Browsing by Author "Hu, Jie-Bi"

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A compact 3D-printed interface for coupling open digital microchips with Venturi easy ambient sonic-spray ionization mass spectrometry
(2015-01-01)
Hu, Jie-Bi
;
Chen, Ting-Ru
;
Chang, Chia-Hsien
;
Cheng, Ji-Yen
;
Chen, Yu-Chie
Digital microfluidics (DMF) based on the electrowetting-on-dielectric phenomenon is a convenient way of handling microlitre-volume aliquots of solutions prior to analysis. Although it was shown to be compatible with on-line mass spectrometric detection, due to numerous technical obstacles, the implementation of DMF in conjunction with MS is still beyond the reach of many analytical laboratories. Here we present a facile method for coupling open DMF microchips to mass spectrometers using Venturi easy ambient sonic-spray ionization operated at atmospheric pressure. The proposed interface comprises a 3D-printed body that can easily be "clipped" at the inlet of a standard mass spectrometer. The accessory features all the necessary connections for an open-architecture DMF microchip with T-shaped electrode arrangement, thermostatting of the microchip, purification of air (to prevent accidental contamination of the microchip), a Venturi pump, and two microfluidic pumps to facilitate transfer of samples and reagents onto the microchip. The system also incorporates a touch-screen panel and remote control for user-friendly operation. It is based on the use of popular open-source electronic modules, and can readily be assembled at low expense.
A pinch-valve interface for automated sampling and monitoring of dynamic processes by gas chromatography-mass spectrometry
(2014)
Ting, Hsu
;
Hu, Jie-Bi
;
Hsieh, Kai-Ta
;
Urban, Pawel L.
;
應用化學系
Gas chromatography (GC) is frequently used in qualitative and quantitative analysis of volatile organic molecules. In its most common embodiment, samples are prepared in the laboratory, and injected into the capillary column using an autosampler. Analytes are separated, and detected by one of several available detection systems, including mass spectrometry (MS). However, this mode of operation is not convenient when monitoring dynamic chemical systems - for example, reaction mixtures. Here we present a facile approach for automated sampling, and subsequent introduction of samples to a GC apparatus in order to enable monitoring of dynamic chemical processes in real time. The proposed system incorporates two pinch valves, a peristaltic pump, a thermoshaker, and an electronic control unit (Raspberry Pi microcomputer) with several relays. The device facilitates dosing small volumes of liquid samples to the injection port of a commercial GC-MS apparatus. A program in C language controls the operation of the pump (on/off, direction of flow) and actuation of the pinch valves, and it initiates GC-MS runs. The system has been characterised with artificial samples, and successfully used in the monitoring of transesterification reactions catalysed by single microbeads containing immobilised lipase, as well as in the monitoring of the extraction of natural products from plant tissue samples. We believe that - following further improvements - this automated approach may be adapted for monitoring industrial processes and environmental analysis.
Automated system for extraction and instantaneous analysis of millimeter-sized samples
(2014)
Hu, Jie-Bi
;
Chen, Ssu-Ying
;
Wu, June-Tai
;
Chen, Yu-Chie
;
Urban, Pawel L.
Adequate sample treatment is critical when employing mass spectrometry (MS) in the analyses of complex biological matrices. Despite various improvements, it is generally difficult to automate the process of preparing solid biological samples for MS analysis. Here we demonstrate a facile approach for automation of the whole analysis (from an untreated sample to the final result). The proposed platform enables disruption and extraction of relatively small samples (individual fruit flies, fragments of tea leaves, powdered drug sampled with a cotton bud), and almost simultaneous analysis of the obtained extract within less than 10 min, and with very little intervention of the analyst. The operation is straightforward: once a sample is placed in the sample chamber, the analyst only needs to press a button on the touch screen of the user interface. The programmed open-source electronic device triggers addition of a small amount of solvent, and subsequent mechanical disruption/extraction of the specimen under controlled conditions (thermostated chamber). A small volume of the extract is directed to the ion source of the mass spectrometer incorporating a Venturi pump. During the operation of the instrument, fluorescence intensities (excitation wavelength windows: 320-380 and 460-500 nm) as well as MS extracted ion currents are recorded simultaneously. In the case of fruit fly samples, similar to 70 signals were recorded in both modes while the analysis of green tea leaves yielded similar to 30 signals. The resulting data reveal time-resolved extraction profiles characterizing every sample.
Capillary hydrodynamic chromatography reveals temporal profiles of cell aggregates
(2016-03-03)
Tang, Ya-Ru
;
Huang, Hsin-Yi
;
Hu, Jie-Bi
;
Rattinam, Rajesh
;
Li, Chun-Hsien
Microbial cells are known to form aggregates. Such aggregates can be found in various matrices; for example, functional drinks. Capillary hydrodynamic chromatography (HDC) enables separation of particles by size using nanoliter-scale volumes of samples. Here we propose an approach based on HDC for characterisation of real samples containing aggregated and non-aggregated bacterial and fungal cells. Separation of cells and cell aggregates in HDC arises from the parabolic flow profile under laminar flow conditions. In the presented protocol, hydrodynamic separation is coupled with different on-line and offline detectors (light absorption/scattering and microscopy). The method has successfully been applied in the monitoring of dynamic changes in the microbiome of probiotic drinks. Chromatographic profiles of yogurt and kefir samples obtained at different times during fermentation are in a good agreement with microscopic images. Moreover, thanks to the implementation of an area imaging detector, capillary HDC could be multiplexed and used to profile spatial gradients in cell suspensions, which arise in the course of sedimentation of cells and cell aggregates. This result shows compatibility of sedimentation analysis and capillary HDC. We believe that the approach may find applications in the profiling of functional foods and other matrices containing aggregated bioparticles. (C) 2016 Elsevier B.V. All rights reserved.
Coffee-ring effects in laser desorption/ionization mass spectrometry
(2013-03-05)
Hu, Jie-Bi
;
Chen, Yu-Chie
;
Urban, Pawel L.
;
應用化學系
;
Department of Applied Chemistry
This report focuses on the heterogeneous distribution of small molecules (e.g. metabolites) within dry deposits of suspensions and solutions of inorganic and organic compounds with implications for chemical analysis of small molecules by laser desorption/ionization (LDI) mass spectrometry (MS). Taking advantage of the imaging capabilities of a modern mass spectrometer, we have investigated the occurrence of "coffee rings" in matrix-assisted laser desorption/ionization (MALDI) and surface-assisted laser desorption/ionization (SALDI) sample spots. It is seen that the "coffee-ring effect" in MALDI/SALDI samples can be both beneficial and disadvantageous. For example, formation of the coffee rings gives rise to heterogeneous distribution of analytes and matrices, thus compromising analytical performance and reproducibility of the mass spectrometric analysis. On the other hand, the coffee-ring effect can also be advantageous because it enables partial separation of analytes from some of the interfering molecules present in the sample. We report a "hidden coffee-ring effect" where under certain conditions the sample/matrix deposit appears relatively homogeneous when inspected by optical microscopy. Even in such cases, hidden coffee rings can still be found by implementing the MALDI-MS imaging technique. We have also found that to some extent, the coffee-ring effect can be suppressed during SALDI sample preparation. (C) 2013 Elsevier B.V. All rights reserved.
Microcontroller-Assisted Compensation of Adenosine Triphosphate Levels: Instrument and Method Development
(2015-01-30)
Hu, Jie-Bi
;
Chen, Ting-Ru
;
Chen, Yu-Chie
;
Urban, Pawel L.
;
應用化學系
In order to ascertain optimum conditions for biocatalytic processes carried out in vitro, we have designed a bio-opto-electronic system which ensures real-time compensation for depletion of adenosine triphosphate (ATP) in reactions involving transfer of phosphate groups. The system covers ATP concentration range of 2-48 mu M. The report demonstrates feasibility of the device operation using apyrase as the ATP-depleting enzyme.
On the dynamics of kefir volatome
(2014)
Hu, Jie-Bi
;
Gunathilake, Sampath
;
Chen, Yu-Chie
;
Urban, Pawel L.
;
應用化學系
Probiotic drinks constitute an important component of the daily diet in the modern society. They contain active microbial strains, which contribute to the chemical composition of these dairy products. The metabolic activity of microbes can affect the flavor and smell of probiotic drinks at room temperature. "Kefir" is an example of fermented milk, which contains various species of bacteria as well as fungi (yeast). In order to gain a better understanding of the metabolic processes shaping the chemical composition of kefir drinks, in the present study, we perform a comparative analysis of volatomes of kefir and single-species cultures of Saccharomyces cerevisiae. Gas chromatography coupled with mass spectrometry enabled the monitoring of volatile metabolites collected onto solid phase microextraction fibres (divenylbenzene/carboxen/polydimethylsiloxane). The temporal profiles of secondary metabolites (isopentyl acetate, ethyl hexanoate, ethyl octanoate, phenethyl acetate, and ethyl decanoate), present in S. cerevisiae cultures and commercial kefir, exhibit similarity. This points to a significant contribution of Saccharomyces strains on the dynamics of the chemical composition of kefir during storage at ambient conditions. On the other hand, commercial yogurt, which contains various species of bacteria but not yeast is much more chemically stable and does not exhibit rapid changes in the ester-type metabolites, which are typical of kefir.
On-Target Labeling of Intracellular Metabolites Combined with Chemical Mapping of Individual Hyphae Revealing Cytoplasmic Relocation of Isotopologues
(2012-06-05)
Hu, Jie-Bi
;
Chen, Yu-Chie
;
Urban, Pawel L.
;
應用化學系
;
Department of Applied Chemistry
A microscale analytical platform integrating microbial cell culture, isotopic labeling, along with visual and mass spectrometric imaging with single-cell resolution has been developed and applied in the monitoring of cellular metabolism in fungal mycelium. The method implements open chips with a two-dimensional surface pattern composed of hydrophobic and hydrophilic zones. Two hydrophilic islands are used as medium reservoirs, while the hydrophobic area constitutes the support for the growing aerial hyphae, which do not have direct contact with the medium. The first island, containing C-12(6)-glucose medium, was initially inoculated with the mycelium (Neurospora crassa), and following the initial incubation period, the hyphae progressed toward the second medium island, containing an isotopically labeled substrate (C-13(6)-glucose). The C-13 atoms were gradually incorporated into cellular metabolites, which was revealed by MALDI-MS. The fate of the chitin-biosynthesis precursor, uridine diphosphate N-acetylglucosamine (UDP-GlcNAc), was monitored by recording mass spectra with characteristic isotopic patterns, which indicated the presence of various C-12/C-13 isotopologues. The method enabled mapping the C-13-labeled UDP-GlcNAc in fungal mycelium and recording its redistribution in hyphae, directly on the chip.