Research Overview
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NLOM Instrumention and Spectroscopy:  Traditional NLOM experimental configurations couple an ultrafast laser to a microscope via galvanometer mirrors for image rendering.  In this configuration, galvanometer mirrors are used to scan the laser focus within the specimen to render en face, 2-D images.  Typically, specimens are limited by the working area of the microscope stage and must be manipulated and oriented relative to a fixed optical axis.  Ultrafast lasers are used to generate nonlinear optical imaging signals because they provide high peak intensities with comparatively low average powers.  The nonlinear dependence of generated imaging signals on incident laser intensity is the basis for optical sectioning in NLOM.  Other optical imaging techniques have utilized silica core optical fibers for more flexible specimen interrogation environments and as a platform for in vivo studies and translational biomedical applications.  Linear and nonlinear interactions of ultrafast laser pulses used in NLOM with silica core fibers can have deleterious effects on temporal (due to dispersion) and spectral (due to Kerr effects) pulse profiles, eroding efficient nonlinear optical signal generation.  We are investigating and characterizing the use of hollow-core photonic band gap fibers for the delivery of near transform limit ultrafast laser pulses for fiber based NLOM. 

We are also developing expanded NLOM signal detection capabilities.  Typical NLOM images are intensity based with limited spectral content.  Recent work from our group has characterized endogenous nonlinear optical signals from tissues and demonstrated NLOM image segmentation by constituent.  Simultaneous detection of multiple wavelengths is limited by signal filtration and the number of available detectors, typically two or three.  We aim to develop spectroscopic detection capabilities for NLOM, where spectra are recorded for each pixel in the image. 

Brain Morphogenesis:  During development, the vertebrate central nervous system is formed by partitioning proliferating primordial cell populations into compartments and gradually refining these populations into distinct functional subregions. In the presumptive midbrain and hindbrain, these compartments are lineage restricted by a sharp boundary interface ensuring that cells from these regions do not mix and that they receive region specific signals to properly develop into the tectum and cerebellum, respectively. Though many of the key regulatory signals of this region are known, our current understanding of how these regions are initiated, formed, and maintained remains poor. In particular, how developmental lineages interact to form functional units of the brain remains an outstanding question and technologically challenging to study. We are developing NLOM and biological reagents to characterize dynamics and interactions of developmental lineages in forming functional structures of the central nervous system. We are studying zebrafish development because its embryo develops outside the mother, is optically transparent, and forms nascent organs within 24 hours. 

Mechanobiology:  Angiogenesis, the sprouting of new vessels from existing vasculature, is vital to normal tissue growth and wound healing and a key component in tissue regeneration and progression of many pathologies. Thus, the promotion or inhibition of angiogenesis has long been a strategic approach in managing wound healing and disease. Furthermore, angiogenesis has been recognized as an important process in regenerative medicine applications of tissue engineering whether initiated from the host or induced in vitro. Current tissue engineering technologies have been limited by diffusion transport of nutrition and waste, thus limiting the ultimate size of engineered tissues. We seek to understand the dependence of angiogenic patterning on extracellular matrix physical properties and ultimately use these properties as engineering design parameters for the controlled integration of vascular networks into engineered tissues.

One aim of our lab is using NLOM to understand how underlying microstructure affects bulk tissue properties.  However, in living tissues, these properties evolve with environmental changes.  From a mechanical perspective, these changes may result in some combination of matrix synthesis, degradation or reorganization affecting tissue anisotropy, viscoelasticity, homogeneity and stiffness.  Our efforts in understanding how tissue microstructure affects bulk properties motivate integration of NLOM with bulk tissue characterization measurements.  We have established the use of model tissue systems for longitudinal studies of biological responses to external stimuli.  Our lab will build on these accomplishments for time-dependent studies of growth and remodeling in tissue engineered constructs exposed to well controlled mechanical environments.                        



Texas A&M University . Biomedical Engineering . Tissue Microscopy Laboratory
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