Michael T. Taylor

Simulation of microfluidic pumping in a genomic DNA blood-processing cassette

Microfluidic cassettes that perform integrated biological sample preparation and DNA analysis require fluidic control and transport mechanisms built into the device. In this study, pneumatically actuated diaphragm pumps and valves were employed to achieve precise fluidic manipulation and enabled the execution of several sample-processing steps within a single cassette. However, the design of the microfluidic cassette to accomplish this multi-step fluidic protocol required a complex three-dimensional fluid path through valves, bends, various sized passageways and a porous filter for cell capture. In order to understand the fluidic behavior in such a device, measurements were taken of the pneumatic pressure delivered to the diaphragm pump as it pushed sample through the complicated fluidic pathway. Simultaneously monitored were the resulting volumetric flow rate, and the corresponding pre- and post-filter fluid pressures. The data enabled the construction of a model that simulated the fluidic action through the device using established fluid mechanics theory that closely matched flow rate and pressure data. The ability to simulate the behavior of diaphragm pumping and resulting fluidic movements in complex microfluidic devices provides a greater comprehension of this phenomenon and a useful tool in the application to future devices for biochemical analysis.

High throughput surface characterization : a review of a new tool for screening prospective biomedical material arrays

The application of high throughput surface characterization (HTSC) to the analysis of polymeric biomaterial libraries is an important advancement for the discovery and development of new biomedical materials and is the focus of this review. The potential for HTSC to identify structure/activity relationships for large libraries of materials can be utilized to accelerate materials discovery as well as providing insight into the underlying biological-material interactions. Furthermore, the correlations identified between surface chemical structure and cellular behavior could not have been predicted by a rational design approach based simply on review of bulk structure, which demonstrates the importance of HTSC in the assessment of cell-material and cell-biomolecular interactions that are dependent on surface properties.

Microchip isoelectric focusing using a miniature scanning detection system

A miniature scanning fluorescent detector has been developed for plastic microchannel isoelectric focusing (mIEF) analysis. The detector, comprised of a lamp and photomultiplier tube (PMT) on a moving stage, measured the real‐time distribution of fluorescently labeled peptides subjected to gel‐free mIEF. During the run, the effective length of the 6‐cm channel was scanned every 9 s. Analysis was completed within 5 min while still obtaining high resolution and sensitivity. In addition, the scanning detector was used to characterize peptide migration properties within the channel by providing simultaneous temporal and spatial measurements.

Fully Automated Sample Preparation for Pathogen Detection Performed in a Microfluidic Cassette

Sample preparation steps including bacterial spore concentration by filtering, washing to remove PCR inhibitors, ultrasonic lysis, pumping of elution containing DNA, mixing with PCR-mix, thermal cycling and real-time PCR were performed automatically in a microfluidic cassette.

Versatile, Adaptable and Programmable Microfluidic Platforms for DNA Diagnostics and Drug Discovery Assays

A PCR DNA diagnostics system based on a hybrid microfluidic platform is described which offers the advantage of disposability for high DNA concentration PCR. PCR results for a 100 μ1 solution of M13 Bacteriophage DNA as well as a β-Actin human DNA TaqMan® assay show positive amplification after automated sample preparation in the block for both cases. Results have also shown successful follow-up decontamination of the reusable platform after each sample preparation and amplification run. The design and processes utilized in this hybrid system has been leveraged to design and develop a fully disposable cartridge platform for detection of Chlamydia and Gonorrhea from urine samples.

3D chemical characterization of frozen hydrated hydrogels using ToF-SIMS with argon cluster sputter depth profiling

Hydrogels have been used extensively in bioengineering as artificial cell culture supports. Investigation of the interrelationship between cellular response to the hydrogel and its chemistry ideally requires methods that allow characterization without labels and can map species in three-dimensional to follow biomolecules adsorbed to, and absorbed into, the open structure before and during culture. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) has the potential to be utilized for through thickness characterization of hydrogels. The authors have established a simple sample preparation procedure to successfully achieve analysis of frozen hydrated hydrogels using ToF-SIMS without the need for dry glove box entry equipment. They demonstrate this on a poly(2-hydroxyethyl methacrylate) (pHEMA) film where a model protein (lysozyme) is incorporated using two methods to demonstrate how protein distribution can be determined. A comparison of lysozyme incorporation is made between the situation where the protein is present in a polymer dip coating solution and where lysozyme is in an aqueous medium in which the film is incubated. It is shown that protonated water clusters H(H2O)n (+) where n = 5-11 that are indicative of ice are detected through the entire thickness of the pHEMA. The lysozyme distribution through the pHEMA hydrogel films can be determined using the intensity of a characteristic amino acid secondary ion fragment.

Disrupting bacterial spores and cells using ultrasound applied through a solid interface

DNA sample processing cartridges that perform cell lysis using ultrasound require a sonication chamber with a wall, or interface, for the transfer of ultrasonic energy to the solution. The interface must present matched impedance to the transfer of energy, yet also provide a barrier to safely contain potential hazardous biological material. The use of a thin but solid polymeric interface was studied using interfaces with a range of frequency response characteristics to the ultrasonic excitation. Measurements of ultrasonically generated acoustic pressure, visual images of cavitation, and measurements of released nucleic acid from sonicated bacterial spores and cells were used to determine the parameters for optimum transfer of ultrasound. Data and theory presented show that cell lysis is a function of the natural frequency of the interface, the preload force between the interface and the ultrasonic transducer, and the amplitude of the transducer.

Microfluidic Bioanalysis Cartridge with Interchangeable Microchannel Separation Components

We have developed a plastic microfluidic cartridge and instrument that processes a sample; aliquots reagents; performs either electrophoretic separation in the case of nucleic acids, or isoelectric focusing in the case of peptides or proteins; and performs time and space-resolved fluorescent detection using solid-state components. The development of this cartridge is but one part of a microfluidic system that includes sample processing, target nucleic acid amplification such as PCR, and separation-based detection of either peptides, proteins or PCR products.