The specific membrane capacitance (SMC) of biological cell membranes correlates with cells’ electrical activity and morphology, which are physiological markers for cellular phenotype and health. Conventionally, SMC measurements are conducted using electro-rotation and Patch-clamping, which entail long time training and stringent operation skills. Both techniques also suffer from limited throughput and lengthy measurement time. In this study, a microfluidic device, which enables impedance spectroscopy measurements, was developed to quantify the SMC of single biological cells. The device has a testing speed of approximately one cell per minute and is relatively easy to operate. Three-dimensional finite element simulations of the microfluidic device confirm the feasibility of this approach. SMC measurement of two AML (Acute Myeloid Leukemia) subtypes and two UCC (Urothelium Cell Carcinoma) subtypes were conducted. Measured SMC results were found to lie in the comparable range with previously reported publications.

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.

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.

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 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.

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.

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.

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.

The specific membrane capacitance (SMC) of biological cell membranes correlates with cells’ electrical activity and morphology, which are physiological markers for cellular phenotype and health. Conventionally, SMC measurements are conducted using electro-rotation and Patch-clamping, which entail long time training and stringent operation skills. Both techniques also suffer from limited throughput and lengthy measurement time. In this study, a microfluidic device, which enables impedance spectroscopy measurements, was developed to quantify the SMC of single biological cells. The device has a testing speed of approximately one cell per minute and is relatively easy to operate. Three-dimensional finite element simulations of the microfluidic device confirm the feasibility of this approach. SMC measurement of two AML (Acute Myeloid Leukemia) subtypes and two UCC (Urothelium Cell Carcinoma) subtypes were conducted. Measured SMC results were found to lie in the comparable range with previously reported publications.

The spine is the most common location of metastatic disease in the skeleton. The occurrence of bone metastasis can lead to severe clinical consequences and a significant decline in quality of life. The evaluation of metastatic disease in the spine has to date been mainly qualitative. More widespread access to multiple imaging modalities has motivated the development of 3D methods to quantitatively evaluate metastatic disease in the spine. Quantitative evaluation is important both in assessing stability of the metastatic spine and the progression/ response of the tumour and bone to treatment over time. Previous studies quantifying stability in the metastatic spine have focused primarily on osteolytic tumours. Local and systemic treatments have impacted the nature of vertebral metastasis, increasing the occurrence of mixed osteolytic and osteoblastic disease. Thus, it is important to focus analyses on models able to accurately represent diverse distribution patterns found in bony metastasis. Preclinical models are widely used in studying the process of metastasis and are able to represent both osteolytic and osteoblastic disease. This proposal aims to establish the biomechanical implications of metastatic disease in the spine through the evaluation of stability and tumour burden in a preclinical model using a multifaceted engineering-based approach. It is hypothesized that the use of automated analysis techniques applied to multimodality imaging will allow quantification of the impact of metastasis on biomechanical stability, tumour burden and bony architecture in the spine, and motivate prediction models that accurately reflect vertebral integrity in both osteolytic and mixed osteolytic/osteoblastic models of spinal metastasis. Specifically, this work aims to: 1) Utilize and compare μMR and μCT based radiologic methods to quantify tumour involvement and vertebral architecture in a rat model of spinal metastasis; and 2) Evaluate the ability of 2D, 3D, and continuum based methods to quantify structural integrity in vertebral metastasis. Overall, this work will focus on developing automated methods to quantify stereologic parameters, and quality in the metastatic spine and the evaluation of stability measures from 2D structural rigidity, Finite Element analysis, image registration and experimental methods. Ultimately this work will yield automated analysis techniques and evaluate the abilities of these methods to predict failure in metastatic vertebrae.