Biological fluids are commonly analyzed in clinical and forensic studies for drug concentration measurements. Conventional quantification procedures are always associated with lengthy sample pretreatment steps to eliminate the interfering compounds that potentially exist in complex biological matrices. The objective of this study was to address these problems employing solid-phase microextraction (SPME) technique. Antibodies (Abs) were employed to serve as an extremely specific extraction phase for direct extraction of analytes from untreated biological matrices based on their exquisite selectivity for antigens (Ags). Much of the research was focused on selecting the most appropriate antibody (Ab) for a particular application based on evaluation of characteristics of various types of Abs obtained from four suppliers. Abs’ binding characteristics were evaluated before and after immobilization in terms of affinity, valence, homogeneity, capacity and cross-reactivity for three benzodiazepines. The performance of immunoaffinity probes of the same type provided by different suppliers was found to be comparable. Finally, the probes’ utility for extraction of benzodiazepines from plasma samples was evaluated. The limit of detection of the method developed in this work was 0.01 ng/mL with upper limits of quantification of 0.5 ng/mL in buffer and 2 ng/mL in plasma. The method’s precision was 12% for extraction from buffer and less than 10% for extraction from plasma. With limits of detection similar to the current state-of-the-art methods available for quantification of drugs in biological matrices, the method presented in this thesis was found advantageous compared to other available methods due to its simplified sample preparation procedure.

Biological fluids are commonly analyzed in clinical and forensic studies for drug concentration measurements. Conventional quantification procedures are always associated with lengthy sample pretreatment steps to eliminate the interfering compounds that potentially exist in complex biological matrices. The objective of this study was to address these problems employing solid-phase microextraction (SPME) technique. Antibodies (Abs) were employed to serve as an extremely specific extraction phase for direct extraction of analytes from untreated biological matrices based on their exquisite selectivity for antigens (Ags). Much of the research was focused on selecting the most appropriate antibody (Ab) for a particular application based on evaluation of characteristics of various types of Abs obtained from four suppliers. Abs’ binding characteristics were evaluated before and after immobilization in terms of affinity, valence, homogeneity, capacity and cross-reactivity for three benzodiazepines. The performance of immunoaffinity probes of the same type provided by different suppliers was found to be comparable. Finally, the probes’ utility for extraction of benzodiazepines from plasma samples was evaluated. The limit of detection of the method developed in this work was 0.01 ng/mL with upper limits of quantification of 0.5 ng/mL in buffer and 2 ng/mL in plasma. The method’s precision was 12% for extraction from buffer and less than 10% for extraction from plasma. With limits of detection similar to the current state-of-the-art methods available for quantification of drugs in biological matrices, the method presented in this thesis was found advantageous compared to other available methods due to its simplified sample preparation procedure.

Doctor of Philosophy / Department of Chemistry / Christopher T. Culbertson / In research and industry, almost all chemical analysis methods involve the separation and detection of compounds. Typically, these separations are performed using traditional methods that require volumes in the 10 μL to 10 mL range of sample and in the 200 mL to 2 L range for solvents. These methods are not suitable for low-concentration, volume-limited samples frequently associated with biochemical studies. One way to overcome these limitations is to move the separation and detection to the microscale. The use of the microscale separation technologies enables the study of biological systems that have, until now, been out of reach due to their small volumes or low concentrations. The research presented in this dissertation will discuss two examples of this shift to microscale separation technologies which can solve some small volume sample challenges. These include the detection of protease activity in blood samples for use in cancer detection and the identification of immune system cascade proteins in the mosquito Anopheles gambiae. In Chapter 2 a microfluidic method and device is proposed to monitor protease activities for cancer detection. In this method nanobiosensors are used to measure enzyme activity in biological fluids. These nanobiosensors consist of iron-iron oxide magnetic nanoparticles that are attached to peptide substrates specific for proteases through a disulfide bond. The nanobiosensors are controlled using a neodymium magnet which is attached through a 3D printed adaptor to a rotating motor for mixing and a linear stage to move the nanoparticles between different sections of the device. The separation and detection sections of the device are explained in Chapter 3. Chapter 3 describes the fabrication and optimization of a simple device for microfluidic isoelectric focusing(IEF). IEF is a separation method in which analytes are separated based upon their isoelectric, i.e. neutral charge, points. A reducing agent can be added to the IEF buffer to detach the nanoparticle from the peptide substrate, releasing it for focusing. IEF is also a concentration as well as separation method that will allow the peptide substrates to be focused up to 10⁶ fold. It has a high peak capacity and produces reliable, reproducible separation patterns based on the isoelectric point of the peptide. To meet the detection limits required for cancer detection with proteases, scanning laser induced fluorescence is selected as the method of detection. This scanning system can monitor the separation over time to observe the parameters affecting the separation which cannot be done with typical point or imaging detection systems and allows better separation. This custom automatic detection system can distinguish focused samples of 500 fM from the background with minimal noise from the scanning system. In Chapter 4 the identification of serine protease and inhibitor binding complexes in A. gambiae hemolymph using magnetic bead immunoaffinity chromatography was attempted. These proteases play a key role in the insect innate immunity system and form irreversible complexes. These complexes can be purified from a complex hemolymph sample using an antibody to one of the complex members. To separate the complexes from the hemolymph, Serpin 2 antibodies were attached to protein A coated magnetic beads and then incubated with the hemolymph. Once the purified complexes and Serpin 2 were eluted, the purified proteases were identified on Orbitrap MS. In an attempt to simplify the isolation of the complexes, a magnetic bead mixing rotor column was developed to help reduce the volume of the elution to increase the concentration. This method, however, was not robust and did not improve the concentration.

The analysis of biological samples in clinical or research settings often requires measurement of analytes from complex and limited matrices. Immunoaffinity separations in miniaturized formats offer selective isolation of target analytes with minimal reagent consumption and reduced analysis times. A prototype capillary-based microfluidic system has been developed for immunoaffinity separations in biological matrices with laser-induced fluorescence detection of labeled antigens or antibodies. The laboratory-constructed device was assembled from two micro syringe pumps, a microchip mixer, a micro-injector, a diode laser with fused-silica capillary flow cell, and a separation capillary column. The columns were prepared from polymer tubing and packed under negative pressure with a stationary phase that consisted of biotinylated antibodies attached to streptavidin-silica beads. A custom software program controlled the syringe pumps to perform step gradient elution and collected the signal as chromatograms. The system performance was evaluated with flow accuracy, mixer proportioning, pH gradient generation, and assessment of detectability. A direct labeling/direct capture immunoaffinity separation of C-reactive protein (CRP) was demonstrated in simulated serum. CRP, a biomarker of inflammation and cardiovascular disease risk assessment, was fluorescently labeled in a one-step reaction and directly injected into the system. A quadratic calibration model was selected and precision and accuracy were reported. Parathyroid hormone was also analyzed by the direct capture approach, but displayed nonspecific binding of human plasma matrix components that limited the useful assay range. Capillary sandwich assays of CRP in human serum and cerebrospinal fluid were performed using both capture and detection antibodies. The detection antibody was labeled and purified offline to minimize signal from labeled matrix components. Four parameter logistic functions were used to model the data and precision and accuracy were evaluated. During the study, 250 nL injection volumes 2.0 µL/min flow rates were employed, minimizing sample and reagent consumption. The microfluidic system was capable of separating antigens from biological matrices and is potentially portable for patient point-of-care settings. Additionally, the flexible design of the separation capillary allows for the analysis of different clinical markers by changing the antibodies and the low assay volume requirements could lead to less invasive patient sampling techniques.LabVIEW version 7 or later is required to open the attached files.

Laboratory test results are important in making decisions regarding a patient's diagnosis and response to treatment. These tests often measure the biomarkers found in biological fluids such blood, urine, and saliva. Immunoassay is one type of laboratory test used to measure the level of biomarkers using specific antibodies. Microfluidics offer several advantages such as speed, small sample volume requirement, portability, integration, and automation. These advantages are motivating to develop microfluidic platforms of conventional laboratory tests. I have fabricated polymer microfluidic devices and developed immunoassays on-chip for potential cancer markers. Silicon template devices were fabricated using standard photolithographic techniques. The template design was transferred to a poly(methyl methacrylate) (PMMA) piece by hot embossing and subsequently bonded to another PMMA piece with holes for reservoirs. I used these devices to perform microchip immunoaffinity electrophoresis to detect purified recombinant thymidine kinase 1 (TK1). Buffer with 1% methylcellulose acted as a dynamic coating that minimized nonspecific adsorption of protein and as sieving matrix that enabled separation of free antibody from antibody-TK1 complexes. Using this technique, I was able to detect TK1 concentration >80 nM and obtained separation results within 1 minute using a 5 mm effective separation length. Detection of endogenous TK1 in serum is difficult because TK1 is present at the pM range. I compared three different depletion methods to eliminate high abundance immunoglobulin and human serum albumin. Cibacron blue columns depleted abundant protein but also nonspecifically bound TK1. I found that ammonium sulfate precipitation and IgG/albumin immunoaffinity columns effectively depleted high abundance proteins. TK1 was salted out of the serum with saturated ammonium sulfate and still maintained activity. To integrate affinity columns in microfluidic devices, I have developed a fast and easy strategy for initial optimization of monolith affinity columns using bulk polymerization of multiple monolith solutions. The morphology, surface area, and porosity, were qualitatively assessed using scanning electron microscopy. This method decreased the time, effort, and resources compared to in situ optimization of monoliths in microfluidic devices. This strategy could be used when designing novel formulations of monolith columns. I have also integrated poly(ethylene glycol dimethacrylate-glycidyl methacrylate) monolith affinity columns in polymer microfluidic devices to demonstrate the feasibility of extracting human interleukin 8 (IL8), a cancer biomarker, from saliva. Initial results have shown that the affinity column (~3 mm) was successfully integrated into the devices without prior surface modification. Furthermore, anti-IL8 was immobilized on the surface of the monolith. Electrochromatograms showed that 1 ng/mL of IL8 can be detected when in buffer while 10 ng/mL was detected when IL8 was spiked in saliva. Overall, these findings can be used to further develop immunoassays in microfluidic platforms, especially for analyzing biological fluids.

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 / As the field of separation science evolves so do the techniques, tools and capabilities of the discipline. The introduction of microfluidics stemmed from a desire to perform traditional analyses faster and on a much smaller scale. The small device sizes exploited in microfluidics permits the investigation of very small volumes of very dilute samples yielding information inaccessible by traditional macroscale techniques. All of the chapters presented in this dissertation illustrate attempts to supplement current microscale techniques with new tools, techniques and analysis schemes for looking at biologically relevant analyses. In chapter two I present the development and characterization of an amphiphilic polymer that has potential as a material for the fabrication of microfluidic devices. This material is composed of a poly(dimethylsiloxane)-poly(ethylene oxide) block copolymer and is dramatically more hydrophilic than the other polymeric materials currently used for the fabrication of microfluidic templates, mainly poly(dimethylsiloxane). Biomolecules such as proteins are notoriously hydrophobic and will tend to adsorb to other hydrophobic surfaces thus the use of a hydrophilic material may serve to reduce or eliminate this problem. The amphiphilic material is of a suitable durability for micromolding and molded channel architectures can be sealed between two layers of the material by simple conformal contact permitting the execution of high speed electrophoretic separations. Chapter three contains initial results obtained while investigating the fluorescent labeling and electrophoretic separation of ecdysteroids. Ecdysteroids are hormones found in insects that are responsible for controlling the process of molting. Here we attempted to analyze these molecules by employing a reactive fluorescent probe, BODIPY FL® hydrazide, that would target the α,β-unsaturated ketone group on the steroid, permitting its analysis by capillary electrophoresis with laser induced fluorescence detection. While optimistic initial results were obtained with the labeling and analysis of similar functional groups on model compounds such as progesterone, labeling of the ecdysteroid molecules was never achieved to a degree that would permit reliable analysis. In chapter four I report the development and use of a microimmunoaffinity column for the analysis of insect serine protease inhibitors, or serpins. These proteins play a very important role in the regulation of insect immune responses and their activity may play an integral role in the effective transmission of the malaria parasite by the mosquito Anopheles gambiae. A microimmunoaffinity column was constructed from magnets, poly(dimethylsiloxane), fused silica capillary and Protein A coated magnetic microspheres. In these initial studies, purified antibodies to serpin protein, as well as purified serpin protein, were used to prepare and investigate the ability to isolate, preconcentrate, and elute serpin proteins for subsequent analysis. By implementing this miniaturized system which incorporates very small fluid volumes we hoped to extend this technique to the analysis of very small samples, and eventually to the analysis of individual small insects. Our work indicates that it is possible to isolate, elute, and detect serpin protein on a traditional western blot membrane. Chapter five presents the development of a novel polymer blend for the fabrication of paper-based microfluidic devices and use of these devices in the performance of diagnostically relevant clinical assays. We took the concept of paper-based microfluidic devices and improved upon the current photoactive polymers used for their fabrication by developing a polymer blend using an acryloxy modified siloxane polymer as well as a commercially available photoactive adhesive, Norland Optical Adhesive 74. This blended polymer resulted in a dramatic reduction in fabrication time as well as improved resolution permitting the reliable patterning of small feature sizes. We also report for the first time a demonstration of these devices performing a two-step spatially separated online chemical derivatization facilitating the analysis of urinary ketones. These devices are predominantly used for the analysis of urine, and their application was extended to the quantitation of nitrite in saliva for the purposes of hemodialysis monitoring. While varied in application, all of the data presented in this dissertation exploits the power of miniaturization to improve current methods of analysis and to extend macroscale techniques to trace biological analytes.

A purificação de subunidades do vírus da raiva pode ser realizada por diferentes metodologias, uma vez purificadas estas subunidades podem ter diversas aplicações em métodos altamente específicos para o diagnóstico laboratorial e pesquisa da raiva. A obtenção de ribonucleoproteínas (RNP) do vírus da raiva pode ser realizada por meio de ultracentrifugação em gradiente de Cloreto de Césio (CsCl), porém este método possibilita a obtenção de RNP semi purificadas. Neste estudo foi utilizado o método de cromatografia de imunoafinidade para obtenção das RNP, os resultados obtidos foram satisfatórios quanto a um maior grau de pureza dessas proteínas, além de propiciar a otimização do processo e redução do tempo operacional, quando comparado a ultracentrifugação em gradiente de CsCl. / Purification of subunits of the rabies virus can be accomplished by different methodologies, once purified these subunits can have several applications in highly specific methods for diagnostic and research laboratory for rabies. Obtaining ribonucleoprotein (RNP) of rabies virus can be performed by ultracentrifugation in a Cesium Chloride (CsCl) gradient, but this method allows to obtain semi purified RNP. This study used the method of immunoaffnity chromatography to obtain the RNP; the results were satisfactory for a higher degree of purity of these proteins in addition to providing process optimization and reduced operating time compared to ultracentrifugation in a cesium chloride gradient.

A purificação de subunidades do vírus da raiva pode ser realizada por diferentes metodologias, uma vez purificadas estas subunidades podem ter diversas aplicações em métodos altamente específicos para o diagnóstico laboratorial e pesquisa da raiva. A obtenção de ribonucleoproteínas (RNP) do vírus da raiva pode ser realizada por meio de ultracentrifugação em gradiente de Cloreto de Césio (CsCl), porém este método possibilita a obtenção de RNP semi purificadas. Neste estudo foi utilizado o método de cromatografia de imunoafinidade para obtenção das RNP, os resultados obtidos foram satisfatórios quanto a um maior grau de pureza dessas proteínas, além de propiciar a otimização do processo e redução do tempo operacional, quando comparado a ultracentrifugação em gradiente de CsCl. / Purification of subunits of the rabies virus can be accomplished by different methodologies, once purified these subunits can have several applications in highly specific methods for diagnostic and research laboratory for rabies. Obtaining ribonucleoprotein (RNP) of rabies virus can be performed by ultracentrifugation in a Cesium Chloride (CsCl) gradient, but this method allows to obtain semi purified RNP. This study used the method of immunoaffnity chromatography to obtain the RNP; the results were satisfactory for a higher degree of purity of these proteins in addition to providing process optimization and reduced operating time compared to ultracentrifugation in a cesium chloride gradient.

Microfluidics is a vibrant and expanding field that has the potential for solving many analytical challenges. Microfluidics shows promise to provide rapid, inexpensive, efficient, and portable diagnostic solutions that can be used in resource-limited settings. Microfluidic devices have gained immense interest as diagnostic tools for various diseases through biomarker analysis. My dissertation work focuses on developing electrokinetically operated integrated microfluidic devices for the analysis of biomarkers indicative of preterm birth risk. Preterm birth (PTB), a birth prior to 37 weeks of gestation, is the most common complication of pregnancy and the leading cause of neonatal deaths and newborn illnesses. In this dissertation, I have designed, fabricated and developed several microfluidic devices that integrate various sample preparation processes like immunoaffinity extraction, preconcentration, fluorescent labeling, and electrophoretic separation of biomarkers indicative of PTB risk. I developed microchip electrophoresis devices for separation of selected PTB biomarkers. I further optimized multiple reversed-phase porous polymer monoliths UV-polymerized in microfluidic device channels for selective retention and elution of fluorescent dyes and PTB biomarkers to facilitate on-chip labeling. Successful on-chip fluorescent labeling of multiple PTB biomarkers was reported using these microfluidic devices. These devices were further developed using a pH-mediated approach for solid-phase extraction, resulting in a ~50 fold enrichment of a PTB biomarker. Additionally, this approach was integrated with microchip electrophoresis to develop a combined enrichment and separation device that yielded 15-fold preconcentration for a PTB peptide. I also developed an immunoaffinity extraction device for analyzing PTB biomarkers directly from a human serum matrix. A glycidyl methacrylate monolith was characterized within microfluidic channels for immobilization of antibodies to PTB biomarkers. Antibody immobilization and captured analyte elution protocols were optimized for these monoliths, and two PTB biomarker proteins were successfully extracted using these devices. This approach was also integrated with microchip electrophoresis for combined extraction and separation of two PTB biomarkers in spiked human serum in <30 min. In the future, these optimized microfluidic components can be integrated into a single platform for automated immunoaffinity extraction, preconcentration, fluorescent labeling, and separation of PTB biomarkers. This integrated microfluidic platform could significantly improve human health by providing early diagnosis of PTBs.