Biomedical subjects

Sungjee Kim

Publications and source records attributed to Sungjee Kim.

9 recordsLinked to original sources

PubMed2006

In-situ encapsulation of quantum dots into polymer microspheres.

We have incorporated fluorescent quantum dots (QDs) into polystyrene microspheres using functionalized oligomeric phosphine (OP) ligands. We find that a uniform distribution of quantum dots is loaded inside each polymer bead. Some local close-packing of quantum dots in the beads is attributed to the self-polymerization of the functionalized ligands. The presence of quantum dots disturbs the nucleation and growth processes during the formation of polymer microspheres and results in a wider size distribution of the quantum dot-embedded polystyrene beads than for the control without dots. The change in quantum efficiency of the quantum dots before (approximately 20%) and after (12%) loading into the beads substantiates the protection of oligomeric phosphine ligands yet indicates that the properties of these quantum dots are still affected during processing.

Cadmium Compounds↗

PubMed2006

Sentinel lymph node mapping of the gastrointestinal tract by using invisible light.

BACKGROUND: Because many gastrointestinal (GI) tumors spread by way of lymphatics, histological assessment of the first draining lymph nodes has both prognostic and therapeutic significance. However, sentinel lymph node mapping of the GI tract by using available techniques is limited by unpredictable drainage patterns, high background signal, and the inability to image lymphatic tracers relative to surgical anatomy in real time. Our goal was to develop a method for patient-specific intraoperative sentinel lymph node mapping of the GI tract by using invisible near-infrared light. METHODS: We developed an intraoperative near-infrared fluorescence imaging system that simultaneously displays surgical anatomy and otherwise invisible near-infrared fluorescence images of the surgical field. Near-infrared fluorescent quantum dots were injected intraparenchymally into the stomach, small bowel, and colon, and draining lymphatic channels and sentinel lymph nodes were visualized. Dissection was performed under real-time image guidance. RESULTS: In 10 adult pigs, we demonstrated that 200 pmol of quantum dots quickly and accurately map lymphatic drainage and sentinel lymph nodes. Injection into the mid jejunum and colon results in fluorescence of a single lymph node at the root of the bowel mesentery. Injection into the stomach resulted in identification of a retrogastric node. Histological analysis in all cases confirmed the presence of nodal tissue. CONCLUSIONS: We report the use of invisible near-infrared light for intraoperative sentinel lymph node mapping of the GI tract. This technology overcomes the limitations of currently available methods, permits patient-specific imaging of lymphatic flow and sentinel nodes, and provides highly sensitive, real-time image-guided dissection.

Animals↗

PubMed2005

Phosphine oxide polymer for water-soluble nanoparticles.

A phosphine oxide polymer was developed using bis(dichlorophosphino)ethane and poly(ethylene glycol). This polymer system was used to transfer various nanoparticles from organic solvents to water, retaining their physical properties and reactivities.

Gels↗

PubMed2005

Intraoperative sentinel lymph node mapping of the lung using near-infrared fluorescent quantum dots.

BACKGROUND: The presence of lymph node metastases is an important prognostic marker with regard to non-small-cell lung cancer (NSCLC). Assessment of the sentinel lymph node (SLN) for the presence of tumor may improve staging. Our objective was to develop an optical noninvasive imaging tool that would permit intraoperative SLN mapping and provide real-time visual feedback for image-guided localization and resection. METHODS: Invisible near-infrared (NIR) light penetrates relatively deeply into tissue and background autofluorescence is low. We have developed a NIR fluorescence imaging system that simultaneously displays color video and NIR images of the surgical field. We recently engineered 15 nm nonradioactive NIR fluorescent quantum dots (QDs) as optimal lymphotrophic optical probes. The introduction of these QDs into lung tissue allows real-time visualization of draining lymphatic channels and nodes. RESULTS: In 12 Yorkshire pigs (mean weight 35 kg) we demonstrated that 200 pmol of NIR QDs injected into lobar parenchyma accurately maps lymphatic drainage and the SLN. All SLNs were strongly fluorescent and easily visualized within 5 minutes of injection. In 14 separate injections QDs localized to a mediastinal node, whereas in 2 injections QDs localized to a hilar intraparenchymal node. Histologic analysis in all cases confirmed the presence of nodal tissue. CONCLUSIONS: We report a highly sensitive rapid technique for SLN mapping of the lung. This technique permits precise real-time imaging and therefore overcomes many limitations of currently available techniques.

Animals↗

PubMed2005

Sentinel lymph node mapping of the pleural space.

STUDY OBJECTIVES: Although the sentinel lymph node (SLN) concept has traditionally been applied to solid organs, we hypothesized that the pleural space might drain into a specific SLN group. The identification of such a nodal group could assist in the staging and treatment of pleural-based diseases, such as mesothelioma, or other lung cancers with visceral pleural invasion. The purpose of this study was to determine whether the pleural space has an SLN group. DESIGN: Sixteen rats underwent right or left pleural space injection of a novel lymph tracer, quantum dots (QDs), which have a hydrodynamic diameter of 15 nm and fluoresce in the near-infrared (NIR) spectrum. Nodal uptake of the entire thorax was imaged with a custom system that simultaneously acquired color video, NIR fluorescence of the QDs, and a merged picture of the two in real-time. Six pigs underwent right or left pleural space injection of QDs and similar imaging. MEASUREMENTS AND RESULTS: In the rat, the QDs drained solely to the highest superior mediastinal lymph node group, corresponding to lymph node station 1, according the regional lymph node classification for lung of the American Joint Committee on Cancer. In one rat, the injection of QDs in the left pleural space resulted in migration to the contralateral station 1 lymph node group. The injection of QDs in the right or left pleural space of the pig resulted in migration solely to the ipsilateral highest superior mediastinal lymph node group. CONCLUSIONS: NIR fluorescence imaging in two species demonstrated that the highest superior mediastinal lymph nodes of station 1 are the SLNs of the pleural space. This study also provides intraoperative feasibility and proof of the concept for identifying lymph nodes communicating with the pleural space on a patient-specific basis, in real-time, and with high sensitivity.

Animals↗

PubMed2003

Near-infrared fluorescent type II quantum dots for sentinel lymph node mapping.

The use of near-infrared or infrared photons is a promising approach for biomedical imaging in living tissue. This technology often requires exogenous contrast agents with combinations of hydrodynamic diameter, absorption, quantum yield and stability that are not possible with conventional organic fluorophores. Here we show that the fluorescence emission of type II quantum dots can be tuned into the near infrared while preserving absorption cross-section, and that a polydentate phosphine coating renders them soluble, disperse and stable in serum. We then demonstrate that these quantum dots allow a major cancer surgery, sentinel lymph node mapping, to be performed in large animals under complete image guidance. Injection of only 400 pmol of near-infrared quantum dots permits sentinel lymph nodes 1 cm deep to be imaged easily in real time using excitation fluence rates of only 5 mW/cm(2). Taken together, the chemical, optical and in vivo data presented in this study demonstrate the potential of near-infrared quantum dots for biomedical imaging.

Animals↗

PubMed2003

Oligomeric ligands for luminescent and stable nanocrystal quantum dots.

We report a new family of oligomeric alkyl phosphine ligands for nanocrystal quantum dots. These oligomeric phosphines show effective binding affinity to quantum dot surfaces. They form thin and secure organic shells that stabilize quantum dots in diverse environments including serum and polymer matrices. They maintain the initial as-grown photoluminescence quantum yield of the quantum dots and enable homogeneous incorporation into various matrices. They present a chemically flexible structure that can be used for further chemistry, such as cross-linking, copolymerization, and conjugation to biomolecules.

Journal Article↗

PubMed2003

Type-II quantum dots: CdTe/CdSe(core/shell) and CdSe/ZnTe(core/shell) heterostructures.

Type-II band engineered quantum dots (CdTe/CdSe(core/shell) and CdSe/ZnTe(core/shell) heterostructures) are described. The optical properties of these type-II quantum dots are studied in parallel with their type-I counterparts. We demonstrate that the spatial distribution of carriers can be controlled within the type-II quantum dots, which makes their properties strongly governed by the band offset of the comprising materials. This allows access to optical transition energies that are not restricted to band gap energies. The type-II quantum dots reported here can emit at lower energies than the band gaps of comprising materials. The type-II emission can be tailored by the shell thickness as well as the core size. The enhanced control over carrier distribution afforded by these type-II materials may prove useful for many applications, such as photovoltaics and photoconduction devices.

Cadmium Compounds↗

PubMed2003

Selection of quantum dot wavelengths for biomedical assays and imaging.

Fluorescent semiconductor nanocrystals (quantum dots [QDs]) are hypothesized to be excellent contrast agents for biomedical assays and imaging. A unique property of QDs is that their absorbance increases with increasing separation between excitation and emission wavelengths. Much of the enthusiasm for using QDs in vivo stems from this property, since photon yield should be proportional to the integral of the broadband absorption. In this study, we demonstrate that tissue scatter and absorbance can sometimes offset increasing QD absorption at bluer wavelengths, and counteract this potential advantage. By using a previously validated mathematical model, we explored the effects of tissue absorbance, tissue scatter, wavelength dependence of the scatter, water-to-hemoglobin ratio, and tissue thickness on QD performance. We conclude that when embedded in biological fluids and tissues, QD excitation wavelengths will often be quite constrained, and that excitation and emission wavelengths should be selected carefully based on the particular application. Based on our results, we produced near-infrared QDs optimized for imaging surface vasculature with white light excitation and a silicon CCD camera, and used them to image the coronary vasculature in vivo. Taken together, our data should prove useful in designing fluorescent QD contrast agents optimized for specific biomedical applications.

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