Session 3 Abstracts
Session 3 Abstracts – Saturday, June 23 – 10:30 AM
Biomaterials / Drug Delivery
Stem-Cell Protective Biomaterials to Improve Transplantation Viability
Sarah Heilshorn, Assistant Professor, Department of Materials Science & Engineering, Stanford University
Stem cell transplantation is a promising therapy for many diseases and injuries; however, current delivery protocols are inadequate. Transplantation by direct injection, which is clinically preferred for its minimal invasiveness, commonly results in less than 5% cell viability. To overcome this limitation, we demonstrate that cell encapsulation within hydrogels of specific mechanical properties significantly improve viability. We have designed an injectable, bio-resorbable, customizable hydrogel using protein-engineering technology. In our Mixing-Induced Two-Component Hydrogel (MITCH), network assembly is driven by stoichiometric peptide-peptide binding interactions. By integrating protein science methodologies with polymer physics models, we manipulate the polypeptide chain interactions and demonstrate the direct ability to tune the network crosslinking density, sol-gel phase behavior, and gel mechanics. This is in contrast to many other physical hydrogels, where predictable tuning of bulk mechanics from the molecular level remains elusive due to the reliance on non-specific and non-stoichiometric chain interactions for network formation. Furthermore, our MITCH materials enable stem cell and growth factor encapsulation at constant physiological conditions – a significant advantage over other commonly used hydrogels. Through a series of in vitro and in vivo studies, we demonstrate that these materials may significantly improve transplanted stem cell retention.
The Dorsal Window Model: An In-Vivo Test to Compare Alginate Micro Vs Macro Encapsulation in Islet Transplantation
Rahul Krishnan, Rajan Arora, Ouwen Liang, Morgan Lamb, Sean M White, Rick Storrs, Clarence Foster, Elliot Botvinick, Bernard Choi, Jonathan RT Lakey.
Background: Studies show that biomaterial encapsulation of islets prolongs their survival and precludes the need for chronic immunosuppressive therapy. Although numerous biomaterial devices and several tissue engineering techniques have been developed for use in islet transplantation, there is an urgent need to develop a simple and inexpensive test to compare and contrast their relative strengths and weaknesses. We have developed a noninvasive, in-vivo method to evaluate the host response to subcutaneous transplantation of biomaterial encapsulated islets, by employing a combination of the mouse dorsal window- chamber model (DW), Laser Speckle Imaging (LSI) and Wide-field Functional Imaging (WiFI).
Methods: Dorsal window chambers were implanted on C57BL/6 albino mice with either a high guluronate alginate sheet or Ultra-Pure Low Viscous Mannuronate(UPLVM) alginate microcapsules containing islets isolated from syngeneic mice. The vascular response to the implants and the ensuing hemodynamic changes were studied using WiFI and LSI(Figure 1) performed over a 7-day period. The images obtained were analyzed to evaluate changes in the relative rate of blood flow and hemoglobin oxygen saturation.
Results: The DW model enables monitoring of the subcutaneous vascular responses to biomaterial encapsulated islet implants, such as arteriolar, venular and venous dilatation and peri-implant neovascularization (Figure 1 A, B, E & F). While a comparable increase in the relative rate of blood flow (Figure 1 C & G) and hemoglobin oxygen saturation (Figure 1 D & H) are observed in both sheet and capsule implants, peri-implant neovascularization was significantly higher in the alginate microcapsule group (Figure 1 E & F).
Conclusions: We believe that our model may be used to better understand and compare the morphological, hemodynamic, biochemical and angiogenetic changes induced by subcutaneous transplantation of various types of biomaterial implants. Future experiments will aim to study the effects on islet viability and function for up to two weeks post- transplantation.
Synthesis of hyperbranched mannose polymers
Ken Lin, Andrea Kasko
UC Los Angeles
Glycomimetics with well-defined and well-controlled structures have multiple applications in biomedicine. However, the difficulty of their synthesis has limited their ability and widespread use. Current approaches produce either small amounts of well-defined oligosaccharides through protection-deprotection chemistry or large amounts of linear glycopolymers from polymerization of sugar monomers with the sugar pendant to the polymer backbone (unlike native polysaccharides which contain the ring in the backbone and often contain branches). Polymerization techniques exist to produce branched glycopolymers, but the saccharide residues remain pendant to the polymer backbone and no saccharides are incorporated into the branching unit. We are synthesizing branched glycopolymers that incorporate saccharide residues into the branch points using an inimer consisting of a saccharide with two reactive sites, a polymerizable vinyl group and a homolytically cleavable halogen. Mannose-containing monomers and inimers were polymerized via ATRP to produce linear and branched polymers which were characterized by 1H NMR and GPC. These polymers bind to mannose binding lectin, a component of the complement system, with increased binding as a function of molecular weight and branching, demonstrating the possible use of these mannose glycopolymers in immunotherapy.
Single-cell Manipulation using Nanopipettes
Michelle M. Maalouf, Paolo Actis, Nader Pourmand
UC Santa Cruz
Manipulation and analysis of individual cells is key in understanding processes that control single-cell behavior in a complex environment. Nanotechnology-based tools having high sensitivity and low invasiveness are holding great promises as new biomedical devices for single cell manipulation. The fully electrical read-out as well as the ease and low cost of fabrication are unique features that give nanopipette technology enormous potential. Our group has used nanopipettes as a biosensor, and is now continuing to use nanopipettes for single-cell manipulation. We developed a single-cell manipulation platform based on quartz nanopipettes. The system uses scanning microscopy techniques to position the nanopipette with nanoscale precision. The nanopipette is fitted with electrodes to mediate voltage-dependent injection or aspiration from individual cells. Nanopipettes improve current injection methods due to its high controllability and high viability of cells post injection. Nanopipette tips cause less disruption to the cell membrane and allows injection into single-cells while in their normal plating conditions which improves viability. This technology also allows for multicomponent injections. We have shown successful injections into mammalian cells, a technique that is a historically difficult task when using a micropipette. Using a similar feedback mechanism as our single-cell injections, our group has continued to use nanopipettes for single-cell manipulations for a project called Single Cell Biopsy, which allows for precise aspiration of contents from a single-cell. We present preliminary results showing the aspiration of minute amounts of cytoplasmic material from a single cell. To further optimize the single-cell manipulation, the devices are interfaced with a microfabricated fluidic chip to immobilize cells onto a 6×6 array, the Cell Sifter. Our technology forms the basis for a fully automated system for high-throughput immobilization and precise injection and aspiration of single cells.
Potential Biodegradable Magnesium-based Ureteral Stents
James Tu, Jaclyn Lock, Huinan Liu
Department of Bioengineering, the Materials Science and Engineering Program, University of California, Riverside
Ureteral stents allow urine to flow through the ureter that may be blocked by various obstructions, such as kidney stones or tumors. The currently used polyurethane-based ureteral stents cause a number of complications that often result in bacterial infection, pain to the patients, and require a secondary removal procedure. Magnesium alloys, a novel group of biodegradable metals, can potentially address these clinical problems. We have previously shown that magnesium inhibits the growth of Escherichia Coli, indicating its antimicrobial properties to prevent urinary tract infections. Additionally, magnesium degrades in physiological solutions and is a crucial ion in many cellular processes, which can eliminate the need for secondary removal procedure. In this study, we analyzed the degradation of magnesium alloys (e.g. oxidized and polished magnesium-yttrium alloys, and magnesium-aluminum-zinc alloy) and pure magnesium by immersion in an artificial urine solution for prescribed periods. Following degradation at each time point, the pH, weight, and magnesium ion concentration were collected to track changes in degradation. Results showed that both oxidized and polished magnesium-yttrium alloys degraded at a faster rate as compared to magnesium-aluminum-zinc alloy and pure magnesium. The faster and slower degrading magnesium alloys can be utilized for either short or long-term ureteral stent applications, respectively. These initial degradation and antimicrobial studies provide important guidelines for designing next-generation biodegradable ureteral stents.
Developing Tumor Targeting Bacteriophage by Controlling the Spacing of Ligands
Dong Shin Choi, Seung-Wuk Lee
By engineering the tropism of a virus, we can govern the communication between the host cell and the virus and give new functions to the virus. Especially, the tropism of bacteriophage, which is one of well studied virus, can be engineered easily and makes a good candidate for drug delivery agent. Unlike mammalian viruses, phages do not have natural tropism for mammalian cells, which make them safe and controlled carrier that can be target and deliver in to the targeted cells. When decorated with Arg-Gly-Asp(RGD) peptide motif, they can detect αv integrins on the cell surface, which are overexpressed on the solid tumor and on the angiogenic tumor vasculature. In this study, the spacing between the RGD peptides on the phage surface is precisely controlled to match the spacing between the integrins on the targeted tumor cells. By coordinating the spacing of receptors and ligands specifically to the tumor cell, the phage can now have better targeting specificity for tumor cells over normal non-targeted cells.
Improved Endothelial Proliferation and Migration on 500 nm Rationally Nanofabricated Titanium
P VandrangiA, SC GottB, H BhaktaA, R KozakaA, MP RaoB and VGJ RodgersA
ADepartment of Bioengineering and BDepartment of Mechanical Engineering, University of California, Riverside
Previous in vitro studies have shown increased endothelial cell adhesion on rationally-patterned nanostructured Ti with features of 750 nm. In this work, we created patterned Ti surfaces with periodic arrays of grooves and spacings ranging from 50 μm to 500 nm via a novel plasma-based dry etching technique that enables machining of Ti with unparalleled resolution. We explore the effect of nano-patterned titanium (Ti) on the yield of endothelial cells in an effort to restore vascular endothelium in sites of stent deployment. Our results demonstrate the superior response of endothelial cells cultured on nanopatterned Ti with smaller groove sizes. More specifically, we compare the proliferation and migration of endothelial cells seeded on 500 nm, 0.75 μm, and 50 μm Ti surface patterns with smooth Ti. The results show that endothelial cells on nanopatterned grooves quickly revert back into their healthy endothelial morphology by gradually elongating along the grooves, and proliferate at a higher rate. We also observe that the cells intuitively migrate to the stent material with the smallest nanopatterned groves (500 nm). Considering the innate endothelial configuration, which is composed of elongated vascular endothelial cells aligned with the direction of blood flow, it has been speculated that rationally designed, nanopatterned Ti surface features could further enhance endothelial cell functions by promoting a more native cellular morphology. In the future, we will study the effect of flow on endothelial cells cultured on these nano-grooved Ti structures.
BioMEMS / Instrumentation
Large-Scale Droplet Microfluidics: from Digital Biology to Targeted Therapy
Abe Lee, Professor and Chair, Department of Bioengineering, UC Irvine
While droplet and bubble microfluidics promise new platforms for diagnostics and therapeutics, challenges remain in scaling up to large numbers of these “micro-vesicles” as reactors and carriers for biotechnology and biomedicine. The droplet emulsions generated in microchannels are uniform in size, have high generation rates, and can encapsulate precise amounts of reagents and samples. The sizes of the droplets can be in the range of biological cells (10s of picoliters) and its intracellular constituents (vesicles, organelles), enabling the concept of “artificial cells” as “theranostic agents” to be controllably produced. The ability to encapsulate reagents/analytes in large arrays of droplets or produce therapeutic vehicles in large quantities would accelerate the translation of this field from academic research to commercial products. This talk will introduce three projects in my lab that map the full scale of biology (molecular-cellular-tissue): (1) a large-scale droplet array platform for DNA studies in “digital biology”. (2) The scaled-up production of multi-functional “smart” particles that combines imaging contrast and targeted drug delivery. (3) Artificial cells that are stable and can perform protein synthesis.
Titanium-Based, Fenestrated, In-Plane Microneedles for Passive Ocular Drug Delivery
Omid Khandan1, Amin Famili4, Malik Y. Kahook4,5, Masaru P. Rao1,2,3|
1Department of Mechanical Engineering, University of California, Riverside, CA USA
2Materials Science & Engineering Program, University of California, Riverside, CA USA
3Department of Bioengineering, University of California, Riverside, CA USA
4Department of Bioengineering, University of Colorado, Denver, CO USA
5Department of Ophthalmology, University of Colorado School of Medicine, Denver, CO USA
BACKGROUND: Drug delivery to the eye remains a key challenge, due to limitations inherent to prevailing techniques. For example, while topical delivery offers simplicity and safety, its efficacy is limited by poor bioavailability, due to natural transport barriers (e.g. corneal epithelium) and clearance mechanisms (e.g. tear flow and conjunctival blood flow). Similarly, while intravitreal injection provides means for circumventing such limitations, non-negligible potential for retinal detachment and other complications adversely affects safety. Herein, we discuss our initial efforts to address these limitations through development of titanium-based microneedles (MNs) which seek to provide a safer, simpler, and more efficacious means of ocular drug delivery.
MATERIALS AND METHODS: Devices with in-plane geometry and through-thickness fenestrations (Fig. 1) that serve as drug reservoirs for passive delivery via diffusive transport from fast-dissolving coatings are demonstrated. Details regarding device design, fabrication, and mechanical testing are presented, as are results from preliminary coating characterization and insertion testing in ex vivo rabbit cornea.
RESULTS: Preliminary studies using model drug coatings have qualitatively demonstrated a good balance of viscosity and wettability on the fenestrated Ti MNs. Mechanical testing under buckling loading indicates that failure occurs within the bounds predicted by finite element analysis. Examination of the MNs after testing indicates a graceful, plasticity-based failure mode, thus suggesting potential for greater safety and reliability than MNs made from brittle materials, such as Si and SiO2. Successful MN penetration into excised rabbit cornea was verified with histological imaging, and no damage to the MN was evident after removal.
CONCLUSIONS: Collectively, these data suggest that fenestrated Ti MNs can safely penetrate into, but not through cornea. Moreover, the ability to achieve insertion manually demonstrates the simplicity of this approach. Efforts are currently underway to evaluate MN efficacy by quantifying drug loading and delivery, in vitro and in vivo.
Shrink-Induced Rapid Production of Silica Nanostructures for Fluorescence-Enhancing Microarrays
Sophia Lin, Himanshu Sharma, Nazila Norouzi, Jolie McLane, Michelle Khine
Efforts to improve the detection sensitivity of fluorescent assays have resulted in modified fluorophores, advanced detection apparatuses, and engineered substrates. Examples of effective substrate modification include metal nanostructures, immobilized nanoparticles, and quantum dots. These substrates are typically fabricated on hard surfaces such as glass and silicon and usually require extensive fabrication steps and special expensive equipment for analysis.
We present an alternative low-cost method for enhancing fluorescent detection capability. Instead of using a traditional glass or silicon substrate, we fabricate our fluorescence-enhancing microarrays using inexpensive pre-stressed thermoplastic sheets. The methods described are inexpensive, and low-cost fabrication technologies are important for point-of-care (POC) applications. To construct the fluorescence- enhancing microarray, we sputter silica (SiO2) onto a polyolefin (PO) film and functionalize the surface with wet chemistry. As a model system, we link biotin onto the activated SiO2-coated PO film, hybridize the target probe with fluorescently conjugated streptavidin, and then shrink the entire substrate to produce a miniature microarray with enhanced fluorescence signal (Figure 1a).
We observe a ~ 100-fold signal enhancement, which is hypothesized to come from both the concentration of biomolecules on the substrate and the constructive interference effects from light scattering within the SiO2 structures (Figure 1b). By leveraging the stiffness mismatch between the thin SiO2 layer deposited on the polymer film, we create nanostructures with fluorescence-enhancing abilities for bound fluorophores (Figure 1c). The SiO2 nanostructures are important for amplifying fluorescence signal. A shrunk PO microarray without the surface SiO2 layer results in less fluorescence enhancement compared to a shrunk SiO2-modified PO microarray (Figure 1d).
The techniques used are simple and inexpensive. We demonstrate that we are able to create sensitive and specific microarrays with significant signal enhancement within minutes. This holds great potential for low-cost POC detection of infectious diseases.
Enhancing the Detection Limit of a Protein Lateral‐Flow Immunoassay Using Aqueous Two‐Phase Micellar Systems
Foad Mashayekhi, Parsa M. Nafisi, Alexander M. Le, Cameron D. Yamanishi, Ricky Y.T. Chiu, Benjamin M. Wu, Daniel T. Kamei
Department of Bioengineering, UCLA
The detection of protein markers at the point-of-need has a wide variety of applications. These include detecting allergens in food samples or bioterrorism agents in-field. For such applications, a sensitive, rapid, and inexpensive detection assay that requires minimal training and power to operate is desired. Due to its ease of use, rapid processing, and minimal power and laboratory equipment requirements, the lateral-flow (immuno)assay (LFA) represents a potential detection method for these applications. However, the detection limit of LFA is inferior to current lab-based assays, such as the enzyme-linked immunosorbent assay, and needs to be improved. A practical solution for improving the detection limit of LFA is to concentrate a target protein in a solution prior to the detection step. In this study, a novel approach was used along with an aqueous two-phase micellar system comprised of the nonionic surfactant Triton X-114 to concentrate a model protein, namely transferrin, prior to its detection. Proteins, however, have been shown to partition, or distribute, fairly evenly between the two phases of an aqueous two-phase system, which in turn results in their limited concentration in one of the two phases. Therefore, larger colloidal gold particles decorated with antibodies for transferrin were used in the concentration step to bind to transferrin and aid its partitioning into the top, micelle-poor phase. By manipulating the volume ratio of the two coexisting micellar phases and combining the concentration step with LFA, the transferrin detection limit of LFA was improved by 10-fold from 0.5 μg/mL to 0.05 μg/mL.
Reconfigurable microfluidics with integrated aptasensors for sensitive detection of cell-secreted cytokines
Timothy Kwa, Ying Liu, Qing Zhou, Yandong Gao, Alexander Revzin
We report the development of a microdevice for quantifying tumor necrosis factor-alpha (TNF-α) secretion from monocytes in real time. By integrating miniature aptamer-modified electrodes with microfluidics, concentration and cellular secretion rates of TNF-α can be determined electrochemically.
In constructing aptasensors, an RNA aptamer specific to TNF-α is thiolated and labeled with a redox reporter molecule (Methylene Blue). Aptamer molecules are then immobilized onto microfabricated gold electrodes via thiol-gold bond. The glass regions around electrodes are functionalized with antibodies to promote cell attachment. The micropatterned surface is then enclosed into a two-layer polydimthethylsiloxane (PDMS) microfluidic device that allows controlled seeding of cells. Built into a microfluidic device is vacuum controlled collapsible chamber that may be lowered over the cell-electrode area to minimize the volume down to 19.6 nL. With the incorporation of an automated multiplexer samples were recorded every 10 minutes with square wave voltammetry over the course of several hours.
The figure below shows (A-B) cells patterned around the electrodes within the microfluidic chamber. The data (C) suggests that lowering chambers around individual electrodes limits cytokine diffusion into the bulk volume, resulting in higher local concentration and generating a stronger signal at the sensing electrodes. Quantifying TNF-α secretion in real-time may provide applications in immunology, tissue injury/regeneration and cancer research.
Advancing Next-Generation Proteomics: A Polymer-patterned Microchamber Enables Integration of the Distinct Protein Separations Comprising Two-Dimensional Electrophoresis
Augusto M. Tentori, Alex J. Hughes, and Amy E. Herr
We introduce a new microfluidic approach for rapid, integrated two-dimensional electrophoresis (2DE), as is critical to advancing the much needed ‘proteomics revolution’. 2DE integrates two serial assays to separate proteins by isoelectric point and size. Determining two physicochemical properties for each protein goes far to establish protein identity, even from complex biospecimens. Unfortunately, conventional benchtop 2DE is labor and time intensive, making the assay a bottleneck for protein studies. Prior microfluidic 2DE platforms have attempted to overcome these limitations, but suffer from information losses during transfer to the second stage. Our novel device microchamber architecture enables the separated species from the 1st dimension to be transferred for sizing without discretization into individual channels. This fundamentally different design strategy overcomes key technical gaps that have plagued advances in on-chip proteomics. Three major advances underpin our unique approach. Firstly, we introduce a new design utilizing microchamber and channel networks housing functional hydrogels. In contrast to previous studies, we use this approach to integrate distinct electrophoresis separations. Secondly, we utilize a novel photopatterning approach that allows spatial definition of physicochemical properties of hydrogels within this geometry. The carrier ampholyte based pH gradient used for isoelectric focusing (IEF) is confined to the microchamber by incorporating immobilines into the polyacrylamide gels flanking the microchamber. This marks a significant advance on state-of–the-art, as spatial definition of chemical properties has not been previously demonstrated. The resulting pH gradient is both linear and stable, with drifts <3μm/min. High performance sample focusing is rapidly achieved in <30min with resolutions of <0.1pH units and 1st dimension peak capacities of ~100. Thirdly, we demonstrate a novel integration approach that harnesses chemical mobilization of the first stage into distinct chamber regions, thus ensuring a rapid (<10min) and lossless (band broadening factors <1.3x) transfer process that preserves 1st dimension separation information.
Quantum-dot based sandwich immunoassay for sensitive detection of Escherichia coli on a cell-phone
Hongying Zhu, Uzair Sikora, and Aydogan Ozcan
UC Los Angeles
We designed a compact (3.5 x 5.5 x 2.4 cm) and cost-effective attachment that enables fluorescent imaging and sensing on a cell-phone. In our design, glass capillaries that are functionalized with anti-E. coli O157:H7 antibodies are employed as the solid substrate to perform quantum-dot based sandwich assay for the specific detection of E. Coli in liquid samples. As illustrated in Figure 1 (A) and (B), battery-powered inexpensive light-emitting-diodes (LEDs) are butt coupled to these functionalized capillaries without the use of any lenses or mechanical alignment stages. The LED light is guided within the capillary sample and excites QD labeled E. coli particles captured on the capillary surface. The fluorescence emission from these QDs is imaged using the cell-phone camera unit through an additional lens that is inserted between the capillary and the cell-phone. Since the fluorescence emission is perpendicular to the excitation path, a simple and cost-effective plastic absorption filter is sufficient to create the dark-field background since the detection path is perpendicular to the excitation path.
We used this fluorescent microscope design on the cellphone to quantify the fluorescent signal from each
capillary based sandwich immunoassay. Figures 1 (C) and (D) represent the dose-response curves for E. Coli in 2% gelatine-PBS buffer and fat-free milk, respectively. As shown in these curves, our detection limit is ~5-10 cfu per mL. We also performed experiments to verify the specificity of this platform using Salmonella contaminated samples (>104-106 cfu/mL), which showed a similar response as the control experiments reported in Figs. 1 (C) and (D).
In summary, we demonstrated a detection limit of ~5-10 cfu per mL E. Coli in both buffer and fat-free milk
samples using a field-portable cell-phone based fluorescent imaging and sensing platform. Our results reveal the promising potential of this cell-phone based E. Coli detection platform for screening water and food contamination.
Shreyas Vasanawala, Associate Professor, Department of Radiology, Stanford University Medical School
Combining Laser Ablation and FRET to Measure the Tension Distribution of Individual Stress Fiber Focal Adhesions
Ching–Wei Chang, Sanjay Kumar
Generation of traction against the extracellular matrix by stress fibers (SFs) via focal adhesions (FAs) is critical to mechanosensing, motility, and tensional homeostasis. However, the spatiotemporal relationship between SF force generation and tension on individual FAs remains poorly understood. Here we directly measure the tension distribution of individual stress fibers in living cells by combining subcellular laser nanosurgery with a vinculin fluorescence resonance energy transfer (FRET) tension sensor. Our results demonstrate that the tension change in FAs following SF ablation is not restricted to the FAs that are in direct contact with the severed SFs but is exhibited by almost all the FAs in the cell: most FAs show a decrease in tension while a minority of FAs has slight increase in tension. This tension distribution evolves with time following SF disruption and varies with the spatial location of the SF, consistent with our previous finding that central and peripheral SFs exhibit different viscoelastic properties and contributions to cell shape stability (Tanner et al., Biophys J 2010). In addition, morphometric analysis reveals that there is a greater change in tension for the FAs aligned in a direction that correlates with the long axis of cell polarity or that of the severed SF. This study enhances our understanding of how cells couple SF contractility to tension on individual FAs, and to our knowledge represents the first combination of laser nanosurgery with a molecular FRET sensor.
Design, Implementation and Characterization of a Dedicated Breast CT Scanner
Peymon Gazi, Kai Yang, George Burkett, John Boone
Dedicated breast CT (bCT) machine may be useful for patients with high risk of developing breast cancer. Previous studies show that bCT outperforms mammography for mass detection, but mammography shows better results in finding calcifications. The Breast Tomography Project at UC Davis has led to the development of two dedicated breast CT scanners that produce high resolution, fully tomographic images, overcoming tissue superposition effects found in mammography while maintaining an equivalent radiation dose. Over 400 patients have been imaged in an ongoing clinical trial. The first and second prototypes of bCT were codenamed Albion and Bodega.
The third prototype, Cambria, was designed and built at the Breast Tomography Research Lab and the first clinical patient scan was successfully implemented on April 12, 2012. Cambria has a similar physical structure as Bodega and Albion. The main differences are in using of a pulsed x-ray tube source instead of continuous x-ray sources and also using the x-ray detector in 1×1 binning mode.
The noise power properties and spatial resolution characteristics of Cambria were investigated. Figure 1 shows the significant improvement in the MTF curves. For this experiment, a very thin piece of metal wire was scanned at the center and edge of a virtual phantom placed in the field of view of the x-ray source. This wire was scanned with different number of projection images: 500, 400 and 300, using both scanners: Bodega and Cambria. The results show that using the pulsed x-ray tube, we were able to restore the MTF degradation caused by motion blurring phenomenon that exists in the CT imaging. Moreover using the detector in 1×1 binning mode improved the visibility of the fine details in the scanned object. For NPS analysis, the noise power spectra were calculated from difference data gerated by subtraction between two identical scans.
In conclusion, quantitative results from this noise power analysis, together with the investigation of the resolution properties, provide guidance for the bCT system operation, optimization and data reconstruction.
GPU accelerated multi-functional spectral-domain optical coherence tomography system at 1300nm
Yan Wang, Christian M. Oh, Michael C. Oliveira, M. Shahidul Islam, Arthur Ortega, B. Hyle Park
We present a GPU accelerated multi-functional spectral domain optical coherence tomography system at 1300nm. A graphic processing unit (GPU) was utilized in the real-time processing program to fulfill the heavy computation of intensity, flow, phase retardation and en face images. The GPU-CPU hybrid processing program is capable of real-time processing and display of every intensity image, comprised of 1024 pixels by 2048 A-lines acquired at 20 frames per second. The update rate for all four images with size of 1024 pixels by 2048 A-lines simultaneously (intensity, phase retardation, flow and en face view) is approximately 10 frames per second, which is five times faster than the purely CPU processing program. Additionally, we report for the first time the characterization of phase retardation and diattenuation by a sample comprised of a stacked set of polarizing film and wave plate. The calculated optic axis orientation, phase retardation and diattenuation match well with expected values. The speed of the each facet of the multi-functional OCT GPU-CPU hybrid acquisition system, intensity, phase retardation, and flow, were separately demonstrated by imaging a horseshoe crab lateral compound eye, a non-uniformly heated chicken muscle, and a microfluidic device. Finally, a mouse brain with a thin skull preparation was imaged with all image views (intensity, phase retardation, flow, en face flow) updating at a rate of 10 frames per second with the en face flow view displaying blood vasculature and demonstrated our ability to do rapid identification of structures in OCT images. Real- time recorded videos when imaging above samples will be presented to demonstrate the fast volume visualization ability of the GPU-CPU hybrid processing program.
Magnetic Particle Imaging for Safe Angiography
Patrick W. Goodwill, Laura R. Croft, Justin J. Konkle, Kuan Lu, Emine U. Saritas, Bo Zheng, Steven M. Conolly
One quarter of all iodinated contrast X-ray clinical imaging studies are now performed on chronic kidney disease (CKD) patients. Unfortunately, the iodine contrast agent used in X-ray is often toxic to CKD patients’ weak kidneys, leading to significant morbidity and mortality. Hence, we are pioneering a new medical imaging method, called Magnetic Particle Imaging (MPI), to replace X-ray and CT iodinated angiography, especially for CKD patients. MPI uses magnetic nanoparticle contrast agents that are much safer than iodine for CKD patients. MPI already offers superb contrast and extraordinary sensitivity. The iron oxide nanoparticle tracers required for MPI are also used in MRI, and some are already approved for human use, but the contrast agents are far more effective at illuminating blood vessels when used in the MPI modality. We have recently developed a systems theoretic framework for MPI called x-space MPI, which has already dramatically improved the speed and robustness of MPI image reconstruction. X-space MPI has allowed us to optimize the hardware for five MPI scanners. Moreover, x-space MPI provides a powerful framework for optimizing the size and magnetic properties of the iron oxide nanoparticle tracers used in MPI. Currently MPI nanoparticles have diameters in the 10-20 nanometer range, enabling millimeter-scale resolution in small animals. X-space MPI theory predicts that larger nanoparticles could enable up to 250 micron resolution imaging, which would represent a major breakthrough in safe imaging for CKD patients.
Crowd-sourced Games Toward Distributed Medical Image Analysis and Tele-Diagnosis
Sam Mavandadi, Stoyan Dimitrov, Steve Feng, Frank Yu, Uzair Sikora, Oguzhan Yaglidere, Swati Padmanabhan, Karin Nielsen, and Aydogan Ozcan
UC Los Angeles
Crowd-sourcing is an emerging concept that has attracted significant attention in recent years as a strategy for solving computationally expensive and difficult problems. In this computing paradigm, pieces of difficult computational problems are distributed to a large number of individuals. Each participant completes one piece of the computational puzzle, sending the results back to a central system where they are all combined together to formulate the overall solution to the original problem.
In this work we investigate whether the innate visual recognition and learning capabilities of untrained humans can be used in conducting reliable microscopic analysis of biomedical samples toward diagnosis. For this purpose, we designed entertaining digital games that are interfaced with artificial learning and processing back-ends to demonstrate that in the case of binary medical diagnostics decisions (e.g., infected vs. uninfected), with the use of crowd-sourced games it is possible to approach the accuracy of medical experts in making such diagnoses. Specifically, using non-expert gamers we report diagnosis of malaria infected red blood cells with an accuracy that is within 1.25% of the diagnostics decisions made by a trained medical professional.
The proposed platform can serve purposes beyond just malaria diagnosis. It can also be used as a training platform for medical experts, and can be extended to other forms of image-based diagnostics other than malaria. As such it can be a general telemedicine platform, potentially influencing education, professional training, and public health policies around the world.
Optical Molecular Imaging for Detecting Changes in Extracellular pH in Oral Neoplasia
Authors: Zhen Luo1, Melissa Loja2, D. Greg Farwell4, Quang C. Luu4, Paul J. Donald4, Regina Gandour-Edwards5, Nitin Nitin1&3
1 Department of Biological and Agricultural Engineering, University of California – Davis
2 School of Medicine, University of California – Davis
3 Food Science and Technology, University of California – Davis
4 Department of Otolaryngology – Head and Neck Surgery, University of California – Davis
5 Department of Pathology, University of California – Davis
It is well known that development of neoplasia leads to an increase in extracellular acidosis (lowering of pH). This decrease in extracellular pH can be a critical marker for the detection and prognosis of disease. The acidic tumor environment has been shown to be associated with increased invasion, metastasis, and resistance to drug therapies. The overall objectives of our study are to develop an optical imaging approach to measure variations in intra-tissue pH and to characterize its potential for detection of early stages of neoplasia.
Intra-tissue uptake and distribution of a topically-applied fluorescently-labeled pH (Low) Insertion Peptide (pHLIP) probe were characterized using both widefield and high resolution imaging techniques respectively. The specificity of measuring extracellular pH using pHLIP was validated in a cell culture model. To evaluate the clinical translational potential of this technology, 11 patients provided 11 clinically normal and 16 distinct clinically abnormal biopsies.
Prior to labeling, abnormal tissue shows less auto-fluorescence than clinically normal tissue in widefield imaging mode. After labeling with pHLIP for 1 hour, abnormal tissue shows a higher level of fluorescence signal due to increased uptake of the pHLIP probe as compared with its paired normal biopsy. High resolution imaging also confirms the increase in mean signal intensity in the abnormal biopsies as compared to the paired normal biopsies. High resolution imaging also shows staining in abnormal tissues with penetration depth greater than 400-500 microns, demonstrating that topical application of the pHLIP probe is effective for delivery of this molecular imaging agent. Imaging results were further correlated with pathological diagnosis.
The results demonstrate that topical application of fluorescently-labeled pHLIP can detect and differentiate clinically normal and abnormal tissues using widefield and high-resolution fluorescent imaging modalities. This technology will provide an effective tool to characterize tumor microenvironment and improve detection and prognosis of oral cancer.