Publications by authors named "Jianan Fu"

7 Publications

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3D Hollow Quasi-Graphite Capsules/Polyaniline Hybrid with a High Performance for Room-Temperature Ammonia Gas Sensors.

ACS Sens 2019 09 6;4(9):2343-2350. Epub 2019 Sep 6.

School of Materials and Energy, Center for Applied Chemistry , University of Electronic Science and Technology of China , Chengdu 611731 , P. R. China.

Designing sensing materials with novel morphologies and compositions is eminently challenging to achieve high-performance gas sensor devices. Herein, an in situ oxidative polymerization approach is developed to construct three-dimensional (3D) hollow quasi-graphite capsules/polyaniline (GCs/PANI) hierarchical hybrids by decorating protonated PANI on the surface of GCs; as a result, an immensely active and sensitive material was developed for sensing ammonia gas at room temperature. Moreover, the GCs possessed a capsule-like hollow/open structure with partially graphitized walls, and PANI nanospheres were uniformly decorated on the GC surfaces. Furthermore, the inflexible and rigid 3D ordered chemistry of these materials provides the resulting hybrids with a large interfacial surface area, which not only allows for rapid adsorption and charge transfer but also provides the necessary structural stability. The 3D hollow GCs/PANI hybrids exhibit excellent performance; the GCs/PANI-3 hybrid is highly sensitive (with a response value of 1.30) toward 10 ppm NH gas and has short response and recovery times of 34 and 42 s, respectively. The GCs/PANI-3 hybrid also demonstrates a good selectivity, repeatability, and long-term stability, which are attributed to the substantial synergistic effect of the GCs and PANI. The design of such a unique 3D ordered framework provides a promising pathway to achieve room-temperature gas sensors for commercial applications.
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http://dx.doi.org/10.1021/acssensors.9b00882DOI Listing
September 2019

Fetal Bovine Serum (FBS): Past - Present - Future.

ALTEX 2018 9;35(1):99-118. Epub 2017 Aug 9.

Division of Physiology, Medical University Innsbruck, Innsbruck, Austria.

The supplementation of culture medium with fetal bovine serum (FBS, also referred to as "fetal calf serum") is still common practice in cell culture applications. Due to a number of disadvantages in terms of quality and reproducibility of in vitro data, animal welfare concerns, and in light of recent cases of fraudulent marketing, the search for alternatives and the development of serum-free medium formulations has gained global attention. Here, we report on the 3rd Workshop on FBS, Serum Alternatives and Serum-free Media, where regulatory aspects, the serum dilemma, alternatives to FBS, case-studies of serum-free in vitro applications, and the establishment of serum-free databases were discussed. The whole process of obtaining blood from a living calf fetus to using the FBS produced from it for scientific purposes is de facto not yet legally regulated despite the existing EU-Directive 2010/63/EU on the use of animals for scientific purposes. Together with the above-mentioned challenges, several strategies have been developed to reduce or replace FBS in cell culture media in terms of the 3Rs (Refinement, Reduction, Replacement). Most recently, releasates of activated human donor thrombocytes (human platelet lysates) have been shown to be one of the most promising serum alternatives when chemically-defined media are not yet an option. Additionally, new developments in cell-based assay techniques, advanced organ-on-chip and microphysiological systems are covered in this report. Chemically-defined serum-free media are shown to be the ultimate goal for the majority of culture systems, and examples are discussed.
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http://dx.doi.org/10.14573/altex.1705101DOI Listing
August 2018

Long period fiber grating in two-core hollow eccentric fiber.

Opt Express 2015 Dec;23(26):33378-85

Long period fiber gratings (LPGs) in a two-core hollow eccentric fiber (TCHF) have been demonstrated experimentally. Two LPGs have been fabricated into the respective core of the TCHF by a high frequency CO2 laser. The coupling characteristics in the TCHF-LPG have been studied using the coupling mode theory (CMT). The resonant peak is mainly caused by the coupling between the core mode LP01 and cladding mode LP81. The experimental results agree well with the simulation results. Furthermore, the sensing properties of the TCHF-LPG have been investigated with respect to bending, temperature and axial strain. Compared with the LPG in the single mode fiber (SMF), the experimental results indicate that the sensitivity of the TCHF-LPGs to bending curvature is low and even very small at some bending directions. In addition, TCHF-LPGs are insensitive to the axial strain while sensitive to the temperature. Therefore, the proposed TCHF-LPGs can efficiently sense the changing temperature that is independent of the strain. Moreover, the TCHF-LPGs can also be applied to two-channel filters without signal crosstalk between two cores.
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http://dx.doi.org/10.1364/OE.23.033378DOI Listing
December 2015

Bending characteristics of a long-period fiber grating in a hollow eccentric optical fiber.

Appl Opt 2015 Sep;54(26):7879-83

In this paper, the bending characteristics of a long-period fiber grating (LPFG) in a hollow eccentric optical fiber (HEOF) have been investigated. Two samples fabricated under different laser exposure directions have been studied experimentally. The results show that the HEOF-LPFG can distinguish specific bending directions. The resonant peak shifts linearly with increasing curvature, but its sensitivity is lower than that of the LPFGs in single-mode fibers. In addition, the exposure direction shows a great influence on the bending characteristics due to the asymmetry of the fiber core. Furthermore, the responses of the HEOF-LPFG to temperature, axial strain, and external refractive index have been measured.
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http://dx.doi.org/10.1364/AO.54.007879DOI Listing
September 2015

Carbon metabolism limits recombinant protein production in Pichia pastoris.

Biotechnol Bioeng 2011 Aug 11;108(8):1942-53. Epub 2011 Mar 11.

Department of Biochemical and Chemical Engineering, Laboratory of Chemical Biotechnology, TU Dortmund University, Emil-Figge-Str 66, D-44227 Dortmund, Germany.

The yeast Pichia pastoris enables efficient (high titer) recombinant protein production. As the molecular tools required are well established and gene specific optimizations of transcription and translation are becoming available, metabolism moves into focus as possible limiting factor of recombinant protein production in P. pastoris. To investigate the impact of recombinant protein production on metabolism systematically, we constructed strains that produced the model protein β-aminopeptidase BapA of Sphingosinicella xenopeptidilytica at different production yields. The impact of low to high BapA production on cell physiology was quantified. The data suggest that P. pastoris compensates for the additional resources required for recombinant protein synthesis by reducing by-product formation and by increasing energy generation via the TCA cycle. Notably, the activity of the TCA cycle was constant with a rate of 2.1 ± 0.1 mmol g CDW-1 h(-1) irrespective of significantly reduced growth rates in high BapA producing strains, suggesting an upper limit of TCA cycle activity. The reduced growth rate could partially be restored by providing all 20 proteinogenic amino acids in the fermentation medium. Under these conditions, the rate of BapA synthesis increased twofold. The successful supplementation of the growth medium by amino acids to unburden cellular metabolism during recombinant protein production suggests that the metabolic network is a valid target for future optimization of protein production by P. pastoris.
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http://dx.doi.org/10.1002/bit.23114DOI Listing
August 2011

Quantitative physiology of Pichia pastoris during glucose-limited high-cell density fed-batch cultivation for recombinant protein production.

Biotechnol Bioeng 2010 Oct;107(2):357-68

Department of Biochemical and Chemical Engineering, TU Dortmund University, Dortmund, Germany.

Pichia pastoris has become one of the major microorganisms for the production of proteins in recent years. This development was mainly driven by the readily available genetic tools and the ease of high-cell density cultivations using methanol (or methanol/glycerol mixtures) as inducer and carbon source. To overcome the observed limitations of methanol use such as high heat development, cell lysis, and explosion hazard, we here revisited the possibility to produce proteins with P. pastoris using glucose as sole carbon source. Using a recombinant P. pastoris strain in glucose limited fed-batch cultivations, very high-cell densities were reached (more than 200 g(CDW) L(-1)) resulting in a recombinant protein titer of about 6.5 g L(-1). To investigate the impact of recombinant protein production and high-cell density fermentation on the metabolism of P. pastoris, we used (13)C-tracer-based metabolic flux analysis in batch and fed-batch experiments. At a controlled growth rate of 0.12 h(-1) in fed-batch experiments an increased TCA cycle flux of 1.1 mmol g(-1) h(-1) compared to 0.7 mmol g(-1) h(-1) for the recombinant and reference strains, respectively, suggest a limited but significant flux rerouting of carbon and energy resources. This change in flux is most likely causal to protein synthesis. In summary, the results highlight the potential of glucose as carbon and energy source, enabling high biomass concentrations and protein titers. The insights into the operation of metabolism during recombinant protein production might guide strain design and fermentation development.
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http://dx.doi.org/10.1002/bit.22836DOI Listing
October 2010

Correlation between TCA cycle flux and glucose uptake rate during respiro-fermentative growth of Saccharomyces cerevisiae.

Microbiology (Reading) 2009 Dec 14;155(Pt 12):3827-3837. Epub 2009 Aug 14.

Laboratory of Chemical Biotechnology, TU Dortmund, 44221 Dortmund, Germany.

Glucose repression of the tricarboxylic acid (TCA) cycle in Saccharomyces cerevisiae was investigated under different environmental conditions using (13)C-tracer experiments. Real-time quantification of the volatile metabolites ethanol and CO(2) allowed accurate carbon balancing. In all experiments with the wild-type, a strong correlation between the rates of growth and glucose uptake was observed, indicating a constant yield of biomass. In contrast, glycerol and acetate production rates were less dependent on the rate of glucose uptake, but were affected by environmental conditions. The glycerol production rate was highest during growth in high-osmolarity medium (2.9 mmol g(-1) h(-1)), while the highest acetate production rate of 2.1 mmol g(-1) h(-1) was observed in alkaline medium of pH 6.9. Under standard growth conditions (25 g glucose l(-1) , pH 5.0, 30 degrees C) S. cerevisiae had low fluxes through the pentose phosphate pathway and the TCA cycle. A significant increase in TCA cycle activity from 0.03 mmol g(-1) h(-1) to about 1.7 mmol g(-1) h(-1) was observed when S. cerevisiae grew more slowly as a result of environmental perturbations, including unfavourable pH values and sodium chloride stress. Compared to experiments with high glucose uptake rates, the ratio of CO(2) to ethanol increased more than 50 %, indicating an increase in flux through the TCA cycle. Although glycolysis and the ethanol production pathway still exhibited the highest fluxes, the net flux through the TCA cycle increased significantly with decreasing glucose uptake rates. Results from experiments with single gene deletion mutants partially impaired in glucose repression (hxk2, grr1) indicated that the rate of glucose uptake correlates with this increase in TCA cycle flux. These findings are discussed in the context of regulation of glucose repression.
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http://dx.doi.org/10.1099/mic.0.030213-0DOI Listing
December 2009