Showing papers by "Mehmet Toner published in 2007"

Isolation of rare circulating tumour cells in cancer patients by microchip technology.

Abstract: Viable tumour-derived epithelial cells (circulating tumour cells or CTCs) have been identified in peripheral blood from cancer patients and are probably the origin of intractable metastatic disease. Although extremely rare, CTCs represent a potential alternative to invasive biopsies as a source of tumour tissue for the detection, characterization and monitoring of non-haematologic cancers. The ability to identify, isolate, propagate and molecularly characterize CTC subpopulations could further the discovery of cancer stem cell biomarkers and expand the understanding of the biology of metastasis. Current strategies for isolating CTCs are limited to complex analytic approaches that generate very low yield and purity. Here we describe the development of a unique microfluidic platform (the 'CTC-chip') capable of efficient and selective separation of viable CTCs from peripheral whole blood samples, mediated by the interaction of target CTCs with antibody (EpCAM)-coated microposts under precisely controlled laminar flow conditions, and without requisite pre-labelling or processing of samples. The CTC-chip successfully identified CTCs in the peripheral blood of patients with metastatic lung, prostate, pancreatic, breast and colon cancer in 115 of 116 (99%) samples, with a range of 5-1,281 CTCs per ml and approximately 50% purity. In addition, CTCs were isolated in 7/7 patients with early-stage prostate cancer. Given the high sensitivity and specificity of the CTC-chip, we tested its potential utility in monitoring response to anti-cancer therapy. In a small cohort of patients with metastatic cancer undergoing systemic treatment, temporal changes in CTC numbers correlated reasonably well with the clinical course of disease as measured by standard radiographic methods. Thus, the CTC-chip provides a new and effective tool for accurate identification and measurement of CTCs in patients with cancer. It has broad implications in advancing both cancer biology research and clinical cancer management, including the detection, diagnosis and monitoring of cancer.

Continuous inertial focusing, ordering, and separation of particles in microchannels

Abstract: Under laminar flow conditions, when no external forces are applied, particles are generally thought to follow fluid streamlines. Contrary to this perspective, we observe that flowing particles migrate across streamlines in a continuous, predictable, and accurate manner in microchannels experiencing laminar flows. The migration is attributed to lift forces on particles that are observed when inertial aspects of the flow become significant. We identified symmetric and asymmetric channel geometries that provide additional inertial forces that bias particular equilibrium positions to create continuous streams of ordered particles precisely positioned in three spatial dimensions. We were able to order particles laterally, within the transverse plane of the channel, with >80-nm accuracy, and longitudinally, in regular chains along the direction of flow. A fourth dimension of rotational alignment was observed for discoidal red blood cells. Unexpectedly, ordering appears to be independent of particle buoyant direction, suggesting only minor centrifugal contributions. Theoretical analysis indicates the physical principles are operational over a range of channel and particle length scales. The ability to differentially order particles of different sizes, continuously, at high rates, and without external forces in microchannels is expected to have a broad range of applications in continuous bioparticle separation, high-throughput cytometry, and large-scale filtration systems.

Multifunctional encoded particles for high-throughput biomolecule analysis.

Abstract: High-throughput screening for genetic analysis, combinatorial chemistry, and clinical diagnostics benefits from multiplexing, which allows for the simultaneous assay of several analytes but necessitates an encoding scheme for molecular identification. Current approaches for multiplexed analysis involve complicated or expensive processes for encoding, functionalizing, or decoding active substrates (particles or surfaces) and often yield a very limited number of analyte-specific codes. We present a method based on continuous-flow lithography that combines particle synthesis and encoding and probe incorporation into a single process to generate multifunctional particles bearing over a million unique codes. By using such particles, we demonstrate a multiplexed, single-fluorescence detection of DNA oligomers with encoded particle libraries that can be scanned rapidly in a flow-through microfluidic channel. Furthermore, we demonstrate with high specificity the same multiplexed detection using individual multiprobe particles.

A microfluidic device for practical label-free CD4+ T cell counting of HIV-infected subjects

Abstract: Practical HIV diagnostics are urgently needed in resource-limited settings. While HIV infection can be diagnosed using simple, rapid, lateral flow immunoassays, HIV disease staging and treatment monitoring require accurate counting of a particular white blood cell subset, the CD4+ T lymphocyte. To address the limitations of current expensive, technically demanding and/or time-consuming approaches, we have developed a simple CD4 counting microfluidic device. This device uses cell affinity chromatography operated under differential shear flow to specifically isolate CD4+ T lymphocytes with high efficiency directly from 10 microlitres of unprocessed, unlabeled whole blood. CD4 counts are obtained under an optical microscope in a rapid, simple and label-free fashion. CD4 counts determined in our device matched measurements by conventional flow cytometry among HIV-positive subjects over a wide range of absolute CD4 counts (R2 = 0.93). This CD4 counting microdevice can be used for simple, rapid and affordable CD4 counting in point-of-care and resource-limited settings.

A high-throughput microfluidic real-time gene expression living cell array

Abstract: The dynamics of gene expression are fundamental to the coordination of cellular responses. Measurement of temporal gene expression patterns is currently limited to destructive low-throughput techniques such as northern blotting, reverse transcriptionpolymerase chain reaction (RT-PCR), and DNA microarrays. We report a scalable experimental platform that combines microfluidic addressability with quantitative live cell imaging of fluorescent protein transcriptional reporters to achieve real-time characterization of gene expression programs in living cells. Integrated microvalve arrays control row-seeding and column-stimulation of 256 nanoliter-scale bioreactors to create a high density matrix of stimulus–response experiments. We demonstrate the approach in the context of hepatic inflammation by acquiring ∼5000 single-time-point measurements in each automated and unattended experiment. Experiments can be assembled in hours and perform the equivalent of months of conventional experiments. By enabling efficient investigation of dynamic gene expression programs, this technology has the potential to make significant impacts in basic science, drug development, and clinical medicine.

Rare cell analysis using sample splitting and dna tags

Abstract: The present invention provides systems, apparatuses, and methods to detect the presence of fetal cells when mixed with a population of maternal cells in a sample and to test fetal abnormalities, e.g. aneuploidy. The present invention involves labeling regions of genomic DNA in each cell in said mixed sample with different labels wherein each label is specific to each cell and quantifying the labeled regions of genomic DNA from each cell in the mixed sample. More particularly the invention involves quantifying labeled DNA polymorphisms from each cell in the mixed sample.

Cell detection and counting through cell lysate impedance spectroscopy in microfluidic devices

Abstract: Cell-based microfluidic devices have attracted interest for a wide range of applications. While optical cell counting and flow cytometry-type devices have been reported extensively, sensitive and efficient non-optical methods to detect and quantify cells attached over large surface areas within microdevices are generally lacking. We describe an electrical method for counting cells based on the measurement of changes in conductivity of the surrounding medium due to ions released from surface-immobilized cells within a microfluidic channel. Immobilized cells are lysed using a low conductivity, hypotonic media and the resulting change in impedance is measured using surface patterned electrodes to detect and quantify the number of cells. We found that the bulk solution conductance increases linearly with the number of isolated cells contributing to solution ion concentration. The method of cell lysate impedance spectroscopy is sensitive enough to detect 20 cells µL–1, and offers a simple and efficient method for detecting and enumerating cells within microfluidic devices for many applications including measurement of CD4 cell counts in HIV patients in resource-limited settings. To our knowledge, this is the most sensitive approach using non-optical setups to enumerate immobilized cells. The microfluidic device, capable of isolating specific cell types from a complex bio-fluidic and quantifying cell number, can serve as a single use cartridge for a hand-held instrument to provide simple, fast and affordable cell counting in point-of-care settings.

Polar stimulation and constrained cell migration in microfluidic channels.

Abstract: Asymmetrical delivery of stimuli to moving cells for perturbing spatially-heterogeneous intracellular signaling is an experimental challenge not adequately met by existing technologies. Here, we report a robust microfluidic platform allowing localized treatment of the front and/or back of moving cells which crawl through narrow channels that they completely occlude. The enabling technical element for this study is a novel design for precise, passive balancing of flow inside the microfluidic device by contacting two fluid streams before splitting them again. The microchannels constrain cell morphology and induce qualitative and quantitative changes in neutrophil chemotaxis that mimic cells crawling through tissues.

Microfabrication-based modulation of embryonic stem cell differentiation

Abstract: Embryonic stem (ES) cells form spontaneous aggregates during differentiation, and cell–cell communication in the aggregates plays an important role in differentiation The development of a controlled differentiation scheme for ES cells has been hindered by the lack of a reliable method to produce uniform aggregate sizes Conventional techniques, such as hanging drop and suspension cultures, do not allow precise control over size of ES cell aggregates To surmount this problem, we microfabricated adhesive stencils to make mouse ES (mES) cell aggregates of specific sizes ranging from 100 µm to 500 µm in diameter With this technique, we studied the effect of the initial aggregate size on ES cell differentiation After 20 days of induction of differentiation, we analyzed the stem cell populations using gene and protein expression assays as well as biochemical functions Notably, we found that germ layer differentiation depends on the initial size of the ES cell aggregate Among the ES cell aggregate sizes tested, the aggregates with 300 µm diameter showed similar differentiation profiles of three germ layers as embryoid bodies made using the “hanging drop” technique The smaller (100 µm) aggregates showed the increased expression of ectodermal markers compared to the larger (500 µm) aggregates, while the 500 µm aggregates showed the increased expression of mesodermal and endodermal markers compared to the 100 µm aggregates These results indicate that the initial size of the aggregate is an important factor for ES cell differentiation, and can affect germ layer selection as well as the extent of differentiation

Methods for the diagnosis of fetal abnormalities

Abstract: The present invention relates to methods for detecting, enriching, and analyzing rare cells that are present in the blood, e.g. fetal cells. The invention further features methods of analyzing rare cell(s) to determine the presence of an abnormality, disease or condition in a subject, e.g. a fetus by analyzing a cellular sample from the subject.

Oxygen uptake rates and liver-specific functions of hepatocyte and 3T3 fibroblast co-cultures.

Abstract: Bioartificial liver (BAL) devices have been developed to treat patients undergoing acute liver failure. One of the most important parameters to consider in designing these devices is the oxygen consumption rate of the seeded hepatocytes which are known to have oxygen consumption rates 10 times higher than most other cell types. Hepatocytes in various culture configurations have been tested in BAL devices including those formats that involve co-culture of hepatocytes with other cell types. In this study, we investigated, for the first time, oxygen uptake rates (OUR)s of hepatocytes co-cultured with 3T3-J2 fibro- blasts at various hepatocyte to fibroblast seeding ratios. OURs were determined by measuring the rate of oxygen disappearance using a ruthenium-coated optical probe after closing and sealing the culture dish. Albumin and urea production rates were measured to assess hepatocyte func- tion. Lower hepatocyte density co-cultures demonstrated significantly higher OURs (2 to 3.5-fold) and liver- specific functions (1.6-fold for albumin and 4.5-fold for urea pro- duction) on a per cell basis than those seeded at higher densities. Increases in OUR correlated well with increased liver-specific functions. OURs (Vm) were modeled by fitting Michaelis-Menten kinetics and the model predictions closely correlated with the experimental data. This study provides useful information for predicting BAL design parameters that will avoid oxygen limitations, as well as maximize metabolic functions. Biotechnol. Bioeng. 2007;97: 188-199.

A microchip approach for practical label-free CD4+ T-cell counting of HIV-infected subjects in resource-poor settings.

Abstract: Simple affordable CD4 cell counting is urgently needed to stage and monitor HIV-infected patients in resource-limited settings. To address the limitations of current approaches, we designed a simple, label-free, and cost-effective CD4 cell counting device using microfluidic technology. We previously described the fabrication of a microfluidic system for high-efficiency isolation of pure populations of CD4+ T cells based on cell affinity chromatography operated under controlled flow. Here, we compare the performance of a microfluidic CD4 cell counting device against standard flow cytometry in 49 HIV-positive subjects over a wide range of absolute CD4 cell counts. We observed a close correlation between CD4 cell counts from the microchip device and measurements by flow cytometry, using unprocessed whole blood from HIV-positive adult subjects. Sensitivities for distinguishing clinically relevant thresholds of 200, 350, and 500 cells/microL are 0.86, 0.90, and 0.97, respectively. Specificity is 0.94 or higher at all thresholds. This device can serve as a functional cartridge for fast, accurate, affordable, and simple CD4 cell counting in resource-limited settings.

Patterned Co‐Culture of Primary Hepatocytes and Fibroblasts Using Polyelectrolyte Multilayer Templates

Abstract: This paper describes the formation of patterned cell co-cultures using the layer-by-layer deposition of synthetic ionic polymers and without the aid of adhesive proteins/ligands such as collagen or fibronectin In this study, we used synthetic polymers, namely poly(diallyldimethylammonium chloride) (PDAC) and sulfonated polystyrene (SPS) as the polycation and polyanion, respectively, to build the multilayer films We formed SPS patterns on polyelectrolyte multilayer (PEM) surfaces either by microcontact printing PDAC onto SPS surfaces or vice-versa To create patterned co-cultures on PEMs, we capitalize on the preferential attachment and spreading of primary hepatocytes on SPS as opposed to PDAC surfaces In contrast, fibroblasts readily attached to both PDAC and SPS surfaces, and as a result, we were able to obtain patterned co-cultures of fibroblast and primary hepatocytes on synthetic PEM surfaces We characterized the morphology and hepatic-specific functions of the patterned cell co-cultures with microscopy and biochemical assays Our results suggest an alternative approach to fabricating controlled co-cultures with specified cell-cell and cell-surface interactions; this approach provides flexibility in designing cell-specific surfaces for tissue engineering applications

Hepatic tissue engineering for adjunct and temporary liver support

Abstract: The severe donor liver shortage, high cost, and complexity of orthotopic liver transplantation have prompted the search for alternative treatment strategies for end‐stage liver disease, which would require less donor material, be cheaper, and less invasive. Hepatic tissue engineering encompasses several approaches to develop adjunct internal liver support methods, such as hepatocyte transplantation and implantable hepatocyte‐based devices, as well as temporary extracorporeal liver support techniques, such as bioartificial liver assist devices. Many tissue engineered liver support systems have passed the “proof of principle” test in preclinical and clinical studies; however, they have not yet been found sufficiently reliably effective for routine clinical use. In this review we describe, from an engineering perspective, the progress and remaining challenges that must be resolved in order to develop the next generation of implantable and extracorporeal devices for adjunct or temporary liver assist. (Liver Transpl 2004;10:1331–1342.)

Analysis Of Rare Cell-Enriched Samples

Abstract: The present invention relates to methods for detecting, enriching, and analyzing rare cells that are present in the blood, e.g., epithelial cells. The invention further features methods of analyzing rare cell(s) to determine the presence of an abnormality, disease or condition in a subject by analyzing a cellular sample from the subject.

Selection of cells using biomarkers

Abstract: The present invention provides systems, apparatuses, and methods to isolate, select or detect the presence of a target cell (e.g., fetal cells) in a sample comprising mixed populations of cells that vastly outnumber the target cells. Target cells include fetal cells, such as nucleated red blood cells, and methods of selecting such cells include diagnosis of fetal abnormalities, i.e., aneuploidy. Furthermore, methods comprise utilizing fetal biomarkers to select fetal cells in a sample comprising fetal and adult cells.

Long-term storage of mouse spermatozoa after evaporative drying.

Abstract: To determine if mouse spermatozoa could be preserved long-term without using liquid nitrogen, mouse spermatozoa in trehalose-EGTA solution were partially evaporatively dried under nitrogen gas (5 min at flow rate10 l/min) and stored for 1 week and 5 months at 4, -20, and -80 degrees C before intracytoplasmic sperm injection. Fertilization rates were neither different with spermatozoa stored at 4, -20, or -80 degrees C for 1 week or 1, 3, and 5 months respectively, nor blastocyst formation rates with spermatozoa stored for 1 week and 1 month. However, spermatozoa stored at 4 and -20 degrees C for 3 months resulted in fewer blastocysts (35.1 and 54.3% respectively) when compared with spermatozoa stored at -80 degrees C (74.4%). Blastocyst formation rates using spermatozoa stored for 5 months at -20 degrees C (57.4%) or -80 degrees C (74.5%) were not significantly different from those stored for 3 months at the same temperatures respectively, but were significantly better than those stored for 5 months at 4 degrees C (10.2%). Blastocysts derived from spermatozoa stored for 3 and 5 months at -20 and -80 degrees C respectively, were then transferred to pseudopregnant mothers to develop into healthy liveborn offspring. No significant differences were found in embryo transfer rates (number of pups born/number of embryos transferred), weaning rates, or sex ratios of resultant pups, which were healthy and reproductively sound. These results demonstrate for the first time that partially evaporatively dried mouse spermatozoa in trehalose-EGTA solution can be preserved for long term at -20 and -80 degrees C. The possibility that the storage temperature must be less than the glass transition temperature is discussed.

Devices and methods for detecting cells and other analytes

Abstract: The invention features methods, devices, and kits for the isolation of analytes (e.g., a cell). A sample containing a desired analyte is introduced into a microfluidic device containing moieties that bind the desired analyte. A shear stress is applied that is great enough to prevent binding of undesired analytes and low enough to allow binding of the analyte of interest. Once bound, the desired analytes can be analyzed (e.g., counted). The invention also features methods for determining a shear stress for isolating a desired analyte.

Osmotic selection of human mesenchymal stem/progenitor cells from umbilical cord blood.

Abstract: The isolation of undifferentiated adult stem/progenitor cells remains a challenging task primarily due to the rare quantity of these cells in biological samples and the lack of unique markers. Herein, we report a relatively straightforward method for isolation of human mesenchymal stem cells (MSCs) based on their unusual resistance to osmotic lysis, which we term "osmotic selection" (OS). MSCs can remarkably withstand significant exposure to hypotonic conditions (> 30 min) with only a reversible impairment in cell proliferation and with no loss of stem cell potential after exposure. Comparison of MSCs to other circulating nonhematopoietic cells revealed a time regime, by which purification of these cells would be attainable without considerable cell loss. OS showed a 50-fold enrichment of fibroblast colony-forming units from umbilical cord blood samples when compared to commonly employed techniques. After upstream processing, isolated cells using OS were immunophenotyped to be CD14-, CD34-, CD45-, CD44+, CD105+, and CD106+, and displayed multipotent differentiation. Preliminary investigations to determine mechanisms responsible for osmolytic resistance revealed MSCs to have an ineffective volume of 59%, with the ability to double cell volume at infinite dilution. Disruption of filamentous actin polymerization by cytochalasin D sensitized MSCs to osmotic lysis, which suggests a cytoskeletal element involved in osmolytic resistance.

V. Guidelines for sedation and analgesia during mechanical ventilation general overview

Abstract: V. Guidelines for Sedation and Analgesia During Mechanical Ventilation General Overview Michael B. Shapiro, MD, Michael A. West, MD, PhD, Avery B. Nathens, MD, PhD, MPH, Brian G. Harbrecht, MD, Fredrick A. Moore, MD, Paul E. Bankey, MD, PhD, Brad Freeman, MD, Jeffrey L. Johnson, MD, Bruce A. McKinley, PhD, Joseph P. Minei, MD, Ernest E. Moore, MD, Ronald V. Maier, MD, and Inflammation and the Host Response to Injury Large Scale Collaborative Research Project

Role of Trehalose in Prevention of Giant Vesicle Adsorption and Encapsulated Solute Leakage in Anhydrobiotic Preservation

Abstract: Anhydrobiotic preservation has the potential to allow the processing and storage of mammalian cells in a state of suspended animation at ambient conditions in trehalose glasses; however, stressesparticularly to the lipid bilayerduring desiccation and rehydration have thus far prevented the full realization of the promise of this technique. Giant gel-phase 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) and liquid-crystalline-phase 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC) vesicles provide a model cell system with which to elucidate the role of trehalose in surface−lipid bilayer interactions, as well as the part played by lipid phase. In the absence of trehalose, DSPC liposomes adsorbed to polystyrene, producing irreversible structural changes and apparent leakage of all intravesicular solute upon drying and rehydration. Addition of trehalose significantly reduced vesicle adsorption with only transient intravesicular solute leakage for the rehydrated vesicles; however, at very low moisture content...

Roles of thermodynamic state and molecular mobility in biopreservation

Abstract: Mehmet Toner Center for Engineering in Medicine/Surgical Services Harvard Medical School Massachusetts General Hospital Shriners Hospital for Children 41.1 Water–Solute Interactions and Intracellular Transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41-3 Intracellular Water and Molecular Mobility • Transmembrane Water Transport Effects 41.2 Molecular Mobility in Preservation . . . . . . . . . . . . . . . . . . . . 41-6 Molecular Mobility in Supercooling and Phase Change • Cryopreservation • Vitrification • Vitrification by Ultrafast Cooling • Vitrification by Desiccation • Lyophilization 41.3 Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41-14 41.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41-15 Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41-16 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41-16

Phenotypic analysis of C57BL/6J and FVB/NJ mice generated using evaporatively dried spermatozoa.

Abstract: Combination of evaporative drying and frozen storage at -80 degrees C has been used successfully to preserve hybrid B6D2F1 mouse spermatozoa. To determine whether this method can be applied equally well to inbred mice, spermatozoa of C57BL/6J and FVB/ NJ mice were evaporatively dried and stored for 1 mo at -80 degrees C before being used for intracytoplasmic sperm injection (ICSI) to produce live offspring. After weaning, 1 male and 1 female mouse from each litter were randomly selected at 8 wk of age for natural mating to produce live offspring. Results showed that spermatozoa from both inbred strains that had been evaporatively dried and subsequently stored at -80 degrees C could be used successfully to derive live, healthy, and reproductively sound offspring by ICSI. No significant differences were found in embryo transfer rate (number of pups born/number of embryos transferred), litter size, weaning rate, body weight, number of pathologic lesions, and amount of contamination by pathogens of mice produced by ICSI using evaporatively dried spermatozoa compared with mice produced by natural mating or by ICSI using fresh (that is, nonpreserved) spermatozoa. Progeny produced by mating mice generated from ICSI using evaporatively dried spermatozoa were normal. Therefore, spermatozoa from inbred mouse strains C57BL/6J and FVB/NJ can be preserved successfully after evaporative drying and frozen storage at -80 degrees C.