Depth profiling of latex blends of fluorinated and fluorine‐free acrylates with laser‐induced secondary mass spectrometry

We explored phase separation and self‐assembly of perfluoroalkyl segments at the surface of polymer films obtained from latices of semifluorinated acrylate copolymers and the corresponding latex blends of nonfluorinated and semifluorinated polyacrylates. With laser‐induced secondary mass spectrometry the fluorine distribution was measured after annealing above the minimum film‐forming temperature of the polymers up to a depth of several micrometers. Depth profiles of a semifluorinated acrylate homopolymer and latex blends thereof with fluorine‐free alkylacrylates with 25, 50, and 75 mol % semifluorinated acrylate as well as a copolymer comprised of alkyl acrylate and semifluorinated acrylate (50/50 mol %) were investigated. In the case of latex blends containing both semifluorinated polyacrylates and fluorine‐free or low‐fluorine polymers, self‐assembly accounted for enrichment of the perfluoroalkyl segments at the surface. Coatings exhibiting low surface energy and having a substantially reduced total fluorine content were obtained. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 360–367, 2003     

Evaluation of Anisole‐Substituted Boron Difluoride Formazanate Complexes for Fluorescence Cell Imaging

Evaluation of three subclasses of boron difluoride formazanate complexes bearing o‐, m‐, and p‐anisole N‐aryl substituents (Ar) as readily accessible alternatives to boron dipyrromethene (BODIPY) dyes for cell imaging applications is described. While the wavelengths of maximum absorption (λ_max) and emission (λ_em) observed for each subclass of complexes, which differed by their carbon‐bound substituents (R), were similar, the emission quantum yields for 7 a – c (R=cyano) were enhanced relative to 8 a – c (R=nitro) and 9 a – c (R=phenyl). Complexes 7 a – c and 8 a – c were also significantly easier to reduce electrochemically to their radical anion and dianion forms compared to 9 a – c . Within each subclass, the o‐substituted derivatives were more difficult to reduce, had shorter λ_max and λ_em, and lower emission quantum yields than the p‐substituted analogues as a result of sterically driven twisting of the N‐aryl substituents and a decrease in the degree of π‐conjugation. The m‐substituted complexes were the least difficult to reduce and possessed intermediate λ_max, λ_em, and quantum yields. The complexes studied also exhibited large Stokes shifts (82–152 nm, 2143–5483 cm^?1). Finally, the utility of complex 7 c (Ar=p‐anisole, R=cyano), which can be prepared for just a few dollars per gram, for fluorescence cell imaging was demonstrated. The use of 7 c and 4′,6‐diamino‐2‐phenylindole (DAPI) allowed for simultaneous imaging of the cytoplasm and nucleus of mouse fibroblast cells.     

Water‐Soluble Triarylborane Chromophores for One‐ and Two‐Photon Excited Fluorescence Imaging of Mitochondria in Cells

Three water‐soluble tetracationic quadrupolar chromophores comprising two three‐coordinate boron π‐acceptor groups bridged by thiophene‐containing moieties were synthesised for biological imaging applications. Compound 3 containing the bulkier 5‐(3,5‐Me₂C₆H₂)‐2,2′‐(C₄H₂S)₂‐5′‐(3,5‐Me₂C₆H₂) bridge is stable over a long period of time, exhibits a high fluorescence quantum yield and strong one‐ and two‐photon absorption (TPA), and has a TPA cross section of 268 GM at 800 nm in water. Confocal laser scanning fluorescence microscopy studies in live cells indicated localisation of the chromophore at the mitochondria; moreover, cytotoxicity measurements proved biocompatibility. Thus, chromophore 3 has excellent potential for one‐ and two‐photon‐excited fluorescence imaging of mitochondrial function in cells.     

Three‐Dimensional Mid‐Infrared Tomographic Imaging of Endogenous and Exogenous Molecules in a Single Intact Cell with Subcellular Resolution

Microscopy in the mid‐infrared spectral range provides detailed chemical information on a sample at moderate spatial resolution and is being used increasingly in the characterization of biological entities as challenging as single cells. However, a conventional cellular 2D imaging measurement is limited in its ability to associate specific compositional information to subcellular structures because of the interference from the complex topography of the sample. Herein we provide a method and protocols that overcome this challenge in which tilt‐series infrared tomography is used with a standard benchtop infrared microscope. This approach gives access to the quantitative 3D distribution of molecular components based on the intrinsic contrast provided by the sample. We demonstrate the method by quantifying the distribution of an exogenous metal carbonyl complex throughout the cell and by reporting changes in its coordination sphere in different locations in the cell.     

Preparation and characterization of nanometer‐thin freestanding polymer foils for laser‐ion acceleration

We report on the production and characterization of polymer‐based ultra‐thin (sub 10 nm) foils suited for experiments on laser‐ion acceleration in the regime of radiation pressure acceleration. Beside the remarkable mechanical stability compared with commonly used diamond‐like‐carbon foils, a very homogeneous layer thickness and a small surface roughness have been achieved. We describe the technical issues of the production process as well as detailed studies of the mechanical stability and surface roughness tests. The capability of producing uniform targets of large area is essential for advanced laser‐ion acceleration projects which are dealing with high repetition rate and extended measurement series, but might also be useful for other applications which require ultra‐thin and freestanding substrates of high quality. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1355–1360     

Manifold preprocessing for laser‐induced breakdown spectroscopy under Mars conditions

Laser‐induced breakdown spectroscopy (LIBS) is currently being used onboard the Mars Science Laboratory rover Curiosity to predict elemental abundances in dust, rocks, and soils using a partial least squares regression model developed by the ChemCam team. Accuracy of that model is constrained by the number of samples needed in the calibration, which grows exponentially with the dimensionality of the data, a phenomenon known as the curse of dimensionality. LIBS data are very high dimensional, and the number of ground‐truth samples (i.e., standards) recorded with the ChemCam before departing for Mars was small compared with the dimensionality, so strategies to optimize prediction accuracy are needed. In this study, we first use an existing machine learning algorithm, locally linear embedding (LLE), to combat the curse of dimensionality by embedding the data into a low‐dimensional manifold subspace before regressing. LLE constructs its embedding by maintaining local neighborhood distances and discarding large global geodesic distances between samples, in an attempt to preserve the underlying geometric structure of the data. We also introduce a novel supervised version, LLE for regression (LLER), which takes into account the known chemical composition of the training data when embedding. LLER is shown to outperform traditional LLE when predicting most major elements. We show the effectiveness of both algorithms using three different LIBS datasets recorded under Mars‐like conditions. Copyright © 2015 John Wiley & Sons, Ltd.     

Chemical maps of patterned samples by microline‐imaging laser‐induced plasma spectrometry

The potential of a microline‐imaging laser‐induced plasma spectrometry (LIPS) system for surface and depth analysis of heterogeneous solid samples in air at atmospheric pressure has been demonstrated. A pulsed Nd : YAG laser beam operating at 532 nm, with a homogeneous energy distribution (flat top laser), was used to generate a microline plasma on the sample surface. Subsequent light from the microline plasma was resolved spectrally and spatially and detected with an imaging spectrograph and an intensified charged‐coupled device detector. A patterned metal sample was chosen as the most appropriate for this study. Three‐dimensional chemical maps of Ni and Cu from the edge connectors of a printed circuit board have been obtained. With this experimental configuration, the lateral resolution (limited by crater width) was 42 µm and the spatial resolution along the spectrometer slit was 17.4 µm. The results illustrate the capability of microline imaging for fast mapping of large‐area samples and for depth profiling purposes. Copyright © 2003 John Wiley & Sons, Ltd.     

Analysis of low‐molecular mass aldehydes in drinking waters through capillary electrophoresis with laser‐induced fluorescence detection

The potential of CZE with LIF detection in the separation and determination of low‐molecular mass aldehydes involving precolumn derivatization with fluorescein 5‐thiosemicarbazide was investigated. Different variables that affect derivatization (pH, fluorescein 5‐thiosemicarbazide concentration, time and temperature) and separation (pH and concentration of the BGE, kind and concentration of surfactants at levels higher and lower than CMC, and applied voltage) were studied. The separation was conducted within 16 min by using borate buffer (60 mM; pH 10) with 10 μM polyethylene glycol tert‐octylphenyl ether as modifier. Good linearity relationships (correlation coefficients ranged from 0.9978 to 0.9994 for aldehydes) were obtained between the peak areas and concentration of the analytes (0.5–100 μg/L). The LODs for aldehydes were achieved at submicrogram‐per‐liter level (0.15–0.35 μg/L), which indicated that the proposed method surpassed other electrophoretric alternatives in terms of LOD, in many cases even at ca. 1000‐fold. The inter‐day precision (RSD, %) of the aldehydes ranged from 5.2 to 8.3%. Finally, the method was successfully applied to bottled drinking‐water samples, and the aldehydes were readily detected at 0.6–4.4 μg/L levels with average recoveries ranging from 99.1 to 103.5%.     

Improvements in depth‐profiling of thick samples by laser‐induced breakdown spectroscopy using linear correlation

In this work, the capability of linear correlation for depth profiling by laser‐induced breakdown spectroscopy (LIBS) is studied for the first time. A software was specially developed for the calculus of the linear correlation coefficients and its representation in the format of depth profiles. Thick layered samples (layers with thickness of tens to hundreds of micrometers) of different nature, archaeological ceramics and polymer coatings on steel, were characterized by LIBS using the conventional approach based on intensity profiles, and the correlation method. The results revealed that, without using any normalization, the comparison of LIB spectra through the linear correlation coefficient gave an improvement of the depth profile quality and the interface localization by minimizing the influence of fluctuations and decay of the signals in the global intensity of spectra, caused by sources other than concentration variations. Copyright © 2006 John Wiley & Sons, Ltd.     

Drawing behavior and characteristics of laser‐drawn polypropylene fibers

Drawing behavior, flow drawing, and neck drawing, was studied for isotacticpolypropylene fibers in CO₂ laser drawing system, and the fiber structure and the mechanical properties of drawn fibers were analyzed. For a certain laser power, flow drawing of polypropylene (PP) was possible up to draw ratio (DR) 19.5. Though the drawing stress was very low, the flow‐drawn PP fiber exhibited oriented crystal structure and improved mechanical properties. On the other hand, neck‐drawing was accomplished from DR 4 to 12, with significant increase in drawing stress that enhanced the development of fiber structure and mechanical properties. Unlike PET, the drawing stress depends not only on the DR, but on irradiated laser power also. The 10–12 times neck‐drawn fibers were highly fibrillated. The fibers having tensile strength 910 MPa, initial modulus 11 GPa, and dynamic modulus 14 GPa were obtained by single‐step laser drawing system. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 398–408, 2006     

Synthesis of silicon‐based polymer films by excimer laser‐induced photo‐reaction of phenylsilane and methylphenylsilane

The synthesis of silicon‐based polymer films was studied by excimer laser (248 nm)‐induced photo‐reaction of phenylsilane and methyl‐phenylsilane at reduced pressure. IR and UV–VIS results showed that the films were composed of Si–C network structures with phenyl rings. Copyright © 2000 John Wiley & Sons, Ltd.     

Live‐Cell Imaging of Endogenous mRNAs with a Small Molecule

Determination of subcellular localization and dynamics of mRNA is increasingly important to understanding gene expression. A new convenient and versatile method is reported that permits spatiotemporal imaging of specific non‐engineered RNAs in living cells. The method uses transfection of a plasmid encoding a gene‐specific RNA aptamer, combined with a cell‐permeable synthetic small molecule, the fluorescence of which is restored only when the RNA aptamer hybridizes with its cognitive mRNA. The method was validated by live‐cell imaging of the endogenous mRNA of β‐actin. Application of the technology to mRNAs of a total of 84 human cytoskeletal genes allowed us to observe cellular dynamics of several endogenous mRNAs including arfaptin‐2, cortactin, and cytoplasmic FMR1‐interacting protein 2. The RNA‐imaging technology and its further optimization might permit live‐cell imaging of any RNA molecules.     

Determination of arsenic species in oyster tissue by microwave‐assisted extraction and liquid chromatography–atomic fluorescence detection

A method for the determination of arsenic species in oyster tissue is established. The extraction of arsenic species is carried out by using low‐power microwaves. Quantitative extraction is obtained at a power of 40 W, and in 5 min, using the extracting agent methanol/water (1 + 1). The measurements are carried out using liquid chromatography–UV irradiation–hydride generation–atomic fluorescence detection (LC–UV–HG–AFS). Three arsenic species were detected in oyster tissue: arsenobetaine (AsBet) (87%), a probable arsenosugar (AsS) (4.9%), and dimethylarsinate (DMA) (4.7%). No influence of the clean‐up, the microwave field or the IR drying system on the stability of the arsenic compounds was observed. The extracts can be kept stable up to 3 days at 4 °C. The performance of the method is proved on fresh samples, as they are usually analysed in routine laboratories. Copyright © 2001 John Wiley & Sons, Ltd.     

Extracellular matrix alterations in low‐grade lung adenocarcinoma compared with normal lung tissue by imaging mass spectrometry

Lung adenocarcinoma (LUAD) is the second most common cancer, affecting both men and women. Fibrosis is a hallmark of LUAD occurring throughout progression with excess production of extracellular matrix (ECM) components that lead to metastatic cell processes. Understanding the ECM cues that drive LUAD progression has been limited due to a lack of tools that can access and report on ECM components within the complex tumor microenvironment. Here, we test whether low‐grade LUAD can be distinguished from normal lung tissue using a novel ECM imaging mass spectrometry (ECM IMS) approach. ECM IMS analysis of a tissue microarray with 20 low‐grade LUAD tissues and 20 normal lung samples from 10 patients revealed 25 peptides that could discriminate between normal and low‐grade LUAD using area under the receiver‐operating curve (AUC) ≥0.7, P value ≤.001. Principal component analysis demonstrated that 62.4% of the variance could be explained by sample origin from normal or low‐grade tumor tissue. Additional work performed on a wedge resection with moderately differentiated LUAD demonstrated that the ECM IMS analytical approach could distinguish LUAD spectral features from spectral features of normal adjacent lung tissue. Conventional liquid chromatography with tandem mass spectrometry (LC‐MS/MS) proteomics demonstrated that specific sites of hydroxylation of proline (HYP) were a main collagen post translational modification that was readily detected in LUAD. A distinct peptide from collagen 3A1 modified by HYP was increased 3.5 fold in low‐grade LUAD compared with normal lung tissue (AUC 0.914, P value <.001). This suggests that regulation of collagen proline hydroxylation could be an important process during early LUAD fibrotic deposition. ECM IMS is a useful tool that may be used to define fibrotic deposition in low‐grade LUAD.     

Determination of genomic N3‐methylthymidine in human cancer cells treated with nitrosamines using capillary electrophoresis with laser‐induced fluorescence

Methylating substances alter DNA by forming N3‐methylthymidine (N3mT), a mutagenic base modification. To develop a sensitive analytical method for the detection of N3mT in DNA based on capillary electrophoresis with laser‐induced fluorescence detection (CE‐LIF), we synthesized the N3mT‐3’‐phosphate as a chemical standard. The limit of detection was 1.9 amol of N3mT, which corresponds to one molecule of N3mT per 1000 normal nucleotides or 0.1%. With this method, we demonstrated that the carcinogenic nitrosamine N’‐nitrosonornicotine (NNN) induced N3mT in the human lung cancer cell line A549. Treatment with NNN also caused an elevated degree of 5‐hydroxymethylcytidine (5hmdC) in DNA, while the methylation degree (i.e. 5‐methylcytidine; 5mdC) stayed constant. According to our data, NNN could, via yet unknown mechanisms, play a role in the formation of N3mT as well as 5hmdC. In this study we have developed a new sensitive analytical method using CE‐LIF for the simultaneous detection of the three DNA modifications, 5mdC, 5hmdC and N3mT.     

One‐Step Synthesis of Small‐Sized and Water‐Soluble NaREF4 Upconversion Nanoparticles for In Vitro Cell Imaging and Drug Delivery

Small (2–28 nm) NaREF₄ (rare earth (RE)=Nd–Lu, Y) nanoparticles (NPs) were prepared by an oil/water two‐phase approach. Meanwhile, hydrophilic NPs can be obtained through a successful phase‐transition process by introducing the amphiphilic surfactant sodium dodecylsulfate (SDS) into the same reaction system. Hollow‐structured NaREF₄ (RE=Y, Yb, Lu) NPs can be fabricated in situ by electron‐beam lithography on solid NPs. The MTT assay indicates that these hydrophilic NPs with hollow structures exhibit good biocompatibility. The as‐prepared hollow‐structured NPs can be used as anti‐cancer drug carriers for drug storage/release investigations. Doxorubicin hydrochloride (DOX) was taken as model drug. The release of DOX from hollow α‐NaLuF₄:20 % Yb³⁺, 2 % Er³⁺ exhibits a pH‐sensitive release patterns. Confocal microscopy observations indicate that the NPs can be taken up by HeLa cells and show obvious anti‐cancer efficacy. Furthermore, α‐NaLuF₄:20 % Yb³⁺, 2 % Er³⁺ NPs show bright‐red emission under IR excitation, making both the excitation and emission light fall within the “optical window” of biological tissues. The application of α‐NaLuF₄:20 % Yb³⁺, 2 % Er³⁺ in the luminescence imaging of cells was also investigated, which shows a bright‐red emission without background noise.