Microfabricated curtains for controlled cell seeding in high throughput microfluidic systems

On-chip sample preparation for complete blood count from raw blood

This paper describes a monolithic microfluidic device capable of on-chip sample preparation for both RBC and WBC measurements from whole blood. For the first time, on-chip sample processing (e.g. dilution, lysis, and filtration) and downstream single cell measurement were fully integrated to enable sample preparation and single cell analysis from whole blood on a single device. The device consists of two parallel sub-systems that perform sample processing and electrical measurements for measuring RBC and WBC parameters. The system provides a modular environment capable of handling solutions of various viscosities by adjusting the length of channels and precisely controlling mixing ratios, and features a new 'offset' filter configuration for increased duration of device operation. RBC concentration, mean corpuscular volume (MCV), cell distribution width, WBC concentration and differential are determined by electrical impedance measurement. Experimental characterization of over 100,000 cells from 10 patient blood samples validated the system's capability for performing on-chip raw blood processing and measurement.

A microfluidic localized, multiple cell culture array using vacuum actuated cell seeding: integrated anticancer drug testing

In this study, we introduced a novel and convenient approach to culture multiple cells in localized arrays of microfluidic chambers using one-step vacuum actuation. In one device, we integrated 8 individually addressable regions of culture chambers, each only requiring one simple vacuum operation to seed cell lines. Four cell lines were seeded in designated regions in one device via sequential injection with high purity (99.9 %-100 %) and cultured for long-term. The on-chip simultaneous culture of HuT 78, Ramos, PC-3 and C166-GFP cells for 48 h was demonstrated with viabilities of 92 %+/-2 %, 94 %+/-4 %, 96 %+/-2 % and 97 %+/-2 %, respectively. The longest culture period for C166-GFP cells in this study was 168 h with a viability of 96 %+/-10 %. Cell proliferation in each individual side channel can be tracked. Mass transport between the main channel and side channels was achieved through diffusion and studied using fluorescein solution. The main advantage of this device is the capability to perform multiple cell-based assays on the same device for better comparative studies. After treating cells with staurosporine or anti-human CD95 for 16 h, the apoptotic cell percentage of HuT 78, CCRF-CEM, PC-3 and Ramos cells were 36 %+/-3 %, 24 %+/-4 %, 12 %+/-2 %, 18 %+/-4 % for staurosporine, and 63 %+/-2 %, 45 %+/-1 %, 3 %+/-3 %, 27 %+/-12 % for anti-human CD95, respectively. With the advantages of enhanced integration, ease of use and fabrication, and flexibility, this device will be suitable for long-term multiple cell monitoring and cell based assays.

Cell-based dose responses from open-well microchambers

Cell-based assays play a critical role in discovery of new drugs and facilitating research in cancer, immunology, and stem cells. Conventionally, they are performed in Petri dishes, tubes, or well plates, using milliliters of reagents and thousands of cells to obtain one data point. Here, we are introducing a new platform to realize cell-based assay capable of increased throughput and greater sensitivity with a limited number of cells. We integrated an array of open-well microchambers into a gradient generation system. Consequently, cell-based dose responses were examined with a single device. We measured IC50 values of three cytotoxic chemicals, Triton X-100, H2O2, and cadmium chloride, as model compounds. The present system is highly suitable for the discovery of new drugs and studying the effect of chemicals on cell viability or mortality with limited samples and cells.

Design of pressure-driven microfluidic networks using electric circuit analogy

This article reviews the application of electric circuit methods for the analysis of pressure-driven microfluidic networks with an emphasis on concentration- and flow-dependent systems. The application of circuit methods to microfluidics is based on the analogous behaviour of hydraulic and electric circuits with correlations of pressure to voltage, volumetric flow rate to current, and hydraulic to electric resistance. Circuit analysis enables rapid predictions of pressure-driven laminar flow in microchannels and is very useful for designing complex microfluidic networks in advance of fabrication. This article provides a comprehensive overview of the physics of pressure-driven laminar flow, the formal analogy between electric and hydraulic circuits, applications of circuit theory to microfluidic network-based devices, recent development and applications of concentration- and flow-dependent microfluidic networks, and promising future applications. The lab-on-a-chip (LOC) and microfluidics community will gain insightful ideas and practical design strategies for developing unique microfluidic network-based devices to address a broad range of biological, chemical, pharmaceutical, and other scientific and technical challenges.

Microfluidic transendothelial electrical resistance measurement device that enables blood flow and postgrowth experiments

Transendothelial electronic resistance (TEER) measurements are performed across a cell layer immobilized on a microfluidic device that also enables the cell layer to interact with a flowing stream of red blood cells (RBCs). A bipolar pulsed square wave potential is applied across a monolayer of bovine pulmonary artery endothelial cells, and the resulting current response is measured and integrated. The overall impedance of the cell layer provides an indicator of cell layer integrity. After cell seeding on the device, a decrease in TEER signal from 22.3 ± 1.6 μC to 3.5 ± 0.4 μC (corresponding to a resistance of 40.9 ± 2.9 Ω·cm(2) to 259.1 ± 27.4 Ω·cm(2)) was observed after 8 h of cell growth. Intracellular nitric oxide (NO) production by the immobilized endothelial cells that had reached confluence was 34% higher than those cells that had not reached confluence, as indicated by the integrated TEER system. Importantly, this NO production by the confluent endothelium was stimulated by ATP released from RBCs flowing under the endothelial cells. In this construct, the described microfluidic device enables both a TEER-based evaluation of cell layer integrity and molecularly communicated interactions of these cells with a flowing stream of blood components.

Fundamentals of microfluidic cell culture in controlled microenvironments

Microfluidics has the potential to revolutionize the way we approach cell biology research. The dimensions of microfluidic channels are well suited to the physical scale of biological cells, and the many advantages of microfluidics make it an attractive platform for new techniques in biology. One of the key benefits of microfluidics for basic biology is the ability to control parameters of the cell microenvironment at relevant length and time scales. Considerable progress has been made in the design and use of novel microfluidic devices for culturing cells and for subsequent treatment and analysis. With the recent pace of scientific discovery, it is becoming increasingly important to evaluate existing tools and techniques, and to synthesize fundamental concepts that would further improve the efficiency of biological research at the microscale. This tutorial review integrates fundamental principles from cell biology and local microenvironments with cell culture techniques and concepts in microfluidics. Culturing cells in microscale environments requires knowledge of multiple disciplines including physics, biochemistry, and engineering. We discuss basic concepts related to the physical and biochemical microenvironments of the cell, physicochemical properties of that microenvironment, cell culture techniques, and practical knowledge of microfluidic device design and operation. We also discuss the most recent advances in microfluidic cell culture and their implications on the future of the field. The goal is to guide new and interested researchers to the important areas and challenges facing the scientific community as we strive toward full integration of microfluidics with biology.