Disruption of Cell Adhesion and Cytoskeletal Networks by Thiol-Functionalized Silica-Coated Iron Oxide Nanoparticles.

One of the major obstacles that limits the use of magnetic nanoparticles in biomedical applications is their potential toxicity. In the present study, we evaluated the cytotoxic effects of thiol-functionalized silica-coated iron oxide (Fe3O4@SiO2-SH) nanoparticles using human lung epithelial cells A549. We investigated the effect of Fe3O4@SiO2-SH nanoparticles on the cell viability, proliferation, cell cycle distribution, adhesion, apoptosis, and the orientation of the cytoskeletal networks, as well as on expression of proteins involved in cell death, cell survival, and cell adhesion. We demonstrated that exposure of A549 cells to Fe3O4@SiO2-SH nanoparticles resulted in severe disruption of the actin microfilaments and microtubule cytoskeleton and reduced the size of focal adhesions. Furthermore, cell adhesion was significantly affected as well as the phosphorylation of focal adhesion kinase (FAK), extracellular-signal-regulated kinase (ERK), and p38. Our findings highlight the need for in-depth cytotoxic evaluation of nanoparticles supporting their safer use, especially in biomedical applications.

Kinase-loaded magnetic beads for sequential in vitro phosphorylation of peptides and proteins.

Post-translational modifications, including phosphorylation, greatly impact the physiological function of proteins, especially those that are natively unfolded and implicated in many neurodegenerative diseases. However, structural and functional studies of such proteins require fully defined phosphorylation, including those that are not physiological. Thus, the kinases ERK2 and GSK-3ß were immobilized to various superparamagnetic beads with carboxylic, aldehyde, Ni2+, or Co3+ functional groups, with a view to efficiently phosphorylate peptides and proteins in vitro. Full phosphorylation of specific synthetic peptides confirmed that beads were successfully loaded with kinases. Remarkably, enzymes covalently immobilized on carboxylated SeraMag beads remained active upon reuse, with residual activity after 10 uses 99.5 ± 0.34% for GSK-3ß and 36.2 ± 2.01% for ERK2. The beads were also used to sequentially phosphorylate recombinant tau, which in vivo is a biomarker of Alzheimer's disease. Thus, a system consisting of two fully active kinases immobilized to magnetic beads is demonstrated for the first time. In comparison to soluble enzymes, the beads are easier to handle, reusable, and thus low-cost. Importantly, these beads are also convenient to remove from reactions to minimize contamination of phosphorylated products or to exchange with other kinases.

Nasal Immunization Using Chitosan Nanoparticles with Glycoprotein B of Murine Cytomegalovirus.

The use of nanoparticles as a delivery system for a specific antigen could solve many limitations of mucosal vaccine applications, such as low immunogenicity, or antigen protection and stabilization. In this study, we tested the ability of nasally administered chitosan nanoparticles loaded with glycoprotein B of murine cytomegalovirus to induce an immune response in an animal model. The choice of chitosan nanoparticle type was made by in vitro evaluation of sorption efficiency and antigen release. Three types of chitosan nanoparticles were prepared: crosslinked with tripolyphosphate, coated with hyaluronic acid, and in complex with polycaprolactone. The hydrodynamic size of the nanoparticles by dynamic light scattering, zeta potential, Fourier transform infrared spectroscopy, scanning electron microscopy, stability, loading efficiency, and release kinetics with ovalbumin were evaluated. Balb/c mice were immunized intranasally using the three-dose protocol with nanoparticles, gB, and adjuvants Poly(I:C) and CpG ODN. Subsequently, the humoral and cell-mediated antigen-specific immune response was determined. On the basis of the properties of the tested nanoparticles, the cross-linked nanoparticles were considered optimal for further investigation. The results show that nanoparticles with Poly(I:C) and with gB alone raised IgG antibody levels above the negative control. In the case of mucosal IgA, only gB alone weakly induced the production of IgA antibodies compared to saline-immunized mice. The number of activated cells increased slightly in mice immunized with nanoparticles and gB compared to those immunized with gB alone or to negative control. The results demonstrated that chitosan nanoparticles could have potential in the development of mucosal vaccines.

Preparation of hyaluronan oligosaccharides by a prokaryotic beta-glucuronidase: Characterization of free and immobilized forms of the enzyme.

Popularity of hyaluronan (HA) in the cosmetics and pharmaceutical industries, led to the investigation and development of new HA-based materials, with enzymes playing a key role. Beta-D-glucuronidases catalyze the hydrolysis of a beta-D-glucuronic acid residue from the non-reducing end of various substrates. However, lack of specificity towards HA for most beta-D-glucuronidases, in addition to the high cost and low purity of those active on HA, have prevented their widespread application. In this study, we investigated a recombinant beta-glucuronidase from Bacteroides fragilis (rBfGUS). We demonstrated the rBfGUS's activity on native, modified, and derivatized HA oligosaccharides (oHAs). Using chromogenic beta-glucuronidase substrate and oHAs, we characterized the enzyme's optimal conditions and kinetic parameters. Additionally, we evaluated rBfGUS's activity towards oHAs of various sizes and types. To increase reusability and ensure the preparation of enzyme-free oHA products, rBfGUS was immobilized on two types of magnetic macroporous bead cellulose particles. Both immobilized forms of rBfGUS demonstrated suitable operational and storage stabilities, and their activity parameters were comparable to the free form. Our findings suggest that native and derivatized oHAs can be prepared using this bacterial beta-glucuronidase, and a novel biocatalyst with enhanced operational parameters has been developed with a potential for industrial use.

Affiblot: a dot blot-based screening device for selection of reliable antibodies.

The key factor in the development of antibody-based assays is to find an antibody that has an appropriate affinity, high specificity, and low cross-reactivity. However, this task is not easy to carry out since the research antibodies on the market may suffer from low specificity and reproducibility. Here, we report on a palm-sized dot blot-based device, called the affiblot, that has a specially designed lid that allows simultaneous semi-quantitative comparison of up to five antibodies from different suppliers regarding their affinity/avidity, cross-reactivity, and batch-to-batch reliability. The only required peripheral equipment is a vacuum pump, a camera, and densitometry software. The affiblot device was tested for its functionality and its measurements were compared against those obtained by standard dot blot and ELISA. The benefit over these methods, when various antibodies are evaluated, is in its simplicity. It allows easy antigen deposition, fast application and the discarding of the solutions, a compact undivided membrane, and therefore significant decrease of labor. The device was tested with specific anti-ApoE, anti-EpCAM, anti-Salmonella, anti-E. coli, and anti-Listeria antibodies from different suppliers. Their properties were compared for their ability to interact specifically with antigen and/or non-target structures and the best-suited antibody for the intended application was identified.

Controlled proteolysis of normal and pathological prion protein in a microfluidic chip.

A microreactor for proteinase K (PK)-mediated protein digestion was developed as a step towards the elaboration of a fully integrated microdevice for the detection of pathological prion protein (PrP). PK-grafted magnetic beads were immobilized inside a polydimethylsiloxane (PDMS) microchannel using a longitudinal magnetic field parallel to the flow direction and a magnetic field gradient, thereby forming a matrix for enzymatic digestion. This self-organization provided uniform pore sizes, a low flow resistance and a strong reaction efficiency due to a very thin diffusion layer. The microreactor's performance was first evaluated using a model substrate, succinyl-ala-ala-ala-paranitroanilide (SAAAP). Reaction kinetics were typically accelerated a hundred-fold as compared to conventional batch reactions. Reproducibility was around 98% for on-chip experiments. This microsystem was then applied to the digestion of prion protein from brain tissues. Controlled proteolysis could be obtained by varying the on-chip flow rate, while a complete proteolysis of normal protein was achieved in only three minutes. Extracts from normal and pathological brain homogenates were finally compared and strong discrimination between normal and pathological samples was demonstrated.

Magnetic proteinase K reactor as a new tool for reproducible limited protein digestion.

As an aid to differentiating between the prion proteins Prp(c) and PrP(Sc), the preparation and use of immobilized Proteinase K (PK) is described. An accumulation of PrP(Sc) in the central nervous system is the one of the causes of neurodegenerative disease. Current routine diagnosis is based on the postmortem detection of the distinct neuropathological lesion profiles of CNS and by the presence of the PK-resistant core of the prion protein isolated from brain lysates. An assay with PK immobilized to magnetic -COOH micro- and nanoparticles can offer a convenient as well as economic method. The individual immobilization steps were verified by measuring the zeta potential of the particles. The stability of the newly developed PK magnetic reactor, observed during kinetics measurements, was highly satisfactory. The calculated values of the apparent Michaelis constant (4.25 mM for native enzyme and 1.28 mM for immobilized enzyme) were determined from Lineweaver-Burk plots. Human growth hormone was digested using the newly prepared magnetic PK reactor and MALDI-TOF-MS analysis of the digests showed satisfactory efficiency. Controlled digestion of PrP(c) from the Mov mouse cell line was demonstrated with Western blot detection.

Epitope mapping of allergen ovalbumin using biofunctionalized magnetic beads packed in microfluidic channels The first step towards epitope-based vaccines.

Specific allergen immunotherapy is frequently associated with adverse reactions. Several strategies are being developed to reduce the allergenicity while maintaining the therapeutic benefits. Peptide immunotherapy is one such approach. Methods for the simple and rapid identification of immunogenic epitopes of allergens (i.e. allergenic epitopes) are ongoing and could potentially lead to peptide-based vaccines. An epitope extraction technique, based on biofunctionalized magnetic microspheres self-organized under a magnetic field in a channel of a simple microfluidic device fabricated from polydimethylsiloxane, was applied in the isolation and identification of prospective allergenic epitopes. Similarly to chromatographic column separations, the easily replaceable plug of self-organized beads in the channel benefits especially from an even larger surface-to-volume ratio and an enhanced interaction of the surfaces with passing samples. Ovalbumin, the major protein of egg white and a typical representative of food allergens, was selected as the model molecule. Highly resistant ovalbumin was at first efficiently digested by a magnetic proteolytic reactor with trypsin treated with l-1-tosylamido-2-phenylethyl chloromethyl ketone and the second step, i.e. capture of allergenic epitopes from the mixture of peptides, was performed by a magnetic immunoaffinity carrier with orientedly immobilized rabbit anti-ovalbumin IgG molecules. Captured peptides were released with 0.05% trifluoroacetic acid. The elution fractions were analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The peptide fragment of ovalbumin HIATNAVLFFGR (m/z: 1345.75, position: 371-382) was identified as a relevant allergenic epitope in this way. Such a microfluidic magnetic force-based epitope extraction technique applied in the epitope mapping of ovalbumin has the potential to be a significant step towards developing safe and cost-effective epitope-based vaccines.

Use of self assembled magnetic beads for on-chip protein digestion.

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.

Oriented immobilization of galactose oxidase to bead and magnetic bead cellulose and poly(HEMA-co-EDMA) and magnetic poly(HEMA-co-EDMA) microspheres.

In order to obtain an active and stable oxidation reactor for daily use in biochemical laboratory we decided to immobilize galactose oxidase orientedly through a carbohydrate chain to the magnetic carriers. We used hydrazide derivatives of non-magnetic and magnetic bead cellulose and of magnetic and non-magnetic poly(HEMA-co-EDMA) microspheres. Activation of the enzyme molecules was done by sodium periodate in the presence of supplements (fucose, CuSO4, catalase). Orientedly immobilized galactose oxidase presents high storage stability and lower susceptibility to inappropriate microenvironmental conditions. Reactor reactivated by three pulses of D-galactose retained practically 100% of its native activity after 6 months. The positive properties of both magnetic carriers were entirely confirmed.

Bioaffinity magnetic reactor for peptide digestion followed by analysis using bottom-up shotgun proteomics strategy.

We report an efficient and streamlined way to improve the analysis and identification of peptides and proteins in complex mixtures of soluble proteins, cell lysates, etc. By using the shotgun proteomics methodology combined with bioaffinity purification we can remove or minimize the interference contamination of a complex tryptic digest and so avoid the time-consuming separation steps before the final MS analysis. We have proved that by means of enzymatic fragmentation (endoproteinases with Arg-C or/and Lys-C specificity) connected with the isolation of specific peptides we can obtain a simplified peptide mixture for easier identification of the entire protein. A new bioaffinity sorbent was developed for this purpose. Anhydrotrypsin (AHT), an inactive form of trypsin with an affinity for peptides with arginine (Arg) or lysine (Lys) at the C-terminus, was immobilized onto micro/nanoparticles with superparamagnetic properties (silica magnetite particles (SiMAG)-Carboxyl, Chemicell, Germany). This AHT carrier with a determined binding capacity (26.8 nmol/mg of carrier) was tested with a model peptide, human neurotensin, and the resulting MS spectra confirmed the validity of this approach.

Functionalized magnetic micro- and nanoparticles: optimization and application to micro-chip tryptic digestion.

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.