Kang Kyun Wang

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

Novel multifunctional magnetic particles (MMPs) conjugated with photosensitizer and vancomycin were fabricated by surface modification of Fe(3)O(4) 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.

Functional Manipulation of Dendritic Cells by Photoswitchable Generation of Intracellular Reactive Oxygen Species

Reactive oxygen species (ROS) play an important role in cellular signaling as second messengers. However, studying the role of ROS in physiological redox signaling has been hampered by technical difficulties in controlling their generation within cells. Here, we utilize two inert components, a photosensitizer and light, to finely manipulate the generation of intracellular ROS and examine their specific role in activating dendritic cells (DCs). Photoswitchable generation of intracellular ROS rapidly induced cytosolic mobilization of Ca(2+), differential activation of mitogen-activated protein kinases, and nuclear translocation of NF-κB. Moreover, a transient intracellular ROS surge could activate immature DCs to mature and potently enhance migration in vitro and in vivo. Finally, we observed that intracellular ROS-stimulated DCs enhanced antigen specific T-cell responses in vitro and in vivo, which led to delayed tumor growth and prolonged survival of tumor-bearing mice when immunized with a specific tumor antigen. Therefore, a transient intracellular ROS surge alone, if properly manipulated, can cause immature DCs to differentiate into a motile state and mature forms that are sufficient to initiate adaptive T cell responses in vivo.

Photofunctional Co-Cr Alloy Generating Reactive Oxygen Species for Photodynamic Applications

We report the fabrication of photofunctional Co-Cr alloy plate that is prepared by a simple modification process for photodynamic application. Photoinduced functionality is provided by the photosensitizer of hematoporphyrin (Hp) that initially generates reactive oxygen species (ROS) such as superoxide anion radical and singlet oxygen. The photosensitizer with carboxyl group was chemically bonded to the surface of the Co-Cr alloy plate by esterification reaction. Microstructure and elemental composition of the Co-Cr alloy plate were checked with scanning electron microscopy (SEM) and energy dispersive X-ray spectrometer (EDS). Fabrication of the photofunctionality of the Co-Cr alloy plate was confirmed with X-ray photoelectron spectroscopy (XPS), reflectance UV-Vis absorption, and emission spectroscopy. Reactive oxygen generation from the photofunctional Co-Cr alloy plate was confirmed by using the decomposition reaction of 1,3-diphenylisobenzofuran (DPBF). The results suggest that the immobilized photosensitizer molecules on the surface of Co-Cr alloy plate still possess their optical and functional properties including reactive oxygen generation. To open the possibility for its application as a photodynamic material to biological system, the fabricated photofunctional Co-Cr alloy is applied to the decomposition of smooth muscle cells.

Controlled Delivery of Extracellular ROS Based on Hematoporphyrin-Incorporated Polyurethane Film for Enhanced Proliferation of Endothelial Cells

The principle of photodynamic treatment (PDT) involves the administration of photosensitizer (PS) at diseased tissues, followed by light irradiation to produce reactive oxygen species (ROS). In cells, a moderate increase in ROS plays an important role as signaling molecule to promote cell proliferation, whereas a severe increase of ROS causes cell damage. Previous studies have shown that low levels of ROS stimulate cell growth through PS drugs-treating PDT and nonthermal plasma treatment. However, these methods have side effects which are associated with low tissue selectivity and remaining of PS residues. To overcome such shortcomings, we designed hematoporphyrin-incorporated polyurethane (PU) film induced generation of extracellular ROS with singlet oxygen and free radicals. The film can easily control ROS production rate by regulating several parameters including light dose, PS dose. Also, its use facilitates targeted delivery of ROS to the specific lesion. Our study demonstrated that extracellular ROS could induce the formation of intracellular ROS. In vascular endothelial cells, a moderated increase in intracellular ROS also stimulated cell proliferation and cell cycle progression by accurate control of optimum levels of ROS with hematoporphyrin-incorporated polymer films. This modulation of cellular growth is expected to be an effective strategy for the design of next-generation PDT.

Eradication of Plasmodium falciparum from Erythrocytes by Controlled Reactive Oxygen Species via Photodynamic Inactivation Coupled with Photofunctional Nanoparticles

We investigated the antimalarial effect of photodynamic inactivation (PDI) coupled with magnetic nanoparticles (MNPs) as a potential strategy to combat the emergence of drug-resistant malaria and resurgence of malaria after treatment. Because the malarial parasite proliferates within erythrocytes, PDI agents need to be taken up by erythrocytes to eradicate the parasite. We used photofunctional MNPs as the PDI agent because nanosized particles were selectively taken up by Plasmodium-infected erythrocytes and remained within the intracellular space due to the enhanced permeability and retention effect. Also, the magnetism of Fe3O4 nanoparticles can easily be utilized for the collection of photofunctional nanoparticles (PFNs), and the uptaken PFNs infected the erythrocytes after photodynamic treatment with external magnetics. Photofunctionality was provided by a photosensitizer, namely, pheophorbide A, which generates reactive oxygen species (ROS) under irradiation. PAs were covalently bonded to the surface of the MNPs. The morphology and structural characteristics of the MNPs were investigated by scanning electron microscopy and X-ray diffraction (XRD), whereas the photophysical properties of the PFNs were studied with Fourier transform infrared, absorption, and emission spectroscopies. Generation of singlet oxygen, a major ROS, was directly confirmed with time-resolved phosphorescence spectroscopy. To evaluate the ability of PFNs to kill malarial parasites, the PDI effect of PFNs was evaluated within the infected erythrocytes. Furthermore, malarial parasites were completely eradicated from the erythrocytes after PDI treatment using PFNs on the basis of an 8 day erythrocyte culture test.

Photophysical Properties of Pheophorbide-a Derivatives and Their Photodynamic Therapeutic Effects on a Tumor Cell Line In Vitro

Pheophorbide-a derivatives have been reported to be potential photosensitizers for photodynamic therapy (PDT). In this study, photophysics of pheophorbide-a derivatives (PaDs) were investigated along with their photodynamic tumoricidal effect in vitro. PaDs were modified by changing the coil length and/or making the hydroxyl group (–OH) substitutions. Their photophysical properties were studied by steady-state and time-resolved spectroscopic methods. The photodynamic tumoricidal effect was evaluated in the mouse breast cancer cell line (EMT6). Lifetime and quantum yield of fluorescence and quantum yields of triplet state and singlet oxygen were studied to determine the dynamic energy flow. The coil length of the substituted alkyl group did not significantly affect the spectroscopic properties. However, the substitution with the hydroxyl group increased the quantum yields of the triplet state and the singlet oxygen due to the enhanced intersystem crossing. In order to check the application possibility as a photodynamic therapy agent, the PaDs with hydroxyl group were studied for the cellular affinity and the photodynamic tumoricidal effect of EMT6. The results showed that the cellular affinity and the photodynamic tumoricidal effect of PaDs with the hydroxyl group depended on the coil-length of the substituted alkyl group.

Target-oriented photofunctional nanoparticles (TOPFNs) for selective photodynamic inactivation of Methicillin-resistant Staphylococcus aureus (MRSA).

To inactivate methicillin-resistant Staphylococcus aureus (MRSA) with minimum damage to host cells and tissue, target-oriented photofunctional nanoparticles (TOPFNs) were fabricated and characterized. MRSA is a predominant infective pathogen even in hospital and non-hospital environments due to its ability to develop high levels of resistance to several classes of antibiotics through various pathways. To solve this major problem, photodynamic inactivation (PDI) method applies to treat antibiotic-resistant bacteria. PDI involves the photosensitizer (PS) and light with a specific wavelength to be able to apply for a non-invasive therapeutic procedure to treat pathogenic bacteria by inducing apoptosis or necrosis of microorganisms. However, most current PDI researches have suffered from the instability of PDI agents in the biological environment due to the lack of selectivity and low solubility of PDI agents, which leads to the low PDI efficiency. In this study, the TOPFNs were fabricated by an esterification reaction to introduce hematoporphyrin (HP) and MRSA antibody to the surface of Fe3O4 nanoparticles. The TOPFNs were designed as dispersible PDI agent in biological condition, which was effectively used for selectively capturing and killing of MRSA. The capture efficiency TOPFNs was compared with PFNs as a negative control. The results showed that the capture efficiency of TOPFNs and PFNs was 95.55% and 6.43% in MRSA and L-929 cell mixed condition, respectively. And TOPFNs have a selective killing ability for MRSA with minimum damage to L-929 cells. Furthermore, PDI effect of TOPFNs was evaluated on the mice in vivo condition in order to check the possibility of practical medical application.

Sensing Estrogen with Electrochemical Impedance Spectroscopy

This study demonstrates the application feasibility of electrochemical impedance spectroscopy (EIS) in measuring estrogen (17β-estradiol) in gas phase. The present biosensor gives a linear response (R 2 = 0.999) for 17β-estradiol vapor concentration from 3.7u2009ng/L to 3.7 × 10−4u2009ng/L with a limit of detection (3.7 × 10−4u2009ng/L). The results show that the fabricated biosensor demonstrates better detection limit of 17β-estradiol in gas phase than the previous report with GC-MS method. This estrogen biosensor has many potential applications for on-site detection of a variety of endocrine disrupting compounds (EDCs) in the gas phase.