Publications by authors named "Sung Young Park"

87 Publications

Real-Time Wireless Monitoring of Cell Proliferation and Detachment Based on pH-Responsive Conductive Polymer Dots.

Anal Chem 2021 Jun 10;93(24):8638-8646. Epub 2021 Jun 10.

Department of IT and Energy Convergence (BK21 FOUR), Korea National University of Transportation, Chungju 380-702, Republic of Korea.

wireless monitoring for cell proliferation and detachment kinetics was conducted using pH-responsive zwitterionic polymer dots (Z-PDs), based on changes in electrochemical signals derived from Z-PD-coated substrates the interaction of charges transferred between Z-PDs and cells. Z-PD-coated substrates were found to be a potent means to monitor and manipulate cell adhesion and detachment because of their high sensitivity over a wide range of pH conditions, and modification of the coated substrates was confirmed using a wireless system. At neutral pH, Z-PD-coated wireless sensors exhibited π-π stacking involving aromatic rings with hydrophobic interactions, thereby promoting cell proliferation; consequently, an increase in the measured resistance was observed. In contrast, Z-PD-coated substrates triggered by acidic and basic conditions promoted cell detachment, which induced an increase in the resistance compared with Z-PD substrates at pH 6.8, as a result of charges transferred to support Z-PD internalization through cell membranes after detachment. Therefore, as a wireless biosensor with excellent pH responsiveness that facilitates cell proliferation and detachment and whose electrochemical signals could be additionally acquired a smartphone, Z-PD biosensors demonstrated a more favorable approach for monitoring cell-surface interactions than conventional optically based methods.
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http://dx.doi.org/10.1021/acs.analchem.1c01778DOI Listing
June 2021

Tunable Pressure Sensor of -Carbon Dot-Based Conductive Hydrogel with Electrical, Mechanical, and Shape Recovery for Monitoring Human Motion.

ACS Appl Mater Interfaces 2020 Nov 4;12(46):51766-51775. Epub 2020 Nov 4.

Department of Green Bio Engineering, Korea National University of Transportation, Chungju 380-702, Republic of Korea.

The reversible volume memories of the inner structures of soft materials with controllable hydrophilic-hydrophobic balance have been widely recognized, for example, hydrogels used in pressure sensors. Mechanical stimuli, such as pressure, vibration, and tensile, may influence the deformation of the hydrogel while simultaneously changing the electronic signal. Here, we designed a hydrophobic carbon dot nanoparticle (-CD) mixed with polyvinyl alcohol and catechol-conjugated chitosan to obtain a hydrogel suitable for pressure and vibration sensor applications. The hydrophobicity of loaded -CD plays an important role in mechanical performance and electronic signal acquisition. It also affects the different rheological reversibility and shape recovery as an impact on the volume transition. These characteristics are influenced by the compactness, dimensional structure, and density of the fabricated hydrogel. As a result, hydrogels with high hydrophobicity have a stiff structure (shear modulus 8123.1 N·m) compared to that of the hydrophilic hydrogel (ranging between 6065.7 and 7739.2 N·m). Moreover, the mechanically dependent volume transition hydrogel affects the electronic resistivity (up to 17.3 ± 1.3%) and capacitance change (up to 145%) when compressed with different forces. The hydrogel with a controlled hydrophobic-hydrophilic inner structure shows a unique sensitivity and great potential for various applications in wearable electronic skins, real-time clinical health-care monitoring, and human-computer interactions.
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http://dx.doi.org/10.1021/acsami.0c16745DOI Listing
November 2020

NIR-vis-Induced pH-Sensitive TiO Immobilized Carbon Dot for Controllable Membrane-Nuclei Targeting and Photothermal Therapy of Cancer Cells.

ACS Appl Mater Interfaces 2020 Aug 12;12(34):37929-37942. Epub 2020 Aug 12.

Department of Green Bio Engineering, Korea National University of Transportation, Chungju 380-702, Republic of Korea.

This study investigated a selective and sensitive theragnosis system for the specific targeting of the membrane and nuclei based on visible-light and pH-responsive TiO-integrated cross-linked carbon dot (C-CD/TiO) for tumor detection and controllable photothermal therapy. The cross-linking system was formed by boronate ester linkages between the TiO-immobilized Dopa-decyl (D-CD) and zwitterionic-formed CD (Z-CD) for nuclear targeting, which showed fluorescence "off" at physiological pH. The fluorescence recovered to the "on" state in acidic cancer cells owing to cleavages of the boronate ester bonds, resulting in the disruption of the Förster resonance energy transfer that generated different CDs useful for tumor-selective biosensors and therapy. D-CD, which is hydrophobic, can penetrate the hydrophobic sites of the cell membrane; it caused a loss in the hydrophobicity of these sites after visible-light irradiation. This was achieved by the photocatalytic activity of the TiO modulating energy bandgap, whereas the Z-CD targeted the nucleus, as confirmed by merged confocal microscopy images. D-CD augmented by photothermal heat also exhibited selective anticancer activity in the acidic tumor condition but showed only minimal effects at a normal site at pH 7.4. After C-CD/TiO injection to an tumor model, C-CD/TiO efficiently ablated tumors under NIR light irradiation. The C-CD/TiO group showed up-regulation of the pro-apoptotic markers such as and in tumor. This material exhibited its potential as a theragnostic sensor with excellent biocompatibility, high sensitivity, selective imaging, and direct anticancer activity via photothermal therapy.
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http://dx.doi.org/10.1021/acsami.0c11979DOI Listing
August 2020

Construction of [email protected] Carbon Dots Nanoflowers as Binder Free Electrode for Reduction and Oxidation of Water.

Materials (Basel) 2020 Jul 13;13(14). Epub 2020 Jul 13.

Department of Chemical and Biological Engineering, Korea National University of Transportation, Chungju 380-702, Korea.

Electrochemical water splitting is known as a potential approach for sustainable energy conversion; it produces H fuel by utilizing transition metal-based catalysts. We report a facile synthesis of [email protected] dots (CDs) nanoflowers supported on nickel foam through a hydrothermal technique in the absence of organic solvents and an inert environment. The synthesized material with a judicious choice of CDs shows superior performance in hydrogen and oxygen evolution reactions (HER and OER) compared to the FeCoO electrode alone in alkaline media. For HER, the overpotential of 205 mV was able to produce current densities of up to 10 mA cm, whereas an overpotential of 393 mV was needed to obtain a current density of up to 50 mA cm for OER. The synergistic effect between CDs and FeCoO accounts for the excellent electrocatalytic activity, since CDs offer exposed active sites and subsequently promote the electrochemical reaction by enhancing the electron transfer processes. Hence, this procedure offers an effective approach for constructing metal oxide-integrated CDs as a catalytic support system to improve the performance of electrochemical water splitting.
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http://dx.doi.org/10.3390/ma13143119DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7411927PMC
July 2020

Mineralized Soft and Elastic Polymer Dot Hydrogel for a Flexible Self-Powered Electronic Skin Sensor.

ACS Appl Mater Interfaces 2020 Jul 15;12(30):34105-34114. Epub 2020 Jul 15.

Department of Chemical and Biological Engineering, Korea National University of Transportation, Chungju 380-702, Republic of Korea.

We propose an integrated, self-powered, flexible electronic skin device containing an alginate-derived polymer dot (A-PD)-incorporated mineralized hydrogel-based energy storage unit and a chitosan-derived n-type carbon dot (N-CD)-based solar cell for an energy-harvesting unit. This study demonstrates a unique architecture of mineralized hydrogel comprising A-PD-incorporated poly(acrylic acid) (PAA)/CaCO/laponite containing soft and sensitive layers, deposited with a polyaniline electrode to serve as an energy storage unit. The self-assembly was achieved through the ionic cross-linking between A-PD and PAA driven by the mineralization process, resulting in excellent dimensional stability and improved mechanical properties of the hydrogel. The sp carbon-rich A-PD enhances the electrochemical performance and the overall photon-to-electrical conversion and storage efficiency for self-powered devices by the formation of the bridge of electrons between the ionized polymer and metal ion. The capacitive sensor developed in this study exhibits high sensitivity in detecting small pressure changes, such as the falling of small water droplets. The self-powered sensing device can detect and monitor various human motions continuously by harvesting light energy from outdoor sunlight. Furthermore, the energy-autonomous device exhibits unique responses for handwriting characters stably and repeatedly. The proposed system may be applicable to human-machine interfaces, biomonitoring systems, secure communication, and wearable devices.
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http://dx.doi.org/10.1021/acsami.0c08677DOI Listing
July 2020

Diselenide-Bridged Carbon-Dot-Mediated Self-Healing, Conductive, and Adhesive Wireless Hydrogel Sensors for Label-Free Breast Cancer Detection.

ACS Nano 2020 07 12;14(7):8409-8420. Epub 2020 Jun 12.

Department of Chemical & Biological Engineering, Korea National University of Transportation, Chungju 380-702, Republic of Korea.

Recently, a great deal of research has focused on the study of self-healing hydrogels possessing electronic conductivity due to their wide applicability for use in biosensors, bioelectronics, and energy storage. The low solubility, poor biocompatibility, and lack of effective stimuli-responsive properties of their sp carbon-rich hybrid organic polymers, however, have proven challenging for their use in electroconductive self-healing hydrogel fabrication. In this study, we developed stimuli-responsive electrochemical wireless hydrogel biosensors using ureidopyriminone-conjugated gelatin (Gel-UPy) hydrogels that incorporate diselenide-containing carbon dots (dsCD) for cancer detection. The cleavage of diselenide groups of the dsCD within the hydrogels by glutathione (GSH) or reactive oxygen species (ROS) initiates the formation of hydrogen bonds that affect the self-healing ability, conductivity, and adhesiveness of the Gel-UPy/dsCD hydrogels. The Gel-UPy/dsCD hydrogels demonstrate more rapid healing under tumor conditions (MDA-MB-231) compared to that observed under physiological conditions (MDCK). Additionally, the cleavage of diselenide bonds affects the electrochemical signals due to the degradation of dsCD. The hydrogels also exhibit excellent adhesiveness and cancer detection ability after exposure to a high concentration of GSH or ROS, and this is comparable to results observed in a low concentration environment. Based on the combined self-healing, conductivity, and adhesiveness properties of the Gel-UPy/dsCD, this hydrogel exhibits promise for use in biomedical applications, particularly those that involve cancer detection, due to its selectivity and sensitivity under tumor conditions.
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http://dx.doi.org/10.1021/acsnano.0c02517DOI Listing
July 2020

Responsive polymers for medical diagnostics.

J Mater Chem B 2020 08 10;8(29):6217-6232. Epub 2020 Jun 10.

NanoScience Technology Center, Department of Materials Science and Engineering, Department of Chemistry, University of Central Florida, FL 32826, USA.

Stimulus-responsive polymers have been used in improving the efficacy of medical diagnostics through different approaches including enhancing the contrast in imaging techniques and promoting the molecular recognition in diagnostic assays. This review overviews the mechanisms of stimulus-responsive polymers in response to external stimuli including temperature, pH, ion, light, etc. The applications of responsive polymers in magnetic resonance imaging, capture and purification of biomolecules through protein-ligand recognition and lab-on-a-chip technology are discussed.
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http://dx.doi.org/10.1039/d0tb00366bDOI Listing
August 2020

Developing clinical cut-off scores for the university of California San Diego performance-based skills assessment in patients with schizophrenia.

Asian J Psychiatr 2020 Jan 16;47:101844. Epub 2019 Oct 16.

Department of Psychiatry, Busan Metropolitan Mental Hospital, Busan, Korea.

This study aimed to obtain University of California San Diego Performance-based Skill Assessment (UPSA) cut-off scores for the purpose of severity classification and to expand the clinical utility of the UPSA for the evaluation of cognitive function in patients with schizophrenia. In total, 191 patients with schizophrenia were recruited. The UPSA, Positive and Negative Symptom Scale (PANSS), Clinical Global Impression-Schizophrenia Scale (CGI-SCH), and Global Assessment Functioning Scale (GAF) were used for the evaluation. The cognitive symptoms item of the CGI-SCH was used as a reference and the subjects were divided into three groups: mild, moderate, and severe. The sensitivity and specificity of the UPSA were analyzed by receiver operating characteristic curves. There were significant differences in the UPSA, CGI-SCH, PANSS, and GAF scores among the groups. In the mild and moderate groups, a UPSA score of 59 was identified as the optimal cut-off score, and a score of 41 was identified as the optimal cut-off score in the moderate and severe groups. Severity can be classified using the UPSA score as follows: ≥ 60 for mild, 41-59 for moderate, and ≤ 40 for severe. The UPSA could be used to assess the degree of daily living dysfunction in patients with schizophrenia.
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http://dx.doi.org/10.1016/j.ajp.2019.101844DOI Listing
January 2020

Reduction-Triggered Paclitaxel Release Nano-Hybrid System Based on Core-Crosslinked Polymer Dots with a pH-Responsive Shell-Cleavable Colorimetric Biosensor.

Int J Mol Sci 2019 Oct 28;20(21). Epub 2019 Oct 28.

Department of Chemical and Biological Engineering, Korea National University of Transportation, Chungju 380-702, Korea.

Herein, we describe the fabrication and characterization of carbonized disulfide core-crosslinked polymer dots with pH-cleavable colorimetric nanosensors, based on diol dye-conjugated fluorescent polymer dots (L-PD), for reduction-triggered paclitaxel (PTX) release during fluorescence imaging-guided chemotherapy of tumors. L-PD were loaded with PTX (PTX loaded L-PD), via π-π stackings or hydrophobic interactions, for selective theragnosis by enhanced release of PTX after the cleavage of disulfide bonds by high concentration of glutathione (GSH) in a tumor. The nano-hybrid system showed fluorescence quenching behavior with less than 2% of PTX released under physiological conditions. However, in a tumor microenvironment, the fluorescence recovered at an acidic-pH, and PTX (approximately 100% of the drug release) was released efficiently out of the matrix by reduction caused by the GSH level in the tumor cells, which improved the effectiveness of the cancer treatment. Therefore, the colorimetric nanosensor showed promising potential in distinguishing between normal and cancerous tissues depending on the surrounding pH and GSH concentrations so that PTX can be selectively delivered into cancer cells for improved cancer diagnosis and chemotherapy.
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http://dx.doi.org/10.3390/ijms20215368DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6862247PMC
October 2019

Live-cell imaging of single mRNA dynamics using split superfolder green fluorescent proteins with minimal background.

RNA 2020 01 22;26(1):101-109. Epub 2019 Oct 22.

Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Korea.

The MS2 system, with an MS2 binding site (MBS) and an MS2 coat protein fused to a fluorescent protein (MCP-FP), has been widely used to fluorescently label mRNA in live cells. However, one of its limitations is the constant background fluorescence signal generated from free MCP-FPs. To overcome this obstacle, we used a superfolder GFP (sfGFP) split into two or three nonfluorescent fragments that reassemble and emit fluorescence only when bound to the target mRNA. Using the high-affinity interactions of bacteriophage coat proteins with their corresponding RNA binding motifs, we showed that the nonfluorescent sfGFP fragments were successfully brought close to each other to reconstitute a complete sfGFP. Furthermore, real-time mRNA dynamics inside the nucleus as well as the cytoplasm were observed by using the split sfGFPs with the MS2-PP7 hybrid system. Our results demonstrate that the split sfGFP systems are useful tools for background-free imaging of mRNA with high spatiotemporal resolution.
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http://dx.doi.org/10.1261/rna.067835.118DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6913125PMC
January 2020

Photothermal-modulated reversible volume transition of wireless hydrogels embedded with redox-responsive carbon dots.

Biomater Sci 2019 Nov 17;7(11):4800-4812. Epub 2019 Sep 17.

Department of IT Convergence, Korea National University of Transportation, Chungju 380-702, Republic of Korea. and Department of Chemical and Biological Engineering, Korea National University of Transportation, Chungju 380-702, Republic of Korea.

The reversible volume transition of redox-responsive hydrogels by near-infrared (NIR) irradiation has recently attracted significant attention as a novel therapy matrix for tracking and treating cancer via stimuli-responsive fluorescence on/off with controllable volume transition via a wireless sensing system. Herein, a NIR-induced redox-sensitive hydrogel was synthesized by blending a hydrogel with IR825-loaded carbon dots (CD) to achieve enhanced mobility of nanoparticles inside a gel network, and reversible volume phase transitions remotely controlled by a smartphone application via the induction of different redox environments. The presence of CD-IR825 in the thermosensitive poly(N-isopropylacrylamide) hydrogel network imparted fluorescence, electronic and photothermal properties to the hydrogels, which resulted in volume shrinkage behavior of the hydrogel upon exposure to NIR laser irradiation due to the redox-sensitive CDs. Under the NIR on/off cycles, the photothermal temperature, fluorescence, and porous structure were reversed after turning off the NIR laser. The hydrogel responsiveness under GSH and NIR light was studied using a wireless device based on the changes in the resistance graph on a smartphone application, generating a fast and simple method for the investigation of hydrogel properties. The in vitro cell viabilities of the MDA-MB cancer cells incubated with the composite hydrogel in the presence of external GSH exhibited a higher photothermal temperature, and the cancer cells were effectively killed after the NIR irradiation. Therefore, the NIR-induced redox-responsive nanocomposite hydrogel prepared herein has potential for use in cancer treatment and will enable the study of nanoparticle motion in hydrogel networks under multiple stimuli via a wireless device using a faster and more convenient method.
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http://dx.doi.org/10.1039/c9bm00734bDOI Listing
November 2019

Recyclable metal nanoparticle-immobilized polymer dot on montmorillonite for alkaline phosphatase-based colorimetric sensor with photothermal ablation of Bacteria.

Anal Chim Acta 2019 Nov 27;1082:152-164. Epub 2019 Jul 27.

Department of IT Convergence, Korea National University of Transportation, Chungju, 380-702, Republic of Korea; Department of Chemical and Biological Engineering, Korea National University of Transportation, Chungju, 380-702, Republic of Korea. Electronic address:

Development of simultaneous bacteria detection and eradication with simple, rapid, and reusable material is important in addressing bacterial contamination issues. In this study, we utilized the expression of alkaline phosphatase (ALP) from bacteria to design fluorescence ON/OFF system for bacteria detection, also using metal oxide nanoparticle for obtaining antibacterial activity and recyclability. The fluorescent-based biosensor with antibacterial activity was prepared by intercalating ALP-sensitive polymer dot (PD) containing β-cyclodextrin (β-CD) onto montmorillonite (MMT) as loading matrix via ionic exchange reaction, followed by immobilization of magnetic iron oxide (FeO) and NIR-responsive cesium tungsten oxide (CsWO). The PD-βCD-MMT/FeO-CsWO nanocomposite exhibited strong fluorescence intensity, which was quenched in the presence of bacterial ALP (0-1000 U/L) due to hydrolysis of p-nitrophenyl phosphate (NPP) into p-nitrophenol (NP) in the hydrophobic site of β-CD. Furthermore, the nanocomposite could detect both gram-negative Escherichia coli and gram-positive Staphylococcus aureus in the range of 10-10 CFU/mL (LOD 5.09 and 4.62 CFU/mL, respectively), and showed high antibacterial activity against bacteria by generating photothermal heat under 5 min NIR irradiation, causing damage to bacterial cells. This material also demonstrated recyclability via magnetic field exposure due to the presence of FeO In addition, the fluorescence can be recovered following pH shock and re-conjugation of β-CD molecules. After 4 cycles, nanocomposite still showed stable photothermal effects and fluorescence-based bacteria detection. Thus, this reusable material offers promising approach for simultaneous bacteria detection and killing, which is simple, rapid, and effective.
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http://dx.doi.org/10.1016/j.aca.2019.07.053DOI Listing
November 2019

Selective redox-responsive theragnosis nanocarrier for breast tumor cells mediated by MnO/fluorescent carbon nanogel.

Eur J Pharm Sci 2019 Jun 29;134:256-265. Epub 2019 Apr 29.

Department of Chemical and Biological Engineering, Korea National University of Transportation, Chungju 380-702, Republic of Korea; Department of IT Convergence, Korea National University of Transportation, Chungju 380-702, Republic of Korea. Electronic address:

A redox-responsive fluorescent carbon nanogel (FCN) was designed as a bioimaging probe for targeted drug delivery to cancer cells. FCN was synthesized by the carbonization of disulfide cross-linked hyaluronic acid in the fluorescence "on" mode, followed by the attachment of manganese oxide (MnO) nanosheets for fluorescence quenching (fluorescence "off"). We hypothesized that the fluorescence intensity of paclitaxel (PTX)-MnO/FCN would suddenly increase (fluorescence "on") in the presence of a high level of glutathione (GSH) in cancer cells, owing to the reduction of MnO to Mn and cleavage of the disulfide bond. Consequently, PTX would be released from the FCN system. Consistent with this hypothesis, the designed system recovered FCN fluorescence and triggered drug release through the cleavage of the disulfide bond by GSH. Moreover, PTX-MnO/FCN demonstrated stable fluorescence intensity after GSH treatment, serving as a potential biosensor. PTX-MnO/FCN exhibited excellent biocompatibility with normal cells and selectively targeted tumor cells, highlighting the therapeutic capabilities of this system. The developed PTX-MnO/FCN structure may serve as a smart drug delivery system with diagnostic and therapeutic properties, good selectivity, and compatibility, and with excellent potential for biomedical applications.
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http://dx.doi.org/10.1016/j.ejps.2019.04.027DOI Listing
June 2019

High performance of electrochemical and fluorescent probe by interaction of cell and bacteria with pH-sensitive polymer dots coated surfaces.

Mater Sci Eng C Mater Biol Appl 2019 Aug 27;101:159-168. Epub 2019 Mar 27.

Department of IT Convergence, Korea National University of Transportation, Chungju 380-702, Republic of Korea; Department of Chemical and Biological Engineering, Korea National University of Transportation, Chungju 380-702, Republic of Korea. Electronic address:

Using pH-switchable fluorescent polymer dots (PD) by means of fluorescent, colorimetric, and electrochemical signals generated from surfaces coated with PD of zwitterionic structure provided a fast and easy method to assess their performance in mammalian cell and bacterial interactions. The PD-coated surfaces showed high sensitivity over a broad range of pH levels by switching reversibly zwitterionic states, which led to an excellent cellular resistance effect by inhibiting the attachment of nearly 95% of mammalian cells. Similarly, they exhibited a strong interaction with the negatively charged surfaces of bacteria, as observed in the fluorescence ON/OFF system. In addition, PD were employed to detect the attachment of mammalian and bacterial cells: we deposited PD on a screen-printed carbon electrode for cyclic voltammetry analysis. Notably, the presence of cells remarkably interfered with the current flow between the PD and the screen-printed carbon electrode surface by causing an impressive decline in both reduction-oxidation signals, implying the high sensitivity of the PD-coated surfaces to cells and bacteria in different pH environments. Therefore, as smart materials with high sensitivity, biocompatibility, selectivity, and accuracy, PD-coated surfaces represent a promising approach to visualizing and controlling biological cell attachment, thereby helping to avoid contamination in biomedical applications.
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http://dx.doi.org/10.1016/j.msec.2019.03.098DOI Listing
August 2019

Zwitterionic carbon dot-encapsulating pH-responsive mesoporous silica nanoparticles for NIR light-triggered photothermal therapy through pH-controllable release.

Biomater Sci 2019 May;7(6):2600-2610

Department of IT Convergence, Korea National University of Transportation, Chungju 380-702, Republic of Korea.

Here, we designed a pH-responsive Indocyanine Green (ICG)-loaded zwitterion fluorescent carbon dot (CD)-encapsulating mesoporous silica nanoparticle (MSN) for pH-tunable image-guided photothermal therapy. ICG was loaded into MSN(CD) via hydrophobic and electrostatic interactions between zwitterionic CDs and ICG to achieve a controlled photothermal temperature with a fluorescent "off/on" system. The porosity of the MSNs was altered after ICG loading because of intermolecular interactions between the CDs and ICG inside the MSN shell and core, which blocked the MSN pore. The acidic environment pH affected the fluorescent signals of the ICG-MSN(CD), reflecting the "off-on" characteristics of the synthesized MSN, which then induced the release of ICG from the matrices. Moreover, the photothermal conversion of ICG-MSN(CD) showed sufficient heat generation to kill cancer cells at an acidic pH with low-temperature elevation at physiological pH. ICG-MSN(CD) demonstrated good cell viability of MDA-MB-231 cells without irradiation; however, high necrosis was observed when the environment was adjusted to acidic pH and after near-infrared irradiation. These pH-responsive photothermal mesoporous silica nanoparticles may have applications in biomedicine, particularly for cancer treatment.
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http://dx.doi.org/10.1039/c9bm00160cDOI Listing
May 2019

Photoluminescence-tunable fluorescent carbon dots-deposited silver nanoparticle for detection and killing of bacteria.

Mater Sci Eng C Mater Biol Appl 2019 Apr 22;97:613-623. Epub 2018 Dec 22.

Department of Chemical and Biological Engineering, Korea National University of Transportation, Chungju 380-702, Republic of Korea; Department of IT Convergence, Korea National University of Transportation, Chungju 380-702, Republic of Korea. Electronic address:

Innovative methods to detect and kill pathogenic bacteria have a pivotal role in the eradication of infectious diseases and the prevention of the growth of antibiotic-resistant bacteria. The combination of fluorescent carbon dots (FCDs) with silver nanoparticles (AgNPs) is an effective material for synergic detection and antimicrobial activity determination. However, the fluorescence quenching of the FCDs owing to an interaction with AgNP is a major limitation. In this study, we designed a system to utilize poly(vinylpyrrolidone) (PVP) and catechol chemistry ([email protected]:FCD) in order to avoid the fluorescence quenching of the FCD-AgNP combination due to Forster Resonance Energy Transfer (FRET). [email protected]:FCD exhibited bright fluorescence, which can be used for bacterial detection, through the promotion of electrostatic binding with the negatively-charged bacterial surface and generation of fluorescence quenching due to aggregation-induced quenching. Furthermore, the presence of silver nanoparticles in [email protected]:FCD produced an excellent bacteria killing efficiency against E. coli and S. aureus, even at low concentrations (0.1 mg/mL). In contaminated river water, the [email protected]:FCD system showed a simple, highly sensitive, and effective performance for both the detection and eradication of bacteria. Therefore, this system offers an auspicious method for the future detection and killing of bacteria.
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http://dx.doi.org/10.1016/j.msec.2018.12.070DOI Listing
April 2019

Membrane and nucleus targeting for highly sensitive cancer cell detection using pyrophosphate and alkaline phosphatase activity-mediated fluorescence switching of functionalized carbon dots.

J Mater Chem B 2018 Oct 7;6(37):5992-6001. Epub 2018 Sep 7.

Department of Chemical & Biological Engineering, Korea National University of Transportation, Chungju 380-702, Republic of Korea.

A specific membrane and nucleus targeted fluorescence OFF-ON-OFF system, using the dodecane/sulfobetaine group of functionalized carbon dots (CD) with a copper ion (Cu-CD) based on the presence of pyrophosphate (PPi) molecules and alkaline phosphatase (ALP) activity, for cancer cell detection was designed. The biosensor could be effectively transported from the cytosol to the nucleus in MDAMB cells, but not in MDCK cells due to the response to a change in pH by CD functionalized with zwitterionic groups. The biosensor also showed a membrane-selective regulated route for fusion of long alkyl chain grafted-CD on cell membranes. As a potential sensor, the fluorescence of the prepared Cu-CD was significantly quenched due to aggregation. In human cancer MDAMB cells, a nearly complete restoration of the fluorescence intensity of the Cu-CD was observed because of the high levels of intracellular PPi, which preferentially bound to Cu. After 10 min, in the MDAMB cells, re-quenching of the CD fluorescence occurred because of the high level of intracellular ALP, which can hydrolyze PPi and release the Cu to re-aggregate the CD. In contrast to MDAMB cells, MDCK cells did not show an obvious response to the specific intracellular biomolecules, thus, enabling the biosensor to be used to distinguish between cancer and normal cells. In conclusion, this biosensor has the potential to be a simple and sensitive cancer diagnostic tool that can differentiate normal cells from cancer cells on coated surfaces and in aqueous states.
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http://dx.doi.org/10.1039/c8tb01364kDOI Listing
October 2018

pH/Redox-Triggered Photothermal Treatment for Cancer Therapy Based on a Dual-Responsive Cationic Polymer Dot.

ChemMedChem 2018 11 5;13(22):2437-2447. Epub 2018 Nov 5.

Department of IT Convergence, Korea National University of Transportation, Chungju, 380-702, Republic of Korea.

In the present study, a pH/redox-responsive cationic polymer dot (CD) was successfully prepared for a near-infrared (NIR)-mediated, simultaneously controllable photothermal temperature guided imaging off/on system to monitor therapeutic delivery. Carbonized disulfide cross-linked branched polyethyleneimine (bPEI) was conjugated with folic acid (FA) as a targeting moiety and partially formed an ionic complex with anionic indocyanine green (ICG) to afford a bPEI-based CD (ICG-CD). This was responsive to mild reductive (glutathione, GSH) and acidic tumor conditions, which enabled the simultaneous biodegradation of those hydrophobic and complex sites. The ICG-CD internalized readily into the cytoplasm of cancer cells by a FA receptor and cationic-mediated endocytosis in the off state, whereas if ICG-CD met intracellular GSH at high concentrations, GSH contributed partially to the recovery of fluorescence and was then internalized into acidic endosomes to induce complete restoration of fluorescence. This tumor-sensitive degradability of the CD not only facilitated ICG release in the tumor location but also allowed controllable photothermal therapy effects of nanoparticles under NIR irradiation, which resulted in improved cancer therapy. Taken together, the results indicate great potential in tumor targeting, intracellular imaging, and controllable therapeutic delivery through a fluorescence off/on assay under the pH/redox conditions of cancer cells.
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http://dx.doi.org/10.1002/cmdc.201800538DOI Listing
November 2018

Redox-responsive FRET-based polymer dot with BODIPY for fluorescence imaging-guided chemotherapy of tumor.

Eur J Pharm Biopharm 2018 Nov 26;132:200-210. Epub 2018 Sep 26.

Department of IT Convergence, Korea National University of Transportation, Chungju 380-702, Republic of Korea; Department of Chemical and Biological Engineering, Korea National University of Transportation, Chungju 380-702, Republic of Korea. Electronic address:

Redox-responsive polymer dot (PD) were synthesized from disulfide cross-linked polymers in a carbonized process to allow quenching effects by loading of boron-dipyrromethene (BODIPY) onto the matrix. The disulfide linkage facilitated degradation of the PD system by intracellular glutathione (GSH), leading to fluorescence recovery by BODIPY and intracellular drug release. The paclitaxel release profile showed that approximately 100% of the drug escaped from the matrix in response to 10 mM GSH, whereas less than 10% was released in the absence of GSH. In vitro studies showed that quenching produced by BODIPY loading enabled visual monitoring of cancer cell death, as the quenching disappeared when BODIPY was released by GSH inside of cancer cells. The PD contain disulfide bonds representing a GSH-triggered ligand; thus, nanocarriers presented enhanced in vivo chemotherapeutic inhibition in xenograft tumor-bearing mice localized at the cancer location, guided by fluorescent off-on system tracking and measured by the release of BODIPY. This platform reacts to the redox level in sensitive manner and cancer cell death can be monitored by fluorescence, making this platform useful for bio-applications, particularly in vitro and in vivo therapy and diagnosis, while considering the cell physiological environment. This system may be useful for wider medical applications.
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http://dx.doi.org/10.1016/j.ejpb.2018.09.025DOI Listing
November 2018

Progressive fuzzy cation-π assembly of biological catecholamines.

Sci Adv 2018 09 7;4(9):eaat7457. Epub 2018 Sep 7.

Department of Chemistry, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea.

Biological functions depend on biomolecular assembly processes. Assemblies of lipid bilayers, actins, microtubules, or chromosomes are indispensable for cellular functions. These hierarchical assembly processes are reasonably predictable by understanding chemical structures of the defined building blocks and their interactions. However, biopigment assembly is rather fuzzy and unpredictable because a series of covalently coupled intermediates from catecholamine oxidation pathways progressively form a higher-level hierarchy. This study reports a different yet unexplored type of assembly process named "cation-π progressive assembly." We demonstrated for the first time that the cation-π is the primary mechanism for intermolecular assembly in dopamine-melanin biopigment. We also found that the self-assembled products physically grow and chemically gain new functions "progressively" over time in which cation-π plays important roles. The progressive assembly explains how biological systems produce wide spectra of pigment colors and broad wavelength absorption through energy-efficient processes. Furthermore, we also demonstrate surface-independent wettability control using cation-π progressive assembly.
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http://dx.doi.org/10.1126/sciadv.aat7457DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6128673PMC
September 2018

Highly Efficient Visible Blue-Emitting Black Phosphorus Quantum Dot: Mussel-Inspired Surface Functionalization for Bioapplications.

ACS Omega 2017 Oct 23;2(10):7096-7105. Epub 2017 Oct 23.

Department of Chemical & Biological Engineering, Department of Polymer Science and Engineering, and Department of IT Convergence (Brain Korea PLUS 21), Korea National University of Transportation, 50 Daehak-ro, Chungju-si, Chungbuk 27909, South Korea.

The preparation of blue-emitting black phosphorus quantum dots (BPQDs) is based on the liquid-phase exfoliation of bulk BP. We report the synthesis of soluble BPQDs showing a strong visible blue-light emission. Highly fluorescent (photoluminescence quantum yield of ≈5% with the maximum emission (λ) at ≈437 nm) and dispersible BPQDs in various organic solvents are first prepared by simple ultrasonication of BP crystals in chloroform in the ambient atmosphere. Furthermore, simple mussel-inspired surface functionalization of BPQDs with catechol-grafted poly(ethylene glycol) in basic buffer afforded water-soluble blue-emitting BPQDs showing long-term fluorescence stability, very low cytotoxicity, and excellent fluorescence live cell imaging capability.
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http://dx.doi.org/10.1021/acsomega.7b01058DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6044902PMC
October 2017

Boronate-based fluorescent carbon dot for rapid and selectively bacterial sensing by luminescence off/on system.

J Pharm Biomed Anal 2018 Sep 23;159:1-10. Epub 2018 Jun 23.

Department of Chemical and Biological Engineering, Korea National University of Transportation, Chungju 380-702, Republic of Korea; Department of IT Convergence, Korea National University of Transportation, Chungju 380-702, Republic of Korea. Electronic address:

Boronic acid, which can bind chemo-selectively and reversibly to diols, could be used for the early detection of bacteria through its affinity-binding reaction with diol groups on the bacterial cell wall. Herein, we describe the use of a diol-modified fluorescent probe (DYE) conjugated to a nanosensor consisting of phenylboronic acid-functionalized fluorescent carbon dot (FCD) to allow quenching via the Förster resonance energy transfer (FRET) process. Phenylboronic acid is well-known for its preferential affinity for diol-containing molecules through cyclic ester bond formation. Therefore, in the presence of glucose-containing bacteria, the DYE in the cyclic ester form will be released from the FCD and replaced by the bacterial cell forming a new cyclic boronate ester bond with the nanoparticle, inducing recovery of the fluorescence. Quantitatively, the system's detection performance at various bacterial concentrations (10-10 CFU/mL) reached ∼100% after 60 min, indicating that the high binding affinity of the diol moeity on the peptidoglycan (sugar)-rich bacteria was enough to displace the DYE from the boronic acid-functionalized FCD platform. Our facile and tunable fluorescence switch-on system was tested for its ability to detect bacteria in water from a contaminated river. Incredibly, the system was most successful in detecting bacteria in the contaminated river water, thus proving it to be a less expensive and more robust affinity biosensor for the detection of contaminating pathogens in various chemoselective ligand-based environments.
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http://dx.doi.org/10.1016/j.jpba.2018.06.043DOI Listing
September 2018

Dual-Responsive Carbon Dot for pH/Redox-Triggered Fluorescence Imaging with Controllable Photothermal Ablation Therapy of Cancer.

ChemMedChem 2018 07 14;13(14):1459-1468. Epub 2018 Jun 14.

Department of Chemical & Biological Engineering, Korea National University of Transportation, Chungju, 380-702, Republic of Korea.

Herein we describe fluorescence resonance energy transfer (FRET) for a pH/redox-activatable fluorescent carbon dot (FNP) to realize "off-on" switched imaging-guided controllable photothermal therapy (PTT). The FNP is a carbonized self-crosslinked polymer that allows IR825 loading (FNP[IR825]) via hydrophobic interactions for cancer therapy. Fluorescence bioimaging was achieved by the internalization of FNP(IR825) into tumor cells, wherein glutathione (GSH) disulfide bonds are reduced, and benzoic imine groups are cleaved under acidic conditions. The release of IR825 from the FNP core in this system may be used to efficiently control PTT-mediated cancer therapy via its photothermal conversion after near-infrared (NIR) irradiation. In vitro and in vivo cellular uptake studies revealed efficient uptake of FNP(IR825) by tumor cells to treat the disease site. In this way we demonstrated in mice that our smart nanocarrier can effectively kill tumor cells under exposure to a NIR laser, and that the particles are biocompatible with various organs. This platform responds sensitively to the exogenous environment inside the cancer cells and may selectively induce the release of PTT-mediated cytotoxicity. Furthermore, this platform may be useful for monitoring the elimination of cancer cells through the fluorescence on/off switch, which can be used for various applications in the field of cancer cell therapy and diagnosis.
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http://dx.doi.org/10.1002/cmdc.201800202DOI Listing
July 2018

Progress in internal/external stimuli responsive fluorescent carbon nanoparticles for theranostic and sensing applications.

J Mater Chem B 2018 Feb 8;6(8):1149-1178. Epub 2018 Feb 8.

Department of Chemical & Biological Engineering and Department of IT Convergence, Korea National University of Transportation, Chungju 380-702, Republic of Korea.

In the past decade, fluorescent carbon nanoparticles (FNPs) prepared from natural resources and biomaterials have been attractive due to their various properties, such as unique optical properties, great biocompatibility, water dispersion, and facile surface functionalization. Depending on the properties of the carbon sources and the subsequent carbonization processes, internal/external stimuli responsive carbon nanoparticles have been generated that are useful for theranostic and sensing applications. In this review, we highlight the recent developments in the use of FNPs in nanomedicine in great detail, particularly for FNPs responding to internal stimuli, including redox, pH, and enzymes, and external stimuli, including temperature, light, and magnetic fields, for drug delivery and sensing applications. Furthermore, we hope to provide insight that could stimulate further research aiming for unparalleled useful applications. As a result, there are many possibilities that can be explored from this smart material.
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http://dx.doi.org/10.1039/c7tb03323kDOI Listing
February 2018

Mechanochemical synthesis of fluorescent carbon dots from cellulose powders.

Nanotechnology 2018 Apr;29(16):165604

Department of IT Convergence (Brain Korea PLUS 21) Korea National University of Transportation, Chungju 380-702, Republic of Korea.

A novel mechanochemical method was firstly developed to synthesize carbon nanodots (CNDs) or carbon nano-onions (CNOs) through high-pressure homogenization of cellulose powders as naturally abundant resource depending on the treatment times. While CNDs (less than 5 nm in size) showed spherical and amorphous morphology, CNOs (10-50 nm in size) presented polyhedral shape, and onion-like outer lattice structure, graphene-like interlattice spacing of 0.36 nm. CNOs showed blue emissions, moderate dispersibility in aqueous media, and high cell viability, which enables efficient fluorescence imaging of cellular media.
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http://dx.doi.org/10.1088/1361-6528/aaad49DOI Listing
April 2018

pH-Responsible fluorescent carbon nanoparticles for tumor selective theranostics via pH-turn on/off fluorescence and photothermal effect in vivo and in vitro.

Nanoscale 2018 Feb;10(5):2512-2523

Department of Chemical & Biological Engineering, Korea National University of Transportation, Chungju 380-702, Republic of Korea.

We developed nanoparticles comprising a photothermal dye (IR825)-loaded carbonized zwitterionic polymer [FNP-I] as "switch-on" pH-responsive fluorescence probes to sense intracellular cancer cells and for near-infrared (NIR) controllable photothermal therapy (PTT) in vivo and in vitro. The fluorescent "off" of FNP-I was activated after reaching the cancer cell environment, where the zwitterionic compartment of FNP lost its hydrophobicity to induce PTT-mediated heat release of IR825 under NIR irradiation in the tumor. Approximately 100% of the IR825 was released from the FNP core to generate high thermal conversion to completely kill the cancer cells. Furthermore, after intravenous treatment of FNP-I into MDAMB-231-cell bearing mice, pH-responsive photothermal therapy was observed, achieving marked ablation of tumor cells with release of IR825 under tumor environment conditions. In addition, fluorescent signals were clearly found at the tumor site after 3 h, decreasing at the 6 h time point. The in vitro and in vivo detection system demonstrated good cellular uptake and biocompatibility as a potential imaging-guided photothermal therapy nanotool for cancer treatment. Interestingly, the synergism of the biosensor and PTT in single FNP-I platform led to more effective cancer cell killing than either monotherapy, providing a new approach for cancer treatment.
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http://dx.doi.org/10.1039/c7nr07900aDOI Listing
February 2018

Determination of Cancer Cell-Based pH-Sensitive Fluorescent Carbon Nanoparticles of Cross-Linked Polydopamine by Fluorescence Sensing of Alkaline Phosphatase Activity on Coated Surfaces and Aqueous Solution.

Anal Chem 2017 12 27;89(24):13508-13517. Epub 2017 Nov 27.

Department of Chemical and Biological Engineering, ‡Department of IT Convergence, and §Department of Polymer Science and Engineering, Korea National University of Transportation , Chungju 380-702, Republic of Korea.

The tumor-specific sensitive fluorescence sensing of cellular alkaline phosphatase (ALP) activity on the basis of host-guest specific and pH sensitivity was conducted on coated surfaces and aqueous states. Cross-linked fluorescent nanoparticles (C-FNP) consisting of β-cyclodextrin (β-CD)/boronic acid (BA) and fluorescent hyaluronic acid [FNP(HA)] were conjugated to fluorescent polydopamine [FNP(pDA)]. To determine the quenching effect of this system, hydrolysis of 4-nitrophenyl phosphate (NPP) to 4-nitrophenol (NP) was performed in the cavity of β-CD in the presence of ALP activated photoinduced electron transfer (PET) between NP and C-FNP. At an ALP level of 30-1000 U/L, NP caused off-emission of C-FNP because of their specific host-guest recognition. Fluorescence can be recovered under pH shock due to cleavage of the diol bond between β-CD and BA, resulting in release of NP from the fluorescent system. Sensitivity of the assays was assessed by confocal imaging not only in aqueous states, but also for the first time on coated surfaces in MDAMB-231 and MDCK cells. This novel system demonstrated high sensitivity to ALP through generation of good electron donor/acceptor pair during the PET process. Therefore, this fluorescence sensor system can be used to enhance ALP monitoring and cancer diagnosis on both coated surfaces and in aqueous states in clinical settings.
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http://dx.doi.org/10.1021/acs.analchem.7b03853DOI Listing
December 2017

Phenolic condensation and facilitation of fluorescent carbon dot formation: a mechanism study.

Nanoscale 2017 Nov;9(43):16596-16601

Department of Chemistry, KAIST, Daejeon 34141, South Korea.

Fluorescent carbon dots have received considerable attention as a result of their accessibility and potential applications. Although several prior studies have demonstrated that nearly any organic compound can be converted into carbon dots by chemical carbonization processes, mechanisms explaining the formation of carbon dots still remain unclear. Herein, we propose a seed-growth mechanism of carbon dot formation facilitated by ferulic acid, a widespread and naturally occurring phenolic compound in the seeds of Ocimum basilicum (basil). Ferulic acid triggers the local condensation of polysaccharide chains and forms catalytic core regions resulting in nanoscale carbonization. Our study indicates that carbon dots generated from natural sources might share the similar mechanism of phenolic compound mediated nanoscale condensation followed by core carbonization.
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http://dx.doi.org/10.1039/c7nr04170eDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5687888PMC
November 2017

Target-specific induced hyaluronic acid decorated silica fluorescent [email protected] for bio-imaging guided near-infrared photothermal therapy.

J Mater Chem B 2017 Sep 17;5(34):7099-7108. Epub 2017 Aug 17.

Department of IT Convergence, Korea National University of Transportation, Chungju 380-702, Republic of Korea.

We describe a novel synthesis method for silica nanoparticles, which involves a combination of these nanoparticles with targetable and nontargetable fluorescent dopamine-conjugated hyaluronic acid (HA-DA) via rational chemical dehydration. The resulting HA-decorated silica fluorescent nanoparticles, electrostatically linked to polyaniline (PANI) to form ionic complexes, possessed high fluorescence intensity and were monodisperse in solution, near-infrared light responsive, and amenable to specific labeling of cancer cell lines. When exposed to near-infrared irradiation, the fluorescent silica nanoparticles exerted photothermal cytotoxicity guided by bioimaging and distinguished malignant cancer cells from normal cells via receptor CD44. Different heating properties of nanoparticles depend on local interactions between different structures, and determination of their efficacy could lead to new thermal treatment options such as noninvasive photothermal therapy.
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http://dx.doi.org/10.1039/c7tb01606aDOI Listing
September 2017