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There has been a growing body of evidence that impaired microvascular perfusion is an indicator for mortality in critical patients. However, there are limited clinical microvascular therapeutics targets. The objective of this thesis is to investigate and intervene upon microvascular disease found in hemorrhagic shock, neoplasia, and inflammation concurrent with acute respiratory distress (ARDS). Chapter one of this thesis focuses on engineering an intervention to improve microvascular perfusion by leveraging the Starling forces in capillaries. Specifically, we designed and implemented a device for the application of negative pressure to reduce tissue interstitial pressure, which transiently increased functional capillary density after hemorrhagic shock, a known metric for microvascular perfusion, without the need for volume resuscitation. Chapter two aims on engineering red blood cells to target the tumor microcirculation and microenvironment. Specifically, we studied red blood cells as a delivery vehicle for RRx-001, an anti-cancer agent, and altered their biomechanics, by selectively inducing tumor adhesion in the tumor microenvironment. This increase in adhesion had an anti-neoplastic effect, with our study showing a 40% decrease in tumor size. In chapter three, we engineered a new intervention for altering microvascular inflammation as seen in the acute respiratory distress syndrome (ARDS). Specifically, we aerosolized Nitric Oxide releasing nanoparticles (NO-nps) to mice suffering of ARDS and found a reduction in peripheral neutrophils, indicative of reduced inflammation. As demonstrated, engineering interventions to improve microvascular perfusion shows great potential as a therapeutic target for a broad range of pathophysiologies, including hemorrhagic shock, cancer, and ARDS.

We study the thermodynamic equilibrium between supercooled liquid and solid using a homemade MEMS device called microtensiometer to directly measure the pressure and temperature of a macroscopic volume of supercooled liquid in equilibrium with solid. Our measurements on water are consistent with the generalized Clapeyron equation, which predict the relation between the pressure of the liquid, the pressure of the solid and the temperature at equilibrium. We also report and discuss remarkable behaviors in the kinetics of equilibration. We found that the equilibration time to reach chemical equilibrium can vary by several orders of magnitude. To better understand this observation, we do a more careful study of the dynamics of transport of supercooled water into ice using a custom-made microfluidic platform. Our results indicate that the dynamics is slower than the prediction of the generalized Clapeyron equation, assuming that the ice remains at atmospheric pressure. We speculate that the transport impacts the pressure in the ice and leads to an effectively lower driving force.

Lower body negative pressure (LBNP), which unloads cardiopulmonary and arterial baroreceptors, is a widely used method for studying various cardiovascular responses to hemorrhaging and orthostatic stress. The purposes of this investigation were to validate the use of LBNP as a research technique for studying the human cardiovascular responses to hemorrhaging and to use LBNP in combination with a dynamic handgrip exercise protocol to determine if gender differences exist in functional sympatholysis. Twenty healthy college-aged male (N = 10) and female (N = 10) participants visited the exercise science laboratory on one occasion. For the first part, participant’s whole left arm, whole left leg, and a portion of their left leg volume-matched to their whole arm was subject to two stages of negative pressure (-30 mmHg and -60 mmHg) lasting 5 minutes each. For the second part, participants performed 3 minute stages of dynamic handgrip exercise at 15%, 30%, and 45% of their max voluntary contraction, with one minute rest intervals taken between each stage, then repeated this protocol again while subject to -30 mmHg LBNP. Responses in heart rate, stroke volume, mean arterial pressure, brachial blood flow, brachial diameter, and forearm muscle oxygenation were continuously recorded. There were minimal differences observed in the cardiovascular responses to negative pressure when applied to the upper body versus when applied to the lower body, and there were no significant gender differences in response to LBNP at rest or during exercise.

Introduction: Chronic wounds are costly to treat and are an increasing health problem. The aetiology of chronic wounds is multi-factorial, but recent evidence suggests that bacteria play an important role and be responsible for a majority of chronic infections. S. epidermidis and P. aeruginosa are commonly associated with chronic wounds. A major part of the virulence is their ability to form biofilms. Biofilms are a complex community of bacteria adhering to surfaces and imbedded in a biopolymer matrix that aids the bacteria in surface attachment, has water, nutrient and oxygen channels and protects the bacteria from host and antimicrobial agents. This high resistance of biofilms presents challenges to the medical community for fighting infections. Recently, topical negative pressure (TNP) dressings have been used in chronic wounds to aid healing. Although there is some research evaluating the effect of TNP dressings on biofilms, there is no research on the efficacy of a combination of TNP dressings and antiseptic instillation. Aims: Our aims were to identify the minimum eradication concentration (MEC) and the minimum biofilm eradication concentration (MBEC) of S. epidermidis and P. aeruginosa against a range of antiseptics and use sub-inhibitory concentrations of antiseptics in an in vitro wound model to assess the efficacy of TNP dressings in combination with antiseptic instillation. Method: Biofilms were generated in a biofilm generator (24 coupons at a time) with a 24 hour batch phase and a 24 hour flow-through phase. Coupons were then transferred to an in vitro wound chamber. Each wound chamber had 6 coupons. Wound chambers were subjected to various frequency of antiseptic instillation with and without TNP. 5 coupons were prepared for quantitative measurements using standard microbiological methods, while 1 coupon was prepared for scanning electron microscopy. Results: S epidermidis: MBEC of PI against S. epidermidis lay between 0.078 mg/ml and 0.156 mg/ml while the MEC was 4.883 μg/ml. The MBEC of HA against S. epidermidis was between 0.025 mg/ml and 0.05 mg/ml while the MEC was 3.125 μg/ml. Increasing frequency of antiseptic instillations without TNP resulted in a reduction in bacterial load ranging from 0.5 to 1.5 log10 reduction. Combining antiseptic instillations with TNP resulted in a greater decrease in bacterial numbers, ranging from 0.5 to almost 2.5 log10 reduction. PI instillation 12 times per day in combination with TNP was the most effective and resulted in an almost 2.5 log10 reduction in bacterial numbers. The SEM images complemented the results observed with colony counts. P aeruginosa: MBEC of PB against P. aeruginosa lay between 0.05 mg/ml and 0.20 mg/ml while the MEC was 0.2mg/ml. The MBEC of HA against P. aeruginosa was > 0.05 mg/ml while the MEC was < 3.125 μg/ml. Similar to the results observed with S. epidermidis, increasing frequency of antiseptic instillation resulted in an increased reduction in bacterial numbers. Combining TNP with PI instillation resulted in a greater decrease in bacterial numbers (7 log10 reduction) compared with PI instillation alone (5 log10 reduction). 3 times per day PB instillation resulted in approximately 0.5 log10 reduction in bacterial numbers. Addition of TNP to 3 times per day PB instillation resulted in a greater decrease in bacterial numbers (1.5 log10 reduction). Although higher frequency of PB instillation resulted in a greater decrease in bacterial load, the additive effect of TNP to PB instillation was not present. The SEM complemented these findings. Conclusion: MBEC of PI against S. epidermidis lay between 0.078 mg/ml and 0.156 mg/ml while the MEC was 4.883 μg/ml. The MBEC of HA against S. epidermidis was between 0.025 mg/ml and 0.05 mg/ml while the MEC was 3.125 μg/ml. MBEC of PB against P. aeruginosa lay between 0.05 mg/ml and 0.20 mg/ml while the MEC was 0.2mg/ml. The MBEC of HA against P. aeruginosa was > 0.05 mg/ml while the MEC was < 3.125 μg/ml. The use of TNP in combination with antiseptic instillation resulted in a greater reduction of bacterial numbers when compared with instillation alone.