Kathy Qian Luo

Nanyang Technological University, Tumasik, Singapore

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Publications (60)206.74 Total impact

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    Scientific Reports 06/2015; 5:10801. DOI:10.1038/srep10801 · 5.58 Impact Factor
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    ABSTRACT: Stem cell tracking can reveal the underlying biological processes of stem-cell-based therapies such as the migration and biodistribution of human mesenchymal stem cells (hMSCs) in cancer therapy. Nanoparticle-based contrast agents offer unprecedented opportunities for achieving this goal due to their unique and tunable imaging capabilities. However, most nanoparticles are still in the process of development due to challenges such as retention time and safety issues, and are inaccessible to most researchers. In this article, we investigate the potential application of core-shell fluorescent silica nanoparticles (i.e. C dots), which are commercially available and approved by the FDA for clinical trials. Specifically we demonstrate that 500 nm C dots have prolonged cellular retention (up to one month), minimal contrast agent transfer (at least three weeks) between cells in a co-culture Boyden chamber system, and minimal influence on the hMSC properties including viability, proliferation, differentiation,
    Journal of Materials Chemistry B 02/2015; DOI:10.1039/C4TB01452A · 4.73 Impact Factor
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    ABSTRACT: Two-dimensional (2D) cultures are commonly used for testing drug effects largely because of their easy maintenance. But they do not represent the spatial interactions of the cells within a tumor. Three-dimensional (3D) cultures can overcome those limitations thus mimicking the architecture of solid tumor. However, it is not easy to evaluate drug effects in 3D culture for a long time. This necessitates the development of a real-time and longitudinal analysis of 3D platforms. In this study, we transfected the plasmid DNA encoding the fluorescence resonance energy transfer (FRET)-based biosensor into human breast cancer cells and generated two cell lines of MCF7-C3 and MDA-MB-231-C3 (231-C3) cells. We used them to determine the activation of caspase-3, whereby healthy cells appear green and apoptotic cells appear blue by FRET imaging. As the caspase sensors can be constantly produced within the cells and quickly respond to caspase activation, we hypothesized that these sensor cells will allow longitudinal detection of apoptosis. MCF7-C3 and 231-C3 spheroids were generated and subjected to histological examination, gene expression studies, drug treatment and FRET analyses. Our results demonstrated that MCF7-C3 cells formed tight 3D spheroids, and mimicked in vivo tumor architecture. The mRNA level of tumorigenic markers such as MMP-9, SOX2 and OCT4A were much higher in cells cultured in 3D than in 2D. Finally, upon treatment with paclitaxel, the FRET effect was reduced at the rim of MCF7-C3 spheroids in a dose and time-dependent manner demonstrating these sensor cells can be used to determine drug-induced apoptosis in a 3D set up. This study supports the possibility of developing a biosensor-based in vitro 3D breast tumor model for determination of anti-cancer drug penetration over a long course of time in a non-invasive manner. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
    Biotechnology and Bioengineering 02/2015; DOI:10.1002/bit.25572 · 4.16 Impact Factor
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    Dataset: c4tb01452a1
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    ABSTRACT: The emerging graphene quantum dots (GQDs) and carbon dots (C-dots) have gained tremendous attention for their enormous potentials for biomedical applications, owing to their unique and tunable photoluminescence properties, exceptional physicochemical properties, high photostability, biocompatibility, and small size. This article aims to update the latest results in this rapidly evolving field and to provide critical insights to inspire more exciting developments. We comparatively review the properties and synthesis methods of these carbon nanodots and place emphasis on their biological (both fundamental and theranostic) applications.
    Small 12/2014; DOI:10.1002/smll.201402648 · 7.51 Impact Factor
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    ABSTRACT: Gold nanorods have the potential to localize the treatment procedure by hyperthermia and influence the fluorescence. The longitudinal plasmon peak contributes to the photothermal effect by converting light to heat. When these nanorods are PEGylated, it not only makes it biocompatible but also acts a spacer layer during fluorescence enhancement. When the PEGylated nanorods are internalized inside the cells through endocytosis, the transverse plasmonic peak combined with the enhanced absorption and scattering properties of the nanorods can enhance the autofluorescence emission intensity from the cell. The autofluorescence from the mitochondria inside cells which reflects the respiratory status of the cell was enhanced two times by the presence of nanorods within the cell. At four minutes the nanorods incubated cells reached the hyperthermic temperature when illuminated continuously with near infrared laser. The cell viability test and autofluorescence intensity curve showed a similar trend indicating the progress of cell death over time. This is the first report to the best of our knowledge to suggest the potential of exploiting the dual capabilities of gold nanorods as photothermal agents and autofluorescence enhancer to track cell death. Copyright © 2014. Published by Elsevier Ireland Ltd.
    Cancer Letters 11/2014; 357(1). DOI:10.1016/j.canlet.2014.11.022 · 5.62 Impact Factor
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    ABSTRACT: Twenty compounds from Garcinia oblongifolia were screened for proapoptotic activity using FRET-based HeLa-C3 sensor cells. Among them, oblongifolins F and G (1 and 2), 1,3,5-trihydroxy-13,13-dimethyl-2H-pyran[7,6-b]xanthone (3), nigrolineaxanthone T (4), and garcicowin B (5) showed significant proapoptotic activity at a concentration of 10 μM. Bioassessments were then performed to evaluate the potential of these compounds for therapeutic application. All five compounds showed significant cytotoxicity and caspase-3-activating ability in cervical cancer HeLa cells, with compounds 1 and 2 having the highest potencies. All five compounds specifically induced caspase-dependent apoptosis, which could be prevented by the pan-caspase inhibitor zVAD-fmk. In particular, 3 induced apoptosis through mitotic arrest. Compounds 1-5 displayed similar IC50 values (3.9-16.5 μM) against the three cancer cell lines HeLa, MDA-MB-435, and HepG2. In addition, compounds 1, 2, and 4 exhibited similar and potent IC50 values (2.4-5.1 μM) against several breast and colon cancer cell lines, including those overexpressing either HER2 or P-glycoprotein. HER2 and P-glycoprotein are known factors that confer resistance to anticancer drugs in cancer cells. This is the first study on the cytotoxicity, caspase-3-activing ability, and specificity of proapoptotic compounds isolated from G. oblongifolia in HeLa cells. The potential application of these compounds against HER2- or P-glycoprotein-overexpressing cancer cells was investigated.
    Journal of Natural Products 04/2014; 77(5). DOI:10.1021/np4007316 · 3.95 Impact Factor
  • Jinjie Xu, Kathy Qian Luo
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    ABSTRACT: Isoflavones are a group of small molecular compounds found in many plants. Genistein is the most well studied isoflavones because of its beneficial effects in reducing menopausal symptoms, anti-oxidant and anti-cancer. The major difficulty in developing isoflavone-based healthcare products is their low water solubility. In this study, the solubility and oral bioavailability of genistein were increased by reducing its particle size using supercritical CO2 as an antisolvent in the precipitation process. The effects of various process parameters including type of solvent, pressure of precipitation, and concentration of genistein solution on particle formation were evaluated. We found that under optimized conditions: dissolving 4 mg/mL genistein in acetone and precipitating them with supercritical CO2 under 100 bar at 40 °C, the size of genistein particles was reduced from its original width of 10-50 μm to ∼254 nm. The reduction of genistein particle size not only increased its water solubility by 2 fold but more importantly increased its 24 h-plasma concentration by 2.6 fold after orally administrated to rats. These results proof the concept of using supercritical CO2 as an antisolvent in the precipitation process to reduce particle size of water insoluble compounds such as genistein and to improve its oral bioavailability.
    Chemical Engineering Research and Design 04/2014; 92(11). DOI:10.1016/j.cherd.2014.03.018 · 2.28 Impact Factor
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    ABSTRACT: People suffering from Diabetes Mellitus (DM) are prone to an array of vascular complications leading to end organ damage. The hallmark of these vascular complications is endothelium dysfunction, which is caused by endothelial cell (EC) apoptosis. Although the endothelial cell (EC) dysfunction induced by hyperglycaemia and fluid shear stress has been studied, the effects of biological factors in the blood of DM patients on EC integrity have not been reported in the in vitro models that mimic the physiological pulsatile nature of the vascular system. This study reports the development of a hemodynamic lab-on-a-chip system to investigate this issue. The pulsatile flow was applied to a monolayer of endothelial cells expressing a fluorescence resonance energy transfer (FRET)-based biosensor that changes colour from green to blue in response to caspase-3 activation during apoptosis. Plasma samples from healthy volunteers and DM patients were compared to identify biological factors that are critical to endothelial disruption. Three types of microchannels were designed to simulate the blood vessels under healthy and partially blocked pathological conditions. The results showed that EC apoptosis rates increased with increasing glucose concentration and levels of shear stress. The rates of apoptosis further increased by a factor of 1.4-2.3 for hyperglycaemic plasma under all dynamic conditions. Under static conditions, little difference was detected in the rate of EC apoptosis between experiments using plasma from DM patients and glucose medium, suggesting that the effects of hyperglycaemia and biological factors on the induction of EC apoptosis are all shear flow-dependent. A proteomics study was then conducted to identify biological factors, demonstrating that the levels of eight proteins, including haptoglobin and clusterin, were significantly down-regulated, while six proteins, including apolipoprotein C-III, were significantly up-regulated in the plasma of DM patients compared to healthy volunteers. This hemodynamic lab-on-a-chip system can serve as a high throughput platform to assess the risk of vascular complications of DM patients and to determine the effects of therapeutics or other interventions on EC apoptosis.
    Integrative Biology 03/2014; 6(8). DOI:10.1039/c3ib40265g · 4.00 Impact Factor
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    ABSTRACT: In this paper we show that acetyltanshinone IIA (ATA), a novel anti-cancer agent, preferentially inhibits cell growth of oestrogen receptor positive (ER+) breast cancer cells and that it is more potent than the commonly used anti-breast cancer agent, tamoxifen. The metabolic product of ATA, hydroquinone tanshinone IIA (HTA) binds to the ERα and causes its degradation mainly in the nucleus via an ubiquitin-mediated proteasome-dependent pathway. In addition, ATA also reduced the mRNA levels of the ERα encoding gene, ESR1, distinguishing ATA from another anti-breast cancer drug, fulvestrant. Finally, ATA reduced the transcription of an ER-responsive gene, GREB1.
    Cancer letters 12/2013; 346(1). DOI:10.1016/j.canlet.2013.12.023 · 5.62 Impact Factor
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    ABSTRACT: 1-[4-(bromomethyl)phenyl]-1,2,2-triphenylethene (2) was synthesized and evaluated for specific fluorescent prestaining of proteins containing cysteine (Cys) in SDS-PAGE. The molecule showed classic aggregation-induced emission (AIE) property in protein labeling and its quantum efficiency was further enhanced upon reacting with Cys. The parameters of reaction such as labeling time, concentration of dye and reducing reagent-tris(2-carboxyethyl)phosphine (TCEP) was examined to obtain the optimal labeling condition. In addition to its specific labeling effect, molecule 2 also showed its advantage over traditional self-quenching dyes through labeling Cys containing BSA with different dye/Cys ratios.
    ACS Applied Materials & Interfaces 05/2013; 5(11). DOI:10.1021/am401486h · 6.72 Impact Factor
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    ABSTRACT: To better understand how hyperglycemia induces endothelial cell dysfunction under the diabetic conditions, a hemodynamic microfluidic chip system was developed. The system combines a caspase-3-based fluorescence resonance energy transfer (FRET) biosensor cell line which can detect endothelial cell apoptosis in real-time, post-treatment effect and with a limited cell sample, by using a microfluidic chip which can mimic the physiological pulsatile flow profile in the blood vessel. The caspase-3-based FRET biosensor endothelial cell line (HUVEC-C3) can produce a FRET-based sensor protein capable of probing caspase-3 activation. When the endothelial cells undergo apoptosis, the color of the sensor cells changes from green to blue, thus sensing apoptosis. A double-labeling fluorescent technique (yo pro-1 and propidium iodide) was used to validate the findings revealed by the FRET-based caspase sensor. The results show high rates of apoptosis and necrosis of endothelial cells when high glucose concentration was applied in our hemodynamic microfluidic chip combined with an exhaustive pulsatile flow profile. The two apoptosis detection techniques (fluorescent method and FRET biosensor) are comparable; but FRET biosensor offers more advantages such as real-time observation and a convenient operating process to generate more accurate and reliable data. Furthermore, the activation of the FRET biosensor also confirms the endothelial cell apoptosis induced by the abnormal pulsatile shear stress and high glucose concentration is through caspase-3 pathway. A 12% apoptotic rate (nearly a 4-fold increase compared to the static condition) was observed when the endothelial cells were exposed to a high glucose concentration of 20 mM under 2 h exhaustive pulsatile shear stress of 30 dyne cm(-2) and followed with another 10 h normal pulsatile shear stress of 15 dyne cm(-2). Therefore, the most important finding of this study is to develop a novel endothelial cell apoptosis detection method, which combines the microfluidic chip system and FRET biosensor. This finding may provide new insight into how glucose causes endothelial cell dysfunction, which is the major cause of diabetes-derived complications.
    Lab on a Chip 04/2013; 13(14). DOI:10.1039/c3lc50105a · 5.75 Impact Factor
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    ABSTRACT: One novel xanthone, oliganthone A (1), was isolated from the stems of the plant Garcinia oligantha. It features the O-bearing C(3)-atom and absence of C(4) compared with the structures of related known xanthones, which have never been reported before. The structure of this compound was elucidated by spectroscopic analysis. Compound 1 showed strong HeLa cell growth-inhibiting effects with IC50 values below 10 μM.
    Helvetica Chimica Acta 03/2013; 96(3). DOI:10.1002/hlca.201200245 · 1.39 Impact Factor
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    ABSTRACT: Novel hybrid materials with multifunctionality are attractive systems because of their efficiency and versatility for carrying out tasks in parallel. In the present work, controllable formation of multifunctional and micrometer-sized composite fibers is gained via incorporating single-walled carbon nanotubes (SWCNTs) and magnetic iron oxide nanoparticles into a biotemplate, M13 phage in liquid-crystalline phase. It is found that these phage composite fibers possess high and durable natural fluorescence except those with SWCNT loadings higher than 10%. SWCNTs, imparting improved mechanical properties and electrical conductivity, align themselves parallel to the long axis of the fibers in the phage matrix. No SWCNTs or magnetic nanoparticles were observed on the external surface of phage composite fibers, so that the superficial phages are still able to provide binding sites for further surface modification. The composite fibers were also demonstrated to be non-cytotoxic platforms to support cell adhesion and growth. The virus-based multifunctional composite fibers, integrating fluorescence, electrical conductivity, magnetism, improved mechanical properties, and biocompatibility, offer a new prospect of an all-in-one tool, as well as potential applications ranging from tissue engineering to biomedical devices.
    RSC Advances 01/2013; 3(43):20437. DOI:10.1039/c3ra43034k · 3.84 Impact Factor
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    ABSTRACT: A new aggregation-induced emission (AIE) compound 1,2-bis[4-(isothiocyanatomethyl)phenyl]-1,2-diphenylethene () was synthesized for use in SDS-PAGE. The molecule is practically nonemissive in solution but becomes highly emissive after reacting with the amine groups of the proteins by either the prestaining or poststaining method. The sensitivity of achieved in the prestaining method is the same as that of Coomassie brilliant blue (CBB), while that observed in the poststaining method is higher than that of CBB. Excellent linear responses with the amount of protein were obtained in both cases. The detection of a mixture of proteins with different molecular weights was successfully achieved.
    The Analyst 10/2012; DOI:10.1039/c2an36002k · 3.91 Impact Factor
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    ABSTRACT: Oblongifolin C (OC) was identified as a potent apoptosis inducer from an herbal plant, Garcinia yunnanensis, during our previous bioassay-guided drug screening. In this study, we investigated the signaling pathways through which OC activated apoptosis in HeLa cells. We also compared the IC(50) values of OC with that of etoposide, paclitaxel and vinblastine in multiple cancer cell lines including HER2 and P-glycoprotein overexpressing cells. In addition, the in vivo antitumor effect of OC was studied in nude mice model. Our results showed that OC induced a caspase-dependent apoptosis by triggering a series of events in HeLa cells including Bax translocation, cytochrome c release, caspase-3 activation, chromosome fragmentation followed by caspase-8 activation, Bid cleavage and eventually cell death. Addition of a pan-caspase inhibitor or overexpression of an anti-apoptotic protein, Bcl-xL, prevented OC-induced cell death. Moreover, OC exhibited a wide anticancer spectrum in multiple cancer cell lines with comparable IC(50) values, regardless of the expression levels of HER2 and P-glycoprotein. In contrast, the IC(50) values of three clinical anticancer drugs, etoposide, paclitaxel and vinblastine were significantly elevated in HER2 and/or P-glycoprotein overexpressing cells. Furthermore, OC showed a similar antitumor effect but lower general toxicity than etoposide against xenografted human tumors in nude mice model. All these data suggested that OC is a promising apoptosis inducer with the potential to be developed into a clinical anticancer drug.
    International Journal of Cancer 09/2012; 131(6):1445-54. DOI:10.1002/ijc.27365 · 5.01 Impact Factor
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    ABSTRACT: The use of the supercritical fluid extraction of emulsion (SFEE) process for the polymer encapsulation of a low aqueous solubility drug substance was investigated, with focus placed on the carbon dioxide extraction step. The effects of process parameters—copolymer ratio, extraction time, pressure, and temperature—on the drug content, encapsulation efficiency, and drug release profile of the polymer–drug composite particle were studied. Ibuprofen and polylactic-glycolic acid were chosen as the model system. Encapsulated particles of 100–300 nm were successfully obtained after freeze-drying. XRD and SEM analyses confirmed the entrapment of ibuprofen in an amorphous polymer matrix and the absence of ibuprofen external to the encapsulated particles. In addition to the solubility of ibuprofen, the particle surface area and, to a small extent, the glass transition temperature were found to influence the drug content and drug release profiles. These understandings are expected to facilitate the rational design of the extraction step of the SFEE process, especially for drugs that are relatively soluble in supercritical carbon dioxide.
    Industrial & Engineering Chemistry Research 06/2012; 52(1):134–141. DOI:10.1021/ie300612r · 2.24 Impact Factor
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    ABSTRACT: The aim of the present study was to develop the PLGA/HP55 nanoparticles with improved hypoglycemic effect for oral insulin delivery. The insulin-loaded PLGA/HP55 nanoparticles were produced by a modified multiple emulsion solvent evaporation method. The physicochemical characteristics, in vitro release of insulin, and in vivo efficacy in diabetic rats of the nanoparticles were evaluated. The insulin encapsulation efficiency was up to 94%, and insulin was released in a pH-dependent manner under simulated gastrointestinal conditions. When administered orally (50 IU/kg) to diabetic rats, the nanoparticles can decrease rapidly the blood glucose level with a maximal effect between 1 and 8 h. The relative bioavailability compared with subcutaneous injection (5 IU/kg) in diabetic rats was 11.3% ± 1.05%. This effect may be explained by the fast release of insulin in the upper intestine, where it is better absorbed by the high gradient concentration of insulin than other regions. These results show that the PLGA/HP55 nanoparticles developed in the study might be employed as a potential method for oral insulin delivery.
    Nanoscale Research Letters 06/2012; 7(1):299. DOI:10.1186/1556-276X-7-299 · 2.48 Impact Factor
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    ABSTRACT: A new aggregation-induced emission (AIE) compound 1,1-dimethyl-2,5-bis[4-(isothiocyanatemethyl)phenyl]-3,4-diphenylsilole (SITC) was synthesized and used to conjugate with aminoallyl-dUTP. The SITC-dUTP can be incorporated enzymatically into DNA strands with the degree of labeling (DOL) up to the theoretic limit.
    Chemical Communications 05/2012; 48(51). DOI:10.1039/c2cc32038j · 6.72 Impact Factor
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    ABSTRACT: In this work, we designed and developed a two-stage delivery system composed of enteric capsule and cationic nanoparticles for oral delivery of insulin. The enteric capsule was coated with pH-sensitive hydroxypropyl methylcellulose phthalate (HP55), which could selectively release insulin from nanoparticles in the intestinal tract, instead of stomach. The biodegradable poly(lactic-co-glycolic acid) (PLGA) was selected as the matrix for loading insulin. Eurdragit(®) RS (RS) was also introduced to the nanoparticles for enhancing the penetration of insulin across the mucosal surface in the intestine. The nanoparticles were prepared with the multiple emulsions solvent evaporation method via ultrasonic emulsification. The optimized nanoparticles have a mean size of 285nm, a positive zeta potential of 42mV. The encapsulation efficiency was up to 73.9%. In vitro results revealed that the initial burst release of insulin from nanoparticles was markedly reduced at pH 1.2, which mimics the stomach environment. In vivo effects of the capsule containing insulin PLGA/RS nanoparticles were also investigated in diabetic rat models. The oral delivered capsules induced a prolonged reduction in blood glucose levels. The pharmacological availability was found to be approximately 9.2%. All the results indicated that the integration of HP55-coated capsule with cationic nanoparticles may be a promising platform for oral delivery of insulin with high bioavailability.
    International Journal of Pharmaceutics 04/2012; 425(1-2):1-8. DOI:10.1016/j.ijpharm.2011.12.055 · 3.79 Impact Factor

Publication Stats

1k Citations
206.74 Total Impact Points

Institutions

  • 2007–2015
    • Nanyang Technological University
      • School of Chemical and Biomedical Engineering
      Tumasik, Singapore
  • 2001–2010
    • The Hong Kong University of Science and Technology
      • Department of Chemical and Biomolecular Engineering
      Chiu-lung, Kowloon City, Hong Kong
  • 2003
    • California Institute of Technology
      • Division of Biology
      Pasadena, California, United States