Otitis media (OM) is a common disease of the middle ear, with 80% of children experiencing an infection before age three. Diagnostic methods rely on interpretation of symptoms from an otoscope, which help physicians visualize the eardrum. To provide precise structural and biochemical information, a prototype non-contact multimodal Raman spectroscopy (RS) and optical coherence tomography (OCT) system and handheld probe were created. Observation of in vitro physiologically-relevant ear models and comparison to in vivo scans from pediatric subjects presenting with OM detail application-specific development. Design challenges for clinical use, including maximum permissible exposure and physical size constraints, are presented.
The anomalous diffusion characteristics of neuronal dynamics are analyzed by label-free, phase-sensitive optical coherence microscopy. The technique provides low-noise images, enabling cellular dynamic characteristics to be measurable. The phase variance is a conventional dynamic parameter that cannot elucidate the ballistic components of neuronal dynamics. Determining the dynamics by phase variance alone omits the ballistic information that can occur from the ion exchange across cellular membranes. The probability density function of phase displacements exerted by cellular dynamics was acquired and the shape of the power-law tail was analyzed. The development of the power-law tail provides a more sensitive dynamic feature.
Otitis media or middle-ear infection is a widespread bacterial/viral disease. Antibiotic-resistant bacteria within biofilms emerge during chronic ear infections and are challenging to treat. We explored Raman spectroscopy (RS) and Optical Coherence Tomography (OCT) to identify and compare unique spectroscopic and microstructural features from primary otopathogenic bacteria in colony, planktonic, and biofilm forms, in vitro. RS was utilized to identify biochemical fingerprints and OCT was used to generate depth-resolved 2D and 3D images to compare refractive indices and optical attenuation coefficients. A combined RS-OCT system will enable real-time visualization and diagnosis of bacterial OM at the point-of-care.
We present Superfast Polarization-sensitive Off-axis Full-field Optical Coherence Microscopy (SPoOF OCM) as a novel all-optical technique for neurophysiology. Both the optical path length and birefringence induced by the millisecond-scale electrical activity of neurons are captured by SPoOF OCM at 4000 frames per second and with a field-of-view of 200×200 µm sq., 1 µm transverse resolution, 4.5 µm axial resolution, and 300 pm phase sensitivity. With an ability to capture responses spanning three orders of magnitude in both space and time, SPoOF OCM meets the exacting needs of a comprehensive neurophysiology tool and overcomes the existing limitations of traditional electrophysiology and fluorescence microscopy.
A biofilm morphology transition is a dynamic process that mediates growth and dispersion. The development of the dynamic process shows the enhancement of the power-law tail that is observed while the biofilms grown at the air-agar interface are submerged in a medium. Environmentally driven morphology transitions of biofilm were analyzed by acquiring the phase displacements of the Doppler shift and linearly decomposed by ballistic (Cauchy) and diffusive (Gaussian) distributions. The analysis provides the internal dynamic characteristics of biofilm that pave the way between the conventional dynamic parameters and the anomalous diffusion parameters.
Intracellular dynamics are dominated by active transport driven by energetic processes far from equilibrium. Cytoskeletal restructuring, membrane motions and molecular motors use GTP and ATP to drive directed transport that is quasi-one-dimensional with speeds from 10 nm/sec to 10 microns/sec and persistence times tp as large as several seconds. Light scattering under these conditions can be in the lifetime-broadened Doppler shift regime as opposed to a random diffusive regime. The isotropic distribution of 1D transport within cells and tissues produces broad-band signatures that do not produce specific Doppler spectral peaks, but produce Doppler spectral edges that can be related to the mean squared speeds inside cells. The wDtp = 1 product provides a natural dividing line between the Doppler and the diffusive regimes, with a broad cross-over range into which many tissue-based light scattering processes fall. In this talk, I will show how the intracellular Doppler character of dynamic light scattering is derived and modeled, and provide experimental support from biodynamic imaging. Biodynamic imaging uses low-coherence digital holography to capture dynamic spectra in three dimensions from living tissue samples. Biodynamic imaging, based on changes in intracellular dynamics caused by applied therapeutics or changing environments, is expanding into multiple applications, including the selection of chemotherapy for personalized cancer care, screening of potential new therapeutics, and the selection of embryos for artificial reproductive technology. I will give an overview of these applications, describing how changes in biophysical behavior provide actionable biomarkers for clinical applications.
The BioCD platform technology uses spinning-disk interferometry to detect molecular binding to target molecular probes in biological samples. Interferometric configurations have included differential phase contrast and in-line quadrature detection. For the detection of extremely low analyte concentrations, nano- or microparticles can enhance the signal through background-free diffraction detection. Diffraction signal measurements on BioCD biosensors are achieved by forming gratings on a disc surface. The grating pattern was printed with biotinylated bovine serum albumin (BSA) and streptavidin coated beads were deployed. The diameter of the beads was 1 micron and strong protein bonding occurs between BSA and streptavidin-coated beads at the printed location. The wavelength for the protein binding detection was 635 nm. The periodic pattern on the disc amplified scattered light into the first-order diffraction position. The diffracted signal contains Mie scattering and a randomly-distributed-bead noise contributions. Variation of the grating pattern periodicity modulates the diffraction efficiency. To test multiple spatial frequencies within a single scan, we designed a fan-shaped grating to perform frequency filter multiplexing on a diffraction-based BioCD.
Biodynamic imaging uses coherence-gated dynamic light scattering to create three dimensional maps of intracellular dynamics in living tissue biopsies. The technique is sensitive to changes in intracellular dynamics dependent on the mechanism of action (MoA) of therapeutics applied in vitro to the living samples. A preclinical trial in the assessment of chemotherapeutic response of dogs with B-cell lymphoma to the doxorubicin-based therapy CHOP has been completed using biodynamic imaging. The trial enrolled 19 canine patients presenting with non-Hodgkin’s B-cell lymphoma. Biopsies were acquired through surgery or through needle cores. The time-varying power spectrum of scattered light after drugs are applied ex vivo to the biopsies represent biodynamic biomarkers that are used in machine learning algorithms to predict the patient clinical outcome. Two distinct phenotypes emerged from the analysis that correlate with patient drug resistance or sensitivity. Cross validation of the algorithms perform with an accuracy of 90% in the prediction of dogs that will respond to treatment. Biodynamic imaging has the potential to help select chemotherapy for personalized cancer care.
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