Simple add-on devices to enhance the efficacy of conventional surface immunoassays implemented on standard labware.

We propose microfluidic add-ons that can be easily added onto standard assay labware such as microwells and slides to enhance the kinetics of immunoassays. We design these monolithic devices having structures that leverage the pipetting step to deliver reagents with deterministic, uniform and strong advection close to the reaction surface. This flow-driven mass transport enhances the flux of analytes to the reaction site and reduces the depletion layer.

Engineering solutions for biological studies of flow-exposed endothelial cells on orbital shakers.

Shear stress is extremely important for endothelial cell (EC) function. The popularity of 6-well plates on orbital shakers to impose shear stress on ECs has increased among biologists due to their low cost and simplicity. One characteristic of such a platform is the heterogeneous flow profile within a well.

Rapid micro-immunohistochemistry.

We present a new and versatile implementation of rapid and localized immunohistochemical staining of tissue sections. Immunohistochemistry (IHC) comprises a sequence of specific biochemical reactions and allows the detection of specific proteins in tissue sections. For the rapid implementation of IHC, we fabricated horizontally oriented microfluidic probes (MFPs) with functionally designed apertures to enable square and circular footprints, which we employ to locally expose a tissue to time-optimized sequences of different biochemicals.

Advection-Enhanced Kinetics in Microtiter Plates for Improved Surface Assay Quantitation and Multiplexing Capabilities.

Surface assays such as ELISA are pervasive in clinics and research and predominantly standardized in microtiter plates (MTP). MTPs provide many advantages but are often detrimental to surface assay efficiency due to inherent mass transport limitations. Microscale flows can overcome these and largely improve assay kinetics.

Capillary Microfluidics for Monitoring Medication Adherence.

Medication adherence is a medical and societal issue worldwide, with approximately half of patients failing to adhere to prescribed treatments. The goal of this Minireview is to examine how recent work on microfluidics for point-of-care diagnostics may be used to enhance adherence to medication. It specifically focuses on capillary microfluidics since these devices are self-powered, easy to use, and well established for diagnostics and drug monitoring.

Transposing Lateral Flow Immunoassays to Capillary-Driven Microfluidics Using Self-Coalescence Modules and Capillary-Assembled Receptor Carriers.

Point-of-care (POC) immunodiagnostic tests play a crucial role in enabling rapid and correct diagnosis of diseases in prehospital care, emergency, and remote settings. In this work, we present a silicon-based, capillary-driven microfluidic chip integrating two microfluidic modules for the implementation of highly miniaturized immunoassays. Specifically, we apply state-of-the-art microfluidic technology to demonstrate a one-step immunoassay for the detection of the cardiac marker troponin I in human serum using sample volumes of ∼1 μL and with a limit of detection (LOD) of ∼4 ng mL within 25 min.

A bead-based immunogold-silver staining assay on capillary-driven microfluidics.

Point-of-care (POC) diagnostics are critically needed for the detection of infectious diseases, particularly in remote settings where accurate and appropriate diagnosis can save lives. However, it is difficult to implement immunoassays, and specifically immunoassays relying on signal amplification using silver staining, into POC diagnostic devices. Effective immobilization of antibodies in such devices is another challenge.

Capillary-Driven Microfluidic Chips for Miniaturized Immunoassays: Patterning Capture Antibodies Using Microcontact Printing and Dry-Film Resists.

The miniaturization of immunoassays using microfluidic devices is attractive for many applications, but an important challenge remains the patterning of capture antibodies (cAbs) on the surface of microfluidic structures. Here, we describe how to pattern cAbs on planar poly(dimethylsiloxane) (PDMS) stamps and how to microcontact print the cAbs on a dry-film resist (DFR). DFRs are new types of photoresists having excellent chemical resistance and good mechanical, adhesive, and optical properties.

Rapid Subtractive Patterning of Live Cell Layers with a Microfluidic Probe.

The microfluidic probe (MFP) facilitates performing local chemistry on biological substrates by confining nanoliter volumes of liquids. Using one particular implementation of the MFP, the hierarchical hydrodynamic flow confinement (hHFC), multiple liquids are simultaneously brought in contact with a substrate. Local chemical action and liquid shaping using the hHFC, is exploited to create cell patterns by locally lysing and removing cells.

Centimeter-Scale Surface Interactions Using Hydrodynamic Flow Confinements.

We present a device and method for selective chemical interactions with immersed substrates at the centimeter-scale. Our implementations enable both, sequential and simultaneous delivery of multiple reagents to a substrate, as well as the creation of gradients of reagents on surfaces. The method is based on localizing submicroliter volumes of liquids on an immersed surface with a microfluidic probe (MFP) using a principle termed hydrodynamic flow confinement (HFC).

Nanoshuttles propelled by motor proteins sequentially assemble molecular cargo in a microfluidic device.

Nanoshuttles powered by the molecular motor kinesin have the potential to capture and concentrate rare molecules from solution as well as to transport, sort and assemble them in a high-throughput manner. One long-thought-of goal has been the realisation of a molecular assembly line with nanoshuttles as workhorses. To harness them for this purpose might allow the community to engineer novel materials and nanodevices.

Hierarchical hydrodynamic flow confinement: efficient use and retrieval of chemicals for microscale chemistry on surfaces.

We devised, implemented, and tested a new concept for efficient local surface chemistry that we call hierarchical hydrodynamic flow confinement (hierarchical HFC). This concept leverages the hydrodynamic shaping of multiple layers of liquid to address challenges inherent to microscale surface chemistry, such as minimal dilution, economical consumption of reagent, and fast liquid switching. We illustrate two modes of hierarchical HFC, nested and pinched, by locally denaturing and recovering a 26 bp DNA with as little as 2% dilution and by efficiently patterning an antibody on a surface, with a 5 μm resolution and a 100-fold decrease of reagent consumption compared to microcontact printing.

Pharmacology on microfluidics: multimodal analysis for studying cell-cell interaction.

Understanding the mechanisms of cell-cell interaction is a key unanswered question in modern pharmacology, given crosstalk defects are at the basis of many pathologies. Microfluidics represents a valuable tool for analyzing intercellular communication mediated by transmission of soluble signals, as occurring for example between neurons and glial cells in neuroinflammation, or between tumor and surrounding cells in cancer. However, the use of microfluidics for studying cell behavior still encompasses many technical and biological challenges.

Flock-based microfluidics.

Flock-based microfluidics are created by depositing hydrophilic microfibers on an adhesive-coated substrate using an electric field. This enables the fabrication of self-powered microfluidics from one or more different kinds of fibers that form 2D and 3D flowpaths, which can wick 40 microliters of liquid per square centimeter. With this approach, large areas of functional wicking materials can be produced at extremely low cost.

Microfluidics in the "open space" for performing localized chemistry on biological interfaces.

Local interactions between (bio)chemicals and biological interfaces play an important role in fields ranging from surface patterning to cell toxicology. These interactions can be studied using microfluidic systems that operate in the "open space", that is, without the need for the sealed channels and chambers commonly used in microfluidics. This emerging class of techniques localizes chemical reactions on biological interfaces or specimens without imposing significant "constraints" on samples, such as encapsulation, pre-processing steps, or the need for scaffolds.

Overflow microfluidic networks: application to the biochemical analysis of brain cell interactions in complex neuroinflammatory scenarios.

Neuroinflammation plays a central role in neurodegenerative diseases and involves a large number of interactions between different brain cell types. Unraveling the complexity of cell-cell interaction in neuroinflammation is crucial for both clarifying the molecular mechanisms involved and increasing efficacy in drug development. Here, we provide a versatile analytical method for specifically addressing cell-to-cell communication, using primary brain cells, a microfluidic device, and a multiparametric readout approach.

Capillary soft valves for microfluidics.

Capillary-driven microfluidics are simple to use and provide the opportunity to perform fast biological assays with nanogram quantities of reagents and microliters of sample. Here we describe capillary soft valves (CSVs) as a simple-to-implement and -actuate approach for stopping liquids in capillary-driven microfluidics. CSVs are inserted between wettable microstructures and work to block liquids owing to a capillary pressure barrier of a few kPa.

Micro-immunohistochemistry using a microfluidic probe.

A flexible method to extract more high-quality information from tissue sections is critically needed for both drug discovery and clinical pathology. Here, we present micro-immunohistochemistry (μIHC), a method for staining tissue sections at the micrometre scale. Nanolitres of antibody solutions are confined over micrometre-sized areas of tissue sections using a vertical microfluidic probe (vMFP) for their incubation with primary antibodies, the key step in conventional IHC.

High-grade optical polydimethylsiloxane for microfluidic applications.

Commercially available polydimethylsiloxane (PDMS) elastomers, such as Sylgard 184® are widely used in soft lithography and for microfluidic applications. These PDMS elastomers contain fillers to enhance their mechanical stability. The reinforcing fillers, often sub-micrometer small SiO(2) particles, tend to aggregate, swell with water, and thereby become cognoscible in a way that can strongly interfere with the visualization of micro-scale events taking place next to PDMS structures.

Overflow microfluidic networks for open and closed cell cultures on chip.

Microfluidics have a huge potential in biomedical research, in particular for studying interactions among cell populations that are involved in complex diseases. Here, we present "overflow" microfluidic networks (oMFNs) for depositing, culturing, and studying cell populations, which are plated in a few microliters of cell suspensions in one or several open cell chambers inside the chip and subsequently cultured for several days in vitro (DIV). After the cells have developed their phenotype, the oMFN is closed with a lid bearing microfluidic connections.

A microfluidic device for depositing and addressing two cell populations with intercellular population communication capability.

We present a method for depositing cells in the microchambers of a sealed microfluidic device and establishing flow across the chambers independently and serially. The device comprises a transparent poly(dimethylsiloxane) (PDMS) microfluidic network (MFN) having 2 cell chambers with a volume of 0.49 microL, 6 microchannels for servicing the chambers, and 1 microchannel linking both chambers.

Controlled deposition of cells in sealed microfluidics using flow velocity boundaries.

We present a method for depositing cells in a sealed microfluidic device. The device consists of a poly(dimethylsiloxane) (PDMS) microfluidic network (MFN) sealed with a Si chip. The Si chip has vias and ports that are connected to high-precision motorized pumps.