Author
Richard B.M. Schasfoort
Other affiliations: MESA+ Institute for Nanotechnology, Radboud University Nijmegen
Bio: Richard B.M. Schasfoort is an academic researcher from University of Twente. The author has contributed to research in topics: Surface plasmon resonance & Analyte. The author has an hindex of 19, co-authored 58 publications receiving 3864 citations. Previous affiliations of Richard B.M. Schasfoort include MESA+ Institute for Nanotechnology & Radboud University Nijmegen.
Papers published on a yearly basis
Papers
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TL;DR: Genetic deletion of Lgr4/5 in mouse intestinal crypt cultures phenocopies withdrawal of Rspo1 and can be rescued by Wnt pathway activation, which will guide future studies towards the application of R-spondins for regenerative purposes of tissues expressing Lgr5 homologues.
Abstract: The adult stem cell marker Lgr5 and its relative Lgr4 are often co-expressed in Wnt-driven proliferative compartments. We find that conditional deletion of both genes in the mouse gut impairs Wnt target gene expression and results in the rapid demise of intestinal crypts, thus phenocopying Wnt pathway inhibition. Mass spectrometry demonstrates that Lgr4 and Lgr5 associate with the Frizzled/Lrp Wnt receptor complex. Each of the four R-spondins, secreted Wnt pathway agonists, can bind to Lgr4, -5 and -6. In HEK293 cells, RSPO1 enhances canonical WNT signals initiated by WNT3A. Removal of LGR4 does not affect WNT3A signalling, but abrogates the RSPO1-mediated signal enhancement, a phenomenon rescued by re-expression of LGR4, -5 or -6. Genetic deletion of Lgr4/5 in mouse intestinal crypt cultures phenocopies withdrawal of Rspo1 and can be rescued by Wnt pathway activation. Lgr5 homologues are facultative Wnt receptor components that mediate Wnt signal enhancement by soluble R-spondin proteins. These results will guide future studies towards the application of R-spondins for regenerative purposes of tissues expressing Lgr5 homologues.
1,133 citations
01 Jan 2008
TL;DR: This book describes the development ofKinetic Models Describing Biomolecular Interactions at Surfaces and the Benefits and Scope of Surface Plasmon Resonance-based Biosensors in Food Analysis.
Abstract: Chapter 1: Introduction to Surface Plasmon Resonance Chapter 2: Physics of Surface Plasmon Resonance Chapter 3: SPR Instrumentation Chapter 4: Kinetic Models Describing Biomolecular Interactions at Surfaces Chapter 5: Kinetic and Thermodynamic Analysis of Ligand-Receptor Interactions: SPR Applications in Drug Development Chapter 6: Surface Chemistry in SPR Technology Chapter 7: Measurement of the Analysis Cycle: Scanning SPR Microarray Imaging of Autoimmune Diseases Chapter 8: Advanced Methods for SPR Imaging Biosensing Chapter 9: Surface Plasmon Fluorescence Techniques for Bioaffinity Studies Chapter 10: SPR Imaging for Clinical Diagnostics Chapter 11: The Benefits and Scope of Surface Plasmon Resonance-based Biosensors in Food Analysis Chapter 12: Future Trends in SPR Technology
778 citations
TL;DR: A microdevice called a "flowFET," with functionality comparable to that of a field-effect transistor (FET) in microelectronics, has been realized and two flowFETs integrated with a channel junction have been used to generate opposite flows inside a single EOF-pumped channel, illustrating the potential of the flowFet as a controlling and switching element in microfluidic networks.
Abstract: The magnitude and direction of the electro-osmotic flow (EOF) inside a microfabricated fluid channel can be controlled by a perpendicular electric field of 1.5 megavolts per centimeter generated by a voltage of only 50 volts. A microdevice called a "flowFET," with functionality comparable to that of a field-effect transistor (FET) in microelectronics, has been realized. Two flowFETs integrated with a channel junction have been used to generate opposite flows inside a single EOF-pumped channel, thus illustrating the potential of the flowFET as a controlling and switching element in microfluidic networks.
533 citations
TL;DR: A critical overview is given on the present state and requirements of POC testing, on microTAS elements suited for implementation in futuremicroTAS devices for Poc testing and microTas systems for the determination of clinical parameters.
Abstract: A currently emerging approach enables more widespread monitoring of health parameters in disease prevention and biomarker monitoring. Miniaturisation provides the means for the production of small, fast and easy-to-operate devices for reduced-cost healthcare testing at the point-of-care (POC) or even for household use. A critical overview is given on the present state and requirements of POC testing, on µTAS elements suited for implementation in future µTAS devices for POC testing and µTAS systems for the determination of clinical parameters.
436 citations
TL;DR: The separation results shown indicate that similar separation quality with respect to conventional FFE systems, as defined by the resolution and peak capacity, can be achieved with μ‐FFE separations when applying much lower electrical voltages.
Abstract: Free-flow electrophoresis (FFE) separation methods have been developed and investigated for around 50 years and have been applied not only to many types of analytes for various biomedical applications, but also for the separation of inorganic and organic substances. Its continuous sample preparation and mild separation conditions make it also interesting for online monitoring and detection applications. Since 1994 several microfluidic, miniaturized FFE devices were developed and experimentally characterized. In contrast to their large-scale counterparts microfluidic FFE (m-FFE) devices offer new possibilities due to the very rapid separations within several seconds or below and the requirement for sample volumes in the microliter range. Eventually, these micro-FFE systems might find application in so-called lab-on-a-chip devices for real-time monitoring and separation applications. This review gives detailed information on the results so far published on m-FFE chips, comprising its four main modes, namely free-flow zone electrophoresis (FFZE), free-flow IEF (FFIEF), free-flow ITP (FFITP), and free-flow field-step electrophoresis (FFFSE). The principles of the different FFE modes and the basic underlying theory are given and discussed with special emphasis on miniaturization. Different designs as well as fabrication methods and applied materials are discussed and evaluated. Furthermore, the separation results shown indicate that similar separation quality with respect to conventional FFE systems, as defined by the resolution and peak capacity, can be achieved with micro-FFE separations when applying much lower electrical voltages. Furthermore, innovations still occur and several approaches for hyphenated, more integrated systems have been proposed so far, some of which are discussed here. This review is intended as an introduction and early compendium for research and development within this field.
172 citations
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TL;DR: An update of the core Wnt/β-catenin signaling pathway is provided, how its various components contribute to disease, and outstanding questions to be addressed in the future are discussed.
4,561 citations
TL;DR: An extension to the soft lithography paradigm, multilayersoft lithography, with which devices consisting of multiple layers may be fabricated from soft materials is described, to build active microfluidic systems containing on-off valves, switching valves, and pumps entirely out of elastomer.
Abstract: Soft lithography is an alternative to silicon-based micromachining that uses replica molding of nontraditional elastomeric materials to fabricate stamps and microfluidic channels. We describe here an extension to the soft lithography paradigm, multilayer soft lithography, with which devices consisting of multiple layers may be fabricated from soft materials. We used this technique to build active microfluidic systems containing on-off valves, switching valves, and pumps entirely out of elastomer. The softness of these materials allows the device areas to be reduced by more than two orders of magnitude compared with silicon-based devices. The other advantages of soft lithography, such as rapid prototyping, ease of fabrication, and biocompatibility, are retained.
4,218 citations
TL;DR: A review of the physics of small volumes (nanoliters) of fluids is presented, as parametrized by a series of dimensionless numbers expressing the relative importance of various physical phenomena as mentioned in this paper.
Abstract: Microfabricated integrated circuits revolutionized computation by vastly reducing the space, labor, and time required for calculations. Microfluidic systems hold similar promise for the large-scale automation of chemistry and biology, suggesting the possibility of numerous experiments performed rapidly and in parallel, while consuming little reagent. While it is too early to tell whether such a vision will be realized, significant progress has been achieved, and various applications of significant scientific and practical interest have been developed. Here a review of the physics of small volumes (nanoliters) of fluids is presented, as parametrized by a series of dimensionless numbers expressing the relative importance of various physical phenomena. Specifically, this review explores the Reynolds number Re, addressing inertial effects; the Peclet number Pe, which concerns convective and diffusive transport; the capillary number Ca expressing the importance of interfacial tension; the Deborah, Weissenberg, and elasticity numbers De, Wi, and El, describing elastic effects due to deformable microstructural elements like polymers; the Grashof and Rayleigh numbers Gr and Ra, describing density-driven flows; and the Knudsen number, describing the importance of noncontinuum molecular effects. Furthermore, the long-range nature of viscous flows and the small device dimensions inherent in microfluidics mean that the influence of boundaries is typically significant. A variety of strategies have been developed to manipulate fluids by exploiting boundary effects; among these are electrokinetic effects, acoustic streaming, and fluid-structure interactions. The goal is to describe the physics behind the rich variety of fluid phenomena occurring on the nanoliter scale using simple scaling arguments, with the hopes of developing an intuitive sense for this occasionally counterintuitive world.
4,044 citations
TL;DR: This work presents a meta-analysis of the literature on food quality and safety analysis and its applications in the context of veterinary drugs and drugs and drug-Induced Antibodies, which focuses on the role of canine coronavirus in the veterinary industry.
Abstract: 5.1. Detection Formats 475 5.2. Food Quality and Safety Analysis 477 5.2.1. Pathogens 477 5.2.2. Toxins 479 5.2.3. Veterinary Drugs 479 5.2.4. Vitamins 480 5.2.5. Hormones 480 5.2.6. Diagnostic Antibodies 480 5.2.7. Allergens 481 5.2.8. Proteins 481 5.2.9. Chemical Contaminants 481 5.3. Medical Diagnostics 481 5.3.1. Cancer Markers 481 5.3.2. Antibodies against Viral Pathogens 482 5.3.3. Drugs and Drug-Induced Antibodies 483 5.3.4. Hormones 483 5.3.5. Allergy Markers 483 5.3.6. Heart Attack Markers 484 5.3.7. Other Molecular Biomarkers 484 5.4. Environmental Monitoring 484 5.4.1. Pesticides 484 5.4.2. 2,4,6-Trinitrotoluene (TNT) 485 5.4.3. Aromatic Hydrocarbons 485 5.4.4. Heavy Metals 485 5.4.5. Phenols 485 5.4.6. Polychlorinated Biphenyls 487 5.4.7. Dioxins 487 5.5. Summary 488 6. Conclusions 489 7. Abbreviations 489 8. Acknowledgment 489 9. References 489
3,698 citations
TL;DR: An overview of flows in microdevices with focus on electrokinetics, mixing and dispersion, and multiphase flows is provided, highlighting topics important for the description of the fluid dynamics: driving forces, geometry, and the chemical characteristics of surfaces.
Abstract: Microfluidic devices for manipulating fluids are widespread and finding uses in many scientific and industrial contexts. Their design often requires unusual geometries and the interplay of multiple physical effects such as pressure gradients, electrokinetics, and capillarity. These circumstances lead to interesting variants of well-studied fluid dynamical problems and some new fluid responses. We provide an overview of flows in microdevices with focus on electrokinetics, mixing and dispersion, and multiphase flows. We highlight topics important for the description of the fluid dynamics: driving forces, geometry, and the chemical characteristics of surfaces.
3,307 citations