The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
Ho Nam Chang - One of the best experts on this subject based on the ideXlab platform.
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Two-stage Depth Filter perfusion culture for recombinant antibody production by recombinant Chinese hamster ovary cell
Biotechnology and Bioprocess Engineering, 2008Co-Authors: Joon Chul Lee, Do Yun Kim, Ho Nam ChangAbstract:A rCHO cell line of DUKX origin 26*-320, producing recombinant antibody against the human platelet, was cultivated in a two-stage Depth Filter perfusion system (DFPS) for 20 days in order to attain high recombinant antibody concentration. The productivity of the first stage DFPS bioreactor reached 53 times that of the batch culture in a controlled stirred tank reactor and was showed 12.1 mg/L antibody concentration at a perfusion rate of 6.0 d^−1. Glucose concentration in the first DFPS was maintained at 1.5 g/L to avoid cell damage in the perfusion culture. A second stage DFPS system was attached to the first DFPS, which resulted in a low glucose concentration of 0.02 g/L and a high antibody concentration of 23.9 mg/L. The two-stage Depth Filter perfusion culture yielded 60% higher product concentration than the batch and 49-fold higher productivity of 69.3 mg/L/d in comparison with that (1.4 mg/L/d) in a batch system. Furthermore, antibody concentration of the second stage was 97% higher than that of the first stage, and the antibody productivities were comparable to that of the first stage. This two-stage DFPS system also showed potential for higher titer production of recombinant antibody and high volumetric productivity for long-term culture of bio-pharmaceutical substances.
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Recombinant antibody production by perfusion cultures of rCHO cells in a Depth Filter perfusion system.
Biotechnology Progress, 2008Co-Authors: Joon Chul Lee, Ho Nam ChangAbstract:Recombinant Chinese hamster ovary cells, producing recombinant antibody against the human platelet, were cultivated in a Depth Filter perfusion system (DFPS). When perfusion cultures with working volume of 1 L were operated at perfusion rates of 5/d and 6/d, volumetric antibody productivities reached values 28 and 34 times higher than that of batch suspension culture in Erlenmeyer flasks and 43 and 53 times higher than that of batch culture in a controlled stirred tank reactor, respectively. Perfusion cultures in the DFPS showed stable antibody production over the whole culture period of up to 20 days. In the DFPS, inoculated cells in suspension were entrapped in a few hours within the Depth Filter matrix by medium circulation and retained there until the void space of the Filter matrix was saturated by the cultured cells. After cells in the Depth Filter matrix reached saturation, overgrown viable cells at a perfusion rate of 5/d or 6/d were continuously collected into waste medium at a density of 2-4 x 10(5) cells/mL, which resulted in stable operation at high perfusion rates, maintaining values of process parameters such as glucose/lactate concentration, pH, and dissolved oxygen concentration. Because the DFPS overcomes most drawbacks observed with conventional perfusion systems, it is preferable to be used as a key culture system to produce monoclonal antibody stably for a long culture period.
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Long-term operation of Depth Filter perfusion systems (DFPS) for monoclonal antibody production using recombinant CHO cells: Effect of temperature, pH, and dissolved oxygen
Biotechnology and Bioprocess Engineering, 2008Co-Authors: Joon Chul Lee, Do Yun Kim, Ho Nam ChangAbstract:Recombinant CHO cells of DG44 origin (CS*13-1.00), expressing a chimeric antibody against the S surface antigen of the Hepatitis B virus, were cultivated in single-stage and two-stage Depth Filter perfusion systems (DFPS) under varying temperature, pH, and oxygen tension conditions to determine their effects on recombinant antibody production. A long-term culture was carried out in a single-stage Depth Filter for 81 days, during which an occasional clog interrupted the experiment. However, this problem was solved via trypsin injection. The DFPS showed a steady production of monoclonal antibody at a concentration of 100∼150 mg/L. As the cultivation temperature was increased from 33 to 37°C, the monoclonal antibody (Mab) concentration increased from 80.33 to 133.47 mg/L. Likewise, the glucose uptake rate (GUR) and lactate production rate (LPR) also increased. With an increase in pH from 6.95 to 7.61, the Mab concentration increased from 61.64 to 94.31 mg/L. When the oxygen tension was increased from 60 to 80%, the Mab concentration increased from 93.78 to 128.30 mg/L.
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High cell density perfusion cultures of anchorage-dependent Vero cells in a Depth Filter perfusion system
Cytotechnology, 1995Co-Authors: Sang Kyo Choi, Ho Nam Chang, Duk Jae OhAbstract:A Depth Filter perfusion system (DFPS) with polypropylene fibers had been demonstrated to support high density cultures of anchorage-independent hybridoma cells. The DFPS provides advantages of high surface-to-volume ratio of 450–600 cm^2/cm^3, low cost set-up, easy operation and scale-up. To test the feasibility of using DFPS for high density cultures of anchorage-dependent cells, Vero cells were cultivated in the DFPS. Gelatin coating on polypropylene fibers in the DFPS was necessary to promote cell attachment and growth. Dissolved oxygen (DO) concentrations could be controlled by sparging air into the reservoir vessel through a Filter sparger. When DO concentration was controlled above 40% of air saturation in the DFPS with 40 μm pore size, the maximum cell concentration as estimated on specific lactate production rate, was 3.81×10^7 cells/ml of the total reactor volume. This viable cell concentration is approximately 18 times higher than that obtained in a T-flask batch culture. Taken together, the results obtained here showed the potential of DFPS for high-density cultures of anchorage-dependent cells.
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Continuous production of tissue plasminogen activator from recombinant CHO cells in a Depth Filter perfusion system
Biotechnology Techniques, 1995Co-Authors: Sang Kyo Choi, Ho Nam ChangAbstract:A Depth Filter perfusion system (DFPS), equipped with a 40-μm polypropylene Depth Filter for cell immobilization, was used for the continuous production of tissue plasminogen activator (t-PA) from recombinant Chinese hamster ovary cells. Final cell density in the DFPS with oxygen control was 1.8×10^7 cells/mL of the total working volume and maximum t-PA productivity was 2.63 mg/L/day. Dissolved oxygen concentration in the Filter matrix was successfully controlled by air sparging and stable operation was possible for more than 20 days.
Abhinav A Shukla - One of the best experts on this subject based on the ideXlab platform.
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Design of a Filter train for precipitate removal in monoclonal antibody downstream processing
Biotechnology and Applied Biochemistry, 2009Co-Authors: Sunitha Kandula, Sudha Babu, Mi Jin, Abhinav A ShuklaAbstract:Protein A chromatography has become widely established for the preparative purification of mAbs (monoclonal antibodies). Low pH elution from Protein A columns followed by neutralization can often lead to precipitation of impurities in the product stream, leading to a visually turbid solution. Pretreatment of the cell culture harvest stream with an increased surface area of the Depth Filter was found to reduce the magnitude of this problem through exploitation of the adsorptive properties of harvest Depth Filters. However, this was not a complete solution. Clarification of this turbid product stream prior to the polishing chromatographic steps in the downstream process posed significant filtration challenges. Development of a staged filtration process with the use of low plugging glass fibre Depth Filters as the first stage prior to membrane filtration through an absolute pore size membrane is described. Finally, a cost calculation is used to drive the selection of the final Filter train for this application. The results presented here are expected to have wide applicability in mAb downstream processing as well as for other turbid solutions encountered in the downstream processing of other biomolecules.
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exploitation of the adsorptive properties of Depth Filters for host cell protein removal during monoclonal antibody purification
Biotechnology Progress, 2006Co-Authors: Yinges Yigzaw, Robert Piper, Minh Tran, Abhinav A ShuklaAbstract:Depth filtration has been widely used during process scale clarification of cell culture supernatants for the removal of cells and cell debris. However, in addition to their filtration capabilities, Depth Filters also possess the ability to adsorb soluble species. This aspect of Depth filtration has largely not been exploited in process scale separations and is usually ignored during cell culture harvest development. Here, we report on the ability of Depth Filters to adsorptively remove host cell protein contaminants from a recombinant monoclonal antibody process stream and characterize some of the underlying interactions behind the binding phenomenon. Following centrifugation, filtration through a Depth Filter prior to Protein A chromatographic capture was shown to significantly reduce the level of turbidity observed in the Protein A column eluate of the monoclonal antibody. The Protein A eluate turbidity was shown to be linked to host cell protein contaminant levels in the Protein A column load and not to the DNA content. Analogous to flowthrough chromatography in which residence time/bed height and column loading are key parameters, both the number of passes through the Depth Filter and the amount of centrifuge centrate loaded on the Filter were seen to be important operational parameters governing the adsorptive removal of host cell protein contaminants. Adsorption of proteins to the Depth Filter was shown to be due to a combination of electrostatic and hydrophobic adsorptive interactions. These results demonstrate the ability to employ Depth filtration as an integrative unit operation combining filtration for particulate removal with adsorptive binding for contaminant removal.
Jindong Tan - One of the best experts on this subject based on the ideXlab platform.
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A Confidence Weighted Real-Time Depth Filter for 3D Reconstruction
2016Co-Authors: Zhenzhou Shao, Zhiping Shi, Yong Guan, Hongxing Wei, Jindong TanAbstract:3D reconstruction is an important technique in the environmental perception and rehabilitation process. With the help of active Depth-aware sensors, such as Kinect from Microsoft and SwissRanger, the Depth map can be captured at the video frame rate together with color information to enable the real-time reconstruction. Particularly, it features prominently in the activity recognition and remote rehabilitation. Unfortunately, the coarseness of the Depth map make it difficult to extract the detailed information in 3D reconstruction of the scene and tracking of thin objects. Especially, geometric distortions occur around the edge of an object. Therefore, this paper presents a confidence weighted real-time Depth Filter for the edge recovery to reduce the extra artifacts due to the uncertainty of each Depth measurement. Also the intensity of Depth map is taken into account to optimize the weighting term in the algorithm. Moreover, the GPU implementation guarantees the high computational efficiency for the real-time applications. Experimental results are shown to illustrate the performance of the proposed method by the comparisons with the traditional methods.
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Intelligent Information Processing - A Confidence Weighted Real-Time Depth Filter for 3D Reconstruction
Intelligent Information Processing VIII, 2016Co-Authors: Zhenzhou Shao, Zhiping Shi, Yong Guan, Hongxing Wei, Jindong TanAbstract:3D reconstruction is an important technique in the environmental perception and rehabilitation process. With the help of active Depth-aware sensors, such as Kinect from Microsoft and SwissRanger, the Depth map can be captured at the video frame rate together with color information to enable the real-time reconstruction. Particularly, it features prominently in the activity recognition and remote rehabilitation. Unfortunately, the coarseness of the Depth map make it difficult to extract the detailed information in 3D reconstruction of the scene and tracking of thin objects. Especially, geometric distortions occur around the edge of an object. Therefore, this paper presents a confidence weighted real-time Depth Filter for the edge recovery to reduce the extra artifacts due to the uncertainty of each Depth measurement. Also the intensity of Depth map is taken into account to optimize the weighting term in the algorithm. Moreover, the GPU implementation guarantees the high computational efficiency for the real-time applications. Experimental results are shown to illustrate the performance of the proposed method by the comparisons with the traditional methods.
Joon Chul Lee - One of the best experts on this subject based on the ideXlab platform.
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Two-stage Depth Filter perfusion culture for recombinant antibody production by recombinant Chinese hamster ovary cell
Biotechnology and Bioprocess Engineering, 2008Co-Authors: Joon Chul Lee, Do Yun Kim, Ho Nam ChangAbstract:A rCHO cell line of DUKX origin 26*-320, producing recombinant antibody against the human platelet, was cultivated in a two-stage Depth Filter perfusion system (DFPS) for 20 days in order to attain high recombinant antibody concentration. The productivity of the first stage DFPS bioreactor reached 53 times that of the batch culture in a controlled stirred tank reactor and was showed 12.1 mg/L antibody concentration at a perfusion rate of 6.0 d^−1. Glucose concentration in the first DFPS was maintained at 1.5 g/L to avoid cell damage in the perfusion culture. A second stage DFPS system was attached to the first DFPS, which resulted in a low glucose concentration of 0.02 g/L and a high antibody concentration of 23.9 mg/L. The two-stage Depth Filter perfusion culture yielded 60% higher product concentration than the batch and 49-fold higher productivity of 69.3 mg/L/d in comparison with that (1.4 mg/L/d) in a batch system. Furthermore, antibody concentration of the second stage was 97% higher than that of the first stage, and the antibody productivities were comparable to that of the first stage. This two-stage DFPS system also showed potential for higher titer production of recombinant antibody and high volumetric productivity for long-term culture of bio-pharmaceutical substances.
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Recombinant antibody production by perfusion cultures of rCHO cells in a Depth Filter perfusion system.
Biotechnology Progress, 2008Co-Authors: Joon Chul Lee, Ho Nam ChangAbstract:Recombinant Chinese hamster ovary cells, producing recombinant antibody against the human platelet, were cultivated in a Depth Filter perfusion system (DFPS). When perfusion cultures with working volume of 1 L were operated at perfusion rates of 5/d and 6/d, volumetric antibody productivities reached values 28 and 34 times higher than that of batch suspension culture in Erlenmeyer flasks and 43 and 53 times higher than that of batch culture in a controlled stirred tank reactor, respectively. Perfusion cultures in the DFPS showed stable antibody production over the whole culture period of up to 20 days. In the DFPS, inoculated cells in suspension were entrapped in a few hours within the Depth Filter matrix by medium circulation and retained there until the void space of the Filter matrix was saturated by the cultured cells. After cells in the Depth Filter matrix reached saturation, overgrown viable cells at a perfusion rate of 5/d or 6/d were continuously collected into waste medium at a density of 2-4 x 10(5) cells/mL, which resulted in stable operation at high perfusion rates, maintaining values of process parameters such as glucose/lactate concentration, pH, and dissolved oxygen concentration. Because the DFPS overcomes most drawbacks observed with conventional perfusion systems, it is preferable to be used as a key culture system to produce monoclonal antibody stably for a long culture period.
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Long-term operation of Depth Filter perfusion systems (DFPS) for monoclonal antibody production using recombinant CHO cells: Effect of temperature, pH, and dissolved oxygen
Biotechnology and Bioprocess Engineering, 2008Co-Authors: Joon Chul Lee, Do Yun Kim, Ho Nam ChangAbstract:Recombinant CHO cells of DG44 origin (CS*13-1.00), expressing a chimeric antibody against the S surface antigen of the Hepatitis B virus, were cultivated in single-stage and two-stage Depth Filter perfusion systems (DFPS) under varying temperature, pH, and oxygen tension conditions to determine their effects on recombinant antibody production. A long-term culture was carried out in a single-stage Depth Filter for 81 days, during which an occasional clog interrupted the experiment. However, this problem was solved via trypsin injection. The DFPS showed a steady production of monoclonal antibody at a concentration of 100∼150 mg/L. As the cultivation temperature was increased from 33 to 37°C, the monoclonal antibody (Mab) concentration increased from 80.33 to 133.47 mg/L. Likewise, the glucose uptake rate (GUR) and lactate production rate (LPR) also increased. With an increase in pH from 6.95 to 7.61, the Mab concentration increased from 61.64 to 94.31 mg/L. When the oxygen tension was increased from 60 to 80%, the Mab concentration increased from 93.78 to 128.30 mg/L.
Hongbin Zha - One of the best experts on this subject based on the ideXlab platform.
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scalable monocular slam by fusing and connecting line segments with inverse Depth Filter
International Conference on Pattern Recognition, 2018Co-Authors: Jiyuan Zhang, Gang Zeng, Hongbin ZhaAbstract:In this paper we propose a fast and robust line-based approach to monocular SLAM. It relies on a novel inverse Depth representation of lines capable of tracking line segments in long image consequences. Tracked lines through frames provide crucial directional and positional knowledge for boosting localization performance, and they are more informative in charactering environments than points especially for urban outdoor and indoor scenes. The developed two-parameter inverse Depth representation of lines is applicable for Kalman Filter to achieve an efficient solver due to its linearity, which has lower computational cost compared to binary descriptors. This Filter is also harmonious with inverse Depth Filter of points, both of which are incorporated under a unified minimization framework to enhance the performance of monocular SLAM. Real world monocular sequences have demonstrated that the proposed SLAM system outperforms the state-of-the-art and produces accurate results in both indoor and outdoor scenes.
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ICPR - Scalable Monocular SLAM by Fusing and Connecting Line Segments with Inverse Depth Filter
2018 24th International Conference on Pattern Recognition (ICPR), 2018Co-Authors: Jiyuan Zhang, Gang Zeng, Hongbin ZhaAbstract:In this paper we propose a fast and robust line-based approach to monocular SLAM. It relies on a novel inverse Depth representation of lines capable of tracking line segments in long image consequences. Tracked lines through frames provide crucial directional and positional knowledge for boosting localization performance, and they are more informative in charactering environments than points especially for urban outdoor and indoor scenes. The developed two-parameter inverse Depth representation of lines is applicable for Kalman Filter to achieve an efficient solver due to its linearity, which has lower computational cost compared to binary descriptors. This Filter is also harmonious with inverse Depth Filter of points, both of which are incorporated under a unified minimization framework to enhance the performance of monocular SLAM. Real world monocular sequences have demonstrated that the proposed SLAM system outperforms the state-of-the-art and produces accurate results in both indoor and outdoor scenes.
