Rapid microbial detection and identification with a high grade of sensitivity and selectivity is a great and challenging issue in many fields, primarily in clinical diagnosis, pharmaceutical, or food processing technology. The tedious and time-consuming processes of current microbiological approaches call for faster ideally on-line identification techniques. The vibrational spectroscopic techniques IR absorption and Raman spectroscopy are noninvasive methods yielding molecular fingerprint information; thus, allowing for a fast and reliable analysis of complex biological systems such as bacterial or yeast cells. In this short review, we discuss recent vibrational spectroscopic advances in microbial identification of yeast and bacterial cells for bulk environment and single-cell analysis. IR absorption spectroscopy enables a bulk analysis whereas micro-Raman-spectroscopy with excitation in the near infrared or visible range has the potential for the analysis of single bacterial and yeast cells. The inherently weak Raman signal can be increased up to several orders of magnitude by applying Raman signal enhancement methods such as UV-resonance Raman spectroscopy with excitation in the deep UV region, surface enhanced Raman scattering, or tip-enhanced Raman scattering.

The identification of avian gender is important for prosperous breeding of birds. Since birds do not possess external genital organs, endoscopic investigations, blood analysis, and molecular biological methods are applied to determine the gender in monomorphic species. However, anesthesia and blood sampling impose stress on the examined bird and should be avoided in terms of animal protection. Here we report on the application of UV-resonance Raman spectroscopy as a minimal invasive method for gender determination of birds via an evaluation of feather pulp samples. Sample preparation for this investigation method is simple and facilitates a quick and easy analysis. The UV-resonance Raman spectra of the feather pulp sample extracts are dominated by DNA and protein signals. The different DNA content in male and female chicken allows for gender differentiation via its characteristic Raman fingerprint. The classification either to male or female chicken is ideally accomplished by support vector machines due to the fact that no unknown classes are involved. Recognition rates of about 95% were compared to less effective results of the unsupervised hierarchical cluster analysis. Within the scope of our investigations, principal component analysis was also applied to determine the important spectral regions for the classification of chicken's feather pulp samples.

For a fast identification of eukaryotic cells such as yeast species without a cultivation step it should be possible to perform the investigation on only one single cell. Since yeasts as eukaryotes are heterogeneous and their Raman spectra are therefore dependent on the measuring position, one Raman spectra is not representative of the whole cell. In this contribution we demonstrate the application of average Raman spectra of a line scan over single yeast cells. These average spectra are used for classification with the help of a support vector machine.

Fast analysis of bioaerosols in clean room environments is necessary in order to prevent contamination of pharmaceutical products, minimize machine downtimes, or both. The detection and identification of microbes will be carried out in several steps: After impaction of the aerosol on a surface, the particles are presorted with glancing light illumination and fluorescence imaging in order to distinguish between abiotic and biotic particles. Since only the biotic particles are of interest, the analysis time can be minimized due to reduction of the data set. The biotic particles are then analyzed further with Raman spectroscopy and identified with a support vector machine.

Various diseases shift the composition of human plasma; hence, the relative quantification of plasma constituents offers the opportunity to use the dynamic and complex composition of plasma to gain information on novel diagnostic and prognostic factors. Since plasma contains, besides water, mostly proteins, UV-resonance Raman spectroscopy (UVRR) seems to be a suitable method for investigating plasma. With this method the signals of aromatic amino acids and proteins are selectively enhanced. In this study an UV-resonance Raman approach was used for the investigation of human plasma of healthy volunteers and patients with thrombotic microangiopathy. For comparison, selected plasma components were analyzed for a more detailed characterization of cryoprecipitates from human plasma.

A rapid analysis of microorganisms is necessary for medical, pharmaceutical or food technology applications to identify harmful bacteria. Conventional identification methods require pure cultures from isolates and are often time demanding. Raman spectroscopy offers an alternative approach to identify microorganisms. With Raman microscopy it is possible to measure structures in the sub micrometer range, and therefore single bacteria cells are accessible. Micro-Raman mapping experiments proof that the bacterium shows a spatial homogeneity, since bacteria normally exhibit no compartments, therefore one spectrum of a single vegetative bacterial cell is sufficient to identify the strain. In contrary bacterial spores and yeast cells exhibit a high spatial dependency of the observed Raman spectra. For heterogeneous samples like single spores or yeast cells a mean spectrum from up to ten different positions is required to describe the complete cell.Using micro-Raman spectra of single bacterial cells and average spectra of yeast cells it is possible to create a database and identify microorganisms on species or even strain level.

ABSTRACT Microorganisms, such as bacteria, which might be present as contamination inside an industrial food or pharmaceutical clean room process need to be identified on short time scales in order to minimize possible health hazards as well as production downtimes causing financial deficits. Here we describe the first results of single-particle micro-Raman measurements in combination with a classification method, the so-called support vector machine technique, allowing for a fast, reliable, and nondestructive online identification method for single bacteria.

Microbial contamination is not only a medical problem, but also plays a large role in pharmaceutical clean room production and food processing technology. Therefore many techniques were developed to achieve differentiation and identification of microorganisms. Among these methods vibrational spectroscopic techniques (IR, Raman and SERS) are useful tools because of their rapidity and sensitivity. Recently we have shown that micro-Raman spectroscopy in combination with a support vector machine is an extremely capable approach for a fast and reliable, non-destructive online identification of single bacteria belonging to different genera. In order to simulate different environmental conditions we analyzed in this contribution different Staphylococcus strains with varying cultivation conditions in order to evaluate our method with a reliable dataset. First, micro-Raman spectra of the bulk material and single bacterial cells that were grown under the same conditions were recorded and used separately for a distinct chemotaxonomic classification of the strains. Furthermore Raman spectra were recorded from single bacterial cells that were cultured under various conditions to study the influence of cultivation on the discrimination ability. This dataset was analyzed both with a hierarchical cluster analysis (HCA) and a support vector machine (SVM).

Eukaryotes (such as yeasts) and prokaryotes (such as bacteria) differ in size, molecular complexity, etc. By definition, eukaryotic cells store their DNA in a separate internal compartment, the so-called nucleus. Owing to this molecular compartmentalization, the identification of yeast cells by vibrational spectroscopy at a single-cell level is challenging. This contribution reports on first results of micro-Raman analysis together with a hierarchical cluster analysis allowing for an online identification method for yeast cells at a single-cell level. For the classification analysis, an average spectrum from 10 different measuring points within a single yeast cell was used to overcome the heterogeneity of the yeast cells. Copyright © 2005 John Wiley & Sons, Ltd.

The ISO standard protocol for determining size of droplets suspended between two layers of silicone oils of differing viscosity was evaluated in experiments using a monosize droplet generator. Cross-sectional areas of 0.27-nl droplets captured in silicone oils decreased linearly with time until droplets disappeared at 26min after application. Rates of decrease in cross-sectional area of droplets were independent of droplet size (range 0.27–269nl), but decreased as the gradient in water vapour concentration between droplet and ambient atmosphere decreased. Saturating silicone oils with water reduced rates of decrease in cross-sectional areas of droplets (−37%). Diffusion studies established that the amount of water diffusing through silicone oil increased linearly with time. Permeance to water vapour was inversely related to thickness of the oil layer. Permeability coefficients averaged 45.8×10−9 and 29.5×10−9m2s−1 for low- (9.6cSt) and high-viscosity (10350cSt) silicone oil and were up to 52-fold higher than for mineral oils of comparable viscosity. Our data suggest that the high water vapour permeability of silicone oil and the solubility of water in silicone oil accounted for the decrease in size of droplets captured in silicone oil. Based on our findings, the ISO standard protocol should be modified to correct for these effects.

Structure data for both triclinic alpha- and gamma-CuMoO4 have been delivered with anisotropic temperature factors at 190 K. The complete tensors of linear thermal expansion coefficients were derived for alpha- and gamma-CuMoO4 using the temperature dependence of lattice parameters within the temperature range 20 K-300 K and 20 K-260 K, respectively. The orientation of principal axes and values of principal expansion coefficients are given for selected temperatures. Their relation to the structure is discussed. The volume expansion coefficient of a CuMoO4 becomes negative below 80 K.

A method has been developed to change or to remove stress in anodically bonded silicon and glass compounds (Pyrex or Tempax). The technology is based on the structural relaxation of the glass at temperatures at which no viscous flow is to be seen. Due to the structural relaxation, a shrinkage of the glass occurs at sufficiently high temperatures and leads to a bend change of the bonded wafers. As a result, at room temperature or at the working temperature stress-free compounds as well as those with lower and even with opposite stress and curvature can be produced. The structural relaxation of the glass has been studied by investigating the shrinkage of glass rods during isothermal annealing. The applicability to the curvature change of anodically bonded silicon and Tempax has been proved. Finally, the influence of the developed method on the decomposition and on the thermal expansion coefficient of the glass has been studied.

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A HIERD setup (HI-ERD=heavy ion elastic recoil detection) is introduced including a semiconductor Δ-E-E telescope for the detection of hydrogen and helium isotopes and a Bragg Ionization Chamber (BIC) for the identification of heavier recoils. An optimum forward scattering geometry with respect to maximum analyzable depth and sensitivity is determined experimentally as well as by calculations for the analysis of oxygen and hydrogen using 35 MeV 35Cl incident ions. As a relevant application of the method, the Na content of borosilicate glass is investigated in samples subject to anodic bonding procedures.

The construction of micromechanic devices is developing from the second to the third dimension. Therefore, a technique is needed that enables bonding between more than two substrates. The author presents two technologies for the anodic bonding of Pyrex-type glass and silicon with more than two substrates. A three-substrate micromachined passive valve, which was assembled by anodic bonding is presented. Theoretical models are shown and technological problems discussed.