detection of protamine was successfully designed. With this method, protamine as a cationic peptide interacts electrostatically with MPA-capped Mn-doped ZnS QDs to form MPA-capped Mn-doped ZnS QD/protamine complexes, which leads to the aggregation of QDs and enhances the RTP intensity. Under the optimized conditions, the RTP intensity change was linearly proportional to the concentration of protamine in the range 0.2-3.0 µg ml(-1), and the limit of detection was 0.14 µg ml(-1). The proposed method was successfully applied to detect protamine in protamine sulfate injection and human serum samples with satisfactory results, and the recovery ranged from 96.5 to 105.6%.