31 August 2012
From the green chlorophyll in plants and algae that we depend upon to transform sunlight into useful energy, to the red heme that carries oxygen to the cells in our bodies, porphyrins are the colors of life. It is not surprising then, that porphyrins have been actively interrogated as tools for diverse applications to improve biotechnology and medicine. With the goal of improving cancer therapy and diagnosis in mind, this thesis examines new modular porphyrin architectures. These constructs have interesting properties that extend beyond their originally intended use as phototherapeutic agents. In Chapter 1, a comprehensive background on porphyrin-based activatable photosensitizers is presented. In Chapter 2, porphyrin singlet oxygen and fluorescence quenching is examined in a model system with respect to Förster theory. Chapter 3 examines a new DNA responsive molecular beacon that was quenched using multiple quenching moieties and its application for nanoparticle aggregation. Chapter 4 describes extremely self-quenched nanovesicles formed from porphyrin-lipid conjugates that displayed a number of desirable properties for nanomedicine applications. Chapter 5 presents a brief discussion and some potential future directions of the research. It is my hope that the data presented in this thesis set the stage for new porphyrin-based approaches to make a translational impact in the battle against cancer and other diseases.
24 February 2009
Degeneration of the intervertebral discs is the most common cause of back pain. The early stages of degeneration affect the nucleus pulposus (NP) of the intervertebral discs followed by a rapid degeneration of the annulus fibrosus. Regeneration of the NP may slow down or reverse the progression of the disease. A new deacetylated derivative of a marine diatomic glycosaminoglycan was developed to obtain a hydrogel formulation proposed to have a reparative effect on damaged NP tissue. The hydration kinetics and viscoelastic behaviour of the hydrogel under shear were studied and compared with the behaviour of nondegenerated human lumbar NP. In vitro studies were conducted using primary cell cultures treated with the drug to study cell viability and extracellular matrix factor expression. In vivo studies using New Zealand White (NZW) rabbits have also been conducted using MRI to quantify disc volume followed by histological and immunohistochemical analysis. Rheological data has indicated that the elastic component of the hydrogel dominates the viscous component over a frequency range of 0.1 to 15.85 rad/s. Proteoglycan expression of the treated cells was found to be 78.4 ± 1.9 (p<0.05) times higher than the untreated controls. RTPCR and immunohistochemical data from in vitro studies have demonstrated that characteristic the chondrocyte markers, aggrecan and collagen II, are expressed in the treated cells. A comparison of disc volumes at 6 weeks post-op has shown that the treated discs have 41% greater volume than the untreated iii discs (p<0.05). The results obtained in this study demonstrate that the sulfated deacetylated glycosaminoglycan derivative is a promising material to be utilized in treatment of NP degeneration.
Computerized Provider Order Entry: Initial Analysis of Current and Predicted Provider Ordering WorkflowAlcide, Niiokai 14 December 2009 (has links)
Background: Computerized Provider Order Entry (CPOE) allows providers to enter medication and service orders electronically. Workflow analysis is a critical component of CPOE implementation. Objectives 1. To develop a nosology for provider ordering workflow. 2. To describe actual provider ordering workflow focusing on chart and computer usage 3. To model the impact of computerized ordering on provider workflow in three future state scenarios Method: 20 hours of participant observation was performed for nosology development, time motion studies totaling 47 and predictive modeling projected effects of possible implementation scenarios Results/Conclusions: Unique nosology was developed. Clinicians spent 27% of their time with the patient, 2.2% writing orders and 1.1% locating patient charts. Our study predicted that the E-All scenario (computerization of all orders) would be the best implementation choice. Limitations: Small sample size (25 clinicians), participant frame of reference and other assumptions may have affected the results of this study.
17 December 2010
Pancreatic islets are heavily vascularized micro-organs containing insulin secreting beta-cells coupled with endothelial cells (EC). These EC slowly deteriorate in static culture, precluding long term study of beta-cell-EC interaction, and likely limiting tissue revascularization post-transplantation. We postulate this EC deterioration is due to an absence of hemodynamics, blood movement. We created a microfluidic device to mimic aspects of hemodynamics, delivering a range of media flow to ex vivo islets. With our resulting desk-top system, we have conducted long term incubations (72 hrs), fixed tissue treatments (maintaining endothelial cell morphology) and real-time live tissue imaging (glucose-stimulated Ca2+-response). Our data show that flow in a microfluidic device maintains EC morphology in ex vivo islets better than non-flowing culture, providing an improved platform to study ex vivo islets and to examine the interaction between beta-cells and EC. Our data also suggest an opportunity to prime islet EC for revascularization using microfluidic flow prior to transplantation.
12 January 2011
Clinical and engineering studies of carotid artery disease typically assume that the common carotid artery (CCA), proximal to the bifurcation, is relatively straight enough to assume fully-developed flow. However, a recent study from our group (Ford et al) showed the surprising presence, in vivo, of strongly skewed velocity profiles in mildly curved CCAs. In this thesis we aim to understand how CCA geometry affects velocity profile skewing. The left and right normal CCAs of 32 participants (62±13 yrs), randomly chosen from NIH’s VALIDATE study (N~450) were digitally segmented from aortic root to bifurcation. It was shown that each segmented CCA could be divided into nominal cervical and thoracic region and that each region could be approximated by planar circular arches. Subsequent CFD simulations of CCA parametric models suggested strong velocity profile skewing both at the inlet and outlet of cervical segment and the effect of various geometric parameters were investigated.
14 December 2010
Previous studies have shown that not all surgical residents can acquire the required skills for performing laparoscopic surgery. Therefore, the training methods can be improved to accommodate trainees with different psychomotor abilities. The first step towards improving training methods is understanding the brain function in performing the laparoscopic surgery training tasks, which can be facilitated by neuroimaging methods such as functional magnetic resonance imaging (fMRI). In this study, a laparoscopic surgery training box for use in fMRI was developed. Experiments confirmed the fMRI-compatibility of the device. Nine right-handed subjects underwent fMRI while performing the surgical training tasks after ten practice sessions in a simulated fMRI environment. Behavioural and fMRI results confirmed the feasibility of using this simulator and revealed the neuroanatomical correlates associated with performing the training tasks. Accordingly, this study may facilitate the evidence-based development of strategies to improve the quality of laparoscopy training and assessment strategies.
Mechanical Evaluation of a Thiol-modified Hyaluronan Elastin-like Polypeptide Nucleus Pulposus Replacement Material in Porcine Intervertebral DiscsLeckie, Ashley 07 January 2011 (has links)
Mechanical low back pain is a disabling condition often associated with degenerative disc disease (DDD). Treatment for DDD includes non-operative pain management, total disc arthroplasty and nucleus pulposus (NP) replacement. A thiol-modified hyaluronan elastin-like polypeptide (TMHA/EP) composite has been under consideration as a NP replacement and has shown promise in vitro. This thesis aims to determine the effects of TMHA/EP composite augmentation on spinal motion segment mechanics in healthy and induced early stage DDD porcine intervertebral discs (IVD). Healthy IVD augmentation on average increased axial compressive stiffness, while bending and rotational stability decreased. Early stage DDD porcine IVD had compromised mechanical integrity in comparison to healthy controls. TMHA/EP augmentation of the mechanically compromised IVDs through two injection techniques worked to restore spinal stability, exhibiting mechanical properties similar to healthy IVDs. This work demonstrates the potential of the injectable TMHA/EP composite in providing initial structural stabilization in early stages of DDD.
Han, Elizabeth Shuang
08 December 2011
This research aimed to help caregivers easily recognize physiological indicators of pediatric anxiety. To this purpose, we first elucidated the physiological indicators of anxiety in children by presenting an anxiety-inducing task while recording biosignals. We discovered patterns suggestive of cardiac reciprocal inhibition, increased respiration rate, and increased electrodermal activity. These patterns informed the optimization of an existing auditory prototype for presenting biosignals to caregivers (biosongs), which maps physiological features to musical elements. The effectiveness of the optimized biosongs for conveying anxiety was evaluated by quantifying the accuracy with which adults could distinguish anxious and calm states by listening to music translated from children's physiological signals. High overall sensitivity (90%), specificity (78%), and accuracy (84%) were achieved, suggesting the promise of biosongs as an effective anxiety screening tool. This technology could lead to profound improvements in caregiving contexts, including anxiety management during medical procedures, and home-based monitoring for chronic conditions.
Development of a Novel Measure of Three-dimensional Bone Connectivity in a Mouse Tibia Fracture Model: Characterizing Torsional Strength and Stiffness Through Failure Surface AnalysisWright, David 04 January 2012 (has links)
The high incidence of long bone fractures and appreciable rate of delayed and non-union (5-10%) necessitates the development of non-invasive tools to monitor healing progression. The objective of this study was to develop a novel µCT-based measure of three-dimensional bone connectivity and to compare its ability to assess fracture callus mechanical stability to previously described measures. Bone connectivity parameters local to the failure surface were found to significantly correlate with mechanical stability, and proved superior to previously developed measures of torsional rigidity. Visualization of the failure surfaces demonstrated a consistent failure pattern indicative of the applied torsional loading, however the locations of the failure surfaces showed varying levels of fracture callus involvement. The results of this proof of concept work indicate the potential utility of bone connectivity analysis in non-invasive assessment of fracture callus stability.
17 August 2012
A new air-shearing technique was designed for the high-throughput production of collagen modules and the assembly of large tissue constructs. >95% of cells embedded in air-sheared modules remained viable after production. Additionally, the module surface could be coated with a confluent monolayer of endothelial cells (ECs). Custom-designed bioreactors (volume > 1 cm3) were built to culture large volumes of modules and enable medium perfusion to the core of packed modular beds. In two separate experiments, this platform was applied to modules containing human adipose-derived mesenchymal stem cells and rat neonatal cardiomyocyte-enriched cells. In both cases, modules fused to form single porous viable tissues. The cardiac tissues were contractile, with a maximum capture rate and excitation threshold of 2.3 + 0.58 Hz and 5.9 + 2.10 V/cm respectively. Efforts were made, with varying success, to create EC-lined pores in tissues by surface seeding modules with ECs prior to loading in bioreactors.
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