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Lemke N, El-Khatib AH, Tchipilov T, Jakubowski N, Weller MG, Vogl J. Procedure providing SI-traceable results for the calibration of protein standards by sulfur determination and its application on tau. Anal Bioanal Chem 2022; 414:4441-4455. [PMID: 35316347 PMCID: PMC9142460 DOI: 10.1007/s00216-022-03974-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 02/04/2022] [Accepted: 02/10/2022] [Indexed: 11/20/2022]
Abstract
Quantitative proteomics is a growing research area and one of the most important tools in the life sciences. Well-characterized and quantified protein standards are needed to achieve accurate and reliable results. However, only a limited number of sufficiently characterized protein standards are currently available. To fill this gap, a method for traceable protein quantification using sulfur isotope dilution inductively coupled plasma mass spectrometry (ICP-MS) was developed in this study. Gel filtration and membrane filtration were tested for the separation of non-protein-bound sulfur in the protein solution. Membrane filtration demonstrated a better performance due to the lower workload and the very low sulfur blanks of 11 ng, making it well suited for high-purity proteins such as NIST SRM 927, a bovine serum albumin (BSA). The method development was accomplished with NIST SRM 927e and a commercial avidin. The quantified mass fraction of NIST SRM 927e agreed very well with the certified value and showed similar uncertainties (3.6%) as established methods while requiring less sample preparation and no species-specific standards. Finally, the developed procedure was applied to the tau protein, which is a biomarker for a group of neurodegenerative diseases denoted “tauopathies” including, e.g., Alzheimer’s disease and frontotemporal dementia. For the absolute quantification of tau in the brain of transgenic mice overexpressing human tau, a well-defined calibration standard was needed. Therefore, a pure tau solution was quantified, yielding a protein mass fraction of (0.328 ± 0.036) g/kg, which was confirmed by amino acid analysis.
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Affiliation(s)
- Nora Lemke
- , Bundesanstalt für Materialforschung und -prüfung (BAM), Richard-Willstätter-Straße 11, 12489, Berlin, Germany.,Charité - Universitätsmedizin Berlin, Hessische Str. 3-4, 10115, Berlin, Germany
| | - Ahmed H El-Khatib
- , Bundesanstalt für Materialforschung und -prüfung (BAM), Richard-Willstätter-Straße 11, 12489, Berlin, Germany.,Department of Pharmaceutical Analytical Chemistry, Faculty of Pharmacy, Ain Shams University, Cairo, Egypt
| | - Teodor Tchipilov
- , Bundesanstalt für Materialforschung und -prüfung (BAM), Richard-Willstätter-Straße 11, 12489, Berlin, Germany
| | | | - Michael G Weller
- , Bundesanstalt für Materialforschung und -prüfung (BAM), Richard-Willstätter-Straße 11, 12489, Berlin, Germany
| | - Jochen Vogl
- , Bundesanstalt für Materialforschung und -prüfung (BAM), Richard-Willstätter-Straße 11, 12489, Berlin, Germany.
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2
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Wu X, Wei Z, Yang J, Zhang G, Long S, Wang X. Construction of solvent resistance
O‐PASS
@
UiO‐66‐NH
2
/
O‐PASS
composite membrane for methylene blue removal. J Appl Polym Sci 2022. [DOI: 10.1002/app.52332] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Xibin Wu
- College of Polymer Science and Engineering Sichuan University Chengdu China
| | - Zhimei Wei
- Institute of Materials Science and Technology, Analytical & Testing Center Sichuan University Chengdu China
- State Key Laboratory of Polymer Materials Engineering (Sichuan University) Chengdu China
| | - Jie Yang
- Institute of Materials Science and Technology, Analytical & Testing Center Sichuan University Chengdu China
- State Key Laboratory of Polymer Materials Engineering (Sichuan University) Chengdu China
| | - Gang Zhang
- Institute of Materials Science and Technology, Analytical & Testing Center Sichuan University Chengdu China
- State Key Laboratory of Polymer Materials Engineering (Sichuan University) Chengdu China
| | - Shengru Long
- Institute of Materials Science and Technology, Analytical & Testing Center Sichuan University Chengdu China
| | - Xiaojun Wang
- Institute of Materials Science and Technology, Analytical & Testing Center Sichuan University Chengdu China
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3
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Sui Y, Wollan D, McRae J, Muhlack R, Tuke J, Wilkinson K. Impact of commercial scale ultrafiltration on the composition of white and rosé wine. Sep Purif Technol 2022. [DOI: 10.1016/j.seppur.2021.120227] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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4
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Yin Z, Aggarwal S, Yeow RJE, Kong L, Chew JW. Membrane filtration of dextran solutions with water and formamide as solvent. SEP SCI TECHNOL 2021. [DOI: 10.1080/01496395.2021.1922447] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- Ziqiang Yin
- School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore, Singapore
| | - Siddharth Aggarwal
- School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore, Singapore
- Chemical Engineering Department, Indian Institute of Technology, Delhi, India
| | - Rique Jie En Yeow
- School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore, Singapore
- Singapore Membrane Technology Centre, Nanyang Environmental and Water Research Institute, Nanyang Technological University, Singapore, Singapore
| | - Lingxuan Kong
- School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore, Singapore
| | - Jia Wei Chew
- School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore, Singapore
- Singapore Membrane Technology Centre, Nanyang Environmental and Water Research Institute, Nanyang Technological University, Singapore, Singapore
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5
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Ren LF, Lin Y, Song H, Sun H, Shao J. Efficient removal of antimony from aqueous solution by sustainable polymer assisted ultrafiltration process. Sep Purif Technol 2021. [DOI: 10.1016/j.seppur.2021.118418] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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6
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Luo H, Li Y, Robbins D, Wang SC, Xi G, Cox M, Nicholson SM, Wei C, Pabst TM, Wang WK. Safety risk management for low molecular weight process-related impurities in monoclonal antibody therapeutics: Categorization, risk assessment, testing strategy, and process development with leveraging clearance potential. Biotechnol Prog 2020; 37:e3119. [PMID: 33373106 PMCID: PMC8365748 DOI: 10.1002/btpr.3119] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 12/04/2020] [Accepted: 12/20/2020] [Indexed: 11/12/2022]
Abstract
Process-related impurities (PRIs) derived from manufacturing process should be minimized in final drug product. ICH Q3A provides a regulatory road map for PRIs but excludes biologic drugs like monoclonal antibodies (mAbs) that contain biological PRIs (e.g. host cell proteins and DNA) and low molecular weight (LMW) PRIs (e.g., fermentation media components and downstream chemical reagents). Risks from the former PRIs are typically addressed by routine tests to meet regulatory expectations, while a similar routine-testing strategy is unrealistic and unnecessary for LMW PRIs, and thus a risk-assessment-guided testing strategy is often utilized. In this report, we discuss a safety risk management strategy including categorization, risk assessment, testing strategy, and its integrations with other CMC development activities, as well as downstream clearance potentials. The clearance data from 28 mAbs successfully addressed safety concerns but did not fully reveal the process clearance potentials. Therefore, we carried out studies with 13 commonly seen LMW PRIs in a typical downstream process for mAbs. Generally, Protein A chromatography and cation exchange chromatography operating in bind-and-elute mode showed excellent clearances with greater than 1,000- and 100-fold clearance, respectively. The diafiltration step had better clearance (greater than 100-fold) for the positively and neutrally charged LMW PRIs than for the negatively charged or hydrophobic PRIs. We propose that a typical mAb downstream process provides an overall clearance of 5,000-fold. Additionally, the determined sieving coefficients will facilitate diafiltration process development. This report helps establish effective safety risk management and downstream process design with robust clearance for LMW PRIs.
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Affiliation(s)
- Haibin Luo
- Purification Process Sciences, Biopharmaceutical Development Department, Biopharmaceuticals R&D, AstraZeneca, One Medimmune Way, Gaithersburg, Maryland, USA
| | - Yuling Li
- Purification Process Sciences, Biopharmaceutical Development Department, Biopharmaceuticals R&D, AstraZeneca, One Medimmune Way, Gaithersburg, Maryland, USA
| | - David Robbins
- Purification Process Sciences, Biopharmaceutical Development Department, Biopharmaceuticals R&D, AstraZeneca, One Medimmune Way, Gaithersburg, Maryland, USA
| | - Sheau-Chiann Wang
- Analytical Sciences, Biopharmaceutical Development Department, Biopharmaceuticals R&D, AstraZeneca, One Medimmune Way, Gaithersburg, Maryland, USA
| | - Guoling Xi
- Purification Process Sciences, Biopharmaceutical Development Department, Biopharmaceuticals R&D, AstraZeneca, One Medimmune Way, Gaithersburg, Maryland, USA
| | - Matthew Cox
- Purification Process Sciences, Biopharmaceutical Development Department, Biopharmaceuticals R&D, AstraZeneca, One Medimmune Way, Gaithersburg, Maryland, USA
| | - Simone M Nicholson
- Safety Science, Biopharmaceutical Development Department, Biopharmaceuticals R&D, AstraZeneca, One Medimmune Way, Gaithersburg, Maryland, USA
| | - Chenghong Wei
- Regulatory Affairs, Biopharmaceutical Development Department, Biopharmaceuticals R&D, AstraZeneca, One Medimmune Way, Gaithersburg, Maryland, USA
| | - Timothy M Pabst
- Purification Process Sciences, Biopharmaceutical Development Department, Biopharmaceuticals R&D, AstraZeneca, One Medimmune Way, Gaithersburg, Maryland, USA
| | - William K Wang
- Purification Process Sciences, Biopharmaceutical Development Department, Biopharmaceuticals R&D, AstraZeneca, One Medimmune Way, Gaithersburg, Maryland, USA
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7
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Yu Z, Moomaw JF, Thyagarajapuram NR, Geng SB, Bent CJ, Tang Y. A mechanistic model to account for the Donnan and volume exclusion effects in ultrafiltration/diafiltration process of protein formulations. Biotechnol Prog 2020; 37:e3106. [PMID: 33289341 DOI: 10.1002/btpr.3106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Revised: 11/16/2020] [Accepted: 11/24/2020] [Indexed: 11/05/2022]
Abstract
Ultrafiltration/diafiltration (UF/DF) is a typical step in protein drug manufacturing process to concentrate and exchange the protein solution into a desired formulation. However, significant offset of pH and composition from the target formulation have been frequently observed after UF/DF, posing challenges to the stability, performance, and consistency of the final drug product. Such shift can often be attributed to the Donnan and volume exclusion effects. In order to predict and compensate for those effects, a mechanistic model is developed based on the protein charge, mass and charge balances, as well as the equilibrium condition across the membrane. The integrated UF/DF model can be used to predict both the dynamic behavior and the final outcome of the process. Examples of the modeling results for the pH and composition variation during the UF/DF operations are presented for two monoclonal antibody proteins. The model predictions are in good agreement with a comprehensive experimental data set that covers different process steps, protein concentrations, solution matrices, and process scales. The results show that significant pH and excipient concentration shifts are more likely to occur for high protein concentration and low ionic strength matrices. As a special example, a self-buffering protein formulation shows unique pH behavior during DF, which could also be captured with the dynamic model. The capability of the model in predicting the performance of UF/DF process as a function of protein characteristics and formulation conditions makes it a useful tool to improve process understanding and facilitate process development.
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Affiliation(s)
- Zhao Yu
- Bioproduct Research and Development, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA
| | - John F Moomaw
- Bioproduct Research and Development, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA
| | - Nagarajan R Thyagarajapuram
- Bioproduct Research and Development, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA
| | - Steven B Geng
- Bioproduct Research and Development, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA
| | - Colin James Bent
- Bioproduct Research and Development, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA
| | - Yu Tang
- Bioproduct Research and Development, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA
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8
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Ekambaram K, Doraisamy M. Surface modification of PVDF nanofiltration membrane using Carboxymethylchitosan-Zinc oxide bionanocomposite for the removal of inorganic salts and humic acid. Colloids Surf A Physicochem Eng Asp 2017. [DOI: 10.1016/j.colsurfa.2017.04.071] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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9
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Chen X, Zhao Y, Moutinho J, Shao J, Zydney AL, He Y. Recovery of small dye molecules from aqueous solutions using charged ultrafiltration membranes. JOURNAL OF HAZARDOUS MATERIALS 2015; 284:58-64. [PMID: 25463218 DOI: 10.1016/j.jhazmat.2014.10.031] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2014] [Revised: 10/20/2014] [Accepted: 10/21/2014] [Indexed: 05/15/2023]
Abstract
Recovery of reactive dyes from effluent streams is a growing environmental challenge. In this study, various charged regenerated cellulose (RC) ultrafiltration (UF) membranes were prepared and tested for removal of three model reactive dyes (reactive red ED-2B, reactive brilliant yellow K-6G, and reactive brilliant blue KN-R). Data were obtained with charged UF membranes having different spacer arm lengths between the base cellulose and the charge functionality. The effects of charge density of the dye molecules, ionic strength of the feed solution, spacer arm length of charged membranes and filtrate flux were studied. Results indicated that dye retention was greatest with the most negatively charged dye molecule. Higher rejection was also observed in low ionic strength solutions. Results were consistent with model calculations based on the partitioning of a charged sphere into a charged cylindrical pore. The membranes with longer spacer arm length had higher rejection coefficients, consistent with the greater negative charge on these membranes. This study confirms that charged UF membranes can effectively recover small reactive dye molecules at low pressures (below 100 kPa) under appropriate solution conditions due to the strong electrostatic repulsion from the membrane pores.
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Affiliation(s)
- Xiuwen Chen
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, PR China
| | - Yiru Zhao
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, PR China
| | - Jennifer Moutinho
- Department of Chemical Engineering, Worcester Polytechnic Institute, Worcester, MA 01609, USA
| | - Jiahui Shao
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, PR China.
| | - Andrew L Zydney
- Department of Chemical Engineering, The Pennsylvania State University, University Park, PA 16802, USA
| | - Yiliang He
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, PR China
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10
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Teella A, Zydney AL, Zhou H, Olsen C, Robinson C. Effects of chemical sanitization using NaOH on the properties of polysulfone and polyethersulfone ultrafiltration membranes. Biotechnol Prog 2014; 31:90-6. [DOI: 10.1002/btpr.2008] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Revised: 10/29/2014] [Indexed: 11/07/2022]
Affiliation(s)
- Achyuta Teella
- Dept. of Chemical Engineering; The Pennsylvania State University, University Park; PA 16802
| | - Andrew L. Zydney
- Dept. of Chemical Engineering; The Pennsylvania State University, University Park; PA 16802
| | - Hongyi Zhou
- Membrane and Separation Technologies; GE Global Research; Niskayuna NY 12309
| | - Cathryn Olsen
- Membrane and Separation Technologies; GE Global Research; Niskayuna NY 12309
| | - Craig Robinson
- GE Healthcare Life Sciences; Research and Development; Westborough MA 01581
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11
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Void exclusion of antibodies by grafted-ligand porous particle anion exchangers. J Chromatogr A 2013; 1282:127-32. [DOI: 10.1016/j.chroma.2013.01.065] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2012] [Revised: 01/15/2013] [Accepted: 01/15/2013] [Indexed: 11/19/2022]
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12
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Bolton GR, Boesch AW, Basha J, LaCasse DP, Kelley BD, Acharya H. Effect of protein and solution properties on the donnan effect during the ultrafiltration of proteins. Biotechnol Prog 2010; 27:140-52. [DOI: 10.1002/btpr.523] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2010] [Revised: 08/16/2010] [Indexed: 11/08/2022]
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13
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Bhushan S, Etzel M. Charged Ultrafiltration Membranes Increase the Selectivity of Whey Protein Separations. J Food Sci 2009; 74:E131-9. [DOI: 10.1111/j.1750-3841.2009.01095.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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14
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Bartlett DW, Colcher D, Raubitschek AA. Rapid and efficient production of radiolabeled antibody conjugates using vacuum diafiltration guided by mathematical modeling. Bioconjug Chem 2008; 19:1927-37. [PMID: 18720981 DOI: 10.1021/bc800223x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Increasing interest in the use of radiolabeled antibodies for cancer imaging and therapy drives the need for more efficient production of the antibody conjugates. Here, we illustrate a method for rapid and efficient production of radiolabeled antibody conjugates using vacuum diafiltration guided by mathematical modeling. We apply this technique to the production of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-conjugated antibodies at the milligram and gram production scale and achieve radiolabeling efficiencies >95% using In-111. Using vacuum diafiltration, antibody-chelate conjugation and purification can be accomplished within the same vessel, and the entire process can be completed in <24 h. Vacuum diafiltration also offers safer and gentler processing conditions by eliminating the need to keep the retentate vessel under positive pressure through applied gas pressure or shear-inducing restriction points in the retentate flow path. Experimental data and mathematical model calculations suggest there exists a weak binding affinity (approximately 10(4)M(-1)) between the charged chelate molecules (e.g., DOTA) and the antibodies that slows the removal of excess chelate during purification. By analyzing the radiolabeling efficiency as a function of the number of diavolumes, we demonstrate the importance of balancing the removal of free chelate with the introduction of metal contaminants from the diafiltration buffer and also illustrate how to optimize radiolabeling of antibody conjugates under a variety of operating conditions. This methodology is applicable to the production of antibody conjugates in general.
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Affiliation(s)
- Derek W Bartlett
- Division of Cancer Immunotherapeutics & Tumor Immunology, Beckman Research Institute and City of Hope National Medical Center, Duarte, California 91010, USA
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15
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Rao S, Zydney AL. High resolution protein separations using affinity ultrafiltration with small charged ligands. J Memb Sci 2006. [DOI: 10.1016/j.memsci.2006.02.035] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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16
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Shaffer JF, Zydney AL. Phosphate clearance for bleach reprocessed polysulfone hemodialyzers: effects of electrostatic interactions. ASAIO J 2005; 51:748-53. [PMID: 16340362 DOI: 10.1097/01.mat.0000185569.27103.88] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Hyperphosphatemia is a major problem for hemodialysis patients due to inadequate phosphate clearance during dialysis. The objective of this study was to understand the effects of bleach reprocessing on phosphate clearance. Data were obtained using Fresenius polysulfone dialyzers exposed to bleach in an in vitro dialysis. The phosphate clearance decreased slightly after a single reprocessing cycle, with more than a 10% reduction observed after 15 cycles. Streaming potential measurements showed that bleach reprocessing caused an increase in the negative charge on the polysulfone membrane, suggesting that the change in phosphate clearance was due to an increase in electrostatic repulsion. The changes in clearance and surface charge were consistent with theoretical calculations of the effects of electrostatic interactions on solute diffusion. These results provide the first evidence that bleach reprocessing can reduce phosphate clearance due to electrostatic interactions between the phosphate anion and negatively charged dialysis membranes.
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Affiliation(s)
- Justin F Shaffer
- Department of Chemical Engineering, The Pennsylvania State University, University Park, PA 16802, USA
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17
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Rao S, Zydney AL. Controlling protein transport in ultrafiltration using small charged ligands. Biotechnol Bioeng 2005; 91:733-42. [PMID: 15895379 DOI: 10.1002/bit.20543] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Previous studies have demonstrated that protein transport during ultrafiltration can be strongly influenced by solution pH and ionic strength. The objective of this study was to examine the possibility of controlling protein transmission using a small, highly charged ligand that selectively binds to the protein of interest. Experiments were performed using bovine serum albumin and the dye Cibacron Blue. Protein sieving data were obtained with essentially neutral and negatively charged versions of a composite regenerated cellulose membrane to examine the effects of electrostatic interactions. The addition of only 1 g/L of Cibacron Blue to an 8 g/L BSA solution reduced the BSA sieving coefficient through the negatively-charged membrane by more than two orders of magnitude, with this effect being largely eliminated at high salt and with the neutral membrane. Protein sieving data were in good agreement with model calculations based on the partitioning of a charged sphere in a charged pore accounting for the change in net protein charge due to ligand binding and the increase in solution ionic strength due to the free ligand in solution.
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Affiliation(s)
- Suma Rao
- Department of Chemical Engineering, The Pennsylvania State University, University Park, PA 16802, USA
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