The use of grafted trypsin magnetic beads in a microchip for performing protein digestion is described. The PDMS device uses strong magnets to create a magnetic field parallel to the flow with a strong gradient pointing through the center of the chip channel. This allows for the formation of a low-hydrodynamic resistance plug of magnetic trypsin beads that serves as a matrix for protein digestion. This device represents an inexpensive way of fabricating a multi open-tubular-like column with an appropriate pore size for proteins. Kinetics studies of the hydrolysis of a model peptide show a 100-fold increase in digestion speed obtained by the microsystem when compared to a batch wise system. This system also offers the great advantage of easy replacement, as the bead matrix is easily washed out and replaced. High performance and reproducibility for digesting recombinant human growth hormone are confirmed by analysing the digest products in both CE and MALDI-TOF MS. Similar sequence coverage (of about 44%) is obtained from MS analysis of products after 10 minutes on-chip and 4 h with soluble trypsin in bulk.

It appears that most glycoproteins found in pathogenic bacteria are associated with virulence. Despite the recent identification of novel virulence factors, the mechanisms of virulence in Francisella tularensis are poorly understood. In spite of its importance, questions about glycosylation of proteins in this bacterium and its potential connection with bacterial virulence have not been answered yet. In the present study, several putative Francisella tularensis glycoproteins were characterized through the combination of carbohydrate-specific detection and lectin affinity with highly sensitive mass spectrometry utilizing the bottom-up proteomic approach. The protein PilA that was recently found as being possibly glycosylated, as well as other proteins with designation as novel factors of virulence, were among the proteins identified in this study. The reported data compile the list of potential glycoproteins that may serve as a take-off platform for a further definition of proteins modified by glycans, faciliting a better understanding of the function of protein glycosylation in pathogenicity of Francisella tularensis.

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The preparation and characterization of a miniaturized trypsin reactor using on-line coupling with an ESI-TOF mass spectrometer are described. L-1-Tosylamido-2-phenylethyl chloromethyl ketone-trypsin was covalently immobilized on poly(glycidyl methacrylate-co-ethylene dimethacrylate) monolith prepared in a 75 lm ID fused silica capillary resulting in a bioreactor with high local concentration of the proteolytic enzyme. Covalent immobilization of trypsin on this support was performed using the epoxide functional groups in either a one-or a multistep reaction. For on-line protein digestion-MS analysis the bioreactor was coupled with the mass spectrometer using a liquid junction microelectrospray interface. The performance of the reactor was tested using an on-line flow through the system with flow rates of 50-300 nL/min. The resulting protein consumption was in the atto-to low femtomole range. Proteolytic activity was characterized in a wide range of conditions with respect to the flow rate, pH, and temperature. Complete protein digestion was achieved in less than 30 s at 258C with the sequence coverage of 80% (cytochrome c), which is comparable to 3 h digestion in solution at 378C. Besides the good performance at laboratory temperature, the immobilized trypsin in the bioreactor also performed well at lower pH compared to the standard in-solution protocols.

A microfluidic fluidized bed composed of antibody-grafted magnetic beads for the fast visual detection of bacteria by in situ expansion phenomena.

The preparation of an easily replaceable protease microreactor for micro-chip application is described. Magnetic particles coated with poly(N-isopropylacrylamide), polystyrene, poly(2-hydroxyethyl methacrylate-co-ethylene dimethacrylate), poly(glycidyl methacrylate), [(2-amino-ethyl)hydroxymethylen]biphosphonic acid, or alginic acid with immobilized trypsin were utilized for heterogeneous digestion. The properties were optimized, with the constraint of allowing immobilization in a microchannel by a magnetic field gradient. To obtain the highest digestion efficiency, sub-micrometer spheres were organized by an inhomogeneous external magnetic field perpendicularly to the direction of the channel. Kinetic parameters of the enzyme reactor immobilized in micro-chip capillary (micro-chip immobilized magnetic enzyme reactor (IMER)) were determined. The capability of the proteolytic reactor was demonstrated by five model (glyco)proteins ranging in molecular mass from 4.3 to 150 kDa. Digestion efficiency of proteins in various conformations was investigated using SDS-PAGE, HPCE, RP-HPLC, and MS. The compatibility of the micro-chip IMER system with total and limited proteolysis of high-molecular-weight (glyco)proteins was confirmed. It opens the route to automated, high-throughput proteomic micro-chip devices.

Monodisperse (4 μm) macroporous crosslinked poly(glycidyl methacrylate) (PGMA) microspheres for use in microfluidic immunomagnetic cell sorting, with a specific application to the capture of circulating tumor cells (CTCs), were prepared by multistep swelling polymerization in the presence of cyclohexyl acetate porogen and hydrolyzed and ammonolyzed. Iron oxide was then precipitated in the microspheres to render them magnetic. Repeated precipitation made possible to raise the iron oxide content to more than 30 wt %. To minimize nonspecific adsorption of the microspheres in a microchannel and of cells on the microspheres, they were coated with albumin crosslinked with glutaraldehyde. Antibodies of epithelial cell adhesion molecule (anti-EpCAM) were then immobilized on the albumin-coated magnetic microspheres using the carbodiimide method. Capture of breast cancer MCF7 cells as a model of CTCs by the microspheres with immobilized anti-EpCAM IgG was performed in a batch experiment. Finally, MCF7 cells were captured by the anti-EpCAM-immobilized albumin-coated magnetic microspheres in an Ephesia chip. A very good rejection of lymphocytes was achieved. Thus, albumin-coated monodisperse magnetic PGMA microspheres with immobilized anti-EpCAM seem to be promising for capture of CTCs in a microfluidic device.

NSE and S100B belong among the so-called structural proteins of the central nervous system (CNS). Lately, this group of structural proteins has been profusely used as specific biomarkers of CNS tissue damage. So far, the majority of the research papers have focused predominantly on the concentrations of these proteins in blood in relation to CNS damage of various origins. Considering the close anatomic and functional relationship between the brain or spinal cord and cerebrospinal fluid (CSF), in case of a CNS injury, a rapid and pronounced increase of the concentrations of structural proteins specifically in CSF takes place. This study inquires into the physiological concentrations of NSE and S100B proteins in CSF, carried out on a sufficiently large group of 601 patients. The detected values can be used for determination of a normal reference range in CSF in a clinical laboratory diagnostics.