Browsing by Author "Li, Po-Han"

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A hybrid nanoparticle matrix for mass spectrometry
(2013)
Li, Po-Han
;
Huang, Shin-Yi
;
Chen, Yu-Chie
;
Urban, Pawel L.
;
應用化學系
We demonstrate hybrid inorganic-organic nanoparticles -based on silicon dioxide and 9-aminoacridine- which can enhance mass spectrometric analysis and imaging in the negative-ion mode. The nanoparticles bind to the surface of cells while still in the liquid phase, which is followed by a controlled release of the organic matrix molecules triggered by alkaline ammonia vapours delivered to the specimen in a closed chamber. First, the method was optimized and tested using standard compounds as analytes. Second, the spatial resolution was verified using a natural fibre (diameter similar to 20 mu m). Third, the method was used in the imaging of molecules present in the outer layer of large algal cells (Closterium acerosum). An important advantage of this method is that nanoparticles loaded with organic matrix can be applied to the biological cells as aqueous suspensions; hence, the release and spreading of metabolites can be limited during sample preparation for MALDI-MS. In addition, since this method does not involve spraying, exposure of experimenters to toxic aerosols is decreased.
Multifunctional Fe(3)O(4)/alumina core/shell MNPs as photothermal agents for targeted hyperthermia of nosocomial and antibiotic-resistant bacteria
(2011-10-01)
Yu, Tsai-Jung
;
Li, Po-Han
;
Tseng, Te-Wei
;
Chen, Yu-Chie
;
應用化學系
The appearance of antibiotic-resistant bacterial strains is a serious problem in medical treatment. Thus, it is imperative to explore new therapeutic approaches and antibiotics with which to treat patients suffering from bacterial infections. Materials & Methods: In this work, we propose a targeted hyperthermia therapeutic approach using alumina-coated iron oxide magnetic nanoparticles (Fe(3)O(4)/alumina core/shell MNPs) as photothermal agents to selectively kill bacteria. Results: Fe(3)O(4) MNPs possess photothermal capabilities under near-infrared (NIR) light illumination. The temperature of the MNP suspension (1.33 mu g/mu l, 60 mu l) under illumination with NIR light increased 20 degrees C over 5 min. Functionalization of the surface of the MNPs with an alumina coating allows them to have targeting capability toward bacteria. The prepared Fe(3)O(4)/alumina core/shell MNPs possess several desirable features, including magnetic properties, absorption capability in the NIR region and the ability to target bacteria. The magnetic properties of the Fe(3)O(4)/alumina MNPs allow conjugated target species to aggregate at a specific location under a magnetic field. A NIR laser can then be used to specifically irradiate the aggregated spot to photokill target bacteria. The cell growth of nosocomial bacteria, including Gram-positive, Gram-negative and antibiotic-resistant bacterial strains, can be effectively inhibited by over 95% within 10 min of light irradiation when targeted by Fe(3)O(4)/alumina MNPs. Conclusion: This approach provides a potential therapeutic approach for treating patients suffering from nosocomial and antibiotic-resistant bacterial infections.
Multifunctional Fe3O4/alumina core/shell MNPs as photothermal agents for targeted hyperthermia of nosocomial and antibiotic-resistant bacteria
(2011-10-01)
Yu, Tsai-Jung
;
Li, Po-Han
;
Tseng, Te-Wei
;
Chen, Yu-Chie
;
應用化學系
The appearance of antibiotic-resistant bacterial strains is a serious problem in medical treatment. Thus, it is imperative to explore new therapeutic approaches and antibiotics with which to treat patients suffering from bacterial infections. Materials & Methods: In this work, we propose a targeted hyperthermia therapeutic approach using alumina-coated iron oxide magnetic nanoparticles (Fe3O4/alumina core/shell MNPs) as photothermal agents to selectively kill bacteria. Results: Fe3O4 MNPs possess photothermal capabilities under near-infrared (NIR) light illumination. The temperature of the MNP suspension (1.33 mu g/mu l, 60 mu l) under illumination with NIR light increased 20 degrees C over 5 min. Functionalization of the surface of the MNPs with an alumina coating allows them to have targeting capability toward bacteria. The prepared Fe3O4/alumina core/shell MNPs possess several desirable features, including magnetic properties, absorption capability in the NIR region and the ability to target bacteria. The magnetic properties of the Fe3O4/alumina MNPs allow conjugated target species to aggregate at a specific location under a magnetic field. A NIR laser can then be used to specifically irradiate the aggregated spot to photokill target bacteria. The cell growth of nosocomial bacteria, including Gram-positive, Gram-negative and antibiotic-resistant bacterial strains, can be effectively inhibited by over 95% within 10 min of light irradiation when targeted by Fe3O4/alumina MNPs. Conclusion: This approach provides a potential therapeutic approach for treating patients suffering from nosocomial and antibiotic-resistant bacterial infections.
Recording temporal characteristics of convection currents by continuous and segmented-flow sampling
(2012)
Li, Po-Han
;
Ting, Hsu
;
Chen, Yu-Chie
;
Urban, Pawel L.
;
應用化學系
Despite the fact that the natural distribution of chemical substances in the three-dimensional world is far from homogeneous, most liquid-phase chemistry involves operations on homogeneous solutions. Here we describe two facile methods for real-time monitoring of liquid-phase chemical heterogeneity induced by convection in millilitre-range volumes. The liquid medium was continuously aspirated from the vial (acting as a "convection chamber''), and driven to online detectors either using continuous or discontinuous (segmented) hydrodynamic flow. In one embodiment, after the initial passage through a flow-through optical detector, the sample was driven to an electrospray ion source-set in front of the orifice of an ion trap mass spectrometer. The system recorded the emergence of chemical waves produced as a result of convection currents from the test substances introduced to the vial. Both variants of the method (using continuous and segmented flow) revealed fluctuations of the analyte concentration before an equilibrium was reached, and the mixture became homogeneous. We believe that this analytical scheme can further be used to study spatiotemporal characteristics of various dynamic chemical systems in liquid phase.
Synthesis of Oligomeric Mannosides and Their Structure-Binding Relationship with Concanavalin A
(2014-07-01)
Li, Chen-Wei
;
Hon, Kai-Wei
;
Ghosh, Bhaswati
;
Li, Po-Han
;
Lin, Hsien-Ya
Small glycodendrimers with a-mannosyl ligands were synthesized by using copper-catalyzed azide-alkyne coupling chemistry and some of these molecules were used as multivalent ligands to study the induction of concanavalin A (Con A) precipitation. The results showed that the monovalent mannose ligand could induce the precipitation of Con A. This unexpected finding initiated a series of studies to characterize the molecular basis of the ligand-lectin interaction. The atypical precipitation is found to be specific to the mannose, fluorescein moiety (FITC), and Con A. Apparently the mannose ligand binds to Con A through hydrogen-bonding interactions, whereas the binding of FITC is mediated by hydrophobic forces.
Using Gold Nanoclusters As Selective Luminescent Probes for Phosphate-Containing Metabolites
(2012-07-03)
Li, Po-Han
;
Lin, Ju-Yu
;
Chen, Cheng-Tai
;
Ciou, Wei-Ru
;
Chan, Po-Han
Glutathione-bound gold nanoclusters (AuNCs@GSH) can emit reddish photoluminescence under illumination of ultraviolet light. The luminescence of the AuNCs@GSH is quenched when chelating with iron ions (AuNCs@GSH-Fe3+), presumably resulting from the effective electron transfer between the nanoclusters and iron ions. Nevertheless, we found that the luminescence of the gold nanoclusters can be restored in the presence of phosphate-containing molecules, which suggested the possibility of using AuNCs@GSH-Fe3+ complexes as the selective luminescent switches for phosphate-containing metabolites. Phosphate-containing metabolites such as adenosine-5'-triphosphate (ATP) and pyrophosphate play an important role in biological systems. In this study, we demonstrated that the luminescence of the AuNCs@GSH-Fe3+ is switched-on when mixing with ATP and pyrophosphate, which can readily be observed by the naked eye. It results from the high formation constants between phosphates and iron ions. When employing fluorescence spectroscopy as the detection tool, quantitative analysis for phosphate-containing metabolites such as ATP and pyrophosphate can be conducted. The linear range for ATP and pyrophosphate is 50 mu M to sub-millimolar, while the limit of detection for ATP and pyrophosphate are similar to 43 and similar to 28 mu M, respectively. Additionally, we demonstrated that the luminescence of the AuNCs@GSH-Fe3+ can also be turned on in the presence of phosphate-containing metabolites from cell lysates and blood plasma.