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Elastic
Scattering Spectroscopy (ESS) for the Detection of Apoptosis
RA: Christine Mulvey
Apoptosis is enhanced by most cancer treatment modalities and, in fact, the initial response to successful cancer treatment is often massive apoptosis. Because of this, apoptosis measurements are the primary method for anticancer drug evaluation in vitro. Unfortunately, all current detection methods are invasive and are often inadequately quantitative.
Our aim in this project is to develop a fast, inexpensive, and noninvasive method of monitoring the state of apoptosis in a cell culture, allowing for assessment of the apoptotic state of a population of cells without perturbing them in any way. Such a method would also enable monitoring of a single cell sample over time, rather than requiring a new culture at each time point, thereby allowing for a more accurate assessment of cellular response by avoiding culture-to-culture biological variability. With these criteria in mind, we are developing instrumentation to use elastic scattering spectroscopy (ESS) as a detection tool for apoptosis in cell cultures. Changes in the morphology of apoptotic cells should produce measurable differences in the way they scatter light. With the proper analysis algorithms, a quantitative determination of the cellular state can be achieved in real-time. Wavelength-dependent measurements in the near-backward direction have shown that ESS is capable of discriminating between treated and control samples as early as 10 to 15 minutes post-treatment, which is much earlier than most conventional assays can detect its onset. We are currently developing an algorithm that uses Mie theory to relate the collected spectra to the morphological features underlying them to give an assessment of the cells’ progress in the apoptotic process.
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Optical
Measurement of Tumor Angiogenesis
RA: Kerry Lee Andken
Tumor angiogenesis is the process of creating new blood vessels to feed the tumor to support its growth. One method of treating tumors is to administer drugs to prevent this process from occurring. Currently, drug performance is based on observed changes in tumor size. This can take several weeks to months to become evident. Because new blood vessels that are not fully formed are leakier than normal vessels, an alternate way to determine the effectiveness of anti-angiogenesis medications is to measure the permeability of the blood vessels at the tumor site. The fewer leaky vessels, the more effective the drug. It is hypothesized that the leakiness of blood vessels can be measured optically and non-invasively. This will allow for a shorter period of time for a drug to be deemed effective, and increase the number of measurements a researcher can make on the same animal, reducing the number of animals needed and reducing biological variability.
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Optical
Neurophysiology Using Speckle Holography
RA:
Kurt Schoener
With
a deep understanding of single neuron events, neurophysiologists have
turned to solving a new problem: How do networks of neurons interact to
produce the functions that we observe, like learning? The tools
currently available to them are not well suited for this endeavor, and
so neurophysiologists have sought for methods of producing
high-resolution spatiotemporal maps of neuronal activity in large areas
of brain tissue. Although tools such as voltage- or
calcium-sensitive dies and Intrinsic Optical Signaling (IOS) each have
their specific limitations, they have proven that there is a wealth of
information to be gained by studying such maps. One important
contribution of IOS is that action potential propagation can be tracked
very well by observing the attendant swelling. The speckle
holography system under development seeks to exploit this phenomenon to
produce the high-resolution spatiotemporal maps neurophysiologists need
without the limitations of current methods.
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Improved mathematical tools for modeling photon transport in tissue
RA: Katherine
Calabro
In the quest to use optical reflectance spectroscopy for medical diagnostics, it is important to quantitatively understand and predict photon transport in turbid media, such as tissue. Many mathematical approaches have been developed to predict photon propagation, such as diffusion theory based on fundamental transport equations, Monte Carlo simulations which are stochastic/statistical in nature, and analytical models that have been developed from empirical observations. Part of the work involved in this project is to find improved wavelength dependent characterization functions for the optical properties of tissue. Physiological parameters can be extracted from these functions, and improved characterization functions result in more accurate parameter extraction. Another part of this project will involve examining how tissue composed of layers with different properties affects the combined reflectance, and how this then affects the inverse problem of extracting properties from reflectance data. This will involve studies on layered mouse skin, especially looking at the differences between the structure of male versus female skin. The work in this project will provide improved mathematical tools for those studying the optical and physiological characteristics of tissue. |
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Optical Detection of Blood-Brain Barrier in vivo
RA: Aysegul Ergin
Brain cancers are one of the leading causes of death among young Americans. They pose a heavy burden on health care system due to high cost of in-hospital care, long term treatment need and high mortality rate. Treatment of brain tumors requires therapeutic agents to be delivered across blood-brain barrier (BBB) to specific regions of the brain at an effective dosage. Blood-brain barrier is a special membrane that lines the blood vessels of the brain and allows the passage of only very small (<400 Daltons) or highly lipid soluble molecules. Since the current chemotherapy methods (intravenous injections) cannot penetrate through BBB, the novel chemotherapy methods focus on delivering the drugs to the tumor sites after disrupting the BBB using biochemicals.
The measurements of drug concentrations delivered to the brain tissue are difficult to determine. There are several conventional laboratory techniques for monitoring local chemotherapeutic drugs but most of them require invasive applications. They do not provide site-specific, real time information and lack rapid time resolution. In this project, we use optical pharmacokinetics (OP) technique based on diffuse scattering spectroscopy to monitor the real-time, site-specific chemotherapy drug concentrations in brain tissue. The OP method determines drug concentrations by measurements of the wavelength dependent optical absorption coefficient of tissue. An optical fiber probe composed of an illumination and collection fibers are gently placed in contact with the brain tissue surface and the brain tissue underlying the probe is sampled within seconds. Analysis of spectral data collected before and after chemotherapy drug administration provides information about the time history drug concentration in the brain with a high temporal resolution.
We believe that non-invasive, optical measurements of drug concentrations using OP technique can provide many advantages over conventional techniques. In this project, the OP technique is also applied to evaluate the efficiency of a new delivery method aimed at localized targeting of brain tumors. The new delivery method involves intra-arterial injection of chemotherapy drugs which rapidly generates high tissue concentration at a specific site after a temporary disruption of BBB to enhance the delivery of drug.
In recent pre-clinical studies, we showed the feasibility of real-time monitoring of BBB disruption by tracking the tissue concentration of Evan’s Blue, a marker of BBB disruption.
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Optical Diagnosis of Cancer Using Elastic Scattering Spectroscopy
RA:
Eladio Rodriguez
Elastic-scattering spectroscopy (ESS) provides a
minimally invasive approach of obtaining spectral measurements of
scattering properties of tissue. The use of this technique allows for
the acquisition of spectral signatures of the underlying tissue, for the
purpose of sensing pathologies, with special interest in cancer. This
method is sensitive to the wavelength dependence of the tissue optical
properties, which vary due to architectural changes at the cellular and
sub-cellular level as a result of the different pathologies. These
changes influence the measured spectral signature, varying depending on
the pathology. The focus of this research is to exploit these changes in
spectral signature with the use and evaluation of different machine
learning methods and pattern recognition systems in order to distinguish
from different pathologies (normal or cancerous tissue) given the
measured spectra.
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