FISH in chips: turning microfluidic fluorescence in situ hybridization into a quantitative and clinically reliable molecular diagnosis tool

Microfluidic systems bear promise to provide new powerful tools for the molecular characterization of cancer cells, in particular for the routine detection of multiple cancer biomarkers using a minute amount of the sample. However, taking miniaturized cell-based assays into the clinics requires the implementation and validation of complex biological protocols on chip, as well as the development of disposable microdevices produced at a low cost. Based on a recently developed microfluidic chip made of Cyclic Olefin Copolymer for cell immobilization with minimal dead volume and controlled shear stress, we developed a protocol performed entirely in the liquid phase, allowing the immobilization and fixation of cells and their quantitative characterization by fluorescence in situ hybridization. We demonstrated first in cell lines and then in two clinical case studies the potential of this method to perform quantitative copy number measurement and clinical scoring of the amplification of the ERBB2 gene, a decisive biomarker for the prescription of HER2+ related targeted therapies. This validation was performed in a blind protocol in two clinical case studies, in reference to the gold standard and clinically used method based on glass slides. We obtained a comparable reproducibility and a minor difference in apparent amplification, which can be corrected by internal calibration. The method thus reaches the standard of robustness needed for clinical use. The protocol can be fully automated, and its consumption of samples and DNA probes is reduced as compared to glass slide protocols by a factor of at least 10. The total duration of the assay is divided by two.

Continuous chemical operations and modifications on magnetic γ-Fe2O3 nanoparticles confined in nanoliter droplets for the assembly of fluorescent and magnetic SiO2@γ-Fe2O3

An automated droplet microfluidic platform is described for the manipulation of magnetic nanoparticles and their assembly with fluorescent silica nanoparticles.

Magneto-immunocapture with on-bead fluorescent labeling of amyloid-β peptides: towards a microfluidized-bed-based operation

Novel combination of Magneto-immunocapture and on-beads fluorescent labeling of Aβ peptides for their sensitive determination in cerebro spinal fluid samples.

Electrochemically assisted micro localized grafting of aptamers in a microchannel engraved in fluorinated thermoplastic polymer Dyneon THV

Electrochemically assisted localized grafting of an aptamer in a microchannel engraved in fluorinated thermoplastic polymer Dyneon THV.

A review of microfabrication and hydrogel engineering for micro-organs on chips

This review highlights recent trends towards the development of in vitro multicellular systems with definite architectures, or "organs on chips". First, the chemical composition and mechanical properties of the scaffold have to be consistent with the anatomical environment in vivo. In this perspective, the flourishing interest in hydrogels as cellular substrates has highlighted the main parameters directing cell differentiation that need to be recapitulated in artificial matrix. Another scaffold requirement is to act as a template to guide tissue morphogenesis. Therefore specific microfabrication techniques are required to spatially pattern the environment at microscale. 2D patterning is particularly efficient for organizing planar polarized cell types such as endothelial cells or neurons. However, most organs are characterized by specific sub units organized in three dimensions at the cellular level. The reproduction of such 3D patterns in vitro is necessary for cells to fully differentiate, assemble and coordinate to form a coherent micro-tissue. These physiological microstructures are often integrated in microfluidic devices whose controlled environments provide the cell culture with more life-like conditions than traditional cell culture methods. Such systems have a wide range of applications, for fundamental research, as tools to accelerate drug development and testing, and finally, for regenerative medicine.

New non-covalent strategies for stable surface treatment of thermoplastic chips

In order to be more extensively used outside of research laboratories, lab-on-chip technologies must be mass-produced using low-cost materials such as thermoplastics. Thermoplastics, however, are generally hydrophobic in their native state, which makes them unsuitable for direct use with biological samples in aqueous solution, and thus require surface coating. This coating should be robust, inexpensive and simple to implement, in order not to hinder the industrial advantage of thermoplastic chips. Cyclic Olefin Copolymer (COC) is a particularly appealing polymer, but it is also difficult to functionalize due to its chemical inertness. Here we introduce and compare the performance of two new approaches for COC coating. One relies on the use of a commercial triblock copolymer, Pluronic® F127. The second approach uses new copolymers synthesized by radical polymerization, and consisting of a dimethylacrylamide (DMA) backbone carrying aliphatic side chains (C22). Two DMA-C22 copolymers were synthesized with various C22/DMA ratios: DMA-S at 0.175% and DMA-M at 0.35%. Different physicochemical properties of the polymers such as critical micellar concentration (CMC), water contact angle, electroosmosis were investigated. Coated COC chips were then tested for their ability to reduce the adsorption of proteins, microparticles, and for protein electrophoresis. For each application we found an optimal treatment protocol to considerably improve the performance of the thermoplastic chip. These treatments use physisorption in situ which requires no photografting or chemical reaction and can be performed by a simple incubation either after chip production, or just prior to use.

Aptamer-conjugated nanoparticles: preservation of targeting functionality demonstrated by microchip electrophoresis in frontal mode

Aptamer-conjugated nanoparticles (Apt-NPs) are increasingly being developed for biomedical purposes and especially for diagnosis and therapy. However, there is no quantitative study of the targeting functionality of such grafted aptamers compared with free aptamers. Thus, we report the first determination of binding parameters for Apt-NP/target complexes, thanks to a continuous frontal analysis in a microchip electrophoresis format (named FACMCE), based on a methodology previously developed by our group. As a model system, the targeting ability of a lysozyme-binding aptamer conjugated to fluorescent maghemite nanoparticles was evaluated and showed evidence that the conjugation does not alter the affinity of this aptamer.

Microchip integrating magnetic nanoparticles for allergy diagnosis

We report on the development of a simple and easy to use microchip dedicated to allergy diagnosis. This microchip combines both the advantages of homogeneous immunoassays i.e. species diffusion and heterogeneous immunoassays i.e. easy separation and preconcentration steps. In vitro allergy diagnosis is based on specific Immunoglobulin E (IgE) quantitation, in that way we have developed and integrated magnetic core-shell nanoparticles (MCSNPs) as an IgE capture nanoplatform in a microdevice taking benefit from both their magnetic and colloidal properties. Integrating such immunosupport allows to perform the target analyte (IgE) capture in the colloidal phase thus increasing the analyte capture kinetics since both immunological partners are diffusing during the immune reaction. This colloidal approach improves 1000 times the analyte capture kinetics compared to conventional methods. Moreover, based on the MCSNPs' magnetic properties and on the magnetic chamber we have previously developed the MCSNPs and therefore the target can be confined and preconcentrated within the microdevice prior to the detection step. The MCSNPs preconcentration factor achieved was about 35,000 and allows to reach high sensitivity thus avoiding catalytic amplification during the detection step. The developed microchip offers many advantages: the analytical procedure was fully integrated on-chip, analyses were performed in short assay time (20 min), the sample and reagents consumption was reduced to few microlitres (5 μL) while a low limit of detection can be achieved (about 1 ng mL(-1)).

Magnetic core shell nanoparticles trapping in a microdevice generating high magnetic gradient

Magnetic core shell nanoparticles (MCSNPs) 30 nm diameter with a magnetic weight of 10% are usually much too small to be trapped in microfluidic systems using classical external magnets. Here, a simple microchip for efficient MCSNPs trapping and release is presented. It comprises a bed of micrometric iron beads (6-8 μm diameter) packed in a microchannel against a physical restriction and presenting a low dead volume of 0.8 nL. These beads of high magnetic permeability are used to focus magnetic field lines from an external permanent magnet and generate local high magnetic gradients. The nanoparticles magnetic trap has been characterised both by numerical simulations and fluorescent MCSNPs imaging. Numerical simulations have been performed to map both the magnetic flux density and the magnetic force, and showed that MCSNPs are preferentially trapped at the iron bead magnetic poles where the magnetic force is increased by 3 orders of magnitude. The trapping efficiency was experimentally determined using fluorescent MCSNPs for different flow rates, different iron beads and permanent magnet positions. At a flow rate of 100 μL h(-1), the nanoparticles trapping/release can be achieved within 20 s with a preconcentration factor of 4000.

Micropillar array chips toward new immunodiagnosis

In this paper, we demonstrate the possibility to use a micropillar array to perform molecular immunodiagnosis. A polydimethylsiloxane (PDMS) microdevice consisting of a rectangular array of micropillars (45 µm in height, 100 × 100 µm square cross section) was used to replace microchannels or gels (polyacrylamide or agarose) to perform electrokinetic separation. This microarray was used to mimic highly diluted gel and to maintain electrolyte within the pillar zone by capillary effect. The electrolyte composition (glycerol and agarose content) was investigated in order to improve protein separation by isoelectric focusing (IEF). The influence of glycerol on focusing time and on the different evaporative contributions was further evaluated. In order to perform an immunodiagnostic of milk allergy, different surface treatments were optimized to prevent milk allergen adsorption on PDMS surface. Poly(dimethylacrylamide)-co-allyl glycidyl ether (PDMA-AGE) as well as gelatin led to a satisfactory signal to noise ratio. Finally the possibility to perform protein mixture separation using this micropillar array chip followed by immunoblotting was demonstrated by using the serum from an allergic individual, confirming the great potential of this analytical platform in the field of immunodiagnosis.

Comparison of different capillary isoelectric focusing methods--use of "narrow pH cuts" of carrier ampholytes as original tools to improve resolution

Two capillary isoelectric focusing (CIEF) systems have first been optimized: one uses a bare silica capillary and 30% (v/v) of glycerol in the separation medium while the other uses a coated capillary and an aqueous background electrolyte. To perform permanent capillary coating, two neutral polymers have been compared: hydroxypropylcellulose (HPC) and polyvinylalcohol (PVA). HPC coating gave best results for electroosmotic flow (EOF) limitation on a wide pH range: as compared to a bare silica capillary, it allowed to decrease EOF by 96% at pH 7.2 after acidic and basic treatments, whereas PVA coating lead only to a 76% decrease. The glycerol CIEF system was more satisfying for the separation of model proteins classically used as pI markers. Finally, the use of "narrow pH cuts" of carrier ampholytes added to commercial ampholyte mixtures allowed increasing resolution up to a factor 2.4 at a chosen pH for the separation of pI markers and milk proteins.

Transient isotachophoresis in carrier ampholyte-based capillary electrophoresis for protein analysis

Transient ITP (t-ITP) has been used in carrier ampholyte-based CE (CABCE) to enhance the sensitivity of protein analysis. The characteristics of carrier ampholytes (CAs) narrow pH cuts-based buffers, when used as BGEs in CE are compatible with t-ITP requirements. Indeed, being the sole buffering species of such solutions, CAs impose a pH close to their pI. Thus, in these solutions, the CAs possess low electrophoretic mobility. As a consequence, by adding an ionic component with high electrophoretic mobility either in the studied sample or in the BGE, a t-ITP step can be generated. This has first been demonstrated for protein test mixtures. Then, the combination of t-ITP with CABCE has been applied to study a real sample, the bovine milk.

Protein tryptic digests analyzed by carrier ampholyte-based capillary electrophoresis coupled to ESI-MS

In this study, narrow pH cuts of carrier ampholytes have been used as buffers in CE for the analysis of protein tryptic digests. Their low conductivity allows very efficient separations under high electric field strength without inducing any significant Joule heating. In this study, the capabilities of narrow pH cuts of carrier ampholytes for the separation of protein tryptic digests have been assessed. Three proteins of different molecular masses have been studied: cytochrome C (horse heart), beta-lactoglobulin B (bovine) and human transferrin. Efficient, rapid and repeatable separations of the peptides resulting from the tryptic digestion have been achieved in this buffer. Moreover, the feasibility of the coupling of carrier ampholyte-based capillary electrophoresis with ESI-MS has been demonstrated through the study of the cytochrome C tryptic digest.

Loading capacity of carrier ampholytes – based buffers in capillary electrophoresis

Narrow pH cuts of carrier ampholytes (CAs), originally designed for IEF, have been used as BGEs in CE. Their physicochemical properties, rather high buffering capacity and low conductivity, allow very efficient protein separations under high electric field strength. Due to their isoelectric properties, CA BGEs are expected to present a low ionic concentration and consequently a low loading capacity. In this study, we developed a simple method that allows the estimation of the loading capacity of a UV-absorbing BGE by CE. We first characterized in terms of loading capacity, classical ammediol-chromate UV-absorbing BGEs and a 10 mM histidine solution, a classical isoelectric buffer. Then, the loading capacity of four different CA-based BGEs has been assessed. Experimental results have shown that the CA-based buffers were presenting a rather high loading capacity, comparable to classical buffer ones and far higher than the one of the 10 mM histidine solution.

Selection of two reliable parameters to evaluate the impact of the mobile-phase composition on capillary electrochromatography performance with monolithic and particle-packed capillary columns

Different models have been described in the literature to evaluate the total porosity of CEC columns: gravimetric, flow as well as conductivity-based methods. In this study, these models have been compared for two kinds of CEC columns: two mixed-mode silica particle stationary phases and different monolithic columns (acrylate or polystyrene divinylbenzene-based). The total porosities measured from the conductivity-based methods were lower than the total column porosities obtained by gravimetric or flow methods for all the investigated columns while the wide distribution of observed values shows that conductivity-based methods discriminate columns more efficiently with very different properties. We propose a conductivity-based method taking into account the actual length proposed by Horvath, to evaluate what we call an "actual electrokinetic" porosity (AEP). This parameter, based on electrokinetic theory only, affords the most consistent evaluation of porosity under experimental CEC conditions for the packed- and acrylate-based monolithic columns. To illustrate the potential of AEP and actual EOF for the estimation of the performances of a CEC system (stationary and mobile phases) we studied the influence of the mobile-phase composition on these parameters for CEC separations with an ammonium embedded packed stationary phase. The AEP and the actual electroosmotic mobility should allow a better understanding of the perfusive EOF and stationary-phase wettability. For neutral compounds (substituted phenols), AEP evaluation allowed us to predict the mobile-phase conditions able to enhance the efficiency while both AEP and actual EOF had to be considered in the case of peptide analysis.

Carrier ampholytes-based capillary electrophoresis as an alternative to capillary zone electrophoresis in classical background electrolytes

Carrier ampholytes (CAs), originally designed for isoelectric focusing (IEF), have been used as background electrolytes (BGE) in capillary zone electrophoresis (CZE). Their main electrophoretic properties, relatively high buffering capacity and low electric conductivity allowed fast (less than 2 min) and high efficient (500,000 theoretical plates/m) separation of a test mixture of proteins under very high electric field strength (more than 1000 V/cm). The results obtained in such buffers have been compared to those obtained in more classical sodium--phosphate and sodium--N-(2-hydroxyethyl)piperazine-N'-(2-ethanesulfonate) background electrolytes. High ionic strength classical buffers were necessary to achieve the separation of the proteins contained in the test mixture. This induced a significant Joule heating and temperature increase inside the capillary whereas a negligible Joule heat was produced in carrier ampholyte buffers even at the above electric field strength (higher than 1000 V/cm).

In-capillary non-covalent labeling of insulin and one gastrointestinal peptide for their analyses by capillary electrophoresis with laser-induced fluorescence detection

The potential of the commercially available dye sypro orange for in-capillary derivatization was evaluated for the detection of insulin and one gastrointestinal peptide (Arg-Arg-gastrin) by capillary electrophoresis with laser induced fluorescence (CE-LIF). The fluorescent emission intensity (lambda(ex) = 488 nm, lambda(em) = 610 nm) of this probe is very low in aqueous medium, and increases strongly in less polar solvent, e.g. methanol. The hydrophobic character of the two analyzed peptides is too low to induce sufficient interaction with the fluorescent probe for good sensitivity when the latter is alone in the background electrolyte. Thus, the potential of several neutral, zwitterionic, cationic and anionic surfactants to favor probe/peptide interactions has been evaluated. It was demonstrated that a borate buffer (pH 8.5) containing tetradecyltrimethylammonium bromide (TTAB) in sub-micellar conditions can be considered as the most suitable buffer for insulin CE-LIF analysis. In addition, the method showed a good linearity between insulin concentration and the peak area of the labeled insulin, allowing quantitative measurements. The sensitivity achieved so far is comparable with that achieved with UV absorption detection, but even at this level it is interesting for microchip analysis, in which fluorescence detection is much more commonly available than UV absorption detection.

Evaluation of capillary isoelectric focusing in glycerol-water media with a view to hydrophobic protein applications

Capillary isoelectric focusing (CIEF) separations are usually performed with neutral coated fused-silica capillaries in aqueous anticonvective media. Glycerol, a very viscous solvent (eta = 945 mPa x s at 25 degrees C), known to help stabilize any kind of proteins and solubilize hydrophobic ones, was tested as an alternative to using commercial gels. Viscosity and electroosmotic mobility were measured as a function of gel or glycerol content in water, and a 30:70 v/v glycerol-water medium appeared as a good compromise for performing CIEF in a bare fused-silica capillary without imposing too high a viscosity. To demonstrate the feasibility of this new CIEF system, a standard mixture of nine model proteins was separated according to their pI with a good agreement between experimental and literature aqueous pIs. Moreover, better resolution was achieved with this system than with the conventional aqueous CIEF system, as two of the model proteins could not be separated in the latter system. Glycerol-water CIEF in bare silica capillary was next applied to the separation of horse radish peroxidase, a complex mixture of protein isoforms. The good concordance with the separation obtained by the conventional CIEF system indicated the adequacy of this new system. Finally, as anticipated from the results obtained for the separation of bacteriorhodopsin, a membrane protein, glycerol-water CIEF performed in bare silica capillary appears to be a promising alternative to conventional aqueous CIEF for hydrophobic protein characterization, under their native form.

Capillary electrophoresis of inorganic anions in hydro-organic media

The capillary electrophoresis separation of four inorganic anions (NO3-, I-, Br- and SCN-) was investigated over the whole range of methanol-water mixture composition. As the separation selectivity was strongly dependent on the solvent composition, the influence of ion-pairing and solvation phenomena was examined in depth in an attempt to explain this modification. First, a series of experiments was performed in methanolic background electrolytes, with counter-ions of different size. Ion-pair formation involving electrolyte ions was assessed to allow for a correction for free electrolyte ion concentration. Ion-pair formation constants between each inorganic anion and electrolyte counter-ion were next determined from the variations of the anion mobility as a function of the free counter-ion concentration. In view of the low values obtained, ion-pair formation alone failed to explain the selectivity variations. Solvation phenomena were then investigated with the help of a theoretical quantum model, the density functional theory (DFT), coupled with a polarizable continuum model to mime non-specific solvent effects. Whereas this model proved successful at predicting the mobility order at infinite dilution in water, it failed to predict the correct order in methanol.

Interaction of fucoidan with the proteins of the complement classical pathway

Fucoidan inhibits complement by mechanisms that so far remain to be unraveled, and the objective of this work was to delineate the mode of inhibition by this sulfated polysaccharide. For that purpose, low molecular weight fractions of algal (Ascophyllum nodosum) fucoidan containing the disaccharide unit [-->3)-alpha-L-Fuc(2SO3(-))-(1-->4)-alpha-L-Fuc(2,3diSO3(-))-(1-->](n) have been studied. Gel co-affinity electrophoresis and a new affinity capillary electrophoresis (ACE) method have been implemented to characterize fucoidan-complement protein complexes. Fucoidan binds C1q, likely to its collagen-like region through interactions involving lysine residues, and then prevents the association of the C1r(2)-C1s(2) subunit, required to form the fully active C1. In addition to C1q, fucoidan forms a complex with the protein C4 as observed by ACE. The fucoidan inhibits the first steps of the classical pathway activation that is of relevance in view of the proinflammatory effects of the subsequent products of the cascade. This study shows that a high level of inhibitory activity can be achieved with low molecular weight carbohydrate molecules and that the potential applicability of fucoidan oligosaccharides for therapeutic complement inhibition is worthy of consideration.

Influence of electrolyte nature on the separation selectivity of amphetamines in nonaqueous capillary electrophoresis: protonation degree versus ion pairing effects

The simultaneous analysis of Ecstasy and its derivatives in an acetonitrile-methanol (80:20 v/v) mixture was previously shown to be strongly dependent on the nature of the electrolyte (acetate versus formate). To elucidate the phenomena involved, systematic experiments were conducted in this solvent medium. Conductivity measurements allowed to evaluate the ion-pairing rate in the background electrolyte (BGE) and thereby distinguish between electrolyte concentration and ionic strength. The influence of electrolyte concentration on analyte effective mobilities micro(eff)) was studied by capillary electrophoresis (CE). As micro(eff) extrapolated to infinite dilution proved to be independent of the nature of the electrolyte, selectivity changes could not be attributed to a modification in the protonation degree of amphetamines. Experimental mobility data were then confronted to existing theoretical mobility models to discriminate between ion pairing or simple ionic strength effect. Ion-pair formation in a BGE containing acetate was highlighted with an ion-pairing model and ion-pair formation constants between each amphetamine and acetate ion were calculated.

Non-aqueous capillary electrophoresis of the positional isomers of a sulfated monosaccharide

A non-aqueous capillary electrophoresis (NACE) method coupled to indirect absorbance detection has been developed for the separation of the three positional isomers of monosulfated fucose. The optimized electrolyte was composed of 12 mM ethanolamine, 2 mM trimesic acid buffer in a methanol-ethanol (1:1, v/v) mixture. As the retained electrolyte entails no separating agent other than the pH buffer, the NACE separation of the positional isomers has been ascribed mainly to selective ion-pairing with the electrolyte counter-ion and the possibility of a selective solvation effect in the alcohol mixture. In the absence of pure isomeric standards, peak identification was completed by MS and NMR spectroscopy and selective enzymatic desulfation. This method should be of interest for the structure elucidation of monosulfated fucose-based polysaccharides and for the screening of sulfoesterase of unknown activity.