bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrophoretic total analysis of trace tetracycline antibiotics in a microchip with amperometry
Authors: Lee Kyung‐Sun , Park So‐Hee , Won So‐Young , Shim Yoon‐Bo 
Published: August 2009

AbstractThe preconcentration, separation, and electrochemical detection of a series of tetracycline (TC) antibiotics in a microfluidic channel were preformed. The electrophoretic experimental parameters to analyze TC, oxytetracycline, chlortetracycline, and doxycycline antibiotics were investigated with a cellulose‐dsDNA‐modified carbon paste electrode. Modification of the electrode improved detection performance by enhancing the signal‐to‐noise characteristics without surface fouling of the electrode. Field‐amplified sample stacking and field‐amplified sample injection techniques were employed for on‐chip preconcentration of the TC series. The sensitivity of the method was improved 10 900‐fold when compared with conventional MEKC‐electrochemical detection analysis. The overall recoveries for TC, oxytetracycline, chlortetracycline, and doxycycline were 87, 89, 87, and 81%, respectively, with 6.0% RSD. The limits of detection for the series were estimated between 1.5 and 4.3 nM. Applicability of the method to beef samples was successfully demonstrated.
Manipulation of microfluidic droplets by electrorheological fluid
Authors: Zhang Menying , Gong Xiuqing , Wen Weijia 
Published: August 2009

AbstractMicrofluidics, especially droplet microfluidics, attracts more and more researchers from diverse fields, because it requires fewer materials and less time, produces less waste and has the potential of highly integrated and computer‐controlled reaction processes for chemistry and biology. Electrorheological fluid, especially giant electrorheological fluid (GERF), which is considered as a kind of smart material, has been applied to the microfluidic systems to achieve active and precise control of fluid by electrical signal. In this review article, we will introduce recent results of microfluidic droplet manipulation, GERF and some pertinent achievements by introducing GERF into microfluidic system: digital generation, manipulation of “smart droplets” and droplet manipulation by GERF. Once it is combined with real‐time detection, integrated chip with multiple functions can be realized.
Miniaturized metal semiconductor metal photocurrent system for biomolecular sensing via chemiluminescence
Authors: Lin Chie‐Chieh , Ko Fu‐Hsiang , Chen Chun‐Chi , Yang Yuh‐Shyong , Chang Feng‐Chi , Wu Chung‐Shu 
Published: August 2009

AbstractA miniaturized metal semiconductor metal photodetector was developed as the core detector for chemiluminescence biosensor. The biosensor utilized the semiconductor manufacturing to fabricate the 83 interdigitated patterns of 250‐nm metal line and 278‐nm space in 100 μm×100 μm active region. The established real‐time detector was operated at 0.4 V to ensure the maximal signal to background ratio of 3600 under illumination intensity of 1.46 mW/cm2. A chemiluminescence in the miniaturized chamber was successfully proposed to determine the model protein concentration in real‐time analysis. Before the emission of light from the catalytic reaction of substrate, the model protein of streptavidin bound to horseradish peroxidase was successfully immobilized onto the sensor surface through the high‐affinity conjugate with biotin. The detection limit of 4.76 nM for streptavidin analysis was obtained under the calibration curve of linear range over 5–100 nM with correlation coefficient of 0.9999.
Enhancement of cellular olfactory signal by electrical stimulation
Authors: Lee Sang Hun , Jeong Se Hoon , Jun Sang Beom , Kim Sung June , Park Tai Hyun 
Published: August 2009

AbstractThe binding of olfactory receptors with odorant molecules initiates olfactory signal transduction, which leads to a cationic influx. In the present study, human embryonic kidney‐293 cells were recombinantly engineered to co‐express olfactory receptors I7 and gustatory cyclic nucleotide gated channels, which increased the cationic influx. The odorant‐induced change in the membrane potential was measured in the extracellular region using microelectrode arrays. A biphasic electrical current stimulation was applied to the cells in order to increase the intrinsic cellular activity. Upon odorants recognition, the electrical cellular activity was enhanced following each electrical stimulation pulse. Compared with odorant‐only stimulation, the electrical stimulation induced up to a fivefold increase in the amplitude of the electrical signal, which was produced in response to the odorants. These results demonstrate that electrical stimulation can enhance cellular activity and increase the response signal for detecting ligand binding. This paradigm of electrical stimulation can be used as a novel method in the field of versatile cell‐based biosensors for detection of specific odorants.
Carbon nanotube‐sensor‐integrated microfluidic platform for real‐time chemical concentration detection
Authors: Yang Li , Li Minglin , Qu Yanli , Dong Zaili , Li Wen J. 
Published: August 2009

AbstractThis paper presents the development of a chemical sensor employing electronic‐grade carbon nanotubes (EG‐CNTs) as the active sensing element for sodium hypochlorite detection. The sensor, integrated in a PDMS‐glass microfluidic chamber, was fabricated by bulk aligning of EG‐CNTs between gold microelectrode pairs using dielectrophoretic technique. Upon exposure to sodium hypochlorite solution, the characteristics of the carbon nanotube chemical sensor were investigated at room temperature under constant current mode. The sensor exhibited responsivity, which fits a linear logarithmic dependence on concentration in the range of 1/32 to 8 ppm, a detection limit lower than 5 ppb, while saturating at 16 ppm. The typical response time of the sensor at room temperature is on the order of minutes and the recovery time is a few hours. In particular, the sensor showed an obvious sensitivity to the volume of detected solution. It was found that the activation power of the sensor was extremely low, i.e. in the range of nanowatts. These results indicate great potential of EG‐CNT for advanced nanosensors with superior sensitivity, ultra‐low power consumption, and less fabrication complexity.
Effects of embedded sub‐micron pillar arrays in microfluidic channels on large DNA electrophoresis
Authors: Chan Yick Chuen , Zohar Yitshak , Lee Yi‐Kuen 
Published: August 2009

AbstractA study of the influences of embedding artificial structures in a microfluidic device for CE with a free buffer solution is presented. Compared with conventional slab‐gel electrophoresis, three major additional effects on the overall system performance are identified when sub‐micron pillar arrays are integrated into a standard CE microsystem. Since DNA molecules have to migrate in‐between and interact with the pillars, pillar geometry is first demonstrated to have a direct impact on the DNA motion pattern. Electric field re‐distribution is another inevitable outcome when features of sub‐micron dimensions are placed inside a microchannel. This effect is verified by a numerical simulation tool. Furthermore, the integration of the closely packed sub‐micron structures dramatically increases the surface to volume ratios in the microfluidic device and therefore generates a large EOF. The consequence of these additional influences implies a complexity in the measured DNA velocity and indicates that careful considerations have to be taken when these devices are used for DNA electrokinetics study or electrophoresis theory re‐examination.
Incorporation of electrospun nanofibrous PVDF membranes into a microfluidic chip assembled by PDMS and scotch tape for immunoassays
Authors: Liu Yingyi , Yang Dayong , Yu Tao , Jiang Xingyu 
Published: August 2009

AbstractThis paper demonstrates a microfluidic chip for multiple immunoassays on electrospun (ES) nanofibrous membranes made of PVDF. This microchip enables the detection of multiple pairs of protein–protein interactions in one experiment by crossing parallel arrays of microchannels. This chip uses ESPVDF membrane with high specific surface area as the substrate to adsorb protein for immobilized immunoassays so that increased levels of protein adsorption may lower the LOD in immunoassays. We employ a simple and effective method for chip assembly by scotch tape to incorporate the ESPVDF membrane into the microchip. We believe that the present work will facilitate the development of methods for the on‐site diagnosis of diseases whose detection is based on antigen–antibody recognition, and improve the efficiencies of certain experiments that need to identify tens to hundreds of protein–protein interactions with relatively low cost in the future.
Environmentally friendly surface modification of PDMS using PEG polymer brush
Authors: Zhang Zhaowei , Feng Xiaojun , Luo Qingming , Liu Bi‐Feng 
Published: August 2009

AbstractA PEG‐NH2‐based environmentally friendly surface modification strategy was developed for PDMS microchips to prevent protein adsorption and to enhance separation performance. PEG‐NH2 was synthesized using a modified synthesis procedure. A two‐step grafting method was used for PDMS modification. FTIR absorption by attenuated total reflection and contact angle measurements verified the successful grafting of PEG‐NH2 onto the PDMS surface. Subsequent EOF Measurements and protein adsorption studies of PEG‐modified PDMS microchips revealed noticeable EOF suppression and resistance to nonspecific protein adsorption for more than 30 days. Separation of four FITC‐labeled amino acids was further demonstrated with high repeatability and reproducibility. Comparison of electrophoresis of 3‐(2‐furoyl)quinoline‐2‐carboxaldehyde‐labeled BSA using PDMS microchips before and after surface modification resulted in significantly improved electrophoretic performance of the PEG‐modified PDMS microchips, suggesting that our PEG grafting method successfully modified PDMS surface property and prevented adsorption of proteins. We expect that this environmentally friendly surface modification method will be useful for future protein separations with long‐term surface stability.
Rapid and efficient proteolysis for proteomic analysis by protease‐immobilized microreactor
Authors: Yamaguchi Hiroshi , Miyazaki Masaya , Honda Takeshi , Briones‐Nagata Maria Portia , Arima Kazunari , Maeda Hideaki 
Published: August 2009

AbstractProteolysis is an important part of protein identification in proteomics analysis. The conventional method of in‐solution digestion of proteins is time‐consuming and has limited sensitivity. In this study, trypsin‐ or α‐chymotrypsin‐immobilized microreactors prepared by a microfluidics‐based enzyme‐immobilization technique were studied for rapid sample preparation in proteomic analysis. The kinetic studies for hydrolysis of substrate by microreactors revealed that immobilized proteases had higher hydrolytic efficiency than those performed by in‐solution digestion. The performance of the microreactors was evaluated by digesting cytochrome c and BSA. Protein digestion was achieved within a short period of time (∼5 min) at 30°C without any complicated reduction and alkylation procedures. The efficiency of digestion by trypsin‐immobilized reactor was evaluated by analyzing the sequence coverage, which was 47 and 12% for cytochrome c and BSA, respectively. These values were higher than those performed by in‐solution digestion. Besides, because of higher stability against high concentration of denaturant, the microreactors can be useful for immediate digestion of the denaturated protein. In the present study, we propose a protease‐immobilized microreactor digestion method, which can utilize as a proteome technique for biological and clinical research.
Rapid detection of Mycoplasma pneumonia in a microfluidic device using immunoagglutination assay and static light scattering
Authors: Kim Keesung , Jung Ho‐Sup , Song Jae‐Young , Lee Man‐Ryul , Kim Kye‐Seong , Suh Kahp‐Yang 
Published: August 2009

AbstractWe present real‐time, rapid detection of Mycoplasma pneumonia in PBS inside a Y‐channel PDMS microfluidic device via optical fiber monitoring of latex immunoagglutination. The latex immunoagglutination assay was performed with serially diluted M. pneumonia solutions using highly carboxylated polystyrene particles of 390 and 500 nm diameter conjugated with monoclonal anti‐M. pneumonia. Proximity optical fibers were located around the viewing cell of the device, which were used to measure the increase in 45° forward light scattering of the aggregated particles. The detection limit are slightly less than 50 pg mL−1 both for 390 and 500 nm microspheres and the detection time do not exceed 90 s.
Highly efficient capture and enumeration of low abundance prostate cancer cells using prostate‐specific membrane antigen aptamers immobilized to a polymeric microfluidic device
Authors: Dharmasiri Udara , Balamurugan Subramanian , Adams André A. , Okagbare Paul I. , Obubuafo Annie , Soper Steven A. 
Published: August 2009

AbstractProstate tumor cells over‐express a prostate‐specific membrane antigen (PSMA) that can be used as a marker to select these cells from highly heterogeneous clinical samples, even when found in low abundance. Antibodies and aptamers have been developed that specifically bind to PSMA. In this study, anti‐PSMA aptamers were immobilized onto the surface of a capture bed poised within a PMMA, microchip, which was fabricated into a high‐throughput micro‐sampling unit (HTMSU) used for the selective isolation of rare circulating prostate tumor cells resident in a peripheral blood matrix. The HTMSU capture bed consisted of 51 ultra‐high‐aspect ratio parallel curvilinear channels with a width similar to the prostate cancer cell dimensions. The surface density of the PSMA‐specific aptamers on an ultraviolet‐modified PMMA microfluidic capture bed surface was determined to be 8.4×1012 molecules/cm2. Using a linear velocity for optimal cell capture in the aptamer‐tethered HTMSU (2.5 mm/s), a recovery of 90% of LNCaP cells (prostate cancer cell line; used as a model in this example) was found. Due to the low abundance of these cells, the input volume required was 1 mL and this could be processed in ∼29 min using an optimized linear flow rate of 2.5 mm/s. Captured cells were subsequently released intact from the affinity surface using 0.25% w/w trypsin followed by counting individual cells using a contact conductivity sensor integrated into the HTMSU that provided high detection and sampling efficiency (∼100%) and did not require staining of the cells for enumeration.
Identification and separation of DNA‐hybridized nanocolloids by Taylor cone harmonics
Authors: Cheng Xinguang , Basuray Sagnik , Senapati Satyajyoti , Chang Hsueh‐Chia 
Published: August 2009

AbstractA rapid (minutes) electrospray bead‐based DNA hybridization detection technique is developed by spraying a mixture of hybridized and unhybridized silica nanocolloids. With proper far‐field control by external electrodes, the trajectory of the ejected nanobeads from the electrospray is governed by specific harmonics of the Laplace equation, which select discrete polar angles along well‐separated field maxima near the conducting Taylor cone. Due to Rayleigh fission and evaporation, beads of different size acquire different total charge after ejection and suffer different normal electrophoretic displacement such that they are ejected along well‐separated field maxima and are deposited in distinct rings on an intersecting plane. As the hybridized DNA is of the same dimension as that of the nanocolloid, the nanocolloids are hence easily differentiated from the unhybridized ones. This technique is highly specific as the high shear stress in the microjet shears away any non‐specifically bound DNA from the nanocolloid surface.
Bacteria concentration using a membrane type insulator‐based dielectrophoresis in a plastic chip
Authors: Cho Yoon‐Kyoung , Kim Suhyeon , Lee Kyusang , Park Chinsung , Lee Jeong‐Gun , Ko Christopher 
Published: August 2009

AbstractWe report an insulator‐based (or, electrodeless) dielectrophoresis utilizing microfabricated plastic membranes. The membranes with honeycomb‐type pores have been fabricated by patterning the SU‐8 layer on a substrate which was pretreated with self‐assembled monolayer of octadecyltrichlorosilane for the easy release. The fabricated membrane was positioned between two electrodes and alternating current field was applied for the particle trap experiments. The particle could be trapped due to the dielectrophoresis force generated by the non‐uniformities of the electric fields applied through the membranes with pores. Simulations using CFD‐ACE+(CFD Research, Huntsville, Alabama) suggested that the dielectrophoresis force is stronger in the edge of the pores where the field gradient is highest. The bacteria could be captured on the near edge of the pores when the electric field was turned on and the trapped bacteria could be released when the field was turned off with the release efficiency of more than 93±7%. The maximal trapping efficiency of 66±7% was obtained under the electric fields (E=128 V/mm and f=300 kHz) when the dilute bacteria solution (Escherichia coli: 9.3×103 cell/mL, 0.5 mS/m) flowed with a flow rate of 100 μL/min.
Optical fiber enzymatic biosensor for reagentless measurement of ethylene dibromide
Authors: Reardon Kenneth F. , Campbell Derek W. , Müller Cord 
Published: August 2009

AbstractA reagentless enzymatic optical biosensor has been constructed to measure the concentration of ethylene dibromide (EDB, 1,2‐dibromoethane), a US EPA Priority Pollutant. This biosensor is based on the haloalkane dehalogenase DhaA, which generates protons as a product of the dehalogenation of EDB. The resulting pH change is detected as a shift in the fluorescence intensity of fluoresceinamine. When layers of fluoresceinamine andRhodococcussp. GJ70 expressing DhaA were immobilized on the tip of an optical fiber, the resulting changes in fluorescence were proportional to the EDB concentration in the range 1–10 μg/L and nonlinear (saturation‐type trend) for concentrations up to 10 mg/L. EDB concentrations as low as 1 μg/L could be detected in aqueous solutions. Both the pH and buffer capacity of the sample had significant effects on the sensor's performance. EDB biosensors were active for at least 37 d, although their sensitivity decreased after 7 d. The biosensor's potential to measure continuously andin situcould make it useful for environmental or water treatment process monitoring systems.
Response surface optimization of mixed substrate solid state fermentation for the production of lovastatin by Monascus purpureus
Authors: Subhagar Seraman , Aravindan Rajendran , Viruthagiri Thangavelu 
Published: August 2009

AbstractThe objective of this work is to enhance the production of lovastatin using Monascus purpureus MTCC 369 in mixed substrate solid state fermentation using various solid substrates and to optimize the combination of the solid substrates by response surface methodology. Solid state fermentation was conducted in a 250 mL Erlenmeyer flask at 30°C for 14 days with initial moisture content of 40% and inoculum size of 10% active culture. Barley, long grain rice and sago starch were found to be the suitable substrates producing maximum lovastatin of 193.7 mg, 190.2 mg and 180.9 mg/g of dry solids. These substrates were further used in various combinations as designed by the central composite design for enhancing the lovastatin production using Monascus purpureus. To the best of our knowledge this is the first report on the production of lovastatin using a mixed substrate solid state fermentation using Monascus purpureus.
The Auxiliary Substrate Concept: From simple considerations to heuristically valuable knowledge
Authors: Babel Wolfgang 
Published: August 2009

AbstractMicroorganisms are used in biotechnology. They are either (i) aim and purpose of a process, e.g. with the production of single cell proteins, or (ii) mean to an end insofar as they serve as a catalyst or “factory” for syntheses (e.g. of products of primary and secondary metabolism, of enzymes and antibiotics) or for the degradation and detoxification of harmful organics and inorganics. In all cases, the efficiency and velocity, finally the productivity, are parameters which essentially determine the economy of the processes. Therefore, search for approaches to optimize these processes is a permanent task and challenge for scientists and engineers. It is shown that the auxiliary substrate concept is suitable to increase the yield coefficients. It is based on the energetic evaluation of organics, on the knowledge that organics as sources of carbon and energy for growth are deficient in ATP and/or reducing equivalents, and says that it is possible to improve the carbon conversion efficiency up to the carbon metabolism determined upper limit. The latter is determined by inevitable losses of carbon along the way of assimilation and anabolism and amounts to about 85% for so‐called glycolytic substrates, e.g. glucose, methanol, and to about 75% for gluconeogenetic substrates, e.g. C2‐substrates (acetic acid, hexadecane). The approach is explained and some experimental examples are presented. By simultaneous utilization of an extra energy source (auxiliary substrate) the yield coefficient can be increased (i) in glucose from about 0.5 to 0.7 g/g (by means of formate), (ii) in acetate from 0.34–0.4 to 0.5–0.65 g/g (by means of formate and thiosulfate, respectively), and (iii) in hexadecane from about 0.94 to 1.26 g/g (by means of formate). The precalculated yield coefficients and mixing ratios agree well with the experimentally attained ones. The approach is easily feasible and economically valuable.
Reactive red azo dye degradation in a UASB bioreactor: Mechanism and kinetics
Authors: Gonzalez‐Gutierrez Linda V. , Escamilla‐Silva Eleazar M. 
Published: August 2009

AbstractTextile industry uses azo dyes in its processes, which are complex organic molecules that are not easy to be degraded. Reactive dyes are especially difficult to remove from wastewater because of the characteristics of the molecule: one or more azo bonds, naphthalene‐disulfonate, triazine or chloro‐triazine, and phenyl‐amine groups. The degradation of the azo dye reactive red 272 was studied under anaerobic conditions in a hybrid Upflow Anaerobic Sludge Bed reactor (UASB) with an activated carbon bed. An adapted consortium of microorganisms was used in the kinetic study (batch) and to inoculate the UASB reactor. The experimental design identified the main factors determining the dye reduction efficiency are the initial concentration of dye and dextrose (as electron donor) and the residence time in the reactor. Dye reduction rate was decreased as the concentration increases in the wastewater; as a result, a kinetic model with a change from first to second order is proposed. The kinetic study showed that the process is first abiotic (adsorption) and then biotic (biodegradation).
Dynamic modelling of bacterial cellulose formation
Authors: Hornung Michael , Biener Richard , Schmauder Hans‐Peter 
Published: August 2009

AbstractThe interest in cellulose produced by bacteria from surface cultures has increased steadily in recent years because of its potential for use in medicine and cosmetics. Unfortunately, the low yield of this production process has limited the commercial usefulness of bacterial cellulose. The aim of this paper is to show the effect of substrate mass transfer on the growth of the bacteria and on their physiological potential for product formation by means of a dynamic mathematical model.