Quantitative analysis of a posterior fossa teratomas with unusual CT and MR Characteristics--illustrative case.

Background: Intracranial teratomas or other cystic lesions with atypical imaging manifestations can still be frequently seen clinically. The specific reasons for unusual imaging manifestations need to be further explored. Observations: A case of adult teratoma in the posterior fossa with unusual imaging manifestations was reported. The chemical composition of its cystic fluid was quantitatively detected, and in vitro imaging simulation experiments were performed on some fluid substances with similar cystic fluid properties to explore the reasons for special imaging manifestations. The content of inorganic substances and protein in the cystic fluid were both low, with no melanin detected. In vitro experiments revealed that MR T1 signals could increase with protein content rising and changes in MR T2 signals presented no obvious correlation with it. CT values increased gradually with protein concentration rising. The substances with similar viscosity had similar CT values, whereas substance viscosity showed no significant correlation with changes in MR signals. Conclusion: The abnormality of imaging manifestations cannot be confirmed as the result of "high protein content", nor can it be simply attributed to bleeding. Further research is required for the impact of the combination of paramagnetic particles and biofluid on imaging.

Electrochemical biosensor for detection of MON89788 gene fragments with spiny trisoctahedron gold nanocrystal and target DNA recycling amplification.

The shape-controlled synthesis of gold nanocrystals via shape induction of hexadecyltrimethylammonium chloride, potassium bromide, and potassium iodide and enantioselective direction of L-cysteine is reported. The resulting gold nanocrystals (STO-Au) offer spiny trisoctahedron nanostructures with good monodispersity and enhanced exposed high-index facets and high catalytic activity. Construction of the electrochemical sensing platform for MON89788 gene involves the modification of STO-Au, thionine (Thi), and labeled bipedal DNA probe 1 or 2 (P1 or P2) for target DNA-induced recycling amplification. In the detection, two surface DNA probes were immobilized on gold electrode via the Au-S bond. Then, hairpin DNA 1 (H1), Thi-STO-Au-P1, and Thi-STO-Au-P2 self-assemble into two-dimensional DNA nanopores (DNPs) on the electrode surface. Target DNA hybridizes with hairpin DNA 2 (H2) to open hairpin structure of H2. The opened H2 binds with H1 in the DNPs to release Thi-STO-Au-P1, Thi-STO-Au-P2, and target DNA by toehold-mediated strand-displacement. The utilization of target DNA-induced recycling allows one target DNA to release 2N STO-Au-labeled DNA strands, promoting significant signal amplification. The detection signal is further enhanced by the catalyzed redox reaction of Thi with STO-Au. The differential pulse voltammetric signal, best measured at - 0.18 V vs. Ag/AgCl, decreases linearly with increasing concentration of MON89788 in the range 0.02-8 × 104 fM, and the detection limit is 0.0048 fM (S/N = 3). The proposed method was successfully applied for electrochemical detection of MON89788 gene fragments in the PCR products from genetically modified soybean. Graphical Abstract We develop l-cysteine controlled synthesis of spiny trisoctahedron gold nanocrystals with good monodispersity and highly exposed high-index facets. The architecture achieves to ultrahigh catalytic activity. The electrochemical biosensor based on gold nanocrystals and target DNA recycling amplification provides advantage of sensitivity, repeatability, and regeneration-free.

Ultrasensitive Fluorometric Angling Determination of Staphylococcus aureus in Vitro and Fluorescence Imaging in Vivo Using Carbon Dots with Full-Color Emission.

Rapid, accurate, and safe screening of foodborne pathogenic bacteria is essential to effectively control and prevent outbreaks of foodborne illness. Fluorescent sensors constructed from carbon dots (CDs) and nanomaterial-based quenchers have provided an innovative method for screening of pathogenic bacteria. Herein, an ultrasensitive magnetic fluorescence aptasensor was designed for separation and detection of Staphylococcus aureus (S. aureus). Multicolor fluorescent CDs with a long fluorescent lifetime (6.73 ns) and high fluorescence stability were synthesized using a facile hydrothermal approach and modified cDNA as a highly sensitive fluorescent probe. CD fluorescence was quenched by Fe3O4 + aptamer via fluorescence resonance energy transfer (FRET). Under optimal conditions, the FRET-based aptasensor can detect S. aureus accompanied by a wide linear range of 50-107 CFU·mL-1 and a detection limit of 8 CFU·mL-1. Compared with other standard methods, this method was faster and more convenient, and the entire test was finished within 30 min. The capability of the aptasensor was simultaneously investigated on food samples. Additionally, the developed CDs exhibited excellent biocompatibility and were thus applied as fluorescent probes for bioimaging both in vitro and in vivo. This new platform provided an excellent application of the CDs for detecting and bioimaging pathogenic bacteria.

Switched photoelectrochemistry of carbon dots for split-type immunoassay.

A novel and general strategy of split-type immunoassay is developed based on redox chemical reaction modulated photoelectrochemistry of carbon dots (CDs). Specifically, the photocurrent of the CDs sensitized titanium dioxide nanoparticles (TiO2 NPs) modified fluorine doped indium tin oxide (FTO) (that is the FTO/TiO2/CDs) electrode was inhibited obviously by KMnO4 due to the oxidation of surface hydroxyl groups of CDs to electron accepting carbonyls. While the inhibited photocurrent of the KMnO4 treated FTO/TiO2/CDs electrode can be restored by ascorbic acid (AA) because of the regeneration of electron donating hydroxyls to promote electron-hole separation. Take carcinoembryonic antigen (CEA) as a model analyte and alkaline phosphate (ALP) as a catalytic label tracer to hydrolyze ascorbic acid 2-phosphate (AAP) for producing AA, which greatly stimulated the photocurrent of the transducer of KMnO4 treated FTO/TiO2/CDs photoelectrode for signal output. This redox chemical reaction modulated PEC strategy enabled the separation of the immunoreaction from the photoelectrode (that is, a split-type PEC detection), eliminating potential damage of biomolecules during the PEC detection processes and leading to enhanced throughput detection as compared to conventional PEC configurations. A low detection limit of 7.0 fg/mL was achieved for CEA. This convenient, split-type PEC immunoassay with high throughput may be easily extended to other bioaffinity assays for versatile targets.

Ultrasensitive "FRET-SEF" Probe for Sensing and Imaging MicroRNAs in Living Cells Based on Gold Nanoconjugates.

MicroRNAs (miRNAs), a kind of single-stranded small RNA molecule, play significant roles in the physiological and pathological processes of human beings. Currently, miRNAs have been demonstrated as important biomarkers critically related to many diseases and life nature, including several cancers and cell senescence. It is valuable to establish sensitive assays for monitoring the levels of intracellular up-regulated/down-regulated miRNA expression, which would contribute to the early prediction of the tumor risk and cardiovascular disease. Here, an oriented gold nanocross (AuNC)-decorated gold nanorod (AuNR) probe with "OFF-enhanced ON" fluorescence switching was developed based on fluorescence resonance energy transfer and surface enhanced fluorescence (FRET-SEF) principle. The nanoprobe was used to specifically detect miRNA in vitro, which gave two linear responses represented by the equation F = 1830.32 log C + 6349.27, R2 = 0.9901, and F = 244.41 log C + 1916.10, R2 = 0.9984, respectively, along with a detection limit of 0.5 aM and 0.03 fM, respectively. Furthermore, our nanoprobe was used to dynamically monitor the expression of intracellular up-regulated miRNA-34a from the HepG2 and H9C2 cells stimulated by AFB1 and TGF-ß1, and the experimental results showed that the new probe not only could be used to quantitively evaluate miRNA oncogene in vitro, but also enabled tracking and imaging of miRNAs in living cells.

Polymorphism of a chiral iron(ii) complex: spin-crossover and ferroelectric properties.

Two solvent-free polymorphs of a chiral iron(ii) complex have been obtained, and their polymorphism dependent spin-crossover and ferroelectric properties have been demonstrated. Polymorph I shows a gradual spin-crossover behavior, whereas polymorph II remains in a high-spin state but shows a typical ferroelectric feature.

Iron(ii)-triazole core-shell nanocomposites: toward multistep spin crossover materials.

The first SCO@SCO core-shell nanomaterials have been synthesized by the step-by-step microemulsion method. The observed gyroscopic core-shell nanocomposites exhibit three-step spin crossover behaviour with thermal hysteresis at around room temperature. This offers an efficient and novel strategy for the development of multistable SCO materials.

Chiral tetrahedral iron(II) cages: diastereoselective subcomponent self-assembly, structure interconversion and spin-crossover properties.

A new class of chiral tetrahedral iron(II) cages were prepared from subcomponent self-assembly with high diastereoselectivity. The cages can be interconverted through imine exchange. The chiral cages displayed a spin transition close to room temperature, and the transition temperatures were affected by the substituent and uncoordinated solvents.

A new approach to light up the application of semiconductor nanomaterials for photoelectrochemical biosensors: using self-operating photocathode as a highly selective enzyme sensor.

Due to the intrinsic hole oxidation reaction occurred on the photoanode surface, currently developed photoelectrochemical biosensors suffer from the interference from coexisting reductive species (acting as electron donor) and a novel design strategy of photoelectrode for photoelectrochemical detection is urgently required. In this paper, a self-operating photocathode based on CdS quantum dots sensitized three-dimensional (3D) nanoporous NiO was designed and created, which showed highly selective and reversible response to dissolved oxygen (acting as electron acceptor) in the electrolyte solution. Using glucose oxidase (GOD) as a biocatalyst, a novel photoelectrochemical sensor for glucose was developed. The commonly encountered interferents such as H2O2, ascorbic acid (AA), cysteine (Cys), dopamine (DA), etc., almost had no effect for the cathodic photocurrent of the 3D NiO/CdS electrode, though these substances were proved to greatly influence the photocurrent of photoanodes, which indicated greatly improved selectivity of the method. The method was applied to detect glucose in real samples including serum and glucose injections with satisfactory results. This study could provide a new train of thought on designing of self-operating photocathode in photoelectrochemical sensing, promoting the application of semiconductor nanomaterials in photoelectrochemistry.

In situ formation of p-n junction: a novel principle for photoelectrochemical sensor and its application for mercury(II) ion detection.

The discovery and development of photoelectrochemical sensors with novel principles are of great significance to realize sensitive and low-cost detection. In this paper, a new photoelectrochemial sensor based on the in situ formation of p-n junction was designed and used for the accurate determination of mercury(II) ions. Cysteine-capped ZnS quantum dots (QDs) was assembled on the surface of indium tin oxide (ITO) electrode based on the electrostatic interaction between Poly(diallyldimethylammonium chloride) (PDDA) and Cys-capped ZnS QDs. The in situ formation of HgS, a p-type semiconductor, on the surface of ZnS facilitated the charge carrier transport and promoted electron-hole separation, triggered an obviously enhanced anodic photocurrent of Cys-capped ZnS QDs. The formation of p-n junction was confirmed by P-N conductive type discriminator measurements and current-voltage (I-V) curves. The photoelectrochemical method was used for the sensing of trace mercuric (II) ions with a linear concentration of 0.01 to 10.0 µM and a detection limit of 4.6×10(-9)mol/L. It is expected that the present study can serve as a foundation to the application of p-n heterojunction to photoelectrochemical sensors and it might be easily extended to more exciting sensing systems by photoelectrochemistry.

Dual responsive enzyme mimicking activity of AgX (X=Cl, Br, I) nanoparticles and its application for cancer cell detection.

Chitosan (CS) modified silver halide (AgX, X=Cl, Br, I) (CS-AgX) nanoparticles (NPs) were found to possess dual responsive enzyme mimetic activities. In the presence of H2O2, they were able to oxidize various colorimertic dyes, namely, peroxidase-like activity. Upon photoactivation, CS-AgX NPs could also oxidize the typical substrates in the absence of H2O2. Taking CS-AgI as an example, it was found that the photostimulated enzyme mimetics of CS-AgI NPs showed several unprecedented advantages over natural peroxidase or other existing alternatives based on nanomaterials, such as excellent enzyme-like activity over a broad pH range (3.0-7.0), the independence of hydrogen peroxide on activity, the easily regulated activity by light irradiation, and the good reutilization without significant loss of catalytic activity. The mechanism of the dual responsive enzyme-like activity of CS-AgI was investigated. On the basis of these findings, the photoactivated CS-AgI was designed to develop a facile, cheap, rapid, and highly sensitive colorimetric assay to detect cancer cells. The detection limit of the method for MDA-MB-231 was estimated to be as low as 100 cells, which was much lower than that reported by the method using peroxidase mimetics based on nanomaterials. We believe that CS-AgX NPs with dual responsive enzyme-mimicking activity, especially the excellent photostimulated enzyme-like activity, may find widely potential applications in biosensors.

Dinuclear nickel(II) triple-stranded supramolecular cylinders: syntheses, characterization and G-quadruplexes binding properties.

Three dinuclear nickel triple-stranded supramolecular cylinders [Ni2(L1)3][ClO4]4 (1), [Ni2(L2)3][ClO4]4 (2) and [Ni2(L3)3][ClO4]4 (3) with bis(pyridylimine) Schiff base containing triphenyl groups in the spacers as ligands were synthesized and characterized. The human telomeric G-quadruplexes binding properties of cylinders 1-3 were evaluated by means of UV-Vis spectroscopy, circular dichroism (CD) spectroscopy and fluorescence resonance energy transfer (FRET) melting assay. UV-Vis studies revealed that the supramolecular cylinders 1-3 could bind to G-quadruplex DNA with high binding constants (Kb values ranging from 0.11-2.2×10(6) M(-1)). FRET melting studies indicated that the cylinders 1-3 had much stronger stabilizing effect on G-quadruplex DNA (ΔTm up to 24.5°C) than the traditional cylinder Ni2L3(4+) just containing diphenylmethane spacers (ΔTm=10.6 °C). Meanwhile, cylinders 1-3 were found to have a modest degree of selectivity for the quadruplex DNA versus duplex DNA in competition FRET assays. Moreover, CD spectroscopy revealed that complex 1 could induce G-quadruplex formation in the absence of metal ions solution and convert antiparallel G-quadruplex into hybrid structure in Na(+) solution. These results provided a new insight into the development of supramolecular cylinders as potential anticancer drugs targeting G-quadruplex DNA.

Novel switchable sensor for phosphate based on the distance-dependant fluorescence coupling of cysteine-capped cadmium sulfide quantum dots and silver nanoparticles.

A novel switchable sensor was developed for the determination of phosphate based on Ce(3+) induced aggregation and phosphate triggered disaggregation of cysteine (Cys)-capped CdS quantum dots (QDs) and silver nanoparticles (AgNPs). The rare earth metal Ce(3+) could aggregate a mixture of QDs and AgNPs, which induced electron or energy transfer between CdS QDs and AgNPs and serious fluorescence quenching. However, phosphate dissociated the formed aggregation of CdS QDs and AgNPs, restoring the enhanced fluorescence of Cys-capped CdS triggered by AgNPs. Although, CdS QDs alone could also be used to detect phosphate through the aggregation-disaggregation mechanism adjusted by Ce(3+) and phosphate. It was found that the distance-dependent interaction between AgNPs and CdS QDs driven by Ce(3+) and phosphate could lead to enhanced quenching or enhancement of the fluorescence of Cys-capped CdS to form a more sensitive detection system for phosphate. The developed method was applied in the detection of phosphate in real water samples with acceptable and satisfactory results.

Development of a novel electrochemical sensor using pheochromocytoma cells and its assessment of acrylamide cytotoxicity.

We report on a sensitive, simple, label-free cell-based electrochemical sensor to monitor the toxic effect of acrylamide on the Pheochromocytoma cells. The surface of the electrode was modified with gold nanoparticles and electrochemically reduced graphene oxide. Cyclic voltammetry, impedance spectroscopy and differential pulse voltammetry were applied to characterize the modified electrode. Reduced graphene oxide was proved to increase electron-transfer rate between the cell and the surface of electrode, while gold nanoparticle retain cell bioactivity. The sensor exhibited good correlation to the logarithmic value of cell numbers ranging from 1.6×10(4) to 1.6×10(7) cells mL(-1), with R.S.D value of 1.68%. The value of differential pulse voltammetry (cell adsorption concentration of 1.6×10(7) cells mL(-1)) decreased with the concentration of acrylamide in range of 0.1-5 mM with the detection limit as 0.04 mM. Scanning electron microscope-based morphological and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide analysis confirmed the results of the electrochemical study. This sensor was proved to be a useful tool for probing the toxicity of cells, and assisted in the development of a labeling-free, simple, rapid and immediate detection method.

Metal ion (silver, cadmium and zinc ions) modified CdS quantum dots for ultrasensitive copper ion sensing.

Metal ion (Ag(+), Cd(2+), Zn(2+)) modified CdS quantum dots (QDs) were synthesized and used for Cu(2+) sensing. Modification by these metal ions could enhance the PL intensity of CdS QDs with the extent of the PL enhancement being related to the concentration of the metal ions. Different metal ion (Ag(+), Cd(2+), Zn(2+)) modified CdS QDs also showed different analytical characteristics for Cu(2+) sensing. In particular, Ag( + ) modified CdS QDs showed greatly enhanced sensitivity for Cu(2+) determination than did the unmodified CdS QDs. A limit of detection (LOD) of 2.0 × 10(-10) M was obtained for Ag(+) modified CdS QDs, which is the lowest LOD obtained using QDs as fluorescence probes for Cu(2+) sensing. This study demonstrates the important role of surface state of QDs in fluorescence sensing.

Ultrasensitive cysteine sensing using citrate-capped CdS quantum dots.

The importance of cysteine (Cys) in biological systems has stimulated a great deal of efforts in the development of analytical methods for the determination of this amino acid. In this work, a novel fluorescent probe for Cys based on citrate (Cit)-capped CdS quantum dots (QDs) is reported. The Cit-capped CdS QDs fluorescent probe offers good sensitivity and selectivity for detecting Cys. A good linear relationship was obtained from 1.0 × 10(-8)mol L(-1) to 5.0 × 10(-5)mol L(-1) for Cys. The detection limit was calculated as 5.4 × 10(-9)mol L(-1). The proposed method was applied to detect Cys in human urine samples, which showed satisfactory results. This assay is based on both the lability of Cit and the strong affinity of thiols to the surface of CdS QDs. The addition of Cys improved the passivation of the surface traps of CdS QDs and enhanced the fluorescence intensity.

Extraction spectrophotometric determination of aluminum in dialysis concentrates with 3,5-ditertbutylsalicylfluorone and ionic liquid 1-butyl-3-trimethylsilylimidazolium hexafluorophosphate.

The paper describes a highly sensitive and selective extraction spectrophotometric method for determination of aluminum in dialysis concentrates with new reagent 3,5-ditertbutylsalicylfluorone abbreviated as DTBSF, in which the ionic liquid 1-butyl-3-trimethylsilylimidazolium hexafluorophosphate abbreviated as [C4tmsim][PF6] was used as novel medium for liquid/liquid extraction of aluminum(III). Under optimal condition, DTBSF reacted with aluminum(III) to form a neutral Al-DTBSF complex rapidly, the complex was then extracted into the [C4tmsim][PF6] phase, the absorbance of the complex in ionic liquid at 542 nm was recorded and used to determine aluminum(III). The apparent molar absorptivity of the complex and detection limit were found to be 3.52x10(6) l mol(-1) cm(-1) and 0.06 microg/l, respectively. The absorbance of the complex at 542 nm increases linearly with the concentration of aluminum(III) up to 3 microg of aluminum(III) in 250 ml of aqueous solution. The interference study show the determination of aluminum is free from interferences of almost all positive and negative ions found in dialysis concentrate samples. The determination of aluminum in dialysis concentrates were carried out by the present method and electrothermal atomic absorption spectrometry (GTAAS). The results were satisfactorily comparable so that the applicability of the proposed method with the ionic liquid system was also investigated. Moreover, the synthesis of and conditions for the formation and extraction of Al-DTBSF complex were investigated as well.