Incorporating Antibody-Coated Microshuttles into a Biomolecular Motor-Driven Sensor Device

Jenna Campbell
Graduate Student
Meyhofer Lab
Mechanical Engineering

The demand for ultralow detection of specific biomarkers using small sample volumes is high in the fields of clinical diagnostics. Current detection methods used such as ELISA are limited by some threshold concentration that is often higher than what is necessary for diagnosis and require sample volumes of hundreds of microliters. More sensitive techniques such as surface plasmon resonance require expensive instrumentation while methods such as raman and mass spectroscopy lose specificity in complex, protein-rich samples. Here, we have developed a microfluidic device that collects and concentrates specific analytes in small 25µm x 25µm concentrator chambers. This concentrator device is driven by nano-scale biomolecular motors that drive antibody coated nano-shuttles into the concentrator region. Here, the shuttles are trapped and a fluorescent signal is read and directly correlates to the number of analytes captured.

Cell and Biomolecule Patterning with Aqueous Two-Phase Systems

Dr. John Frampton
Postdoctoral Research Fellow
Takayama Lab
Biomedical Engineering

Mixtures of two polymer solutions sometimes form two distinct liquid phases. Pairs of such polymers, known as aqueous two-phase systems, have been used for over 50 years by biologist and chemists to separate and purify biological materials such as cells, DNA and protein. More recently, ATPSs have emerged as powerful and easy to use tools for patterning cells and biomolecules for biomedical applications. This presentation will include a background of the unique properties of ATPSs that make them especially useful in the fields of microfluidics and tissue engineering. Applications including droplet microfluidics, stem cell culture and multiplexed immunoassays will be discussed.

Optofluidic Capillaries for bio-chemical applications

Dr. Yunbo Guo
Postdoctoral Research Fellow
Prof. Xudong Fan Group
Biomedical Engineering

Optofluidics organically integrates microfluidics and photonics and is an emerging technology in biological and chemical analysis. In this talk, I will overview the recent studies in bio-chemical sensing applications of optofluidics. Particularly, I will report the research progress in our lab in developing diverse optofluidic devices using two unique configurations: thin-walled capillary based optofluidic ring resonator (OFRR) and multi-hole capillary based optofluidic platforms. The first one has been developed to be OFRR-based label-free biosensor, microfluidic laser based intra-cavity sensors, and on-column optical detectors for micro-gas chromatography (μGC), while the second one has been developed to be optofluidic Fabry-Pérot based label-free biosensor, optofluidic Surface-Enhanced Raman Spectroscopy (SERS), and fluorescence immunoassay biosensor. All of these devices take advantage of superior fluidic handling capability and high sensitivity, and have been used in detecting various biological and chemical analytes in either liquid or vapor phase.

A High-throughput Microfluidic Platform for Profiling Photosensitizer Efficacy in Cancer Therapeutic Applications

Xia Lou
Graduate Student
Prof. Euisik Yoon Group
Electrical Engineering and Computer Science

In vitro screening is an essential step for anti cancer drug development. However, it is facing the challenges of throughput, physiological relevance, and especially technology for profiling photosensitizer efficacy in Photodynamic therapy(PDT) is lacking look into. We developed a microfluidic platform for evaluating PDT efficacy in terms of a variety of therapeutic factors including drug concentration, dissolved oxygen level, fluence (illumination dose), incubation time, photosensitizer and cell line types. High throughput screening is realized with parallel on-going efficacy assay with vast cell arrays with combined parameter-controls. We hope this microfluidic platform could provide a method of comprehensive photosensitizer efficacy assay and help quickly set up a photosensitizer database with each drug's efficacy variance information and provide guidelines for patient treatment.

Constant flow-driven microfluidic oscillators: recent progress to minimize external controllers for cell study

Dr. Sung Jin Kim
Postdoctoral Research Fellow
Takayama Lab
Biomedical Engineering

A microfluidic device that recreates enviroments having periodic biochemical and physical stimulation is important for cell study. For this task, however, microfluidic devices exploit numerous external control units, thus greatly increasing operational cost. As a first step to address this issue, we have implemented a constant flow-driven oscillator. In this seminar, we present recent progress related to the oscillator. Specfically, we will present control of duty cycles, widely tunable oscillation periods, and the oscillator's operating conditions.

3D Carbon Nanotube Surfaces for Microfabrication

Dr. John Hart
Assistant Professor
Mechanical Engineering and Art & Design
University of Michigan
www.mechanosynthesis.com

The capabilities of microfabrication materials and processes have in large part guided progress in microfluidics.  While planar patterning of soft and hard materials is ubiquitous, it remains challenging to fabricate robust three-dimensional (3D) surface structures, especially in high throughput.  I will present our research toward the use of vertically aligned carbon nanotube (CNT) “forests” as a platform for 3D microfabrication and surface engineering.  Low-density CNT forest microstructures grown by chemical vapor deposition are manipulated by “capillary forming”, wherein a solvent is condensed onto the substrate and infiltrates each microstructure by self-directed capillary rise.  By understanding the relationship between shrinkage of the vapor-liquid-solid interface and the resultant heterogeneous strain distribution within the CNT forest, we have engineered shape transformations that create robust freeform microstructures and complex multi-directional textures.  These 3D CNT surfaces are compatible with downstream microfabrication processing and can be implemented as, for example, nanocomposite master templates for replica molding of textured polymer microstructures, and mechanosensitive transducers driven by chemically-selective swelling of hydrogels.  Development of this technology in the laboratory has demanded an understanding of process reliability issues for CNT growth, and inspired us to build an automated CNT growth system that will enable high-throughput experimentation and application-focused engineering.  To conclude, I will hope to begin a brief discussion with the audience on the needs and opportunities for improved microfabrication materials in their research.

The Study of Metabolic Activities of Cells

Yashar Genjen
Graduate Student
Reddy Lab
Mechanical Engineering

Metabolism is one of the most basic functions of a cell. Since metabolic processes are never 100% efficient, they release heat outputs that are in order of picowatts. While calorimetric methods have been extensively used for measurements involving biological samples, their limited resolution (nanowatts at best) has made study of metabolism on level of single cells impossible. Thus, measurements involving cells usually report on an imaginary average cell. Due to the inherent heterogeneity of cell cultures, an earnest study of metabolic activities of cells needs to account for cell to cell differences. In order to overcome this challenge, I am developing a microfabricated calorimetric platform that will enable measurements of the metabolic activity of single cells with picowatt (pW) sensitivity.

Dr. Michelle Khine
Associate Professor
Biomedical Engineering
UC Irvine

The challenge of micro- and nano-fabrication lies in the difficulties and costs associated with patterning at such high resolution. Instead of relying on traditional fabrication techniques largely inherited from the semiconductor industry we have developed a radically different approach. We pattern at the large scale, which is easy and inexpensive, and rely on the heat-induced relaxation of pre-stressed polymer sheets – commodity shrink-wrap film – to achieve our desired structures. Using this approach, we have demonstrated that we can create fully functional and complete microfluidic devices with integrated nanostructures, printed electronics, and even optical components, all within minutes. These devices can be created for only pennies per chip and without any dedicated costly equipment. Because this process is compatible with roll-to-roll plastic processing, it is also scalable and cost-effective enough for point of care applications.

Automated Microfluidic Cryoprotectant Exchange Platform for Improved Oocyte Cryopreservation

David Lai
Graduate Student
Takayama Lab
Biomedical Engineering

It is now estimated that 1 in every 47 women will develop some form of invasive cancer before the age of 40 (1). Treatment for such cancer which involves surgical extraction followed by non-target specific radio- and chemotherapy leaves patients with a high risk of permanent infertility. With increasing cancer survival rates OncoFertility Preservation has become a significant quality of life issue for cancer survivors. Vitrification has recently become the preferred method for preservation of human oocytes due to higher survival rates and time efficiency compared to slow-rate freezing. However few standard and reliable vitrification protocols exist, leaving a large potential for scientific study, improvement and optimization. The mixing of droplets during vitrification is a fluidic process and can be precisely and reproducibly controlled using a microfluidic device. Our goal is to use our precision to develop an automated platform to control cryoprotectant exchange thus minimizing oocyte shrinkage and re-expansion to alleviate intracellular mechanical stresses. We hypothesize that a precisely controlled cryoprotectant exchange made possible by our microfluidic platform will increase oocyte survivability, fertility rates, and improved embryonic development by alleviating the mechanical stresses induced by manual vitrification/warming. Our preliminary data demonstrate high variability between trials by the same embryologist and between individual embryologists with manual vitrification/warming. However despite high variability, in all cases the oocytes experience a sudden initial increase in cryoprotectants, causing a drastic increase in extracellular osmolarity that dehydrates the oocyte. To improve the vitrification process, we have developed a device that utilizes a computer-controlled Braille display to precisely deliver high viscosity fluids such as concentrated ethylene glycol, DMSO and sucrose. A variety of design features have been tested to obtain a balance between ease of use and functionality. Using the Kedem Katchalsky equations (2) that describe simultaneous movement of water and permeating solutes, we have determined that an increasing linear concentration profile will successfully prepare cells for vitrification while minimizing osmotic and mechanical stress. Our future work will assess our platform against published manual vitrification results with oocyte cryosurvival, intra-oocyte organelle distribution, fertilization, as well as the ability of oocytes to support embryo development to the blastocyst stage and/or establish normal pregnancies.

Targeted transport by kinesin trafficking

Neha Kaul
Graduate Student
Mechanical Engineering

Cargo transport within biological cells is achieved by a large diversity of motor proteins that use chemical energy from the cell to generate directed movement along the cytoskeleton.  Cellular transport is known to be targeted to specific destinations with high spatial fidelity, the loss of which is the underlying cause for neurodegenerative disorders such as Alzheimer’s and Parkinson’s. Kinesin-1 is a well-studied motor protein responsible for intracellular vesicular transport along cytoskeletal microtubules, yet it remains entirely unclear which mechanism(s) target this motor to specific cellular domains. We hypothesize that dynamic posttranslational modifications on the microtubules directly influence their interaction with kinesin-1, thus regulating intracellular traffic. In order to examine the direct effect of microtubule modifications on kinesin-based transport, we characterized the single molecule motility properties of fluorescently labeled kinesin-1 on modified and unmodified microtubules in vitro using purified, mammalian proteins and total internal reflection fluorescence (TIRF) microscopy. In my presentation I will discuss recent findings and highlight the need for microfluidics-based, experimental approaches to study the kinetic properties of molecular motors when limited quantities of proteins are available.

A Novel Microengineered Cell Stretching Device for Subcellular Mechanistic Analysis of Cytoskeletal Tension

Jenn Mann
Graduate Student
Prof. Jianping Fu Group
Mechanical Engineering

External forces are increasingly recognized as major regulators of cell structure and function, yet the underlying mechanism by which cells sense force and transduce it into intracellular biochemical signals and behavioral responses (‘mechanotransduction’) is largely undetermined. To aid in the mechanistic study of mechano­transduction, we devised a novel cell stretching device that allows for quantitative control and real-time measurement of mechanical stimuli and cellular biomechanical responses. Using this device, we studied the subcellular dynamic responses of contractile force and adhesion remodeling of vascular smooth muscle cells (VSMCs) to stretch. Our data showed that VSMCs could acutely enhance their contraction to resist rapid cell deformation, but they could also allow slow adaptive inelastic cytoskeletal reorganization in response to sustained cell stretch. Our study may help elucidate the mechanotransduction system in smooth muscle cells, and thus contribute to our understanding of pressure-induced vascular disease processes.

Micro Sensors for in situ Analysis of Volatile Organic Compounds

Kee Scholten
Graduate Student
Prof. Edward Zellers
Department of Applied Physics

The need for in situ determinations of volatile organic compounds (VOC) in applications such as environmental monitoring, biomedical diagnostics, and homeland security continues to drive the creation of microfluidic components for micro gas chromatographs (uGC), particularly microfabricated sensor arrays operating on different transduction mechanisms. Toward that end, we are exploring different microfabricated sensing technologies:  chemiresistors employing temperature modulated tin-oxide nanowire ensembles (NW-CR), chemiresistors employing thiolate-monolayer-protected gold nanoparticle films (MPN-CR), and optofluidic ring resonators (OFRR) employing polymeric or MPN coatings. NW-CRs consist of NWs bridging an electrode gap on a micro-hotplate; temperature dependent VOC oxidation produces conductivity changes. MPN-CRs consist of thin sorptive MPN films deposited over interdigital electrodes; VOC sorption leads to swelling-induced changes in tunneling current. OFRRs consist of microfluidic channels that support an optical whispering gallery mode within the structures wall; VOC interaction with an internal sensing layer induces measurable changes in resonant frequency. The fabrication and initial characterization of each device is presented here.  Chemiresistors of each type were assessed for VOC sensitivity and specificity using Monte Carlo assisted extended disjoint principal component regression, and MPN-CRs are presented as an integratedcomponent in a uGC analysis system. Detection of VOCs using mesoscopic OFRRs has been demonstrated, and a novel OFRR is presented as a lab-on-chip platform for VOC optical transduction.