A microfluidic device was created for single-cell capture and analysis using polydimethylsiloxane (PDMS) channels and a glass substrate to develop a microfluidic single-cell impedance sensor for cell diagnostics. The device was fabricated using photolithography to create a master mold which in turn will use soft lithography to create the PDMS components for constant device production. The commercial software, COMSOLTM Multiphysics, was used to quantify the fluid dynamics in shallow micro-channels. The device will be able to capture a cell and sequester it long enough to enable measurement of the impedance spectra that can characterize cell. The proposed device will be designed to capture a single cell and permit back-flow to flush out excess cells in the chamber. The device will be designed to use syringe pumps and the syringe-controlled channel will also be used to capture and release the cell to ensure cell control and device reusability. We hypothesize that these characteristics along with other proposed design factors will result in a unique microfluidic cell-capture device that will enable single-cell impedance sensing and characterization.

A micro-electrophysiological analysis system (-EPAS) using various microfabrication techniques for single cell study was developed. Conventional microfabrication techniques combined with plastic and polymer microfabrication techniques have been used to realize the system. The system is capable of performing patch clamp recording and whole cell electrical impedance spectroscopy (EIS) on a single cell. Methodologies for single cell manipulation were developed. The ion channel activities of primary cultured bovine chromaffin cells were measured in both the patch clamping mode and the whole cell EIS mode. Membrane capacitance of the chromaffin cell was calculated from these measurements. Increases in the capacitances were observed when certain ion channels were blocked using toxins. The dielectric properties of human breast cancer cell lines from different pathological stages were measured and compared to a normal human breast cell line in the whole cell EIS mode. The measured properties were correlated to the pathological stages of the breast cancer cell lines. Decreases in the membrane capacitances were observed for the more pathologically progressed cancer cell lines.

Doctor of Philosophy / Department of Chemistry / Christopher T. Culbertson / Analytical separations form the bulk of experiments in both research and industry. The choice of separation technique is governed by the characteristics of the analyte and purpose of separation. Miniaturization of chromatographic techniques enables the separation and purification of small volume samples that are often in limited supply. Capillary electrophoresis and immunoaffinity chromatography are examples of techniques that can be easily miniaturized with minimum loss in separation efficiency. These techniques were used in the experiments presented in this dissertation. Chapter 1 discusses the underlying principles of capillary electrophoresis and immunoaffinity chromatography. In the second chapter, the results from immunoaffinity chromatography experiments that utilized antibody-coated magnetic beads to purify serine proteases and serine protease inhibitors (serpins) from A. gambiae hemolymph are presented and discussed. Serine proteases and serpins play a key role in the insect innate immunity system. Serpins regulate the activity of serine proteases by forming irreversible complexes with the proteases. To identify the proteases that couple to these serpins, protein A magnetic beads were coated with SRPN2 antibody and then incubated with A. gambiae hemolymph. The antibody isolated both the free SRPN2 and the SRPN2-protease complex. The purified proteases were identified by ESI-MS from as few as 25 insects. In Chapter 3, an integrated glass/PDMS hybrid microfluidic device was utilized for the transportation and lysis of cells at a high throughput. Jurkat cells were labeled with 6-CFDA (an internal standard) and DAF-FM (a NO specific fluorophore). Laser-induced fluorescence (LIF) detection was utilized to detect nitric oxide (NO) from single Jurkat cells. The resulting electropherograms were used to study the variation in NO production following stimulation with lipopolysaccharide (LPS). 3 h LPS-stimulation resulted in a two fold increase in NO production in both bulk and single cell analysis. A comparison of bulk and single cell NO measurements were performed and the average NO production in single cells compared well to the increase measured at the bulk cell level. Chapter 4 discusses the preliminary experiments with a T-shaped microfluidic device that exploit the property of poly(dimethylsiloxane) (PDMS) as an electroactive polymer (EAP), to enhance fluid mixing. EAPs deform when placed in an electric field. A thin layer of PDMS was sandwiched between chrome electrodes, positioned on the horizontal arms of the T design, and the electrolyte-filled fluidic channel. A potential difference across the PDMS layer caused it to shrink and stretch, thereby increasing the channel volume. The electrodes were actuated at 180[degrees] out of phase and this caused the fluid stream in the vertical channel to fold and stretch resulting in enhanced contact surface area and shorter diffusion distances of the fluid, thereby improving mixing efficiency. All the experiments presented in this dissertation demonstrate the application of miniaturized chromatographic techniques for the efficient analysis of small volume biological samples.

Doctor of Philosophy / Department of Chemistry / Christopher T. Culbertson / Recent approaches in analytical separations are being advanced towards the “lab-on-a-chip” concept in which multiple lab functions are integrated into micro/nano fluidic platforms. Among the variety of separation techniques that can be implemented on microfluidic devices, capillary electrophoresis is the most popular as it provides high efficiency, simple, fast and low cost separations. In addition, integrating miniaturized fluid manipulation tools into microfluidic devices with separations is essential for a variety of biological applications. Chapter 1 discusses the fundamentals of capillary electrophoresis and miniaturized fluid manipulation tools and provides an over view of single cell analysis in microfluidics. In chapter 2, the integration of miniaturized peristaltic pumps into multilayer microfluidic platforms is discussed. In addition, device characterization, precise fluid control and high throughput single cell analysis are discussed. As a proof of principle, T-lymphocytes were loaded with two fluorescent probes Carboxyfluorescein diacetate (CFDA) and Oregon green (OG). Thousands of single cells were automatically transported, lysed on these devices and analytes from the lysate were electrophoretically separated. 1120 cells were analyzed over the course of 80 min (14 cells/min) and separation characteristics of analytes released from individual cells were investigated. In the third chapter, the development of microfluidic platforms for the electrochemical detection of nitric oxide (NO) and other reactive nitrogen species (RNS) at the single cell level is discussed. A microfluidic system was developed to perform rapid cell lysis followed by electrochemical detection. Miniaturized microband electrodes were designed and integrated with a microfluidic separation channel. Three alignment techniques (in-channel, end-channel and off-channel configurations) were used to detect the electrochemical response of the analyte of interest. Furthermore, a model analyte (CFDA) was used to demonstrate the potential of performing the simultaneous dual detection with electrochemical and laser induced fluorescence detection. In addition, the same microfluidic platform was adapted to detect intracellular superoxide using laser induced fluorescence. In the fourth chapter, the off-chip integration of optical fiber bridges with multilayer microfluidic chips is discussed. A multimode optical fiber (~10cm long) was integrated between the single cell lysing spot and a spot downstream of the separation channel in order to detect both intact cells and the analyte in the lysate. This technique was used to create two detection spots on the microfluidic platform with the use of a single excitation source and single detector. Fluorescently labeled T-lymphocytes were automatically transported and lysed in a manner similar to that described in chapter 2. Hundreds of single cells were analyzed and the absolute migration time was determined for the analytes in the lysate. In addition, the separation characteristics of fluorescently labeled protein kinase B peptide substrates were investigated. Furthermore, this technique was used to measure cell size and the velocity of intact cells (discussed in 5th chapter) by making use of a light tunneling concept available in multimode optical fibers. All the experiments presented in this dissertation exploit the use of multilayer microfluidic platforms to investigate intracellular components in single cells in a high throughput manner that has several advantages over current conventional techniques.

<p>Cancer comprises a collection of diseases, all of which begin with abnormal tissue growth from various stimuli, including (but not limited to): heredity, genetic mutation, exposure to harmful substances, radiation as well as poor dieting and lack of exercise. The early detection of cancer is vital to providing life-saving, therapeutic intervention. However, current methods for detection (e.g., tissue biopsy, endoscopy and medical imaging) often suffer from low patient compliance and an elevated risk of complications in elderly patients. As such, many are looking to “liquid biopsies” for clues into presence and status of cancer due to its minimal invasiveness and ability to provide rich information about the native tumor. In such liquid biopsies, peripheral blood is drawn from patients and is screened for key biomarkers, chiefly circulating tumor cells (CTCs). Capturing, enumerating and analyzing the genetic and metabolomic characteristics of these CTCs may hold the key for guiding doctors to better understand the source of cancer at an earlier stage for more efficacious disease management.</p><p> The isolation of CTCs from whole blood, however, remains a significant challenge due to their (i) low abundance, (ii) lack of a universal surface marker and (iii) epithelial-mesenchymal transition that down-regulates common surface markers (e.g., EpCAM), reducing their likelihood of detection via positive selection assays. These factors potentiate the need for an improved cell isolation strategy that can collect CTCs via both positive and negative selection modalities as to avoid the reliance on a single marker, or set of markers, for more accurate enumeration and diagnosis.</p><p> The technologies proposed herein offer a unique set of strategies to focus, sort and template cells in three independent microfluidic modules. The first module exploits ultrasonic standing waves and a class of elastomeric particles for the rapid and discriminate sequestration of cells. This type of cell handling holds promise not only in sorting, but also in the isolation of soluble markers from biofluids. The second module contains components to focus (i.e., arrange) cells via forces from acoustic standing waves and separate cells in a high throughput fashion via free-flow magnetophoresis. The third module uses a printed array of micromagnets to capture magnetically labeled cells into well-defined compartments, enabling on-chip staining and single cell analysis. These technologies can operate in standalone formats, or can be adapted to operate with established analytical technologies, such as flow cytometry. A key advantage of these innovations is their ability to process erythrocyte-lysed blood in a rapid (and thus high throughput) fashion. They can process fluids at a variety of concentrations and flow rates, target cells with various immunophenotypes and sort cells via positive (and potentially negative) selection. These technologies are chip-based, fabricated using standard clean room equipment, towards a disposable clinical tool. With further optimization in design and performance, these technologies might aid in the early detection, and potentially treatment, of cancer and various other physical ailments.</p> / Dissertation

A comprehensive understanding of how the body and all its components function is essential when this knowledge is exploited for medical purposes. The achievements in biological and medical research during last decades has provided us with the complete human genome and identified signaling pathways that governs the cellular processes that facilitates the development and maintenance of higher order organisms. This has brought about the realization that diseases such as cancer is a consequence of genomic aberrations that effects these signaling pathways, endowing cancer cells with the capacity to circumvent homeostasis by acquiring features like self-sustained proliferation and insensitivity to apoptosis. The increased understanding of biology and medicine has been made possible by the development of advanced methods to carry out biological and clinical analyses. The demands of a method often differ regarding in what context it will be applied. It may be acceptable for method to be laborious and time consuming if it is used in basic research, but for medical purposes molecular methods need to be fast and straightforward to perform. Innovative technologies should preferentially address the demands of both researchers and clinicians and provide data not possible to obtain by other methods. An example of such a method is the in situ proximity ligation assay (in situ PLA). In this thesis I have used this method to determine the activity status, at the single-cell level, of the transforming growth factor-β (TGF-β) signaling pathway and activating protein-1 (AP-1) family of transcription factors.  Both of these pathways are frequently involved in cancer development and progression. In addition to this research I herein also present further modifications of in situ PLA, and analyses thereof, to increase the utility and resolution of this assay.

The fascinating capability of cellular self-organization during tissue development and repair is a central question in developmental biology and regenerative medicine. Understanding the dynamic morphogenic and regenerative processes of biological tissues will have important implications in biology and medicine. Nevertheless, the elucidation of the cellular self-organization processes is hindered by a lack of effective tools for monitoring the spatiotemporal gene expression distribution and a lack of ability to perturb the self-organization processes in living cells and tissues. Multimodal modularities that allow both single cell perturbation and gene detection are required to enable a new paradigm in the investigation of complex tissue morphogenic processes. To address this critical challenge in the field of developmental and regenerative medicine, we are developing a multimodal gold nanorod-locked nucleic acid (GNR-LNA) composite for single cell gene expression analysis in living cells and tissues at the transcriptional level. Using antisense RNA sequences, we design LNA probes for detecting specific molecular targets in living cells. The LNA probes bind to the GNR spontaneously due to the intrinsic affinity between the GNR and LNA. In close proximity, the fluorescent probes are effectively quenched by the GNR. Therefore, a fluorescent signal is only observed when the specific target thermodynamically displaces the LNA probe from the GNR. Furthermore, the GNR also serves as a transducer for photothermal ablation. Thus, we established a novel modularity for imaging the spatiotemporal gene expression distribution in living cells and tissues. The single cell analysis capability of our techniques enables us to adopt a unique approach to study the tissue regenerative processes during normal development and diseases, and this will have a profound impact on regenerative medicine and disease treatment in future. Moreover, we applied this GNR-LNA probe to explore the endothelial cell mRNA dynamics during capillary morphogenesis. Three different types of cells were identified due to their different roles during endothelial cell capillary-like formation process. Our findings indicated that the endothelial cell behavior is directly related to the Dll4 mRNA expression, and Dll4 expression in ECs determine the cell fate. Our GNR-LNA probe enable us to investigate the correlations between Dll4 mRNA expression and cell behavior during capillary morphogenesis. Experimental results indicated that: (1) When the endothelial cells aggregate, the cells migrate with certain displacement, the Dll4 mRNA expression decreases. (2) When the endothelial cells sprout, the cells migrate with small displacement but the cell shape changes to an ellipse shape, the Dll4 mRNA expression begin to increase. (3) When the endothelial cells elongate and form cell-cell contract with adjacent cells, the Dll4 expression decreased to a certain level and keep stable until the cell activity change to another stage. Furthermore, it has been demonstrated endothelial cells compete for the leader cell position during wound healing, collective cell migration, and tip cell formation during angiogenic process. It has been demonstrated that endothelial cells compete for the tip cell formation through Notch signaling pathway. However, how the mechanical force regulates tip cell formation is still unclear, and if mechanoregulation of tip cell formation through Notch pathway still unknown. Mechanical and chemical regulations of tissue morphogenesis and angiogenesis are being investigated in both in vitro capillary-like network formation assay and in vivo mice retina angiogenesis assay. Here, we investigated the mechanoregulation of mechanotransduction of tissue morphogenesis and angiogenesis using both in vitro endothelial cell tube formation model and in vivo mice retina blood vessel development model. Our results demonstrated that (1) Notch pathway negatively regulates tip cell formation: inhibition of Notch pathway (DAPT) enhances tip cell formation, induces Dll4 and Notch1 activity, activation of Notch pathway (Jag1 peptide) inhibits tip cell formation, suppresses Dll4 and Notch1 activity. (2) Mechanical force negatively regulate tip cell formation: (a) Decrease mechanical force via Rho kinase inhibitor Y-27632, myosin II inhibitor Blebbistatin, or laser ablation, enhances tip cell formation and induces Dll4 activity through mediation of Dll4-Notch1 lateral inhibition, (b) increase mechanical force via traction force inducer Nocodazole and Calyculin A, suppresses tip cell formation and inhibits Dll4 activity through activation of Notch pathway. (3) Mechanical force negatively regulates tip cell formation partially via mediation of Notch pathway. Mechanical force is necessary for tip cell formation and negatively regulate tip/stalk selection via Dll4-Notch1 lateral inhibition. Interruption of mechanical force enhance tip cell formation via suppression of Dll4-Notch1 lateral inhibition, thus resulting the increase of Dll4 expression. Enhance of mechanical force inhibits tip cell formation via activation of Dll4-Notch1 lateral inhibition, thus resulting the decreases of Dll4 expression. All these finding wills have great significance for various biomedical applications, such as tissue engineering, cancer, and drug screening.

Recent advances in micro technologies have equipped researches with novel tools for interacting with biological molecules and cells. This thesis focuses on the design, fabrication and application of microfluidic platforms for stimuli-responsive drug delivery and the electromechanical characterization of single cells. Stimuli-responsive hydrogels are promising materials for controlled drug delivery due to their ability to respond to changes in local environmental conditions. In particular, nanohydrogel particles have been a topic of considerable interest due to their rapid response times compared to micro and macro-scale counterparts. Owing to their small size and thus low drug-loading capacity, these materials are unsuitable for prolonged drug delivery. To address this issue, stimuli-responsive implantable drug delivery micro devices by integrating microfabricated drug reservoirs with smart nano-hydrogel particles embedded composite membranes have been proposed. In one proposed glucose-responsive micro device, crosslinked glucose oxidase enables the oxidation of glucose into gluconic acid, producing a microenvironment with lower pH values to modulate the pH-responsive nanoparticles. In vitro glucose-responsive drug release profiles were characterized and normoglycemic glucose levels in diabetic rats with device implantation were also recorded. The biophysical properties of single cells have recently been demonstrated as an important indicator of disease diagnosis. Existing technologies are capable of characterizing single parameter either electrical or mechanical rapidly, but not both, which could only collect limited information for cell status evaluation. To address this issue, two microfluidic platforms capable of simultaneously characterizing both the electrical and mechanical properties of single cells based on electrodeformation and integrated impedance spectroscopy with micropipette aspiration have been proposed. In one proposed microfluidic device, a negative pressure was used to suck cells continuously through the aspiration channel with impedance profiles measured. By interpreting impedance profiles, transit time and impedance amplitude ratio can be quantified as cellular mechanical and electrical property indicators. Neural network based cell classification was conducted, demonstrating that two biophysical parameters could provide a higher cell classification success rate than using electrical or mechanical parameter alone.

Recent advances in micro technologies have equipped researches with novel tools for interacting with biological molecules and cells. This thesis focuses on the design, fabrication and application of microfluidic platforms for stimuli-responsive drug delivery and the electromechanical characterization of single cells. Stimuli-responsive hydrogels are promising materials for controlled drug delivery due to their ability to respond to changes in local environmental conditions. In particular, nanohydrogel particles have been a topic of considerable interest due to their rapid response times compared to micro and macro-scale counterparts. Owing to their small size and thus low drug-loading capacity, these materials are unsuitable for prolonged drug delivery. To address this issue, stimuli-responsive implantable drug delivery micro devices by integrating microfabricated drug reservoirs with smart nano-hydrogel particles embedded composite membranes have been proposed. In one proposed glucose-responsive micro device, crosslinked glucose oxidase enables the oxidation of glucose into gluconic acid, producing a microenvironment with lower pH values to modulate the pH-responsive nanoparticles. In vitro glucose-responsive drug release profiles were characterized and normoglycemic glucose levels in diabetic rats with device implantation were also recorded. The biophysical properties of single cells have recently been demonstrated as an important indicator of disease diagnosis. Existing technologies are capable of characterizing single parameter either electrical or mechanical rapidly, but not both, which could only collect limited information for cell status evaluation. To address this issue, two microfluidic platforms capable of simultaneously characterizing both the electrical and mechanical properties of single cells based on electrodeformation and integrated impedance spectroscopy with micropipette aspiration have been proposed. In one proposed microfluidic device, a negative pressure was used to suck cells continuously through the aspiration channel with impedance profiles measured. By interpreting impedance profiles, transit time and impedance amplitude ratio can be quantified as cellular mechanical and electrical property indicators. Neural network based cell classification was conducted, demonstrating that two biophysical parameters could provide a higher cell classification success rate than using electrical or mechanical parameter alone.

We have employed a differential detector combined with dielectrophoretic (DEP) translation in a microfluidic channel to monitor dielectric response of single cells and particularly to track phenomenon related to apoptosis. Two different cell lines were studied; Chinese hamster ovary cells (CHO) and MRC5 cells. Dielectric response was quantified by a factor called Force Index. Force Index was studied statistically to identify apoptotic subpopulations. Another direction of this work was to monitor changes in the cytoplasm conductivity following inhibition of mitochondrial ATP production by Oligomycin. To make the DEP response mostly sensitive to the cytoplasm conductivity, medium conductivity and DEP frequency were adjusted such that Clausius Mossotti factor and hence DEP response become less sensitive to cell radius. Chinese hamster ovary cells were used in this work and the impact of different concentrations of Oligomycin has been studied. We show that following exposure to Oligomycin at 8 μg/ml, cytoplasm conductivity drops. The majority of the changes takes place within one hour of exposure to the drug. Furthermore, double shell models has been used to estimate cytoplasm conductivity in a medium with conductivity of 0.42 S/m and the drop in the cytoplasm conductivity following treatment with Oligomycin was estimated to be ≈ 0.16 S/m. The magnitude of the decrease in the cytoplasm conductivity is evidence that Glycolysis is active as an energy production pathway within the cell. This approach can be used to quantify Glycolysis versus mitochondria ATP production which has an application in Warburg effect in cancer cells and monitoring bioprocesses.