Different types and sizes of micro- and nanoparticles have been synthesized and developed for numerous applications. It is crucial to characterize the particle sizes. Traditional dynamic light scattering, a predominant method used to characterize particle size, is unable to provide depth resolved information or imaging functions. Doppler variance optical coherence tomography (OCT) measures the spectral bandwidth of the Doppler frequency shift due to the Brownian motion of the particles utilizing the phase-resolved approach and can provide quantitative information about particle size. Spectral bandwidths of Doppler frequency shifts for various sized particles were quantified and were demonstrated to be inversely proportional to the diameter of the particles. The study demonstrates the phase-resolved Doppler variance spectral domain OCT technique has the potential to be used to investigate the properties of particles in highly scattering media.
Optical coherence tomography (OCT) is a non-invasive and promising imaging modality with high resolution that is an
order of magnitude higher than current diagnostic techniques. However, its use in detecting early-stage cancer is limited
due to insufficient contrast level in biological tissue, which can be enhanced by harnessing contrast agents [e.g., gold
nanoparticles (Au NPs)]. Enhanced penetration by creating micropassages and distribution by ultrasonic force (multimodal
topical delivery) was proven to overcome two major barriers (stratum corneum and epithelial barriers) in topically
administering Au NPs using an in vivo oral dysplasia hamster model (overall 150% enhanced OCT contrast). Expanded
progress on a highly efficient and versatile Au NP-releasing polymer microneedle platform showed a promising next
generation multi-modal delivery of Au NPs.
The salivary pellicle plays an important role in oral physiology, yet noninvasive in situ characterization and mapping of this layer remains elusive. The goal of this study is to develop an optical approach for the real-time, noninvasive mapping and characterization of salivary pellicles using optical coherence tomography (OCT) and optical coherence microscopy (OCM). The long-term goals are to improve diagnostic capabilities in the oral cavity, gain a better understanding of physiological and pathological processes related to the oral hard tissues, and monitor treatment responses. A salivary pellicle is incubated on small enamel cubes using human whole saliva. OCT and OCM imaging occurs at 0, 10, 30, 60 min, and 24 h. For some imaging, spherical gold nanoparticles (15 nm) are added to determine whether this would increase the optical signal from the pellicle. Multiphoton microscopy (MPM) provides the baseline information. In the saliva-incubated samples, a surface signal from the developing pellicle is visible in OCT images. Pellicle "islands" form, which increase in complexity over time until they merge to form a continuous layer over the enamel surface. Noninvasive, in situ time-based pellicle formation on the enamel surface is visualized and characterized using optical imaging.
Contrast in optical coherence tomography (OCT) images can be enhanced by utilizing surface plasmon resonant gold nanoparticles. To improve the poor in vivo transport of gold nanoparticles through biological barriers, an efficient delivery strategy is needed. In this study, the improved penetration and distribution of gold nanoparticles were achieved by microneedle and ultrasound, respectively, and it was demonstrated that this multimodal delivery of antibody-conjugated PEGylated gold nanoparticles enhanced the contrast in in vivo OCT images of oral dysplasia in a hamster model.
In this presentation, we demonstrate a novel optical tomography technique, thermoelastic
optical Doppler tomography (ODT). Short laser pulses are used to generate thermoelastic
waves in biological samples. Optical phase variations in response to wave propagation
are detected using ODT. It is shown that areas of different elastic property in the phantom
can be clearly resolved.
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