Investigating surface acoustic waves and fluorescence techniques for lab-on-a-chip diagnostics

There is an emerging need for low-cost medical diagnostics for both high and middle to low-resource settings. Surface acoustic waves microfluidics are emerging lab-on-a-chip technologies which have the potential to provide all-in-one solution to actuate liquids and sense biomarkers, thus enabling point-of-care bioassays. DNA has become a key biomarker for a range of medical conditions, including infectious diseases, as it provides critical information on the pathogen or the response of the patients to particular treatment, on a personalized basis. This thesis will examine the effects of surface acoustic waves on DNA hybridization, with a view to integrate molecular diagnostic assays onto acousto-fluidic devices. The work used fluorescence to characterize the binding of DNA in a range of conditions, and revealed nucleobase-specific quenching (NB-S Quench) of fluorophores when attached to DNA as a double strand. This latter effect was examined as a replacement for common analytical markers used in standard techniques, such as melting curves, which typically rely on dyes which recognize DNA strands non-specifically (such as groove binders). The technique has been shown to be suitable for determine the concentration of DNA, performing DNA amplification and identifying the presence and melting temperature of target DNA. This work will have an impact on research into low-cost medical diagnostics, and improve the understanding of fluorescence of DNA modified with fluorophores, contributing to the understanding of future work in these areas

Patient Satisfaction and Surgeon Experience: A Follow-Up to the Reduction Mammaplasty Learning Curve Study

Background: While it is known that increasing surgeon experience is correlated with improved efficiency and safety in the reduction mammaplasty procedure, it is unclear whether these improvements lead to an erosion in patient satisfaction. Methods: The authors distributed the Breast-Q questionnaire to all patients who underwent bilateral reduction mammaplasty at their institution between 1995 and 2007. Univariate and multivariate analyses were performed to assess the relationship between postoperative patient satisfaction scores and surgeon experience, as well as to characterize those patients with particularly high or low satisfaction scores, in general. Results: A total of 279 (26.1%) completed surveys were analyzed. No statistically significant erosion in either Satisfaction with Breasts (SWB) or Satisfaction with Outcomes (SWO) scores were witnessed with increasing surgeon experience or efficiency. Patients older than 40 years demonstrated significantly higher SWB scores than younger patients (P = .004), while patients who suffered postoperative soft tissue necrosis demonstrated significantly lower SWB (P = .003) and SWO (P = .010) scores. Conclusions: Gains in operative efficiency with increasing surgeon experience do not appear to come at the expense of patient satisfaction in the reduction mammaplasty procedure. Younger patients and those who experience postoperative soft tissue necrosis appear to be at higher risk for reporting lower postoperative patient satisfaction scores

Hyperspectral Imaging as an Early Biomarker for Radiation Exposure and Microcirculatory Damage

BACKGROUND: Radiation exposure can lead to detrimental effects in skin microcirculation. The precise relationship between radiation dose received and its effect on cutaneous perfusion still remains controversial. Previously, we have shown that hyperspectral imaging (HSI) is able to demonstrate long-term reductions in cutaneous perfusion secondary to chronic microvascular injury. This study characterizes the changes in skin microcirculation in response to varying doses of ionizing radiation and investigates these microcirculatory changes as a possible early non-invasive biomarker that may correlate with the extent of long-term microvascular damage.METHODS: Immunocompetent hairless mice (n=66) were exposed to single fractions of superficial beta-irradiation in doses of 0, 5, 10, 20, 35, or 50 Gy. A HSI device was utilized to measure deoxygenated hemoglobin levels in irradiated and control areas. HSI measurements were performed at baseline before radiation exposure and for the first three days post-irradiation. Maximum macroscopic skin reactions were graded, and histological assessment of cutaneous microvascular densities at four weeks post-irradiation was performed in harvested tissue by CD31 immunohistochemistry.RESULTS: CD31 immunohistochemistry demonstrated a significant correlation (r=0.90, p<0.0001) between dose and vessel density reduction at four weeks. Using HSI analysis, early changes in deoxygenated hemoglobin levels were observed during the first three days post-irradiation in all groups. These deoxygenated hemoglobin changes varied proportionally with dose (r=0.98, p<0.0001) and skin reactions (r=0.98, p<0.0001). There was a highly significant correlation (r= 0.91, p<0.0001) between these early changes in deoxygenated hemoglobin and late vascular injury severity assessed at the end of four weeks.CONCLUSIONS: Radiation dose is directly correlated with cutaneous microvascular injury severity at four weeks in our model. Early post-exposure measurement of cutaneous deoxygenated hemoglobin levels may be a useful biomarker for radiation dose reconstruction and predictor for chronic microvascular injury

Skin perfusion and oxygenation changes in radiation fibrosis

BACKGROUND: Ionizing radiation is known to have deleterious chronic effects on skin, including fibrosis and poor wound healing, hypothesized as mediated by ischemia and hypoxia. Past studies have been unable to simultaneously investigate changes in perfusion and oxygenation as separate parameters. Hyperspectral imaging has emerged as a tool with which to concurrently measure skin perfusion and oxygenation. The authors investigated the use of hyperspectral imaging in a novel murine model of chronic radiation injury. METHODS: Areas of flank skin (n = 20) on hairless mice were exposed to a 50-Gy dose of beta-radiation. Hyperspectral imaging acquisition was performed at select points through 8 weeks. Immunohistochemical staining and gene expression analysis were performed to evaluate cutaneous vascular density, epidermal cell hypoxia, and angiogenic factors. RESULTS: All irradiated areas developed a chronic-phase wound by day 28. Hyperspectral imaging demonstrated a 21 percent decline in perfusion on day 56 (p \u3c 0.001), whereas oxygenation levels were unchanged. A 1.7-fold reduction in blood vessel density was measured in irradiated skin compared with control tissue (p \u3c 0.001), but no difference in epidermal cell hypoxia was observed. Vascular endothelial growth factor and related receptor expression were significantly lower in irradiated tissue. CONCLUSIONS: The authors\u27 analysis does not support the presence of hypoxia in chronic-phase irradiated skin but suggests that hypoperfusion may be a predominant characteristic. The concurrent states of hypoperfusion and normoxia may be explained by the lower metabolic demands of fibrosed tissue