Hybrid Microfluidic Devices For On-Demand Manipulation and Screening of Neurons and Organs of Small Model Organisms

Caenorhabditis elegans and Drosophila melanogaster are widely used model organisms for neurological and cardiac studies due to their simple neuronal and cardiac systems, genome similarity to humans, and ease of maintenance in laboratories. However, their 50m-1mm sizes and continuous mobility impede their precise spatiotemporal manipulation, thereby, reducing the throughput of biological assays. By integrating glass capillaries into microfluidic devices and using 3D-printed fixtures for precise control, we have developed hybrid lab-on-a-chip devices to facilitate the processes of animal manipulation and stimuli control, using modules for single-organism selection, orientation, imaging and chemical stimulation. These microdevices enabled us to manipulate organisms individually and to orient them at any desired direction for imaging purposes. The applications of these hybrid microdevices were demonstrated in the optical and fluorescent imaging of C. elegans cells as well as cardiac screening of Drosophila larvae. This technique can be applied in fundamental biology, toxicology, and drug discovery

Application of micro/nanorobot in medicine

The development of micro/nanorobots and their application in medical treatment holds the promise of revolutionizing disease diagnosis and treatment. In comparison to conventional diagnostic and treatment methods, micro/nanorobots exhibit immense potential due to their small size and the ability to penetrate deep tissues. However, the transition of this technology from the laboratory to clinical applications presents significant challenges. This paper provides a comprehensive review of the research progress in micro/nanorobotics, encompassing biosensors, diagnostics, targeted drug delivery, and minimally invasive surgery. It also addresses the key issues and challenges facing this technology. The fusion of micro/nanorobots with medical treatments is poised to have a profound impact on the future of medicine

Microfluidic Planar Phospholipids Membrane System Advancing Dynamics Studies of Ion Channels and Membrane Physics

The interrogation of lipid membrane and biological ion channels supported within bilayer phospholipid membranes has greatly expanded our understanding of the roles membrane and ion channels play in a host of biological functions. Several key drawbacks of traditional electrophysiology systems used in these studies have long limited our effort to study the ion channels. Firstly, the large volume buffer in this system typically only allows single or multiple additions of reagents, while complete removal either is impossible or requires tedious effort to ensure the stability of membrane. Thus, it has been highly desirable to be able to rapidly and dynamically modulate the (bio)chemical conditions at the membrane site. Second, it is difficult to change temperature effectively with large thermal mass in macro device. Third, traditional PPM device host vertical membranes, therefore incompatible with confocal microscopy techniques. The miniaturization of bilayer phospholipid membrane has shown potential solution to the drawbacks stated above. A simple microfluidic design is developed to enable effective and robust dynamic perfusion of reagents directly to an on-chip planar phospholipid membrane (PPM). It allows ion channel conductance to be readily monitored under different dynamic reagent conditions, with perfusion rates up to 20 µL/min feasible without compromising the membrane integrity. It is estimated that the lower limit of time constant of kinetics that can be resolved by our system is 1 minute. Using this platform, the time-dependent responses of membrane-bound ceramide ion channels to treatments with La3+ and a Bcl-xL mutant were studied and the results were interpreted with a novel elastic biconcave distortion model. Another engineering challenge this dissertation takes on is the integration of fluorescence studies to micro-PPM system. The resulting novel microfluidic system enables high resolution, high magnification and real-time confocal microscope imaging with precise top and bottom (bio)chemical boundary conditions defined by perfusion, by integrating in situ PPM formation method, perfusion capability and microscopy compatibility. To demonstrate such electro-optical chip, lipid micro domains were imaged and quantitatively studied for their movements and responses to different physical parameters. As an extension to this platform, a double PPM system has been developed with the aim to study interactions between two membranes. Potential application in biophysics and biochemistry using those two platforms were discussed. Another important advantage of microfluidics is its lower thermal mass and compatibility with various microfabrication methods which enables potential integration of local temperature controller and sensor. A prototype thermal PPM chip is also discussed together with some preliminary results and their implication on ceramide channel assembly and disassembly mechanism

Silicon nanofluidic membrane for electrostatic control of drugs and analytes elution

Individualized long-term management of chronic pathologies remains an elusive goal despite recent progress in drug formulation and implantable devices. The lack of advanced systems for therapeutic administration that can be controlled and tailored based on patient needs precludes optimal management of pathologies, such as diabetes, hypertension, rheumatoid arthritis. Several triggered systems for drug delivery have been demonstrated. However, they mostly rely on continuous external stimuli, which hinder their application for long-term treatments. In this work, we investigated a silicon nanofluidic technology that incorporates a gate electrode and examined its ability to achieve reproducible control of drug release. Silicon carbide (SiC) was used to coat the membrane surface, including nanochannels, ensuring biocompatibility and chemical inertness for long-term stability for in vivo deployment. With the application of a small voltage (≤ 3 V DC) to the buried polysilicon electrode, we showed in vitro repeatable modulation of membrane permeability of two model analytes—methotrexate and quantum dots. Methotrexate is a first-line therapeutic approach for rheumatoid arthritis; quantum dots represent multi-functional nanoparticles with broad applicability from bio-labeling to targeted drug delivery. Importantly, SiC coating demonstrated optimal properties as a gate dielectric, which rendered our membrane relevant for multiple applications beyond drug delivery, such as lab on a chip and micro total analysis systems (µTAS)

A Microfluidic Device for Impedance Spectroscopy

Recently, microfluidics has become a versatile tool to investigate cellular biology and to build novel biomedical devices. Dielectric spectroscopy, on the other hand, allows non-invasive probing of biological cells. Information on the cell membrane, cytoplasm, and nucleus can be obtained by dielectric spectroscopy provided that appropriate tools are used in specific frequency ranges. This dissertation includes fabrication, characterization, and testing of a simple microfluidic device to measure cell dielectric properties. The dielectric measurements are performed on human T-cell leukemia (Jurkat), mouse melanoma (B16), mouse hepatoma (Hepa), and human costal chondrocyte cells. Dielectric measurements consist of measuring the complex impedance of cell suspensions as a function of frequency. Physical models are fitted to raw impedance data to obtain parameters for cell compartments. The dielectric measurements are further supported by dielectrophoresis (DEP) experiments. Crossover frequency, which is the applied frequency when the DEP force is equal to zero, is recorded for cells by changing buffer conductivity. Cell membrane properties are also estimated from the crossover frequency measurements. Sensing capability of the microfluidic device to external stimuli is tested with Jurkat, chondrocyte, and Hepa cells. Jurkat and chondrocyte cells are suspended in buffers with changing osmolarity, and cell membrane properties are probed. Results indicate osmotic swelling of Jurkat cells. Interestingly similar changes were not observed in chondrocyte cells. Ion efflux from Hepa cells is quantified by conductivity measurements, and ionic flux from an average cell is calculated. Finally, a separability parameter is introduced and plotted for Jurkat and B16 cells pair. The separability parameter is based on the difference of two cells\u27 Clausius-Mossotti factors, which is a function of the dielectric parameters of the cells, field frequency, and buffer conductivity. Using the separability maps one can choose the optimum conditions for cell separation using DEP

Development of a PDMS Based Micro Total Analysis System for Rapid Biomolecule Detection

The emerging field of micro total analysis system powered by microfluidics is expected to revolutionize miniaturization and automation for point-of-care-testing systems which require quick, efficient and reproducible results. In the present study, a PDMS based micro total analysis system has been developed for rapid, multi-purpose, impedance based detection of biomolecules. The major components of the micro total analysis system include a micropump, micromixer, magnetic separator and interdigitated electrodes for impedance detection. Three designs of pneumatically actuated PDMS based micropumps were fabricated and tested. Based on the performance test results, one of the micropumps was selected for integration. The experimental results of the micropump performance were confirmed by a 2D COMSOL simulation combined with an equivalent circuit analysis of the micropump. Three designs of pneumatically actuated PDMS based active micromixers were fabricated and tested. The micromixer testing involved determination of mixing efficiency based on the streptavidin-biotin conjugation reaction between biotin comjugated fluorescent microbeads and streptavidin conjugated paramagnetic microbeads, followed by fluorescence measurements. Based on the performance test results, one of the micromixers was selected for integration. The selected micropump and micromixer were integrated into a single microfluidic system. The testing of the magnetic separation scheme involved comparison of three permanent magnets and three electromagnets of different sizes and magnetic strengths, for capturing magnetic microbeads at various flow rates. Based on the test results, one of the permanent magnets was selected. The interdigitated electrodes were fabricated on a glass substrate with gold as the electrode material. The selected micropumps, micromixer and interdigitated electrodes were integrated to achieve a fully integrated microfluidic system. The fully integrated microfluidic system was first applied towards biotin conjugated fluorescent microbeads detection based on streptavidin-biotin conjugation reaction which is followed by impedance spectrum measurements. The lower detection limit for biotin conjugated fluorescent microbeads was experimentally determined to be 1.9 x 106 microbeads. The fully integrated microfluidic system was then applied towards immuno microbead based insulin detection. The lower detection limit for insulin was determined to be 10-5M. The total detection time was 20 min. An equivalent circuit analysis was performed to explain the impedance spectrum results

NASA Tech Briefs, February 2006

Topics discussed include: Nearly Direct Measurement of Relative Permittivity; DCS-Neural-Network Program for Aircraft Control and Testing; Dielectric Heaters for Testing Spacecraft Nuclear Reactors; Using Doppler Shifts of GPS Signals To Measure Angular Speed; Monitoring Temperatures of Tires Using Luminescent Materials; Highly Efficient Multilayer Thermoelectric Devices; Very High-Speed Digital Video Capability for In-Flight Use; MMIC DHBT Common-Base Amplifier for 172 GHz; Modular, Microprocessor-Controlled Flash Lighting System; Generic Environment for Simulating Launch Operations; Modular Aero-Propulsion System Simulation; X-Windows Socket Widget Class; Infrastructure for Rapid Development of Java GUI Programs; Processing Raman Spectra of High-Pressure Hydrogen Flames; X-Windows Information Sharing Protocol Widget Class; Simulating Humans as Integral Parts of Spacecraft Missions; Analyzing Power Supply and Demand on the ISS; Polyimides From a-BPDA and Aromatic Diamines; Making Plant-Support Structures From Waste Plant Fiber; Large Deployable Reflectarray Antenna; Periodically Discharging, Gas-Coalescing Filter; Ion Milling On Steps for Fabrication of Nanowires; Neuro-Prosthetic Implants With Adjustable Electrode Arrays; Microfluidic Devices for Studying Biomolecular Interactions; Studying Functions of All Yeast Genes Simultaneously; Polarization Phase-Compensating Coats for Metallic Mirrors; Tunable-Bandwidth Filter System; Methodology for Designing Fault-Protection Software; and Ground-Based Localization of Mars Rovers

Mechanobiology of Complex Loading in Functional Spinal Units

A majority of back pain, a costly condition and leading cause of disability, is mechanical in origin involving the intervertebral disc, facet joints, or ligamentum flavum. Mechanical loading may be beneficial or detrimental to spinal tissues depending on loading mode, magnitude, frequency, and duration. Ex vivo mechanobiology systems have been used to explore how axial loading parameters influence intervertebral disc biology, but flexion/extension (F/E) and combined rotations, loading modes relevant to back pain, have not been investigated. Moreover, biological responses in facet cartilage (FC) and ligamentum flavum (LF) have not been studied. A novel experimental platform was developed to assess simultaneous biological responses to six degrees-of-freedom (DOF) loading of intact functional spinal units (FSUs) in annulus fibrosus (AF), nucleus pulposus (NP), FC and LF. A bioreactor previously validated for assessment of axially compressed FSUs was attached to a robotic testing system and validated for rigid fixation and unrestricted movement in F/E and axial torsion (AT). At first, neutral F/E of varying range-of-motion and cycle number was applied. F/E loading elicited a predominantly catabolic response from spinal tissues with significant up-regulation of catabolic gene expression in AF and FC. Range-of-motion modulated aggrecan fragmentation in AF. AT was then added to F/E in small and large magnitudes to simulate mild and severe axial asymmetries treated clinically. F/E with coupled AT was pro-inflammatory in all spinal tissues and was pro-catabolic in AF and LF. In FC, which is gapped by torsion on one side and compressed on the other, pro-inflammatory changes were higher in gapped joints, and catabolic loss of matrix was higher in compressed joints. These findings point to a role for altered segmental mechanics in driving pro-inflammatory, catabolic processes in spinal tissues that may play a role in spinal disorders involved in back pain. Finally, multiple regression analysis was performed to assess how well mechanical responses predicted changes in gene expression. Mechanical predictors accounted for more variation in gene expression in FC and LF than AF and NP. The development of this system provides spine and orthopaedic research with a novel experimental platform that can evaluate complex loading and simulated in vivo motions

Microfuidic Devices and Open Access Tool for Localized Microinjection and Heart Monitoring of Drosophila Melanogaster

This thesis aims to address the current research gaps associated with the use of Drosophila larvae as an in-vivo model for cardiac toxicity and cardiac gene screening. In objective 1, we have developed a hybrid multi-tasking microfluidic platform that enables desired orientation, reversible immobilization, and localized microinjection of intact Drosophila larvae for recording heart activities upon injection of controlled dosages of different chemicals. In objective 2. we have developed software for in-vivo quantification of essential heartbeat parameters on intact Drosophila larvae. Several image segmentation and signal processing algorithms were developed to detect the heart, extract the heartbeat signal, and quantify heart rate and arrhythmicity index automatically, while other heartbeat parameters were quantified semi-automatically using the M-mode. In objective 3a, we demonstrated the application of our microfluidic device and heartbeat quantification software for investigating the effect of different chemicals (e.g., serotonin and heavy metals) on Drosophila larval heart function. Also, we applied our technology to genetically modified Drosophila larvae to investigate the effect of metal responsive transcription factor (MTF-1) against heavy metals cardiac toxicity (objective 3b)

Microfuidic Devices and Open Access Tool for Localized Microinjection and Heart Monitoring of Drosophila Melanogaster

This thesis aims to address the current research gaps associated with the use of Drosophila larvae as an in-vivo model for cardiac toxicity and cardiac gene screening. In objective 1, we have developed a hybrid multi-tasking microfluidic platform that enables desired orientation, reversible immobilization, and localized microinjection of intact Drosophila larvae for recording heart activities upon injection of controlled dosages of different chemicals. In objective 2. we have developed software for in-vivo quantification of essential heartbeat parameters on intact Drosophila larvae. Several image segmentation and signal processing algorithms were developed to detect the heart, extract the heartbeat signal, and quantify heart rate and arrhythmicity index automatically, while other heartbeat parameters were quantified semi-automatically using the M-mode. In objective 3a, we demonstrated the application of our microfluidic device and heartbeat quantification software for investigating the effect of different chemicals (e.g., serotonin and heavy metals) on Drosophila larval heart function. Also, we applied our technology to genetically modified Drosophila larvae to investigate the effect of metal responsive transcription factor (MTF-1) against heavy metals cardiac toxicity (objective 3b)