Peripheral arterial disease (PAD) is an atherosclerotic disease of the extremities that leads to high rates of myocardial infarction and stroke, increased mortality, and reduced quality of life. PAD is especially prevalent in diabetic patients, and is commonly modeled by hind limb ischemia in mice to study collateral vessel development and test novel therapies. Current techniques used to assess recovery cannot obtain quantitative, physiological data non-invasively. Here, we have applied hyperspectral imaging and swept source optical coherence tomography (OCT) to study longitudinal changes in blood oxygenation and vascular morphology, respectively, intravitally in the diabetic mouse hind limb ischemia model. Additionally, recommended ranges for controlling physiological variability in blood oxygenation with respect to respiration rate and body core temperature were determined from a control animal experiment. In the longitudinal study with diabetic mice, hyperspectral imaging data revealed the dynamics of blood oxygenation recovery distally in the ischemic footpad. In diabetic mice, there is an early increase in oxygenation that is not sustained in the long term. Quantitative analysis of vascular morphology obtained from Hessian-filtered speckle variance OCT volumes revealed temporal dynamics in vascular density, total vessel length, and vessel diameter distribution in the adductor muscle of the ischemic limb. The combination of hyperspectral imaging and speckle variance OCT enabled acquisition of novel functional and morphological endpoints from individual animals, and provides a more robust platform for future preclinical evaluations of novel therapies for PAD.
Nanotechnology and the various properties of gold nanoparticles (AuNPs) are quickly changing the field of cancer
detection and treatment. Photoacoustic detection methods show an increase in sensitivity using gold nanoparticle
antibody conjugation, which selectively targets melanoma cancer cells. Instead of targeting melanoma tumors,
we tag single cells, analogous to circulating metastatic melanoma cells. Using an in vitro, stationary cell system
and planar samples, we demonstrate an average of 24% improved optical detectability of melanoma cells tagged
with AuNPs over unprocessed melanoma cells. Tagged cells showed a raised plateau of absorbance from 470nm
to 550nm. Untagged cells showed a general decline in absorption as wavelength increased. The results of our
study have the potential to not only better develop photoacoustic detection of melanoma, but also extend the
viability and use of photoacoustics into detection of otherwise unpigmented cancers.
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