Applications of modern micro-Raman spectroscopy for cell analyses.

Raman spectroscopy assesses the chemical composition of a sample by exploiting the inherent and unique vibrational characteristics of chemical bonds. Initial applications of Raman were identified in the industrial and chemical sectors, providing a rapid non-invasive method to identify sample components or perform quality control assessments. Applications have since increased and sample sizes decreased, leading to the onset of micro-Raman spectroscopy.

Micro-Raman detection of nuclear membrane lipid fluctuations in senescent epithelial breast cancer cells.

Originally identified in cultured cells, oncogenic cellular senescence is a growth-arrest mechanism which may inhibit tumor development by limiting the ability of cells to divide. However, literature shows that these cells secrete tumor-inducing and tumor-suppressing proteins leading to poor prognosis. Understanding the progression of oncogenic cellular senescence and associated mechanisms provides important implications for improving tumorigenesis therapeutic treatments.

The network formation assay: a spatially standardized neurite outgrowth analytical display for neurotoxicity screening.

We present a rapid, reproducible and sensitive neurotoxicity testing platform that combines the benefits of neurite outgrowth analysis with cell patterning. This approach involves patterning neuronal cells within a hexagonal array to standardize the distance between neighbouring cellular nodes, and thereby standardize the length of the neurite interconnections. This feature coupled with defined assay coordinates provides a streamlined display for rapid and sensitive analysis.

100% efficient sub-nanoliter sample introduction in laser-induced breakdown spectroscopy and inductively coupled plasma spectrometry: implications for ultralow sample volumes.

Recently, nanoflow nebulizers with low-volume drain-free spray chambers became available for inductively coupled plasma-mass spectrometry application for analysis of very small sampling volumes. The present technical note reports on a different approach for 100% efficient subnanoliter sample introduction, the application of monodisperse piezoelectric microdroplet dispensers which generate 40-50 microm droplets with high reproducibility if nozzles of 30 microm diameter are applied. The droplets having volumes below 0.

Analyses of mouse breath with ion mobility spectrometry: a feasibility study.

Exhaled breath can provide comprehensive information about the metabolic state of the subject. Breath analysis carried out during animal experiments promises to increase the information obtained from a particular experiment significantly. This feasibility study should demonstrate the potential of ion mobility spectrometry for animal breath analysis, even for mice.

Temperature gradient focusing in miniaturized free-flow electrophoresis devices.

Temperature gradient focusing is a method to separate and focus any charged analytes even without accessible isoelectric point, and has been already widely used in CE. In this paper, we demonstrate the application of temperature gradient focusing to free-flow electrophoresis. Besides focusing and separation experiments of proteins, the stability of the temperature gradient under flow conditions and the temperature dependence of fluorescence dyes have also been investigated.

Linearized equations for the reduced ion mobilities of polar aliphatic organic compounds.

Over the years, ion mobility spectrometry has evolved into a powerful technique for rapid identification of analytes in very complex sample matrixes such as human breath. Every analyte detected has a characteristic ion mobility value (and a retention time when additional preseparation techniques are employed) which is used to identify the peaks in a spectrum either by comparison with reference analytes or by simultaneous mass spectrometric measurements. In this study, the mass-mobility correlations between compounds in three different homologous series are used to predict the mobilities of the other substances in the same series in a medium of synthetic air.

Peptide and protein quantification: a map of the minefield.

The increasing popularity of gel-free proteomics technologies has created a strong demand for compatible quantitative analysis methods. As a result, a plethora of different techniques has been proposed to perform gel-free quantitative analysis of proteomics samples. Each of these methods comes with certain strengths and shortcomings, and they often are dedicated to a specific purpose.

MCC/IMS signals in human breath related to sarcoidosis-results of a feasibility study using an automated peak finding procedure.

A feasibility study using an ion mobility spectrometer coupled with a multi-capillary column (MCC) was started to identify characteristic peaks of volatile compounds in exhaled human breath samples of 10 ml volume. The breath of 20 patients with sarcoidosis and suspicion of sarcoidosis because of mediastinal lymph node enlargement was investigated. Using a set of procedures for data processing and scoring a sector of interest was determined within the IMS-chromatogram.

Peak assignment in multi-capillary column-ion mobility spectrometry using comparative studies with gas chromatography-mass spectrometry for VOC analysis.

Over the past years, ion mobility spectrometry (IMS) as a well established method within the fields of military and security has gained more and more interest for biological and medical applications. This highly sensitive and rapid separation technique was crucially enhanced by a multi-capillary column (MCC), pre-separation for complex samples. In order to unambiguously identify compounds in a complex sample, like breath, by IMS, a reference database is mandatory.

Breath analysis-performance and potential of ion mobility spectrometry.

Ion mobility spectrometry is a fast and sensitive analytical method for the detection of gas phase analytes in the ppb(v)-ppt(v) range under ambient conditions (pressure and temperature). Ion mobility spectrometers coupled with rapid pre-separation like multi-capillary columns (MCC/IMS) are suitable for the selective characterization of complex and humid mixtures. Recently, MCC/IMS have been applied to analyses of human breath for early diagnosis as well as medication and therapy control.

Ion mobility spectrometry coupled with multi-capillary columns for metabolic profiling of human breath.

Recently, ion mobility spectrometry (IMS) started to be used for direct breath analysis with respect to metabolic profiling, biomarker finding and gas trace analysis. The present review describes the basic operation of an ion mobility spectrometer including the ionization process, humidity effects and sampling procedures. To enhance the resolution, pre-separation by multi-capillary columns (MCCs) is discussed and examples for IMS chromatograms are presented.

Tip-enhanced Raman scattering (TERS) of oxidised glutathione on an ultraflat gold nanoplate.

Tip-enhanced Raman scattering (TERS) spectra of a short immobilised peptide on a single transparent gold nanoplate are presented.

Structure of si(111)-in nanowires determined from the midinfrared optical response.

The anisotropic optical response of Si(111)-(4x1)/(8x2)-In in the midinfrared, where ab initio studies predict significant changes in the band structure between competing models of this important quasi-1D system, has been measured using infrared spectroscopic ellipsometry (IRSE) and reflection anisotropy spectroscopy (RAS). Both IRSE and RAS of the (8x2) phase show that the anisotropic Drude tail of the (4x1) phase is replaced by two peaks at 0.50 and 0.

Separation of proteins using a novel two-depth miniaturized free-flow electrophoresis device with multiple outlet fractionation channels.

A novel free-flow electrophoresis glass chip design with two-depth etched structures for the separation and fractionation of proteins is presented. The microfluidic structures etched in two depths enhance the flow characteristics inside the miniaturized device. A novel nine-port outlet interface enables the fractionation of the separated analytes.

Chemical and structural changes in a pH-responsive mixed polyelectrolyte brush studied by infrared ellipsometry.

This work provides direct chemical and structural insight into pH-dependent changes of an ultrathin (d=12 nm) mixed polyelectrolyte brush. In-situ infrared spectroscopic ellipsometry was used for the first time to study the gradual pH-responsive behavior of the brush, constituted of weak anionic and cationic polyelectrolytes, poly(acrylic acid) (PAA) and poly(2-vinylpyridine) (P2VP), respectively. The pH-dependent infrared fingerprints in the mid-infrared spectral range were analyzed as a function of chemical and structural changes in the mixed brush caused by pH changes.

The production of free-standing large aspect ratio metal nanofilms by femtosecond laser separation.

We demonstrate a new method for the production of free-standing metal films of thickness down to several tens of nanometres. Films of different metals as well as multilayer structures have been produced by means of femtosecond laser-induced separation of evaporated layers from a plane glass surface. This technology enables the production of large-area films with different properties for optical or nanotechnological applications.

Impact of fixation on in vitro cell culture lines monitored with Raman spectroscopy.

Raman spectroscopy provides chemical-rich information about the composition of analytes and is a powerful tool for biological studies. With the ability to investigate specific cellular components or image whole cells, compatible methods of sample preservation must be implemented for accurate spectra to be collected. Unfortunately, the effects of many commonly used sample preservation methods have not been explored with cultured cells.

Analysis of tyrosine-phosphorylated proteins in rat brain mitochondria.

Mitochondrial protein phosphorylation is emerging as a central event in mitochondrial signaling. In particular, tyrosine phosphorylation is proving to be an unappreciated mechanism involved in regulation of mitochondrial functions. Tyrosine kinases and phosphatases have been identified in mitochondrial compartments and there is a steadily increasing number of new identified tyrosine-phosphorylated proteins implicated in a wide spectrum of mitochondrial functions.

A rapid, reliable, and automatable lab-on-a-chip interface.

We present a prototype for a universal world-to-chip interface for electrical and fluidic connections to lab-on-a-chip devices. The concept is based on spring supported connections to secure and define the contact force for each wire and tubing. We demonstrate the functionality of a manual system and propose the design of an automated system.

Transparent silver microcrystals: synthesis and application for nanoscale analysis.

Micrometer-sized atomically flat silver nanoplates with a thickness of 10-20 nm were obtained in a one-pot reduction of silver nitrate with hydrazine sulfate without surfactants or polymers. The optically transparent triangles and hexagons have been proven to be excellent substrates for experiments with a tip-enhanced Raman transmission setup.

Glycerophospholipid profiling by high-performance liquid chromatography/mass spectrometry using exact mass measurements and multi-stage mass spectrometric fragmentation experiments in parallel.

A profiling method for glycerophospholipids (GPs) in biological samples was developed using reversed-phase high-performance liquid chromatography (RP-HPLC) coupled to hybrid linear ion trap-Fourier transform ion cyclotron resonance mass spectrometry (LIT-FTICRMS) with electrospray ionization (ESI) in the negative ionization mode. The method allowed qualitative (identification and structure elucidation) and relative quantitative determination of various classes of GPs including phosphatidylcholines, phosphatidylethanolamines, phosphatidylinositols, phosphatidylserines, phosphatidic acids, phosphatidylglycerols, and cardiolipins in a single experiment. Chromatographic separation was optimized by the examination of different buffer systems and special emphasis was paid on the detection by ESI-MS.

Perspectives for spatially resolved molecular spectroscopy--Raman on the nanometer scale.

Nano-objects and cellular components are of great interest in biological sciences. Tip-enhanced Raman scattering (TERS) is a tool that allows addressing of such features for structural investigations without the need of further labelling. After brief introduction to the basic aspects of the technique an overview of present application of TERS is given.

Electrical generators driving microhollow and dielectric barrier discharges applied for analytical chemistry.

Scaling down the size of plasma discharges would reduce the amount of gases, liquids, and consumables required, which in turn would decrease the operating costs. Nevertheless, the application of a specialized plasma generator for microhollow cathode discharges (MHCD) and dielectric barrier discharges are driven with commercially available power sources. Those generators are bulky and expensive and their overall efficiency is poor.

Recent developments in peptide-based nucleic acid delivery.

Despite the fact that non-viral nucleic acid delivery systems are generally considered to be less efficient than viral vectors, they have gained much interest in recent years due to their superior safety profile compared to their viral counterpart. Among these synthetic vectors are cationic polymers, branched dendrimers, cationic liposomes and cell-penetrating peptides (CPPs). The latter represent an assortment of fairly unrelated sequences essentially characterised by a high content of basic amino acids and a length of 10-30 residues.