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A new concept of immunosensing plateform for senstitive detection of biomarkers
Claire Smadja, Associate Professor, University Paris Sud
We propose a new concept of ultra-sensitive and very specific immunosensing platform dedicated to the quantification of potential biomarker of Alzheimer disease (AD) in biological fluids. High Sensitivity is required for the earliness of AD diagnostic. Accordingly, a controlled and adaptative surface functionalization of a silicon wafer with carboxylated alkyltrichlorosilane has been performed. The surface has been characterized by AFM and XPS. The survey spectrum of silicon surface, performed by XPS, after, 1, 3, 6, 12 and 24h of silanisation , highlights a significant increase in the functionalization efficiency upon time. The oxidation reaction, has been also investigated by XPS and showed components related to the carboxylic group. AFM measurements showed a surface enhancement consistent with a homogenous development of the carboxylic group on the surface. In the second part of our work, we evaluated the biological activity of the grafted antibodies involved in (AD) biomarker detection onto this silanized surface by fluorescent microscopy. A sandwich immunoassay dedicated to the sensitive detection of a biomarker of Alzheimer disease (AD), A? 1-42, was carried out. The fluorescent signal corresponded perfectly to the level of A? 1-42 tested in our experimental conditions relying on a strategy analogous to the gold standard technic such as Enzyme Linked ImmunoSorbent Assays (ELISA). Although the sandwich immunoassay relies on a quite complex experiment, these results demonstrates that the controlled silanized surface provides a novel and viable way to determine biomarkers with high sensitivity and specificity and open the route to an original development of immunosensing applications on such surfaces
Dielectrophoretic separation and concentration of pathogens in a blood sample
Emilie Bisceglia, PhD, CEA
Considering the vast range of analytical technologies that can be applied to microbiological characterization of clinical and environmental samples, sample preparation appears to be – more than ever – the critical bottleneck for the global performance and robustness of the next generations of diagnostic systems. Indeed, it is still a major challenge to directly isolate pathogens from a complex biological sample.
In the present study, a dielectrophoresis (DEP)- based method is investigated to separate micro-organisms from blood cell constituants. Under a highly non-uniform electric field obtained thanks to a specific electrodes design, conditions were found allowing red and white blood cells and pathogens to go through negative and positive DEP, respectively. The method is robust enough to isolate different species of bacteria (S. epidermidis (Gram +) and E. coli (Gram –)) and yeasts (C. albicans).
These experimental results will be correlated with the predictions of the theory, models and simulations, and the mechanisms of action and future use of this method for diagnostic systems will be discussed.
Integrated micro-Fluidic Pump Technology for LoC Application
Alexander Govyadinov, Senior Technologist, HP Inc. (former Hewlett-Packard)
The fundamental action of the low-cost high efficiency bubble driven inertial micro-fluidic pump is investigated computationally and experimentally. The pump has no moving parts and consists of a thermal resistor placed asymmetrically within a straight channel connecting two reservoirs. Using Computational Fluid Dynamics tools the pumping efficiency and the pump curves are calculated as functions of the channel geometry, location of the actuator, and fluid viscosity. A variety of microfluidic geometries with embedded inertial pumps have been fabricated and tested experimentally. The results of numerical modeling broadly agree with the experimental measurements. Potential applications of the small form-factor and easy-to-integrate inertial microfluidic pumps are discussed.
New microfluidic chip for the production of spherical gelled capsules for cell encapsulation
Prisca Dalle, Ph-Student, CEA/LETI
Implantation of Langerhans islet in alginate shell is an alternative for the treatment of diabetes type 1 [1,2]. Finding an adapted process for cell encapsulation is a challenge. The process must product spherical and monodisperse capsules in a limited time with a good reproducibility. Up to now conventional systems are mainly manual which induces batch disparities and do not provide repeatable clinical results.
This paper reports a novel microfluidic device coupling a production of alginate droplets in an oil flow with a flow focusing device [3,4] and a phase transfer module that automatically transfers the droplets in an aqueous phase [5]. This module allows a 100% extraction of monodiperse and spherical alginate droplets from the oil phase to a calcium gelling solution. The entire process is done at physiological pH without any surfactant. This novel microfluidic device is the first step towards a full automated and reproducible process for cell encapsulation.
High precision drilling strategy for the integration of electrochemical cells in Cyclic Olefin Copolymer microfluidic devices
Ait-Ali Imene, , INL
Among the different detection strategies, electrochemistry offers significant advantages when implemented in microfluidic devices. However, integration in total polymer microsystems can be challenging due to material compatibility and only few techniques have been reported. In the case of Cyclic Olefin Copolymer (COC), authors have shown successful integration using classical photolithography for metals , screen printing for carbone and drilling for PEDOT .
Here, an alternative strategy to integrate electrochemical cells composed of two and three electrodes into total COC polymeric microsystems will be presented. This strategy is based on the combination of hot-embossing and high precision drilling in order to precisely locate microdisc electrodes in the microchannel. The main advantage of this strategy is its versatility in terms of electrode materials and electrode functionalization. Indeed, this approach can use any conductive materials that can be produced in a cylinder shape and the surface functionalization can be carried out before electrode integration in microfluidic channels.
In this presentation, the strategy will be explained and the integration of Pt and Ag microdisc electrodes will be demonstrated. Moreover, Pt electrode functionnalization with iridium oxide for pH measurements will be shown. Results based on in-situ amperometric and potentiometric measurements will be presented.
Single cell analysis of surface proteins for cancer molecular diagnosis
Rajan Kumar, President, Genome Data Systems, Inc.
Gene expression patterns of cells in a tumor could be predictive of its future course. However, clinical samples provide only a small amount of material for analysis. Moreover, there are no suitable technologies for protein analysis of such samples. Currently practiced methods of immunocytology and flow cytometry are limited by their sensitivity and specificity for small numbers of cells. A microfluidic technology was developed to determine cell surface protein expression by imaging and analyzing the movement of cells as they flow over patches of cognate immobilized antibodies. Expression of interleukin 13 receptor alpha 2 (IL13R-alpha 2) on as few as 50 cells could be determined with 99% sensitivity and specificity in sorted populations of a breast cancer cell line. Cells were not labeled during analysis and could be collected subsequently for reanalysis. In a mixture of cells, the method was able to distinguish between IL13R-alpha 2 positive and Her2 (ErbB2) positive cells with 98% accuracy. Fine needle aspirate samples from mouse xenograft human breast cancer tumors were sufficient for determination of their IL13R-alpha 2 status with high accuracy. The described technology will have significant impact on monitoring of cancer patients using minimally invasive sampling such as fine needle aspirates.
Design-for-Manufacture Approaches in Microfluidic Product Development
Sebastiaan Garst, Production Manager, MiniFAB
Microfluidic-enabled devices need to be robust, reliable, cost-effective, and manufacturable in high volumes. However, as is common in emerging fields, the design rules are not yet well established and vary vendor to vendor. Conventional CAD approaches and assumptions based on the existing generic design rules do not necessarily lead to the best and cheapest microfluidic product development.
To achieve a successful product, many design functions must be integrated into a small number of manufacturing steps, with a focus on minimizing the number of parts and materials. The viable strategies for micro-manufacturing are more restricted compared to the macro world. Smart division of function between the disposable and the instrument can drive successful product development and manufacturing.
Deep understanding of these Design-for-Manufacture approaches unique to microfluidics enables successful product development and manufacturing transfer.
Protein binding and non-binding surfaces on biochips
Olya Savvina, Customer and Marketing Support, Anteo Diagnostics Ltd
Design requirements for miniaturized and/or multiplexed assay systems require stringent device fabrication where materials such as silicon wafers, splutter coated metal oxides, ceramics and/or high-performance thermoplastics are used. Regardless whether the biochip is array- or microfluidics-based, its performance is critically dependent on certain regions having protein binding capability while other regions require the opposite. Many surface modification approaches have been developed many of which involve multi-step processing and are applicable to only a subset of materials and surfaces.
To simplify surface fabrication of such devices, metal polymer solutions call Mix&GoTM were developed. Metal ions in polymeric form are able to interact with any material having electron donating potential. In isolation, each metal chelation point is not strong enough to anchor a biomolecule but the avidity benefits of the polymeric construct changes almost any surface into one that gently but strongly binds proteins. The resulting benefits are improved assay sensitivity, broader dynamic range, better reproducibility and simpler manufacturing. Applying PEGlated blockers with particular binding “motifs” that interact with Mix&Go turns these blocked regions into non-binding surfaces. As such, Mix&Go represents a “one size fits all” surface chemistry approach in situations where maintaining protein function simplicity and are key requirements.
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