Junghwan Oh

Optical coherence tomography speckle reduction by a partially spatially coherent source

Speckle in optical coherence tomography (OCT) images originates in the high spatial coherence of incident light that enables interference of light backscattered from spatially heterogenous tissue specimens. We report results of a numerical simulation and an experiment to test speckle reduction using a partially spatially coherent source. A Gaussian-Schell model for a partially spatially coherent source is used in the OCT simulation. For the experiment, such a source was generated by a spatially coherent boardband light source and a multimode fiber. The advantage of using a multimode fiber in combination with a broadband source is the large number of photons per coherence volume. To illustrate speckle reduction with a partially spatially coherent source, we record low-coherence interferograms of a scattering surface using single-mode and multimode source fibers. Interferograms recorded using a single-mode source fiber are indicative of those observed using conventional OCT. Speckle in OCT images recorded using a multimode source fiber is substantially reduced.

Increased optical contrast in imaging of epidermal growth factor receptor using magnetically actuated hybrid gold/iron oxide nanoparticles

We describe a new approach for optical imaging that combines the advantages of molecularly targeted plasmonic nanoparticles and magnetic actuation. This combination is achieved through hybrid nanoparticles with an iron oxide core surrounded by a gold layer. The nanoparticles are targeted in-vitro to epidermal growth factor receptor, a common cancer biomarker. The gold portion resonantly scatters visible light giving a strong optical signal and the superparamagnetic core provides a means to externally modulate the optical signal. The combination of bright plasmon resonance scattering and magnetic actuation produces a dramatic increase in contrast in optical imaging of cells labeled with hybrid gold/iron oxide nanoparticles.

Detection of vulnerable plaque in a murine model of atherosclerosis with optical coherence tomography

The aim of this study was to evaluate the feasibility of optical coherence tomography (OCT) to identify the components of vulnerable plaques in a well‐established murine model of human atherosclerosis.

Pulsed Magneto-motive Ultrasound Imaging Using Ultrasmall Magnetic Nanoprobes

Nano-sized particles are widely regarded as a tool to study biologic events at the cellular and molecular levels. However, only some imaging modalities can visualize interaction between nanoparticles and living cells. We present a new technique, pulsed magnetomotive ultrasound imaging, which is capable of in vivo imaging of magnetic nanoparticles in real time and at sufficient depth. In pulsed magneto-motive ultrasound imaging, an external high-strength pulsed magnetic field is applied to induce the motion within the magnetically labeled tissue and ultrasound is used to detect the induced internal tissue motion. Our experiments demonstrated a sufficient contrast between normal and iron-laden cells labeled with ultrasmall magnetic nanoparticles. Therefore, pulsed magnetomotive ultrasound imaging could become an imaging tool capable of detecting magnetic nanoparticles and characterizing the cellular and molecular composition of deep-lying structures.

8B-2 Imaging of Iron Oxide Nanoparticles Using Magneto-Motive Ultrasound

Due to its excellent spatial resolution, fast and reliable performance, cost and wide availability, ultrasound should be considered the imaging modality of choice for many applications including molecular imaging. However, ultrasound imaging cannot image molecular content of tissue due to trade-off between spatial resolution and penetration depth. Consequently, contrast agents have been developed both to enhance the contrast of ultrasound images and to make the images molecularly specific. Most ultrasound contrast agents, however, are micrometer sized and may not be applicable to wide range of pathology-specific cellular and molecular imaging. We have developed an imaging technique - magneto-motive ultrasound (MMUS) imaging, capable of imaging magnetic nanoparticles subjected to time-varying magnetic field. The result of our studies indicate that magnetically excited nanoparticles can be used as contrast agents in magneto-motive ultrasound imaging thus expanding the role of ultrasound imaging to cellular scales and molecular sensitivity.

Marine polysaccharide-based nanomaterials as a novel source of nanobiotechnological applications.

Research on marine polysaccharide-based nanomaterials is emerging in nanobiotechnological fields such as drug delivery, gene delivery, tissue engineering, cancer therapy, wound dressing, biosensors, and water treatment. Important properties of the marine polysaccharides include biocompatibility, biodegradability, nontoxicity, low cost, and abundance. Most of the marine polysaccharides are derived from natural sources such as fucoidan, alginates, carrageenan, agarose, porphyran, ulvan, mauran, chitin, chitosan, and chitooligosaccharide. Marine polysaccharides are very important biological macromolecules that widely exist in marine organisms. Marine polysaccharides exhibit a vast variety of structures and are still under-exploited and thus should be considered as a novel source of natural products for drug discovery. An enormous variety of polysaccharides can be extracted from marine organisms such as algae, crustaceans, and microorganisms. Marine polysaccharides have been shown to have a variety of biological and biomedical properties. Recently, research and development of marine polysaccharide-based nanomaterials have received considerable attention as one of the major resources for nanotechnological applications. This review highlights the recent research on marine polysaccharide-based nanomaterials for biotechnological and biomedical applications.

Pulsed magneto-acoustic imaging

Nanoparticles are attracting considerable interest as contrast agents for many different imaging modalities. Moreover, imaging the events at the cellular and molecular level is possible by using nanoparticles that have the desired targeting moiety. Unfortunately, ultrasound imaging cannot visualize the nano-structures directly due to its limited spatial resolution and contrast. We present a new technique, pulsed magneto-acoustic imaging, capable of imaging magnetic nanoparticles indirectly. In this method, a high-strength pulsed magnetic field is used to induce motion within the magnetically labeled tissue and ultrasound is used to detect internal tissue motion. Experiments on tissue-mimicking phantoms and ex-vivo animal tissues demonstrated a clear contrast between normal and iron-laden samples labeled with 5 nm magnetic nanoparticles. In addition, the sensitivity of this new imaging technique was investigated for different concentrations of magnetic agents. The results of the study suggest that magnetic nanoparticles can be used as contrast agents in pulsed magneto-acoustic imaging. Furthermore, PMA imaging could become an imaging tool capable of visualizing the cellular and molecular composition of deep-lying structures.

Investigations on laser hard tissue ablation under various environments

The purpose of this study was to investigate the effect of liquid environments upon laser bone ablation. A long-pulsed Er,Cr:YSGG laser was employed to ablate bovine bone tibia at various radiant exposures under dry, wet (using water or perfluorocarbon) and spray environmental conditions. Energy loss by the application of liquid during laser irradiation was evaluated, and ablation performance for all conditions was quantitatively measured by optical coherence tomography (OCT). Microscope images were also used to estimate thermal side effects in tissue after multiple-pulse ablation. Wet using water and spray conditions equally attenuated the 2.79 microm wavelength laser beam. Higher transmission efficiency was obtained utilizing a layer of perfluorocarbon. Dry ablation exhibited severe carbonization due to excessive heat accumulation. Wet condition using water resulted in similar ablation volume to the dry case without carbonization. The perfluorocarbon layer produced the largest ablation volume but some carbonization due to the poor thermal conductivity. Spray induced clean cutting with slightly reduced efficiency. Liquid-assisted ablation provided significant beneficial effects such as augmented material removal and cooling/cleaning effects during laser osteotomy.

Hemoglobin contrast in magnetomotive optical Doppler tomography

We introduce a novel contrast mechanism for imaging blood flow by use of magnetomotive optical Doppler tomography (MM-ODT), which combines an externally applied temporally oscillating high-strength magnetic field with ODT to detect erythrocytes moving according to the field gradient. Hemoglobin contrast was demonstrated in a capillary tube filled with moving blood by imaging the Doppler frequency shift, which was observed independently of blood flow rate and direction. Results suggest that MM-ODT may be a promising technique with which to image blood flow.

Doxorubicin-loaded fucoidan capped gold nanoparticles for drug delivery and photoacoustic imaging.

Polymer nanoparticles are emerging as a useful tool for a wide variety of biomedical and therapeutic applications. The present study demonstrates the multifunctional doxorubicin-loaded fucoidan capped gold nanoparticles (DOX-Fu AuNPs) for drug delivery and photoacoustic imaging (PAI). Biocompatible AuNPs were synthesized using a naturally occurring fucoidan (Fu) as a capping and reducing agent. The Fu AuNPs synthesis was determined using UV-visible spectrum, and it was further characterized using high resolution transmission electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction analysis. The release of DOX from DOX-Fu AuNPs was greater in acidic pH (4.5) than in neutral pH (7.4). The in vitro cytotoxic effect of fucoidan, Fu AuNPs, DOX, and DOX-Fu AuNPs inhibited the proliferation of human breast cancer cells with an inhibitory concentration of 35μg/mL, 30μg/mL, 15μg/mL, and 5μg/mL at 24h. DOX-Fu AuNPs induced both early and late apoptosis in a concentration-dependent manner compared with untreated control cells. The ability of DOX-Fu AuNPs as a contrast agent for in vitro breast cancer imaging with PAI has been evaluated. These results suggest that the multifunctional DOX-Fu AuNPs for drug delivery and PAI can soon provide considerable contribution to human health.