1, CREATE WAY
#04-13/14 Enterprise Wing and #B-101
- BioSyM Seminar on 6th July 2012 (Friday) @ 3 pm, BioSyM Conference Room, S16-07
- ELECTROCHEMICAL BIOSENSOR DEVELOPMENT FOR STUDIES IN NEUROSCIENCE AND DRUG SCREENING
Nitrogen derived free radicals, such as nitric oxide (NO), and peroxynitrite (ONOO-) play a central role in normal physiological processes. However, the high reactivity and short-lifetime of these reactive oxygen and nitrogen species make their detection difficult and thus, very sensitive detection methods are in strong demand. Electrochemical biosensors were developed based on biocompatible thin films, nanomaterials, and conducting polymers that have been used either for direct detection or as matrices for immobilizing the biomolecules. Various experiments were performed to characterize the biosensors and immunosensors. The applications of the proposed biosensors were conducted for the determination of target compounds in vitro and in vivo real sample analysis, thus increasing our understanding of the various mechanisms of these reactive nitrogen species (NO, ONOO-) and their protein counterparts (nNOS, iNOS) in the biological environment.
Seminar on "Small scale rheology for screening scarce materials", 2nd July 2012, 11 am
- COMBINATORIAL PHYSICAL MARKERS FOR MULTIPOTENCY
Mesenchymal stem cells (MSCs) have garnered significant interest from the scientific community owing to their ability to develop into many mature cell types for applications in regenerative medicine. To generate lineage committed MSCs for applications involving adipose, bone, cartilage or muscle regeneration, soluble chemical growth factors are typically supplemented to culture media as part of a differentiation cocktail. In addition to soluble factor signaling, subtle changes to the cell’s local biophysical microenvironment can also have significant effect on whether the cell remain in their immature (multipotent) state or becomes committed to a specific lineage. This often leads to a heterogeneous mixture of MSCs that differ in their stage of commitment and extent of differentiation. The functional heterogeneity of culture expanded MSCs therefore pose a significant challenge to the efficacy and safety of potential MSC-based therapies, as implanted culture expanded MSCs may play out a biology that is different from their intended purpose. This is further complicated by the lack of immunophenotype markers that are indicative of MSC multipotency. In this work, we examined several quantitative features of bone marrow derived MSCs and correlated each mechanical property with their differentiation potential. The parameters include cell size, spread area, elasticity, nuclear to cytoplasmic ratio and relative nuclear fluctuation. Of particular interest is whether any of these physical signatures or combinations thereof, could prospectively identify multilineage subpopulations among different adult and fetal MSCs from precommitted progenitors. We find that among the different mechanical properties screened, only cell elasticity and nuclear fluidity significantly correlate with the differentiation behavior of MSCs. These findings can be recapitulated in vivo, indicating that this MSC classification methodology could be useful in capturing cells that are therapeutically relevant. Together this work establishes a minimal set of physical criteria for defining multipotency and could provide predictive measures for the identification of commitment towards multiple cell types.
@ BioSyM Conference Room, S16-07, NUS
Speaker: Prof. Eric M. Furst,
Department of Chemical and Biomolecular Engineering and Center for Molecular and Engineering Thermodynamics,
University of Delaware, USA
Abstract: Rheological measurements that characterize the flow properties of a substance can be difficult to perform for many emerging materials, especially when a material is demanding to synthesize or prohibitively expensive. Fortunately, microrheology methods can be used when a material's availability is limited, since it requires small sample volumes, ranging on the order of 1nL-10μL. In addition, microrheology has several complementary features that make it indispensable for characterizing scarce materials, specifically those developed for therapeutic applications. These factors include measurement acquisition times on the order of seconds, a large dynamic
frequency response, and exquisite sensitivity to incipient properties. Microrheology uses the motion dispersed micrometer-diameter probe particles to measure the surrounding material's rheology. The technique can be divided into two approaches that are distinguished by the driving force of the probe motion. In the first, active microrheology, the embedded probe particles move in response to an external force, typically generated by optical tweezers or magnetic fields. In the second, passive microrheology, the Brownian or thermal motion of the embedded probe particles is measured and the rheological properties are calculated by the Generalized Stokes–Einstein Relation (GSER). The introduction of passive microrheology has stimulated many of the advances in biomaterial microrheology over the past two decades.
In this talk, I will describe recent work on high-throughput viscometry and rheology using a combination of microrheology and microfluidics. A series of microrheology samples is generated as droplets in an immiscible spacer fluid using a microfluidic T-junction. The compositions of the sample droplets are continuously varied over a wide range. Viscosity measurements are made in each droplet using multiple particle tracking microrheology. I will review the key design and operating parameters, including the droplet size, flow rates, rapid fabrication methods and passive microrheology techniques. The combination of microrheology with microfluidics maximizes the number of viscosity measurements while simultaneously minimizing the sample preparation time and amount of material, and should be particularly suited to the characterization of protein solution viscosities of therapeutic agents. I will conclude with an outlook of future work, including active non-linear microrheology and high-throughput rheological fingerprinting.
- BioSyM Seminar on 8th June 2012 (Friday) @ 3 pm, BioSyM Conference Room, S16-07
- Speaker 1: Dr.Christopher Ochs
- OXYGEN SENSORS FOR MICROFLUIDIC 3D CELL CULTURES
- Abstract:The real-time detection of multiple analyte concentrations (such as O2, CO2, glucose, growth factors) and the monitoring of variations in the physical environment (e.g. temperature, pH, ionic strength) are vital for the understanding of cell growth and proliferation, the communication between cells and their reaction to physical or biological stimuli. Recently, there has been interest in the cultivation of cells in temperature gradients or under mechanical stress, especially to gain information about biochemical signaling pathways between cells, mechanotransduction, and migration behavior in 3D cell cultures. However, up to date, most techniques only allow for the bulk analysis of the extracellular media. Methods exploring the independent and parallel analysis of multiple analytes in complex cell cultures remain to be discovered. A suitable approach will have to present a large number of individually addressable sensors immobilized in direct proximity to the cells, allowing for detection of the local concentration while simultaneously having negligible effect on cell proliferation or the composition of the biological environment. We aim to fabricate a range of cell culture compatible bead-based probes, which can be equipped with sensor molecules depending on the analyte of interest. The beads are rendered biocompatible and functional by applying a suitable layer-by-layer (LbL) coating (e.g., PEG). A microfluidic device custom-built for the control and manipulation of certain biophysical parameters is then loaded with the cells and sensor beads of interest. Using confocal fluorescence microscopy, the obtained signal from the beads can be quantified and changes in cell morphology, viability and migration behavior in response to external stimuli (e.g. drug addition, temperature or oxygen gradient) can be monitored. We also envisage the use of computer models to extrapolate concentrations between data points (= sensor beads) and to calculate a continuous analyte distribution in the cell culture over time. Oxygen is an important factor influencing cell viability, migration, and differentiation; hypoxia has been linked with increased resistance to radiation therapy and certain anticancer drugs. We developed sensor beads based on layer-by-layer (LbL) assembled polyelectrolytes modified with an oxygen-sensitive luminescent dye and demonstrate potential of these biosensors to examine the effect of oxygen gradients in 3D cell cultures. The bead fluorescence intensity in response to various oxygen concentrations is investigated and their cell culture compatibility is evaluated. The oxygen distribution in a novel microfluidic device is simulated for various oxygen gradients and validated experimentally using oxygen sensors beads. Some preliminary results are presented to demonstrate the potential of LbL-assembled oxygen sensors for the measurement of the local oxygen tension around cells.
- Speaker 2: Mr.Kong Tian Fook
- Liquid metal radio-frequency microcoil for magnetic resonance relaxometry
- Abstract: In recent years, labs on a chip (LOC) or micro total analysis systems (mTAS), have been the main sources of innovation for microfluidic technology. The introduction of microsolidics, a fabrication method for multi-layered three-dimensional (3D) metallic structures in microchannels has revolutionized how metallic conductors are integrated in the LOC platform. The key advantage of using liquid-metal technology is the ability of making flexible complex 3D electrical conductors, confined in a microchannel, with only a few fabrication steps. In this talk, we demonstrate a novel technique to fabricate three-dimensional multilayer liquid-metal microcoils together with the microfluidic network by lamination of dry adhesive sheets. The microcoil was characterized for 0.5 T 1H magnetic resonance relaxometry (MRR) measurements. In addition, we used the liquid-metal microcoil to perform a parametric study on the transverse relaxation rate of human red blood cells at different hematocrit levels.
- BioSyM Seminar on 27th April 2012 (Friday) @ 3 pm, SMART Conference Room, S16-05
- Speaker 1: Dr.Binu Kundukad
- Gelation of the genome by topoisomerase II targeting anticancer drugs
- Abstract: Topoisomerase II regulates the topology of DNA by catalysis of a double strand passage reaction. Inhibition of this reaction prevents cell replication, and, thus, is a pathway targeted by anticancer drugs. The passage reaction was inhibited by AMP-PNP, a non-hydrolyzable analog of ATP, as well as the drug ICRF-193. Microrheology assays showed gelation due to the formation of a self-catenated network of circular DNA molecules. A cell-killing mechanism is proposed by gelation of the genome through TOP2-mediated interlocking of looped DNA segments of the replicated chromosomes.
- A Real-Time Microscopic 3D Factory - Holographic Optical Tweezers with Volume Holographic Microscope
- Abstract: Since their introduction in the 1980s, optical tweezers have permeated research in the biological and physical sciences. Microscopes with optical tweezers are used to observe, move and manipulate small objects like microsphere-based system, and cells. As the experimental complexity grows, the need for multiple trapping arises. Holographic optical tweezers (HOT) utilize a spatial phase modulator to create multiple traps and do real-time 3D manipulation. In SMART, we combined HOT techniques with volume holographic microscope (VHM). VHM captures three-dimensional intensity information on a two-dimensional camera using a volume hologram (VH) in the imaging system. It allows multiple focal planes to be recorded without scanning. With these techniques combined, we can manipulate small objects in 3D space and visualize multifocal planes information simultaneously.
- BioSyM Seminar on 30th March 2012 (Friday) @ 3 pm, SMART Conference Room, S16-05
- Speaker 1: Dr.Poon Zhiyong
- Therapeutic applications of Mesenchymal Stem Cells
- Abstract: Approaches for the use of mesenchymal stem cell (MSC)-based therapy towards the treatment of degenerative and autoimmune diseases is evolving; however, owing to the functional heterogeneity of culture expanded MSCs, a central challenge has been to classify MSC subpopulations in a way that offers predictable and effective therapeutic results following their use. We demonstrate how microfluidic tools and biophysical cell cytometry aid in this process, and show that MSC subpopulations isolated in this manner are predisposed for different therapeutic applications.
- Speaker 2: Mr.Ng Wei Qing Justin
- How does the amyloid-beta peptide perturb neuronal membrane fluidity? A Microfluidics system approach
- Abstract: The Amyloid-beta peptide (Abeta), is implicated in the pathology of Alzheimer's disease. Neuronal uptake and accumulation of Abeta within the cytoplasm causes the formation of amyloid-plaques, disrupting cellular function and eventually leading to cell death. Abeta also has action at the neuronal membrane through its binding to gangliosides such as GM1, and neuronal receptors such as NMDA and glutamate receptors. Binding of Abeta to the neuronal membrane is thought to perturb membrane fluidity as well as the phase organization of the membrane, resulting in downstream effects such as alteration metabolism pathways, all of which result in altered cellular and membrane function. This study uses a microfluidics approach to recreate a 3D microenvironment where neurons can grow healthily and the environmental factors can be easily manipulated. The effects on the neuronal cell membrane from addition of Abeta is examined via confocal fluorescence-correlation spectroscopy.
- BioSyM Seminar on 2nd March 2012 (Friday) @ 3 pm, SMART Conference Room, S16-05
- Speaker 1: Dr.Ng Chee Ping
- The Ballad of the Swedish Chef, Mixed Berries and Waffles:
Development of Functional Microwell Arrays for Cytometry of Rare Cells in Bone Marrows and Endometriosis
- Abstract: We are developing functional hydrogel microwell arrays for image cytometry of clinical specimens to study fundamental questions in endometriosis and stem cell biology. In particular, our interests lie in understanding the prevalence and mechanism of colony forming rare cells in endometriosis and bone marrows. Compared to traditional assays where cells have to be plated sparsely on cell culture dishes, the high aspect ratio arrays fabricated from soft photolithography allow the isolation of individual cells or a small group of cells in a more physiologically relevant microenvironment by maintaining their cytokine interactions with their neighbors. In this seminar, I will provide an update on our progress on the development of these microwells, using expanded mesenchymal stem cells for high content characterization and analysis such as well stability and cell behavior. I will also touch on our collaboration with Prof. Han's team on exploring the use of inertial microfluidics to deplete red blood cells from peritoneal and bone marrow samples for downstream studies of nucleated cells. The physical method utilized a spiral shaped device to separate the desired nucleated cells and red blood cells based on their size difference. The feasibility of the device was assessed by analyzing the sorted cells using flow cytometry for enrichment efficiency and screening the cells for the prevalence of colony forming units using traditional plating methods. These technologies may eventually form part of a powerful system diagnostics platform for translational research of complex clinical fluid specimens and also a great recipe for making hearty delicious cornflake waffles with mixed berries.
- The Effect Of Endothelial Dll4 Exosomes On Endothelial Cell Sprouting
- Abstract: Angiogenesis is the formation of new blood vessels from existing vasculature. Delta-like ligand 4 (Dll4), a notch ligand, is known to play an important role in this process by regulating endothelial cell differentiation. When stimulated by a VEGF gradient, endothelial cells differentiate into two distinct cell types, tip and stalk cells. Tip-cells lead the front of a forming sprout, while stalk cells trail behind, supporting the newly formed sprout. Dll4, which is upregulated in tip cells, is known to repress the expression of tip-cell specific genes in the neighbouring cells, hence, allowing tip-stalk cell specification. It has been hypothesized that during Dll4-Notch signalling, following the activation of the Notch receptor, endocytosis of Dll4 leads to its targeting to endosomes and subsequent packaging into exosomes. Exosomes are nanovesicles that have been reported to play a role in cellular communications via their ability to carry biological molecules. Work by Sheldon et al., showed that Dll4 if packaged into exosomes, can affect Notch signalling and promote a tip-cell phenotype. By utilizing microfluidic devices to investigate the effect of endothelial derived exosomes on angiogenic sprouting, our results show that endothelial-derived Dll4-exosomes repress angiogenic sprout formation instead.
SMART Biomedical CAREER TALK 2011/2012, by Dr.Thomas Murphy of Research Instruments and Origen Laboratories on 8th Dec 2011 (Thursday), 4 pm @ Seminar Room 1, Centre for Life Sciences (CeLS)
- Dr. Thomas Murphy is a cell biologist with over 10 years’ experience in molecular cell biology and target identification and validation. His particular research interests include biological imaging, cell signaling, and angiogenesis. Prior to joining Research Instruments, Dr. Murphy worked as an Applications Scientist at Thermo Scientific (Dharmacon RNAi Technologies), to advise fellow scientists on advancements being made in the field of RNA interference. During his post-doctoral fellowship, he worked at the Novartis Institute for Functional Genomics (GNF) in San Diego, where he was responsible for conceiving and implementing siRNA-based genomic screens against inflammatory and oncology pathways. He received his B.A. in Biology from Occidental College, followed by his Ph.D. from the Molecular Biology Institute at University of California, Los Angeles. He has also held research positions at UC San Francisco and Amgen Inc. Dr. Murphy is currently Chief Scientific Officer at Research Instruments and heads their Life Science applications team. He is also General Manager of Origen Laboratories, a laboratory service provider which specializes in performing microarray-based research projects for clients.
- BioSyM Seminar on 28th Nov 2011 (Monday) @ 3 pm, SMART Conference Room, S16-05
- Cell Encapsulation induced angiogenesis on a chip
Cell-encapsulating alginate beads have the potential to serve as a sustained release system for delivering therapeutic agents in vivo while protecting the cells from the body’s natural immunity response. To date, there is still no representative in vitro model for cell-encapsulation therapy that would provide a suitable platform for quantitative analysis of physiological responses to secreted factors, specifically designed for angiogenesis therapeutics. Here, we introduce a novel angiogenesis-on-a-chip system for the evaluation and quantification of capillary growth from an intact endothelial cell monolayer in response to soluble factors released from human fetal lung fibroblasts encapsulated in beads. We confirmed that cell-encapsulating beads induced an angiogenic response in vitro, demonstrated by a strong correlation between the encapsulated cell density in the beads and the length of the vascular lumen formed in vitro. Cell-encapsulating beads were further shown to exert an angiogenic activity in a subcutaneous mouse model, forming an extensive network of functional luminal structures perfused with red blood cells.
BioSyM Seminar on 28th Oct 2011 @ 3 pm, SMART Video Conference Room, S16-05
- From Lipids to their global analysis by mass spectrometry
When one was to discuss biomolecules, DNA, RNA and proteins usually come to mind. Lipids, on the other way are gravely neglected despite their integral impact on biological systems such as acting as second messengers, homeostasis and maintaining structural integrity. Although still poorly defined, some experts estimate the number of distinct molecular species of the lipidome at 10,000 to 100,000, some of which are already targeted as therapeutic targets. Given the diversity and complexity of lipids, advanced analytical methods (termed lipidomics) are needed to describe them globally, and subsequently address fundamental questions such as lipid function as well as applied biology and biotechnology. In this talk, I will attempt to first discuss the many functions and importance of lipids in biological systems. With that, we will shift focus onto the modern techniques and applications on disease biology with my work on dengue as an example.
- BioSyM Seminar on 14th Oct 2011 @ BioSyM Meeting room, S16-07
- Speaker: Dr.Hemant Vijaykumar Unadkat, MIRA Research Institute, Department of Tissue Regeneration, University of Twente, The Netherlands
Title: Braille for cells: Cells to phenotypes
Abstract: Evolution in materials processing and synthesis techniques allows us to fabricate and synthesize biomaterials with variable properties and composition. However, present methods for testing a multitude of these biomaterials or their properties are not apt enough except a few. One of the important properties for implantable biomaterials is their surface topography. Unfortunately, nature does not prescribe the optimal surface topography for a given biomedical application, and the number of possible surface patterns that can be created is virtually unlimited, considering that cells are in the order of tens of micrometers whereas patterns can be created at nanometer resolution. The underlying mechanisms defining the interplay of cells with substrates are only partially understood. I’ll discuss the potential of a high throughput screening platform (TopoChip) for screening and directing cell fate by means of surface topographies. The topographies used in the TopoChip are randomly generated using mathematical algorithms. In my talk, I will show that by combining the power of high-throughput screening with mathematical design of micrometer-range surface topographies we can decipher the “Braille code” of cell-topography interactions
BioSyM Seminar on 30th Sept 2011 @ 3 pm, SMART Video Conference Room, S16-05
- Speaker 1: Dr.Vijay Raj Singh
- Photon reassignment for structured light microscopy for deep tissue 3D imaging applications
- Abstract: In this talk, a new method will be presented for 3D visualization of biological tissues utilizing structured light wide-field microscopic imaging system. This method provides the capability to image deeper into biological tissue by reassigning fluorescence photons generated from off-focal plane excitation. Recently, novel methods for 3D resolved imaging based on structured light illumination have been developed by several groups (Wilson et al, Gustasson et al, and Mertz et al) allowing wide-field visualization of the focal plane while rejecting out-of-focus background “haze”. While these methods improve image contrast, the loss of out-of-focal plane fluorescent photons limits image signal-to-noise ratio (SNR). Proposed method seeks to better utilize these “lost” photons by using the ‘prior knowledge’ about the optical transfer function of the structured light illumination. Utilizing a maximum likelihood approach, the most likely fluorophores distribution in 3D is identified that produces the observed image stacks under structured and uniform illumination using an iterative maximization algorithm. The proposed model is first validated with the simulation data where the results show the substantial improvement in SNR compare to existing methods and then it further applied for experimentally recorded data. Results show the significant optical sectioning capability of tissue sample while preserving the photons count, which is usually not achievable with other existing structured light imaging methods.
- Speaker 2: Dr.Du Ning
- Compression and self entanglement of single DNA molecules under electric field
- Abstract: The use of electric fields to transport DNA has become an essential technique for a variety of research areas including molecular biology, gene therapy, and fundamental studies of polyelectrolytes. In most applications, non-linear electrokinetics due to the interplay of negatively charged DNA and the electric field are neglected. Here we experimentally study the effects of a uniform electric field on the conformation of fluorescently labeled single DNA molecules. We demonstrate that a moderate electric field (∼200 V/cm) strongly compresses isolated DNA polymer coils into isotropic globules. Insight into the nature of these compressed states is gained by following the expansion of the molecules back to equilibrium after halting the electric field. We observe two distinct types of expansion modes: a continuous molecular expansion analogous to a compressed spring expanding, and a much slower expansion characterized by two long-lived metastable states. Fluorescence microscopy and stretching experiments reveal that the metastable states are the result of intramolecular self-entanglements induced by the electric field. These results have broad importance in DNA separations and single molecule genomics, polymer rheology, and DNA-based nanofabrication.
- SMART BioSym Seminar on Tuesday, August 23, 2011, 1:30 pm
Speaker: Ki Hean Kim, Ph.D., Assistant Professor in Mechanical Engineering and Integrative Biosciences and Biotechnology Pohang University of Science and Technology (POSTECH), Pohang, Korea
Title: Polarization-sensitive optical coherence tomography: its clinical applications and development
Abstract: Polarization-sensitive optical coherence tomography (PS-OCT) is a 3D tissue imaging technique which provides information of structure and birefringence. PS-OCT can be used as non-invasive optical tissue biopsy down to a few millimeters. In this talk, clinical studies and technological development of PS-OCT will be presented. Clinical studies are human vocal fold and human burn imaging. Technological development is a new PS-OCT method, which is based on depolarized light and frequency multiplexing, to increase its functionality.
BioSyM Monthly Seminar on 25th May 2011 @ 8 pm, SMART Video Conference Room, S16-05
- Speaker 1: Ali Asgar Bhagat
- Microfluidic technologies for circulating tumor cell (CTCs) isolation
- Speaker 2: Li Jie
- Molecular mechanism of activation of the EGFR kinase studied using umbrella sampling and transition path sampling
- BioSyM Monthly Seminar on 27th April 2011 @ 8 pm, SMART Video Conference Room, S16-05
- Speaker 1: Dipanjan Bhattacharya
- Development of Digital Scanned Laser Sheet Microscope for 3D live tissue imaging
- Speaker 2: Sharon Ong
- Automated Tracking of Cells and Conduits from Time-Lapse Confocal Microscopy Images
- BioSyM graduate students Seminar (BioGraSS) on 29th March 2011 @ 12.30 pm, BioSyM Conference Room
Speaker 1: Guofeng Guan
- Deformabillity-based Cytometry With Active Control of Microfluidic Channels
Speaker 2: Tan Chin Wen
- Stem cells in endometriosis
- BioSyM graduate students Seminar (BioGraSS) on 18th Feb 2011 @ 12.30 pm, BioSyM Conference Room
- Speaker 1: Sei Hien Lim
- Induction of Angiogenesis in Microfluidic Devices using Prolyl Hydroxylase Inhibitors
- Speaker 2: Pradeep Anand Ravindranath
- Robust inhibition of Hepatitis C viral propagation
BioSyM Monthly Seminar on 16th Feb 2011 @ 8 am, SMART Video Conference Room, S16-05
Speaker 1: Young Kum Park
- Stem Cell Differentiation within 3D Mmicrofluidic Environment
Speaker 2: Hoi Siew Kit
- Optical Trapping and its Applications in Microfluidics
- SMART BioSyM Invited Seminar: 8 Feb 2011 @ SMART S16 Level 5 Conference Room, 4 - 5 pm
- Title: Infection Treatment Vaccination as a Model of Protection Against Malaria
- Speaker: Jingyang Chen
- Jingyang Chen is a biologist in the Laboratory of Malaria Immunology and Vaccinology (LMIV) at the National Institute of Allergy and Infectious Diseases (NIAID) in the United States. He currently works on non-human primate models of malaria and second generation sequencing of clinical samples from longitudinal studies in Tanzania and Mali.
- BioSyM graduate students Seminar (BioGraSS) on 13th Jan 2011 @ 12.30 pm, BioSyM Conference Room
- Speaker 1: Yuchun Liu
- Vascularised bone tissue engineering using human umbilical cord blood derived endothelial progenitor cells (EPC) and fetal bone marrow-mesenchymal stem cells (MSC)
- Speaker 2: Wong Cheng Lee
- High throughput sorting of cells into different phases of the cell cycle using inertial microfluidics
- 10, 11 Jan 2011, BioSyM - Mechanobiology Institute Joint Workshop @ Shaw Foundation Alumni House Auditorium, 11 Kent Ridge Drive, Singapore 119244.