Current Seminars (2015-2016)

The Seminar Series begin at 12:30pm unless otherwise specified. Food will be served before the seminars. Financial support for the seminars was kindly provided by the Rackham Graduate School.

April 6, 2015

Optofluidic Lasers on Chip

12:30-1:30pm | 1200 EECS

Dr. Rong Fan

A major challenge in tissue engineered organ transplantation is revascularization. How to fabricate a perfusable microvascular network in neotissues to support the tissue growth in vivo is crucial. We are working to tackle this problem by developing a two-step approach for synthesizing neotissues with perfusable microvasculature. First we use a microfluidic system to create a large-scale endothelialized microvessels that can be retrieved to form a free-standing microvascular network. Second, this microvascular network is used as a template to seed perivascular and tissue specific cells to grow neotissues. This modular approach is generic and versatile for the potential application to a range of functional tissues including liver, bone, and pancreatic tissues.

March 23, 2015

Microfluidic Reduction of Osmotic Stress in Oocyte and Zygote Vitrification

12:30-1:30pm | 1180 Duderstadt

David Lai

The successful cryopreservation of embryos and oocytes has significantly expanded the scope of infertility treatment but one of the major concerns is the osmotic stress due to the high amounts of cryoprotectant agents (CPAs) used. Modern cryopreservation, through the use of equilibration steps and advanced vitrification solutions, have largely overcome challenges of cryosurvival. However, it is unclear how the rate of cell shrinkage may affect cryosurvival or sub-lethal damage. The cell membrane is thought to be a viscoelastic shell highly susceptible to strain rates, and the rate and extent of cell shrinkage and expansion can be accurately modelled using the Kedem-Katchalsky (K-K) equations. Using microfluidics to automate the vitrification CPA exposure as defined by the K-K equations, the automated microfluidics protocol decreased the shrinkage rate of the oocyte and zygote by 13.8 times over its manual-pipetting alternative while keeping the minimum cell volume constant. Oocytes and zygotes with lower shrinkage rate during CPA exposure experienced less osmotic stress resulting in better morphology, higher cell quality, and improved embryo development. The microfluidic procedure resulted in murine zygotes with little to no membrane buckling as quantified by a significantly smoother cell surface and more spherical cellular morphology. The membrane also sustained less damage as quantified by an increased cytoplasmic lipid retention in vitrified and warmed bovine oocytes, as well as an lower influx of extracellular material in CPA exposed murine zygotes. The microfluidic protocol described has immediate applications for improving the quality of animal and human oocyte, zygote, and embryo cryopreservation. On a fundamental level, the clear demonstration that at the same minimum cell volume, cell shrinkage rate affects sub-lethal damage should be broadly useful for cryobiology and helpful in guiding future improvements in cell, organoid, and tissue cryopreservation.

March 9, 2015

Computing with Microfluidics

11:30-12:30pm | The Johnson Room of Lurie Engineering

Elliot Hui

Microfluidics has endeavored to bring the advantages of integrated circuits to chemical and biological processes. However, system integration still falls far short of microelectronics, as on-chip pumps and valves typically require off-chip electronic and pneumatic components in order to function, thus increasing cost, complexity, and size. Pneumatic microfluidic valves are similar in many ways to electronic transistors, suggesting the possibility of constructing mechanical computers out of microfluidic circuits. Following this strategy, we have built a variety of digital logic systems, including a programmable finite state machine. These logic circuits can control networks of pumps and valves for liquid handling, allowing multistep laboratory procedures to be encoded into autonomous microfluidic networks. These devices contain no electronics and are powered simply by a static pressure differential. We envision that this technology will be attractive for laboratory automation and point-of-care medical applications.

February 23, 2015

Biocompatible oxygen microsensors for the interrogation of three dimensional tissues

12:30-1:30pm | 1006 Dow

Sasha Cai Lesher-Perez

Microenvironmental oxygen levels play an important role in regulating cellular behavior and function, dictating the mode of proliferation, metabolism, and cell interaction with each other and their environment. Advances and prevalence of in vitro generated three-dimensional (3D) cultures for modeling cellular/tissue processes, regenerative medicine/tissue engineering precursors and solutions, and drug discovery and development platforms requires parallel development of systems to monitor, and characterize these 3D tissue cultures. Currently there is a limited amount of sensors that can robustly measure both the external and internal oxygen measurements of these 3D in vitro tissues, in a real time, continuous format. We present our development of dispersible optical microsensors, compatible in a variety of tissue culture formats, which we use to measure oxygen in and around 3D in vitro tissue cultures. This talk will specifically: 1) describe flow-focusing generation of PDMS-microbeads which we further develop into oxygen sensing microbeads (microsensors); 2) highlight the benefit of using phase fluorimetry within 3D tissue imaging over the more common intensity-quenching oxygen measurements; 3) demonstrate the incorporation of these microsensors into a few culture platforms, and discussing the next foreseen applications of our distributable microsensors.

February 9, 2015

Comprehensive Single Cell Assay Chips for the Study of Cancer Metastasis and Heterogeneity

12:30-1:30pm | 1180 Duderstadt

Dr. Yu-Chih Chen

Due to the genomic and epigenetic instability of cancer cells, tumors are highly heterogeneous and difficult to treat. Additionally, cancer metastasis, which account for 90% of cancer mortality, is a complicated multi-step process. As such ideal assays should be high-throughput and provide single-cell resolution and microenvironmet control, enlightening individual cell properties rather than the average behavior of the bulk tumor. Here, we have developed microfluidic platforms meeting these requirements to investigate three critical stages of metastasis. First, a single-cell migration chip was developed to model cancer cell migration from the primary tumor. The motility of cells under the influence of chemo-attractants can be measured on-chip. After the assays, highly motile cells and non-motile cells can be retrieved for further culture and mRNA expression analysis. Second, to understand cell survival in the circulatory system, a single-cell suspension culture chip was developed, improving the throughput of single-cell anoikis assays and single-cell derived sphere formation by orders of magnitude utilizing hydrodynamic single cell positioning. Third, to investigate interactions between cancer cells and stromal cells, three cell-cell interaction platforms were developed. Innovations including control of interacting cell ratios, valveless isolation of co-culture using two-phase flow, continuous nutrient renewal enabled by 3D integration, and dual adherent-suspension co-culture were attained. In addition, a selective single-cell retrieval technique that selectively detaches and retrieves targeted single cells has been developed for incorporation in our microfluidic platforms. The technique neither affects cell viability nor alters mRNA expression for qRT-PCR. These single cell platforms provide numerous advantages over traditional methods including: (1) ability to monitor and track individual cells, (2) control of various micro-environments on-chip for emulation of bio-processes, (3) accommodation of high-throughput screening, (4) capability to handle rare cell samples, and (5) potential to retrieve interesting single cells for further culture and analysis.

January 26, 2015

A radial flow microfluidic device for high-throughput affinity-isolation of circulating tumor cells (CTCs)

12:30-1:30pm | 1180 Duderstadt

Vasudha Murlidhar

Circulating tumor cells (CTCs) are believed to be implicated in the spread of cancer, or metastasis. These cells offer a fluid biopsy for studying the tumor and can potentially provide useful insight into the process. However, they are extremely rare in the blood, causing their retrieval to be very challenging. Antibody-based or affinity isolation of CTCs, a commonly used method for CTC capture has been employed by many microfluidic technologies. However, many of these technologies are limited by low throughputs, typically in the range of 1-3ml/hr. Here we present a radial flow microfluidic device, the OncoBean Chip that can efficiently isolate CTCs at a flow rate of 10 ml/hr due to a varying shear profile across the device. Recoveries with cell lines yielded a mean efficiency >80% at this high throughput. We also show some applications of the OncoBean Chip in the study of CTCs from early lung cancer.

January 12, 2015

Label-free high throughput microfluidic device for the isolation of circulating tumor cells from breast cancer patients

12:30-1:30pm | 1180 Duderstadt

Eric Lin

A necessary step in distant metastasis is the hematogenous dissemination of cancer cells from the primary tumor site to remote sites. The presence of circulating tumor cells (CTCs) in the peripheral blood represents a strong and independent prognostic factor for decreased disease-free and overall survival in many solid malignancies. Immune-affinity based capture is the most commonly used method for the isolation of CTCs which utilizes antibodies to capture tumor cells expressing specific proteins. However, immune-affinity based approaches offer low throughput (~1mL/hr) and considerable cell loss (~20-40%) resulting from heterogeneous expression of biomarkers on CTCs. Various label-free approaches utilizing physical properties of CTCs have been developed to overcome the limitations of immune-affinity based isolation techniques, including micro-filters, microscale laminar vortices, inertial migration of particles, and integrated systems. Here we present an inertial microfluidic-based separation technique for high throughput and label-free isolation of CTCs that yields the highest throughput with high CTC recovery and high blood cell removal among all the label-free technologies.

December 4, 2014

Probing multicellular communication in the context of the tumor ecosystem

12:00-1:00pm | 1109 FXB

Dr. David Beebe

The role of cell-cell communication in many aspects of cancer (initiation, progression, resistance) is becoming increasingly apparent. We have developed a number of simple tools to improve our ability to manipulate and probe the nature of these multicellular interactions both in isolation and in the context of the tumor microenvironment. These include 2D and 3D compartmentalized culture platforms to explore paracrine signaling and matrix interactions as well as lumen-based organotypic models to understand structure/function relationships. In addition, we have developed tools to enable multianalyte extraction from small precious samples from patients. We are applying these tools to understand how cell-cell communication influences various aspects of cancer development in the context of the tumor ecosystem. Examples include the transition from DCIS to IDC in breast cancer, metastasis to bone in prostate cancer, angiogenesis in kidney cancer, hormone response in breast cancer and resistance to therapy in multiple myeloma.

November 10, 2014

Microdroplet-enabled co-cultivation and characterization of microbial communities

12:30-1:30pm | 1180 Duderstadt

Steven Chen

The majority of existing microbial species, in particular bacteria living in synergistic communities, have not been cultured in the laboratory. One important reason behind this “unculturability” is that conventional laboratory cultivation is aimed at pure cultures of individual species. We have developed a microfluidic device for highly parallel co-cultivation of symbiotic microbial communities in droplets and demonstrated its effectiveness in detecting synergistic interactions among microbes. In addition to cultivation, there is a need to identify specific species for high-throughput characterization of these synergistic communities through 16S rRNA analysis. Currently, we have utilized this technology to cultivate the human oral microbiome. Through a platform system, we isolated and cultivate select functional consortia within the oral microbiome. This is accomplished by using our droplet system in conjunction with the Bioflux® to cultivate and expand the selected communities. For further high-throughput characterization, we are developing the necessary technology to perform Fluorescence in-situ Hybridization (FISH) on device in droplets. To achieve this, we developed method by which to perform washing within droplets through the use of functionalized beads to bind bacteria. Then by utilizing porous barriers, we can exchange the droplet contents to perform the washing procedure. By combining this technology with other droplet manipulation techniques, various assays requiring washing can be performed in droplets.

October 27, 2014

Engineering a physiologically relevant human on a chip

12:30-1:30pm | 1180 Duderstadt

Joseph Labuz

A physiologically relevant human-on-a-chip would be a powerful tool for drug discovery and screening, disease modeling, and many other applications. Recent studies have been able to recapitulate critical functional and environmental characteristics of individual organs in miniaturized, engineered systems, but how to correctly scale networks of these organs-on-a-chip to form a functional human analog remains an open question. As shown by a series of simple blood-adipose tissue experiments, rational design of inter-organ scaling relationships is essential, yet current approaches are unable to address these concerns. Scaling by allometric principles is based on several assumptions that may not hold true in these microscale, in vitro systems. On the other hand, more rigorous approaches such as designing networks by mass and residence time require a priori knowledge of drug metabolism and relevant organs, making implementation of a generalized model challenging. Building from these paradigms, we propose a metabollically supported functional scaling concept centered around maintaining in vivo cellular metabolic rates on chip. Specifically, by limiting oxygen availability in vitro, we can force cells to assume a basal metabolic rate that more closely mimics that found in vivo. Further, by dividing organs into functionally 2D or functionally 3D classes and implementing various engineering workarounds, we propose avenues to overcome challenges associated with this novel scaling approach.

October 13, 2014

Continuous Isolation, Labeling and Collection of Pancreatic Cancer CTCs using an Integrated Microfluidic Device

12:30-1:30pm | 1180 Duderstadt

Rhonda Jack

Extensive studies involving genetic material of CTCs is expected to considerably develop this concept and thereupon to develop effective therapeutics that are tailored to meet each patient’s need. Several challenges need to be overcome in order to harness the wealth of information that can be gained from CTC studies such as the rarity of such cells among other blood cells, where CTCs occur as rarely as 1 to 1 million among other mononuclear blood cells. In this vein we discuss the use of an integrated, continuous microfluidic device designed to isolate and label CTCs disseminated from pancreatic cancer tumors on chip. The 3-part device exploits the use of inertial forcers to presort CTCs from whole blood a 1.2mL/min followed by passive on-chip mixing and incubation with EpCAM coated beads, and thereafter on-chip magnetic sorting of CTCs from any remaining blood cells. Cells were stained positively for DAPI and CK-19 as well as negatively with CD45. We demonstrate that the isolated CTCs are not only viable but that the rate of WBC decontamination is favorable for downstream RNA work. Based on PANC-1 cell-line experiments with the device, an 85% recovery rate of cancer cells from other blood cells was consistently achieved. Testing of metastatic patient samples with the device has yielded viable CTCs from patients at varying disease stages. With the achievement of such high counts of CTCs, coupled with high purity rates we propose that the use of this system in characterizing CTCs and studying cancer will in part contribute to understanding this aggressive disease in a non-invasive, efficient manner.

September 25, 2014

New Microanalytical Techniques for Studying Bacteria

12:30-1:30pm | 2150 Dow

Dr. Edgar Goluch

Bacteria exhibit remarkable abilities to organize and adapt themselves in dynamic environments; however, relatively few quantitative techniques exist for studying bacterial behavior. Their small size (sub-micrometer dimensions) and motility (up to several body lengths per second) presents exceptional challenges for bacterial cell analysis. These unique characteristics must be addressed in order to investigate the chemical and physical micro-environments that bacterial cells respond to and create.In this talk, I will present several bioanalytical tools that my group is developing and optimizing specifically for microbiological applications. We utilize micro/nano-fluidic devices to manipulate and isolate bacterial cells. Once the cells are positioned in the devices, we use surface plasmon resonance imaging (SPRi) to study biofilm formation and removal, and microfabricated electrochemical sensors to detect the production of toxins. These systems are quite versatile as they can be used to study microbial species in complex environments, with applications ranging from biophysics to point-of-care diagnostics to industrial processes.

September 15, 2014

Mesoscopic simulation methods for suspensions and polymers in microfluidic devices, with application to separations

12:30-1:30pm | 1180 Duderstadt

Dr. Ronald Larson

We use mesoscopic simuation methods, including Brownian Dynamics and Stochastic Rotation Dynamics simulations to demonstrate migration and separation mechanisms in microfluidics in geometries of size comparable to that of the object to be separated, such as a DNA polymer, or a biolotical cell. Besides simple size exclusion mechanisms, which include both sieving and volume bypass effects, three other migration mechanisms are explored. These are 1) deformation-hydrodynamic coupling, including wall-hydrodynamic interaction, which causes polymers to drift away from the wall towards the center of a straight channel; 2) depletion-convection coupling, in which depletion layers in thin channels are convected across wide side chambers, creating a one-sided diffusion barrier to polymers or colloids that leads to depletion from the entire side chamber, and 3) stream-curvature-induced migration, in which polymers traveling along curved streamlines migrate towards the center of curvature. We show how to use these methods to design optimal separations.