This research is primarily focused on the study of tumors in experimental animal models using functional imaging in the presence of various contrast agents. The study of malignant tumor angiogenesis, oxygen saturation, glucose and amino acid metabolisms will lead to better methods for cancer detection as well as diagnosing and managing cancer. Non invasive in vivo diagnostic imaging technique is an area of great clinical interest in present days. In this study, noninvasive in vivo photoacoustic tomography and conventional fluorescence imaging together with multiphoton microscopic tomography were implemented to study the malignant tumor morphology and physiology. Tumor structure and angiogenesis were successfully imaged by photoacoustic tomography and conventional fluorescence imaging. The important malignant tumor cellular parameters such as oxygen saturation and αvβ3 integrin concentration were measured in living small animals (rodents) using the novel photoacoustic tomography technique. By implementing multiphoton microscopy using Cy3.5 NHS ester contrast agent, tumor amino acid metabolism was successfully studied in cell culture. This method will at least give you a relative concentration map of amino acid in cells. Non invasive in vivo imaging can be achieved by modifying the current multiphoton imaging setup. A new method for studying amino acid and glucose metabolisms of tumor cells using multiphoton imaging was developed.

This research is primarily focused on the study of tumors in experimental animal models using functional imaging in the presence of various contrast agents. The study of malignant tumor angiogenesis, oxygen saturation, glucose and amino acid metabolisms will lead to better methods for cancer detection as well as diagnosing and managing cancer. Non invasive in vivo diagnostic imaging technique is an area of great clinical interest in present days. In this study, noninvasive in vivo photoacoustic tomography and conventional fluorescence imaging together with multiphoton microscopic tomography were implemented to study the malignant tumor morphology and physiology. Tumor structure and angiogenesis were successfully imaged by photoacoustic tomography and conventional fluorescence imaging. The important malignant tumor cellular parameters such as oxygen saturation and αvβ3 integrin concentration were measured in living small animals (rodents) using the novel photoacoustic tomography technique. By implementing multiphoton microscopy using Cy3.5 NHS ester contrast agent, tumor amino acid metabolism was successfully studied in cell culture. This method will at least give you a relative concentration map of amino acid in cells. Non invasive in vivo imaging can be achieved by modifying the current multiphoton imaging setup. A new method for studying amino acid and glucose metabolisms of tumor cells using multiphoton imaging was developed.

A new glucose affinity sensor based on a homogeneous fluorescence resonance energy transfer (FRET) assay system was developed to monitor the competitive binding between concanavalin A (ConA) and dextran. The FRET quenching kinetics of the donor were analyzed from frequency-domain (FD) measurements as functions of both glucose and acceptor-protein concentrations using a Förster-type decay kinetics model. The results showed that the FD measurements and donor decay kinetics can indicate quantitative changes in the presence of glucose at concentrations ranging from 0 to 224 mg/dL. The second set of experiments proved the feasibility of performing analyte sensing with FD lifetime spectroscopy using microsphere-based sensors in multiple scattering solutions. A well characterized pH-sensitive fluorophore was entrapped in poly(ethylene glycol) microspheres. The particles were then immersed in a buffered polystyrene solution of various pH. Measurements of phase shift and modulation of the generated and multiply scattered fluorescent light were acquired as the modulation frequency of the incident excitation light varied from 10 to 120 MHz. After the measured data were analyzed with the coupled diffusion equations, the obtained lifetimes from the scattering measurements matched values from non-scattering measurements. Lastly, a new two-speed Monte Carlo (MC) simulation was developed to predict light propagation through the sensors and thus was used to evaluate these sensors and to design these sensors for implantation. The model used random packing structure and considered geometric optics and two light propagation speeds. Experimental measurements of phase-shift and modulation of excitation light were made on a cubic phantom with non-fluorescent resin microspheres of 74 µm diameter, and compared to those computed from the MC simulation. The results showed that the mean phase shift (PS) deviation was 0.736° and the mean amplitude deviation was 42%. Quantitative changes in detected fluorescence phase-shift and modulation were investigated for microsphere diameter, volume fraction, refractive index, and fluorophore lifetime. We also found that even though the sensitivity of PS change in the presence of scattering was the same as the value without scattering, the values of PS were magnified due to the scattering effects.

Horses with high energy requirements are generally fed two large concentrate meals per day, either in the form of grain or pellets. The postprandial elevation of blood glucose resulting from this type of feeding has the potential to alter production of hormones such as leptin. Leptin is an adipose-derived protein that promotes satiety in normal animals. The objective of this study was to determine if feeding large amounts of concentrate twice each day would alter serum leptin concentration. Nine horses were placed into three groups (A, B, and C) and each group was rotated through three feeding schedules (2x, 3x, and 4x) in a 3 x 3 Latin square design. Horses were fed twice per day on the 2x schedule, three times per day on the 3x schedule, and four times per day on the 4x schedule. Horses were fed the same total amount of concentrate per day throughout the study, although meal size varied with the number of times the horse was fed per day. Horses were weighed and scored for body condition on the first day of each period. Each treatment period lasted for 11 days. Blood was drawn on days one, four, and seven of each period and leptin concentration was determined by radioimmunoassay. On the afternoon of the tenth day of each period, horses were fitted with jugular catheters and blood was drawn every two hours for 24-hours to determine the circadian rhythm of leptin secretion. Additionally, blood was taken 30 minutes prior to and every 30 minutes after the morning meal to determine postprandial plasma glucose concentrations. Mean and peak glucose values were higher on the 2x schedule than the 3x or 4x schedules (P < 0.05). Leptin concentration was highest in horses on the 3x schedule, although when these data were normalized to baseline (day one) values, leptin was highest on the 2x schedule (P < 0.05). Serum leptin concentration was highly correlated with body condition score (P < 0.01), but not gender (P = 0.82), and leptin increased throughout the study (P < 0.05). Data from the 24-hour collection showed that serum leptin concentration varied with time in horses on the 2x but not the 4x schedule (P < 0.05). Linear regression of data from the 2x schedule indicates that the pattern of change may be modeled by a quadratic equation (P < 0.05). This study demonstrates that feeding horses large carbohydrate meals twice per day disrupts the normal pattern of leptin in the horse, possibly affecting appetite and other physiological processes.

The need for overnight and continuous monitoring of glucose levels in diabetic patients is profound, especially among juveniles. Implantation of a chemical assay which responds optically to changes in glucose concentration shows promise as a technology capable of continuously monitoring blood sugar with little invasion into the body. Previous fluorescent chemical assays, based on the affinity binding reaction between Concanavalin A protein and dextran, performed well but suffered from limited dermal penetration. In this work, a novel replacement for the dextran molecule (glycosylated dendrimer) was fabricated and tested to determine if it would improve the overall response of the sensing chemistry to glucose. Experiments were carried out and it was found that the assay’s functionality was based on the controlled aggregation of the Con A protein and the modified dendrimer molecule. This new assay proved to be specific to glucose, reversible, and independent of fluorophore dye attached to the protein. This research was furthered by encapsulation of the new assay into a PEG hydrogel which showed response to glucose but, due to leeching, did not perform well under repeated exposures. A new method for encapsulation was proposed based on poration of the hydrogel to create micropores capable of holding the assay chemistry and allowing it to react to incoming glucose, while the surrounding polymer restricted leeching. Preliminary results with previous assays proved the potential of a mannitol based poration procedure, but unforeseen complications in lyophilization of the new sensor assay restricted its completion. Due to instability of Con A in solution, it was hypothesized that the immobilization of it onto the surface of an active substrate would increase its stability overtime as seen in previous works. The immobilization procedure was performed on Con A for both polystyrene spheres and gold (nanoshells and colloid). Both results showed an adequate amount of protein on the surface of the particles, but little binding activity was demonstrated. Overall, the improvements to the sensor chemistry response were notable and the potential for stabilization and enhancement of the response through the use of an active substrate is promising.

Thèse d'exercice : Pharmacie : Université de Nantes : 2005. / Bibliogr. f. 79-80 [14 réf.].

Thesis (M. Phil.)--University of Hong Kong, 2001. / Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references. Available also from Dissertation Abstracts.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 125-132). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--University of Texas at Austin, 2002. / Vita. Includes bibliographical references. Available also from UMI Company.