Jebum Lee

Hyukju Na

Tyler Hiew

The Intelligent Computer Architecture & Systems Research Laboratory (CASL) is located within the College of Informatics, Department of Computer Science and Engineering at Korea University in Seoul. Research focuses on intelligent computer architecture and systems.

지능형 컴퓨터 구조 및 시스템 연구실(CASL)은 고려대학교 정보과대학 컴퓨터학과에 소속되어 있다. 주요 연구 분야는 지능형 컴퓨터 구조 및 시스템이다.

Dendritic cell-based cancer immunotherapy requires tumour antigens to be delivered efficiently into dendritic cells and their migration to be monitored in vivo . Nanoparticles have been explored as carriers for antigen delivery, but applications have been limited by the toxicity of the solvents used to make nanoparticles, and by the need to use transfection agents to deliver nanoparticles into cells. Here we show that an iron oxide–zinc oxide core–shell nanoparticle can deliver carcinoembryonic antigen into dendritic cells while simultaneously acting as an imaging agent. The nanoparticle–antigen complex is efficiently taken up by dendritic cells within one hour and can be detected in vitro by confocal microscopy and in vivo by magnetic resonance imaging. Mice immunized with dendritic cells containing the nanoparticle–antigen complex showed enhanced tumour antigen specific T-cell responses, delayed tumour …

A multifunctional core–shell nanoparticle for dendritic cell-based cancer immunotherapy

It is well known that the coercivity of magnetic nanomaterials increases up to a maximum and then decreases to zero with decreasing particle size. However, until now, no single synthesis method has been able to produce magnetic nanoparticles with a wide range of sizes, i.e., from 10 to 500 nm, in order to uncover the coercivity evolution. Here we report the characterization of magnetite (Fe 3 O 4 ) multi-granule nanoclusters (MGNCs) to demonstrate the transitional behaviour of coercivity. The M–H curves indicate that our samples had a relatively high saturation magnetization ( M S ) value of ~70 emu/g and that the coercivity ( H c ) increased to the maximum value of ~48 Oe until the nanoclusters reached a size of ~120 nm; the coercivity then gradually decreased to zero.

Magnetic multi-granule nanoclusters: A model system that exhibits universal size effect of magnetic coercivity

Early detection of the protein marker troponin I in patients with a higher risk of acute myocardial infarction ,,,, can reduce the risk of death from heart attacks ,,,, . Most troponin assays are currently based on the conventional enzyme linked immunosorbent assay and have detection limits in the nano- and picomolar range. Here, we show that by combining viral nanoparticles, which are engineered to have dual affinity for troponin antibodies and nickel, with three-dimensional nanostructures including nickel nanohairs, we can detect troponin levels in human serum samples that are six to seven orders of magnitude lower than those detectable using conventional enzyme linked immunosorbent assays ,,,,, . The viral nanoparticle helps to orient the antibodies for maximum capture of the troponin markers. High densities of antibodies on the surfaces of the nanoparticles and nanohairs lead to greater binding of the troponin …

A highly sensitive and selective diagnostic assay based on virus nanoparticles

Polyvinylpyrrolidone (PVP)-coated sub-5nm monosize Fe 3 O 4 nanoparticles were synthesized by reduction of Fe(III) acetylacetonate in the presence of PVP polymer as surfactant in one-pot polyol process. Their microstructure and magnetic properties were characterized by XRD, TEM/HRTEM and VSM. It is found that the nanoparticles have high crystallinity with distinct lattices and the magnetic measurements reveal their well-defined superparamagnetic behavior at room temperature. Such Fe 3 O 4 nanoparticles with tailorable size and tunable magnetic properties are promising for biomedical applications.

One-pot polyol synthesis of monosize PVP-coated sub-5 nm Fe3O4 nanoparticles for biomedical applications

Magnetite particles of 2–4 nm were synthesized by an economic, biocompatible chemical coprecipitation route, with their size tuned by the reaction temperature. The microstructure and morphology of the nanoparticles were characterized by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM), whereas the magnetic properties were investigated by vibrating sample magnetometry (VSM) and superconducting quantum interference device (SQUID). It is found that the nanoparticles demonstrate well-defined superparamagnetic behavior as prepared and after annealing. Distinct lattices were observed which manifest the high crystallinity of such ultrasmall particles and the finite-size effect was revealed by analyzing the corresponding microstructure and magnetism.

Sub 5 nm magnetite nanoparticles: Synthesis, microstructure, and magnetic properties

The magnetic properties and microstructural evolution of Zr-doped FePt alloy films prepared by dc-magnetron sputtering were investigated. Compared to an undoped binary film, Zr-doped FePt alloy films showed accelerated ordering transformation kinetics accompanying smaller grains: we were able to fabricate a Zr-doped FePt film [e.g., ] possessing very fine grain size (5 nm in average) and high coercivity (7.3 kOe) within 10 min annealing at 500 °C. It is thought that the point defects and lattice strain introduced by Zr-doping activated the nucleation rate of the ordered phase. In particular, for Zr-doped FePt films containing less than 45 at. % Pt, the ordered phase was decomposed into a disordered phase after excessive annealing due to the formation of a Pt–Zr compound, most likely that reduces the effective Pt content in the ordered phase.

Rapid ordering of Zr-doped FePt alloy films

We explored the feasibility of magnetite (Fe 3 O 4 )-gold (Au) core–shell nanocrystals as a useful vehicle for biomedical application such as cell separation. Streptavidin-fluorescein isothiocyanate (STA-FITC) was conjugated to the surface of the Fe 3 O 4 -Au core–shell nanocrystals using a carbodimide activation protocol. These nanocrystals were further tested for their ability to bind CD4 + T lymphocytes, bound to biotin-labeled anti-CD4 mAbs, isolated from the spleen of C57BL/6 mice. Our data show that the Fe 3 O 4 -Au nanocrystals successfully pulled down CD4 + T lymphocytes from the whole splenocytes with high specificity. Therefore, our nanocrystals provide an efficient tool for the cell separation process and further present the dramatic potential to be applied to other areas of biomedical application including diagnosis, monitoring, and treatment of human diseases.

Synthesis of streptavidin-FITC-conjugated core–shell Fe3O4-Au nanocrystals and their application for the purification of CD4+ lymphocytes

(Figure Presented) Stripped wires: Multifunctional (magnetic and optical) iron-gold barcode nanowires were electrochemically fabricated using nanoporous templates. Structural analysis by TEM elemental line scan and mapping (see images) clearly revealed the well-separated, bamboo-like nanostructures composed of Fe and Au strips.

Iron-gold barcode nanowires

The effects of current transients on the magnetic response of GMR sensors is studied. It is shown that GMR sensors with an FeMn exchange layer exhibit large magnetic changes after a single ESD current transient. The energy which results in magnetic failure is only 0.9 nJ, which is much less than the 6 nJ which causes physical melting damage to the GMR sensor. These serious magnetic changes are explained in terms of resetting of the FeMn exchange layer direction due to the elevated temperature and internal magnetic field during the current transient. It is concluded that ESD stress testing of GMR sensors has revealed a new and important magnetic failure mechanism in GMR sensors.

Magnetic changes in GMR heads caused by electrostatic discharge

Aptamers, single-stranded nucleic acids, provide a unique opportunity as amplifiable molecules using polymerase chain reaction (PCR) as well as recognition molecules like antibodies. We report a highly sensitive detection of Escherichia coli by taking advantage of the aptamer amplification as well as the specific binding of aptamers onto E. coli. This unique approach consists of three steps. First, the target E. coli was captured by antibody-conjugated magnetic beads. Second, the RNA aptamers were bound onto the surface of captured E. coli in a sandwich way. Finally, the heat-released aptamers were amplified by using real-time reverse-transcriptase-PCR (RT-PCR). The aptamer amplification in this approach has enabled a sensitive detection of microorganisms, such as the detection of 10 E. coli in 1ml sample. When compared to the amplification of nucleic acids extracted from the target microorganisms, this …

A sensitive method to detect Escherichia coli based on immunomagnetic separation and real-time PCR amplification of aptamers

Integrated circuits (ICs) are challenged to deliver historically anticipated performance improvements while increasing the cost and complexity of the technology with each generation. Front‐end‐of‐line (FEOL) processes have provided various solutions to this predicament, whereas the back‐end‐of‐line (BEOL) processes have taken a step back. With continuous IC scaling, the speed of the entire chip has reached a point where its performance is determined by the performance of the interconnect that bridges billions of transistors and other devices. Consequently, the demand for advanced interconnect metallization rises again, and various aspects must be considered. This review explores the quest for new materials for successfully routing nanoscale interconnects. The challenges in the interconnect structures as physical dimensions shrink are first explored. Then, various problem‐solving options are considered …

Materials quest for advanced interconnect metallization in integrated circuits

Lately, the isolation of DNA using magnetic nanoparticles has received increased attention owing to their facile manipulation and low costs. Although methods involving their magnetic separation have been extensively studied, there is currently a need for an efficient technique to isolate DNA for highly sensitive diagnostic applications. We describe herein a method to isolate and purify DNA using biofunctionalized superparamagnetic nanoparticles synthesized by a modified polyol method to obtain the desired monodispersity, followed by surface modification with meso-2,3-dimercaptosuccinic acid (DMSA) containing carboxyl groups for DNA absorption. The DMSA-coated magnetic nanoparticles (DMSA-MNPs) were used for the isolation of DNA, with a maximum yield of 86.16%. In particular, we found that the isolation of DNA using small quantities of DMSA-MNPs was much more efficient than that using commercial …

Isolation of DNA using magnetic nanoparticles coated with dimercaptosuccinic acid

Cobalt nanowires were fabricated by DC electrodeposition onto anodic aluminium oxide (AAO) templates. The effects of AAO pore diameter, current density, pH, annealing and deposition under external magnetic fields on the structure and magnetic properties of the nanowire arrays were studied. It is found that the smaller pore size produces high crystallinity, resulting in improved magnetic performance at low current density. The pH can transform fcc-Co phase to hcp-Co phase, with the easy axis along the nanowire axis switched over to the perpendicular direction. Annealing demonstrates excellent thermal stability of the magnetic nanowire arrays at high temperature. The application of external magnetic field during deposition influences the growth habit of the nanowires, leading to the change in the magnetic properties.

Control of magnetic anisotropy of Co nanowires

Magnetite (Fe 3 O 4 )-mesoporous silica (mSiO 2 ) core-shell nanoparticles are attractive heavy metal ion adsorbents. However, most studies have focused on the use of superparamagnetic Fe 3 O 4 nanoparticles as core materials, resulting in low magnetic field responses due to their low susceptibility and saturation magnetization ( M s ) values. Here, we report the synthesis, microstructure, and properties of ferrimagnetic Fe 3 O 4 -mSiO 2 core-shell nanoparticles, focusing on the effects of the magnetic core size on their removal efficiency. We analyzed the magnetic properties and structural changes of the surface according to the magnetic core size and elucidated the correlation with the removal efficiency of heavy metal ions. Fe 3 O 4 cores with diameters of 103, 123, or 207 nm were synthesized by a modified polyol method, while the silica layer with a porous structure was coated using a sol-gel reaction. Amino …

Effect of the magnetic core size of amino-functionalized Fe3O4-mesoporous SiO2 core-shell nanoparticles on the removal of heavy metal ions

The microstructure and magnetic properties of polycrystalline Fe films with thicknesses of 200–1000 Å have been investigated. The films were prepared by rf sputtering onto SiO 2 substrates. The investigation was prompted by the lack of data on sputtered Fe films in this thickness regime as well as disagreement in the data for evaporated films. In addition to thickness, substrate temperature and deposition pressure were varied to examine their effect on the microstructure. The film microstructure was characterized by x‐ray diffraction, transmission electron microscopy, and Auger spectroscopy. The polycrystalline films did not display a strong preferred orientation and had average grain sizes of 60–85 Å. Surface oxide layers formed upon exposure to air ranged from 10 to 80 Å, the thicker oxides formed on films with lower density. Magnetic hysteresis measurements were made with a vibrating sample magnetometer …

Magnetic Properties of Sputtered Fe Thin Films: Processing and Thickness Dependence

Magnetite nanocrystals of 2–4nm were synthesized by a chemical coprecipitation method, by which the particle size was controlled by the reaction temperature. The nanocrystals were investigated by XRD, TEM/HRTEM, VSM and SQUID. It is found that the nanocrystals reveal well-defined superparamagnetic behavior before and after annealing, while the observation of the distinct lattices manifest the high crystallinity of the ultrasmall particles.

Sub 5 nm Fe3O4 nanocrystals via coprecipitation method

Novel multifunctional magnetic particles (MMPs) conjugated with photosensitizer and vancomycin were fabricated by surface modification of Fe3O4 particles. The capacities to target, capture and inactivate pathogenic bacteria and good biocompatibility suggest that the MMPs have great potentials as photodynamic inactivation agents for serious bacterial contamination.

Photosensitizer and vancomycin-conjugated novel multifunctional magnetic particles as photoinactivation agents for selective killing of pathogenic bacteria

A cross-point-type phase-change random access memory (PRAM) cell without an access transistor is successfully fabricated with the In/sub 2/Se/sub 3/ resistor, which has much higher electrical resistivity than conventionally used Ge/sub 2/Sb/sub 2/Te/sub 5/ and of which electrical resistivity can be varied by the factor of 10/sup 5/ related with the degree of crystallization. Thus, the switching power can be delivered more effectively due to its higher electrical resistivity and device failure related to phase decomposition can be avoided since In/sub 2/Se/sub 3/ is single phase binary compound. The static-mode switching (dc test) is tested for the 5 /spl mu/m In/sub 2/Se/sub 3/ PRAM device. In the first sweep, the as-grown amorphous In/sub 2/Se/sub 3/ resistor showed the high resistance state at low voltage region. However, when it reached the threshold voltage, the electrical resistance of the device was drastically …

Switching behavior of indium selenide-based phase-change memory cell

Engineering and application of nanomaterials have recently helped advance various biomedical fields. Zinc oxide (ZnO)-based nanocomposites have become one of the most promising candidates for biomedical applications due to their biocompatibility, unique physicochemical properties, and cost-effective mass production. In addition, recent advances in nano-engineering technologies enable the generation of ZnO nanocomposites with unique three-dimensional structures and surface characteristics that are optimally designed for in vivo applications. Here, we review recent advances in the application of diverse ZnO nanocomposites, with an especial focus on their development as vaccine adjuvant and cancer immunotherapeutics, as well as their intrinsic properties interacting with the immune system and potential toxic effect in vivo. Finally, we summarize promising proof-of-concept applications as prophylactic and therapeutic vaccines against infections and cancers. Understanding the nano-bio interfaces between ZnO-based nanocomposites and the immune system, together with bio-effective design of the nanomaterial using nano-architectonic technology, may open new avenues in expanding the biomedical application of ZnO nanocomposites as a novel vaccine platform.

Application of ZnO-based nanocomposites for vaccines and cancer immunotherapy

The electrical resistivity and mechanical hardness of reactively sputtered tantalum nitride (TaN) thin films on ceramic substrates have been investigated. Depending on the nitrogen/argon gas flow rate ratio (defined as R), the resistivity of the tantalum nitride films varied unusually widely (10 7 orders) from metal to insulator. The big increase in the resistivity of the tantalum nitride films as the R value increased may be due to the theoretically predicted Ta vacancies and anti-site defects (excess N atoms occupying Ta sites) or thermodynamically stable N-rich phase formation under N-rich conditions. N-rich TaN film in this study (R=2) had a dramatically increased resistivity and seems to be a good candidate material as a seed layer and a capping layer of GMR sensor in data storage, while low-resistive stoichiometric TaN (R=0.5) is a good candidate material as a barrier layer in semiconductors with its low contact …

Electrical and mechanical properties of tantalum nitride thin films deposited by reactive sputtering

Intelligent Computer Architecture & Systems Research Lab (CASL)

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ReAx: Resource-efficient Asynchronous Execution for Accelerating LLM Fine-tuning at the Edge

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