Yoon Seon Jeong

Cellular Uptake, Cytotoxicity, and Innate Immune Response of Silica−Titania Hollow Nanoparticles Based on Size and Surface Functionality

Silica-titania hollow nanoparticles (HNPs) with uniform diameters of 25, 50, 75, 100, and 125 nm were fabricated by dissolution and redeposition method in order to evaluate size dependent cellular response. Surface-modified HNPs with cationic, anionic, and neutral functional group were prepared by silane treatment. We systematically investigated cellular internalization, toxicity, and innate immune response of HNPs in human breast cancer (SK-BR-3) and mouse alveolar macrophage (J774A.1) cells. Size- and surface functionality-dependent cellular uptake of HNPs was investigated by fluorescence labeling (fluorescein isothiocyanate), inductively coupled plasma-emission spectroscopy, and ultrastructural resolution using transmission electron microscopy. Viability, reactive oxygen species, and apoptosis/necrosis of HNP-treated J774A.1 revealed the size-dependent phenomenon. Innate immune response of HNP-treated macrophages was measured by three cytokines such as interleukin-1, interleukin-6, and tumor necrosis factor α. Among the HNPs of different sizes, 50-nm HNPs demonstrated the highest toxic influence on macrophages. Among the HNPs with surface functionalities, cationic HNPs demonstrated the most toxic effect on J774A.1 and the highest uptake efficiency. The toxicity results of HNP-treated macrophages were consistent with the cellular internalization efficiency. These findings provide size- and surface functionality-dependent nanotoxicity and uptake of HNPs, and lead to HNPs for bioapplications such as drug delivery and imaging probe.

Fluorescent Polymer Nanoparticle for Selective Sensing of Intracellular Hydrogen Peroxide

Fluorescent boronate-modified polyacrylonitrile (BPAN) nanoparticles of 50 nm diameter were fabricated for use as a selective H(2)O(2) sensor. The fluorescence intensity changed and an emission peak shifted when BPAN nanoparticles selectively interacted with H(2)O(2), relative to other reactive oxygen species (ROS). The BPAN nanoparticles undergo photoinduced electron transfer (PET) between a Schiff base moiety and boronate, which enhances the fluorescence and makes the nanoparticles suitable for selective ROS recognition. We demonstrate the use of these nanoparticles as a detector of endogenous H(2)O(2) produced in living cells. The representative features of the fluorescent BPAN nanoparticles that make them particularly attractive for H(2)O(2) and ROS detection are the following: they are easily synthesized as PET sensors; they exhibit a characteristic emission peak and peak shift that distinguishes reaction with H(2)O(2) from other ROS; and compared to organic compounds, the sensing moiety on BPAN polymer nanoparticles is more thermally stable and has superior mechanical properties, enabling their use in various biomedical applications.

Cellular uptake, cytotoxicity, and ROS generation with silica/conducting polymer core/shell nanospheres

The cellular response to conducting polymer (CP) nanospheres with similar physical properties was evaluated by in vitro cellular uptake and cytotoxicity in mouse macrophage RAW 264.7 and rat pheochromocytoma PC-12 cells. Four different CPs (polythiophene, poly(3,4-ethylenedioxythiophene), polyaniline, and polypyrrole) were deposited onto silica nanoparticles with a diameter of ca. 22 nm. Cellular uptake of silica/CP core/shell nanospheres in both cell lines was observed by transmission electron microscopy and they were internalized via phagocytosis and endocytosis. Cytotoxic effects were systemically assessed using live-cell microscopy, viability, oxidative stress, and lactate dehydrogenase assays. Silica/polythiophene core/shell nanospheres were the most toxic in both cell lines examined, because of the cellular effects of sulfur atoms. On the other hand, silica/polypyrrole core/shell nanospheres caused the lowest levels of toxicity in both cell lines. Furthermore, both rat and mouse cell viability was concentration-dependent with the nanospheres. These findings enhance nanotoxicological information regarding CP nanospheres when used with macrophage and neuronal cells, which may be useful in their application in bioelectronic and biomedical fields.

Fluorescent europium-modified polymer nanoparticles for rapid and sensitive anthrax sensors.

Novel fluorescent polyacrylonitrile nanoparticles were synthesized by microemulsion polymerization and Schiff base modification. By further modification with europium, the polyacrylonitrile nanoparticles could be used as a highly sensitive and rapid sensor for Bacillus anthracis spore detection in aqueous solution. The europium-modified polyacrylonitrile nanoparticles were readily combined with dipicolinic acid as a unique biomarker of B. anthracis, leading to high fluorescence emission. These nanoparticles enabled ratiometric detection without instrument-specific calibration due to the internal fluorescence reference. Additionally, the europium-modified polyacrylonitrile nanoparticle sensors exhibited a remarkable limit of detection (10pM) for dipicolinic acid and outstanding selectivity (160×) over aromatic ligands in aqueous solution. The ultrafine nanoparticle sensor showed a high capability for detecting anthrax due to the increased surface area-to-volume ratio and enhanced dispersibility.

Fluorescent boronic acid-modified polymer nanoparticles for enantioselective monosaccharide detection

We report the fabrication of new fluorescent boronic acid-modified polyacrylonitrile (B-PAN) nanoparticles for an enantioselective monosaccharide sensor. Polyacrylonitrile (PAN) nanoparticles of 50 nm diameter were synthesized by radical polymerization. After boronic acid modification, the B-PAN nanoparticles showed enhanced fluorescence due to a photo-induced electron transfer mechanism. The B-PAN nanoparticles enabled molecular recognition in aqueous solution owing to covalent bonds with diol-containing compounds, resulting in application for enantiomer detection of monosaccharides. The fluorescence intensity changed when B-PAN nanoparticles interacted with the enantiomers of monosaccharides, including D-/L-glucose, D-/L-galactose, and D-/L-fructose. The B-PAN nanoparticles provide a new direction for the development of enantioselective monosaccharide sensors and could be subsequently expanded to a platform of versatile fluorescence sensors.

Design of biomimetic cellular scaffolds for co-culture system and their application:

The extracellular matrix of most natural tissues comprises various types of cells, including fibroblasts, stem cells, and endothelial cells, which communicate with each other directly or indirectly to regulate matrix production and cell functionality. To engineer multicellular interactions in vitro, co-culture systems have achieved tremendous success achieving a more realistic microenvironment of in vivo metabolism than monoculture system in the past several decades. Recently, the fields of tissue engineering and regenerative medicine have primarily focused on three-dimensional co-culture systems using cellular scaffolds, because of their physical and biological relevance to the extracellular matrix of actual tissues. This review discusses several materials and methods to create co-culture systems, including hydrogels, electrospun fibers, microfluidic devices, and patterning for biomimetic co-culture system and their applications for specific tissue regeneration. Consequently, we believe that culture systems with appropriate physical and biochemical properties should be developed, and direct or indirect cell–cell interactions in the remodeled tissue must be considered to obtain an optimal tissue-specific microenvironment.

Metal enhanced fluorescence (MEF) for biosensors: General approaches and a review of recent developments

Fluorescence-based biosensor platforms have been intensively investigated not only to increase the sensitivity but also to improve the performance of biosensors. By exploiting metal from the macroscopic down to the nanoscopic surface, various architectures have been devised to manipulate fluorescence signals (enhancement, quenching) within near-optical fields. The interaction of a metallic surface with proximal fluorophores (in the range of 5-90 nm) has beneficial effects on optical properties such as an increased quantum yield, improved photostability and a reduced lifetime of fluorophores. This phenomenon called metal-enhanced fluorescence (MEF) has been extensively used in biosensory applications. However, their applications for biological analysis practically remain challenging in biological microenvironments. Therefore, this review primarily provides a general overview of MEF biosensor systems from the basic mechanism to state-of-the-art biological applications. The review also covers the pros and cons of MEF biosensor as well as discussions about further directions in biological perspectives.