Ruben Carbonell - Academia.edu (original) (raw)

Papers by Ruben Carbonell

Research paper thumbnail of Purification of Adeno-Associated Virus (AAV) Serotype 2 from Spodoptera frugiperda (Sf9) Lysate by Chromatographic Nonwoven Membranes

Membranes

The success of adeno-associated virus (AAV)-based therapeutics in gene therapy poses the need for... more The success of adeno-associated virus (AAV)-based therapeutics in gene therapy poses the need for rapid and efficient processes that can support the growing clinical demand. Nonwoven membranes represent an ideal tool for the future of virus purification: owing to their small fiber diameters and high porosity, they can operate at high flowrates while allowing full access to target viral particles without diffusional limitations. This study describes the development of nonwoven ion-exchange membrane adsorbents for the purification of AAV2 from an Sf9 cell lysate. A strong anion-exchange (AEX) membrane was developed by UV grafting glycidyl methacrylate on a polybutylene terephthalate nonwoven followed by functionalization with triethylamine (TEA), resulting in a quaternary amine ligand (AEX-TEA membrane). When operated in bind-and-elute mode at a pH higher than the pI of the capsids, this membrane exhibited a high AAV2 binding capacity (9.6 × 1013 vp·mL−1) at the residence time of 1 mi...

Research paper thumbnail of A Course in Transport Phenomena in Multicomponent, Multiphase, Reacting Systems

Most of the systems that are of interests to chemical engineers involve two or more phases, sever... more Most of the systems that are of interests to chemical engineers involve two or more phases, several chemical components, and a strong coupling between heat, mass and momentum transport. A survey of current training of graduate students in chemical engineering reveals the need for a rigorous treatment of multi-component, multi-phase systems. This paper suggests an approach to the rigorous analysis of multiphase systems.

Research paper thumbnail of The hydrodynamics of trickling flow in packed beds. Part II: Experimental observations

AIChE Journal, 1986

The hydrodynamics of trickling flow in packed beds is modeled by representing the porous medium a... more The hydrodynamics of trickling flow in packed beds is modeled by representing the porous medium as an array of parallel conduits of circular cross section. First, a straight tube model is developed and analytical solutions are obtained for the relative permeabilities of the gas and liquid phases. Then a periodically constricted tube model is proposed and the equations of motion are solved numerically t o determine the effect that surface tension forces have on the relative permeabilities. The constricted tube model predicts that the relative permeabilities of the phases are appreciably sensitive to surface tension forces, a prediction that seems at odds with experimental observations. This discrepancy may be caused by the assumption of fully wetted surface area of particles employed in the model. The straight tube model confirms experimental results indicating that the liquid phase relative permeability is, for practical purposes, insensitive to the gas flow rate and to the gas-to-liquid density and viscosity ratios. Both conduit models show that the gas phase relative permeability curves are strong functions of the gas phase Reynolds number when this parameter is small. For large gas Reynolds numbers, a single curve for the relative permeability as a function of saturation is obtained. These trends are observed in previous experimental studies.

Research paper thumbnail of Nonequilibrium Model for Sorption and Swelling of Bulk Glassy Polymer Films with Supercritical Carbon Dioxide

Macromolecules, 2005

A new procedure is introduced for the calculation of solubility isotherms of plasticizing agents ... more A new procedure is introduced for the calculation of solubility isotherms of plasticizing agents in glassy polymer matrices with particular application to the case of absorption of supercritical gases in bulk glassy polymer films. The model presented is an extension of the nonequilibrium thermodynamics for glassy polymers (NET-GP) approach, modified to allow for the calculation of the effects of pressure, temperature, and gas concentration on the glass transition. Mass sorption and onedimensional swelling behavior are analyzed for the carbon dioxide (CO 2)-poly(methyl methacrylate) (PMMA) system at high pressure. A quantitative comparison is presented between the model performance and experimental data measured using quartz crystal microbalance (QCM) and high-pressure ellipsometry (HPE).

Research paper thumbnail of Interfacial Effects and the Anomalous Swelling Behavior of Supported Polymer Thin Films in Supercritical Carbon Dioxide

The 2006 Annual Meeting, 2006

ABSTRACT: This work investigates the effects of temperature, initial thickness and material subst... more ABSTRACT: This work investigates the effects of temperature, initial thickness and material substrate upon sorption and consequent dilation of thin supported polymeric films in supercritical carbon dioxide. High-Pressure Quartz Crystal Microbalance measurements demonstrate that there is an Excess Gibbs Adsorption of carbon dioxide at the polymer/substrate interface, which strongly depends upon temperature, pressure and nature of the solid substrate. This accumulation of carbon dioxide at the submerged surface can ...

Research paper thumbnail of A theory of diffusion and reaction in porous media

Research paper thumbnail of Kinetic Behavior of Microencapsulated ?-Galactosidase

Biotechnology and Bioengineering, 1975

Escherichia coli beta-D-galactosidase (E.C. 3.2.1.23) was immobilized in cellulose nitrate membra... more Escherichia coli beta-D-galactosidase (E.C. 3.2.1.23) was immobilized in cellulose nitrate membrane microcapsules and the reaction kinetics with o-nitrophenyl-beta-D-galactopyranoside (ONPG), lactose, and whole milk were studied using both continuous stirred tank and packed bed reactor configurations. The results of the experiments gave effectiveness factors of 0.3 for ONPG, 0.6 to 0.7 for lactose in solution, and close to unity for lactose in milk. Using a coupled mass transfer and kinetic model, it was possible to estimate the permeability of the microcapsule membrane from the reactor data. Membrane permeabilities on the order of 5 X 10(-3) and 3 X 10(-4) cm/sec were estimated for ONPG and lactose, respectively. It was determined that the membrane was the limiting mass transfer resistance for the overall reaction. The analysis showed that within the microcapsule, the reaction is reaction rate limited for lactose and slightly diffusion limited for ONPG.

Research paper thumbnail of Alkaline-Stable Chromatographic Resins

Research paper thumbnail of Design of protease-resistant peptide ligands for the purification of antibodies from human plasma

Journal of Chromatography A, 2016

A strategy is presented for developing variants of peptide ligands with enhanced biochemical stab... more A strategy is presented for developing variants of peptide ligands with enhanced biochemical stability for the purification of antibodies from animal sera. Antibody-binding sequences HWRGWV, HYFKFD, and HFRRHL, previously discovered by our group, were modified with non-natural amino acids to gain resistance to proteolysis, while maintaining target affinity and selectivity. As trypsin and α-chymotrypsin were chosen as models of natural proteolytic enzymes, the basic (arginine and lysine) and aromatic (tryptophan, phenylalanine, and tyrosine) amino acids were replaced with non-natural analogs. Using the docking software HADDOCK, a virtual library of peptide variants was designed and screened in-silico against the known HWRGWV binding site on the pFc fragment of IgG. A pool of selected sequences with the highest predicted free energy of binding was synthesized on chromatographic resin, and the resulting adsorbents were tested for IgG binding and resistance to proteases. The ligand variants exhibited binding capacities and specificities comparable to the original sequences, yet with much higher proteolytic resistances. The sequences HWMetCitGWMetV and HFMetCitCitHL was used for purifying polyclonal IgG from IgG-rich fractions of human plasma, with yields and purity above 90%. Notably, due to electrical neutrality, the variant showed higher selectivity than the original sequence. Binding isotherms were also constructed, which confirmed the docking predictions. This method represents a general strategy for enhancing the biochemical stability as well as the affinity and selectivity of natural or synthetic peptide ligands for bioseparations.

Research paper thumbnail of Mechanisms of Particle Deposition from Ultrapure Chemicals onto Semiconductor Wafers: Deposition from Bulk Liquid during Wafer Submersion

Journal of Colloid and Interface Science, 1993

Abstract The liquid-based deposition of inorganic particles onto semiconductor silicon wafers wit... more Abstract The liquid-based deposition of inorganic particles onto semiconductor silicon wafers with a native oxide layer has been investigated experimentally by exposing wafers to a variety of sample contaminants in stirred aqueous solutions. Test results clearly demonstrate the importance of electrostatic wafer/particle interactions in cleanroom-liquid particle deposition. A simple theoretical model based on Derjaguin-Laundau-Verwey-Overbeek (DLVO) theory and hydrodynamic boundary layer resistances has been found to successfully predict the observed wafer contamination levels. While deposition from bulk deionized (DI) water is often absent when an electrostatic repulsion exists between the wafer surface and the contaminant, dramatic particle contamination can occur if the forces are attractive. The solution ionic strength and the particle diameter have a controlling influence on deposition levels. The model predicts that as device dimensions shrink, it will be increasingly difficult to control wafer surface contamination by smaller particles.

Research paper thumbnail of Spin Coating of Photoresists Using Liquid Carbon Dioxide

Industrial & Engineering Chemistry Research, 2004

A novel high-pressure carbon dioxide (CO2) spin-coating apparatus was designed and constructed to... more A novel high-pressure carbon dioxide (CO2) spin-coating apparatus was designed and constructed to produce high-quality thin films of CO2-soluble photoresists based on 1H,1H-perfluorooctyl methacrylate/tert-butyl methacrylate copolymers. Film thicknesses were correlated to various process variables including rotational speed, solution viscosity, and evaporative driving force. The effects of these operating conditions on the film thickness and uniformity were compared to those of a theoretical model adapted for spin coating in CO2. Excellent correlation was found between the theoretical predictions and observed film properties, with the final films being of sufficient quality for use in photolithography. The potential of this spin-coating process in CO2 for developing a novel “dry lithography” is discussed.

Research paper thumbnail of Iminodiacetic Acid (IDA) Cation-Exchange Nonwoven Membranes for Efficient Capture of Antibodies and Antibody Fragments

Membranes, 2021

There is strong need to reduce the manufacturing costs and increase the downstream purification e... more There is strong need to reduce the manufacturing costs and increase the downstream purification efficiency of high-value therapeutic monoclonal antibodies (mAbs). This paper explores the performance of a weak cation-exchange membrane based on the coupling of IDA to poly(butylene terephthalate) (PBT) nonwoven fabrics. Uniform and conformal layers of poly(glycidyl methacrylate) (GMA) were first grafted to the surface of the nonwovens. Then IDA was coupled to the polyGMA layers under optimized conditions, resulting in membranes with very high permeability and binding capacity. This resulted in IgG dynamic binding capacities at very short residence times (0.1–2.0 min) that are much higher than those achieved by the best cation-exchange resins. Similar results were obtained in the purification of a single-chain (scFv) antibody fragment. As is customary with membrane systems, the dynamic binding capacities did not change significantly over a wide range of residence times. Finally, the exc...

Research paper thumbnail of End‐to‐end collaboration to transform biopharmaceutical development and manufacturing

Biotechnology and Bioengineering

Research paper thumbnail of Nonwoven Ion-Exchange Membranes with High Protein Binding Capacity for Bioseparations

Membranes

This study presents the preparation and characterization of UV-grafted polybutylene terepthalate ... more This study presents the preparation and characterization of UV-grafted polybutylene terepthalate (PBT) ion exchange nonwoven membranes for chromatographic purification of biomolecules. The PBT nonwoven was functionalized with sulfonate and secondary amine for cation and anion exchange (CEX and AEX), respectively. The anion exchange membrane showed an equilibrium static binding capacity of 1300 mg BSA/g of membrane, while the cationic membranes achieved a maximum equilibrium binding capacity of over 700 mg hIgG/g of membrane. The CEX and AEX membranes resulted in dynamic binding capacities under flow conditions, with a residence time of 0.1 min, of 200 mg hIgG/mL of membrane and 55 mg BSA/mL of membrane, respectively. The selectivity of the PBT-CEX membranes was demonstrated by purifying antibodies and antibody fragments (hIgG and scFv) from CHO cell culture supernatants in a bind-an-elute mode. The purity of the eluted samples exceeded 97%, with good log removal values (LRV) for bot...

Research paper thumbnail of Targeted Capture of Chinese Hamster Ovary Host Cell Proteins: Peptide Ligand Binding by Proteomic Analysis

Biotechnology and Bioengineering

Research paper thumbnail of Targeted Capture of Chinese Hamster Ovary Host Cell Proteins: Peptide Ligand Discovery

International Journal of Molecular Sciences

The growing integration of quality-by-design (QbD) concepts in biomanufacturing calls for a detai... more The growing integration of quality-by-design (QbD) concepts in biomanufacturing calls for a detailed and quantitative knowledge of the profile of impurities and their impact on the product safety and efficacy. Particularly valuable is the determination of the residual level of host cell proteins (HCPs) secreted, together with the product of interest, by the recombinant cells utilized for production. Though often referred to as a single impurity, HCPs comprise a variety of species with diverse abundance, size, function, and composition. The clearance of these impurities is a complex issue due to their cell line to cell line, product-to-product, and batch-to-batch variations. Improvements in HCP monitoring through proteomic-based methods have led to identification of a subset of “problematic” HCPs that are particularly challenging to remove, both at the product capture and product polishing steps, and compromise product stability and safety even at trace concentrations. This paper des...

Research paper thumbnail of Silica resins and peptide ligands to develop disposable affinity adsorbents for antibody purification

Biochemical Engineering Journal

Research paper thumbnail of Optimization of Sequence, Display, and Mode of Operation of IgG-Binding Peptide Ligands to Develop Robust, High-Capacity Affinity Adsorbents That Afford High IgG Product Quality

International Journal of Molecular Sciences

This work presents the use of peptide ligand HWRGWV and its cognate sequences to develop affinity... more This work presents the use of peptide ligand HWRGWV and its cognate sequences to develop affinity adsorbents that compete with Protein A in terms of binding capacity and quality of the eluted product. First, the peptide ligand was conjugated to crosslinked agarose resins (WorkBeads) at different densities and using different spacer arms. The optimization of ligand density and display resulted in values of static and dynamic binding capacity of 85 mg/mL and 65 mg/mL, respectively. A selected peptide-WorkBeads adsorbent was utilized for purifying Mabs from Chinese Hamster Ovary (CHO) cell culture supernatants. The peptide-WorkBeads adsorbent was found able to withstand sanitization with strong alkaline solutions (0.5 M NaOH). The purity of the eluted product was consistently higher than 95%, with logarithmic removal value (LRV) of 1.5 for host cell proteins (HCPs) and 4.0 for DNA. HCP clearance was significantly improved by adding a post-load washing step with either 0.1 M Tris HCl pH...

Research paper thumbnail of Longitudinal and lateral thermal dispersion in packed beds. I: Theory

Aiche Journal, 1985

A new model is developed for the transient thermal response of a packed bed. using the method of ... more A new model is developed for the transient thermal response of a packed bed. using the method of spatial averaging. Equations for the average temperature of the fluid and the solid phase are derived from the point equations for thermal energy in each phase. The new model exhibits some unusual convective and dispersive coupling between the equations for the average fluid and solid temperatures. The response of the model equations to a pulse disturbance is analyzed. It is found that after a sufficiently long time has elapsed, the temperature pulses for the fluid and solid phases will be separated by a constant distance and will spread or disperse about their centroids at an equal rate. The pulse separation predicted by the new model equations is larger than that predicted using more conventional analyses of heat transfer in packed beds. Effective thermal conductivities measured under steady state conditions can differ significantly from those observed in transient experiments due to the spread in temperature pulses caused by heat exchange between phases. Estimates are made of the magnitude of the more important terms affecting longitudinal and lateral effective thermal conductivities under flow conditions, in order to make possible a direct comparison between theory and experiment in a companion paper.

Research paper thumbnail of Transport and fate of reactive trace gases in red spruce needles. 2. Interpretations of flux experiments using gas transport theory

Environ Sci Technol, 1993

A mathematical description of the multicomponent transport of gaseous species into needles of con... more A mathematical description of the multicomponent transport of gaseous species into needles of conifer trees is presented. Detailed physiology of the stomatal zone is taken into account, and diffusion through the atmospheric boundary layer, wax-filled antechamber, stomata, and substomatal cavity are described starting from the fundamental equations for multicomponent gas diffusion. The model was used to analyze the results from two sets of exposure experiments in which red spruce saplings were exposed to gas-phase H202 or to a combination of H202, S02, and 03. Model calculations indicate that the waxfilled antechamber may provide a porous zone in which water can condense, thus protecting the sensitive inner tissues below the stomata from exposure to water-soluble, toxic, trace gases (such as SO2 and H202). The model was found to be sensitive to the accuracy of measurements of leaf temperature, dewpoint temperature of the chamber inlet and exit air, and gas flow rate and may provide some insight into the role of atmospheric pollutants in forest decline.

Research paper thumbnail of Purification of Adeno-Associated Virus (AAV) Serotype 2 from Spodoptera frugiperda (Sf9) Lysate by Chromatographic Nonwoven Membranes

Membranes

The success of adeno-associated virus (AAV)-based therapeutics in gene therapy poses the need for... more The success of adeno-associated virus (AAV)-based therapeutics in gene therapy poses the need for rapid and efficient processes that can support the growing clinical demand. Nonwoven membranes represent an ideal tool for the future of virus purification: owing to their small fiber diameters and high porosity, they can operate at high flowrates while allowing full access to target viral particles without diffusional limitations. This study describes the development of nonwoven ion-exchange membrane adsorbents for the purification of AAV2 from an Sf9 cell lysate. A strong anion-exchange (AEX) membrane was developed by UV grafting glycidyl methacrylate on a polybutylene terephthalate nonwoven followed by functionalization with triethylamine (TEA), resulting in a quaternary amine ligand (AEX-TEA membrane). When operated in bind-and-elute mode at a pH higher than the pI of the capsids, this membrane exhibited a high AAV2 binding capacity (9.6 × 1013 vp·mL−1) at the residence time of 1 mi...

Research paper thumbnail of A Course in Transport Phenomena in Multicomponent, Multiphase, Reacting Systems

Most of the systems that are of interests to chemical engineers involve two or more phases, sever... more Most of the systems that are of interests to chemical engineers involve two or more phases, several chemical components, and a strong coupling between heat, mass and momentum transport. A survey of current training of graduate students in chemical engineering reveals the need for a rigorous treatment of multi-component, multi-phase systems. This paper suggests an approach to the rigorous analysis of multiphase systems.

Research paper thumbnail of The hydrodynamics of trickling flow in packed beds. Part II: Experimental observations

AIChE Journal, 1986

The hydrodynamics of trickling flow in packed beds is modeled by representing the porous medium a... more The hydrodynamics of trickling flow in packed beds is modeled by representing the porous medium as an array of parallel conduits of circular cross section. First, a straight tube model is developed and analytical solutions are obtained for the relative permeabilities of the gas and liquid phases. Then a periodically constricted tube model is proposed and the equations of motion are solved numerically t o determine the effect that surface tension forces have on the relative permeabilities. The constricted tube model predicts that the relative permeabilities of the phases are appreciably sensitive to surface tension forces, a prediction that seems at odds with experimental observations. This discrepancy may be caused by the assumption of fully wetted surface area of particles employed in the model. The straight tube model confirms experimental results indicating that the liquid phase relative permeability is, for practical purposes, insensitive to the gas flow rate and to the gas-to-liquid density and viscosity ratios. Both conduit models show that the gas phase relative permeability curves are strong functions of the gas phase Reynolds number when this parameter is small. For large gas Reynolds numbers, a single curve for the relative permeability as a function of saturation is obtained. These trends are observed in previous experimental studies.

Research paper thumbnail of Nonequilibrium Model for Sorption and Swelling of Bulk Glassy Polymer Films with Supercritical Carbon Dioxide

Macromolecules, 2005

A new procedure is introduced for the calculation of solubility isotherms of plasticizing agents ... more A new procedure is introduced for the calculation of solubility isotherms of plasticizing agents in glassy polymer matrices with particular application to the case of absorption of supercritical gases in bulk glassy polymer films. The model presented is an extension of the nonequilibrium thermodynamics for glassy polymers (NET-GP) approach, modified to allow for the calculation of the effects of pressure, temperature, and gas concentration on the glass transition. Mass sorption and onedimensional swelling behavior are analyzed for the carbon dioxide (CO 2)-poly(methyl methacrylate) (PMMA) system at high pressure. A quantitative comparison is presented between the model performance and experimental data measured using quartz crystal microbalance (QCM) and high-pressure ellipsometry (HPE).

Research paper thumbnail of Interfacial Effects and the Anomalous Swelling Behavior of Supported Polymer Thin Films in Supercritical Carbon Dioxide

The 2006 Annual Meeting, 2006

ABSTRACT: This work investigates the effects of temperature, initial thickness and material subst... more ABSTRACT: This work investigates the effects of temperature, initial thickness and material substrate upon sorption and consequent dilation of thin supported polymeric films in supercritical carbon dioxide. High-Pressure Quartz Crystal Microbalance measurements demonstrate that there is an Excess Gibbs Adsorption of carbon dioxide at the polymer/substrate interface, which strongly depends upon temperature, pressure and nature of the solid substrate. This accumulation of carbon dioxide at the submerged surface can ...

Research paper thumbnail of A theory of diffusion and reaction in porous media

Research paper thumbnail of Kinetic Behavior of Microencapsulated ?-Galactosidase

Biotechnology and Bioengineering, 1975

Escherichia coli beta-D-galactosidase (E.C. 3.2.1.23) was immobilized in cellulose nitrate membra... more Escherichia coli beta-D-galactosidase (E.C. 3.2.1.23) was immobilized in cellulose nitrate membrane microcapsules and the reaction kinetics with o-nitrophenyl-beta-D-galactopyranoside (ONPG), lactose, and whole milk were studied using both continuous stirred tank and packed bed reactor configurations. The results of the experiments gave effectiveness factors of 0.3 for ONPG, 0.6 to 0.7 for lactose in solution, and close to unity for lactose in milk. Using a coupled mass transfer and kinetic model, it was possible to estimate the permeability of the microcapsule membrane from the reactor data. Membrane permeabilities on the order of 5 X 10(-3) and 3 X 10(-4) cm/sec were estimated for ONPG and lactose, respectively. It was determined that the membrane was the limiting mass transfer resistance for the overall reaction. The analysis showed that within the microcapsule, the reaction is reaction rate limited for lactose and slightly diffusion limited for ONPG.

Research paper thumbnail of Alkaline-Stable Chromatographic Resins

Research paper thumbnail of Design of protease-resistant peptide ligands for the purification of antibodies from human plasma

Journal of Chromatography A, 2016

A strategy is presented for developing variants of peptide ligands with enhanced biochemical stab... more A strategy is presented for developing variants of peptide ligands with enhanced biochemical stability for the purification of antibodies from animal sera. Antibody-binding sequences HWRGWV, HYFKFD, and HFRRHL, previously discovered by our group, were modified with non-natural amino acids to gain resistance to proteolysis, while maintaining target affinity and selectivity. As trypsin and α-chymotrypsin were chosen as models of natural proteolytic enzymes, the basic (arginine and lysine) and aromatic (tryptophan, phenylalanine, and tyrosine) amino acids were replaced with non-natural analogs. Using the docking software HADDOCK, a virtual library of peptide variants was designed and screened in-silico against the known HWRGWV binding site on the pFc fragment of IgG. A pool of selected sequences with the highest predicted free energy of binding was synthesized on chromatographic resin, and the resulting adsorbents were tested for IgG binding and resistance to proteases. The ligand variants exhibited binding capacities and specificities comparable to the original sequences, yet with much higher proteolytic resistances. The sequences HWMetCitGWMetV and HFMetCitCitHL was used for purifying polyclonal IgG from IgG-rich fractions of human plasma, with yields and purity above 90%. Notably, due to electrical neutrality, the variant showed higher selectivity than the original sequence. Binding isotherms were also constructed, which confirmed the docking predictions. This method represents a general strategy for enhancing the biochemical stability as well as the affinity and selectivity of natural or synthetic peptide ligands for bioseparations.

Research paper thumbnail of Mechanisms of Particle Deposition from Ultrapure Chemicals onto Semiconductor Wafers: Deposition from Bulk Liquid during Wafer Submersion

Journal of Colloid and Interface Science, 1993

Abstract The liquid-based deposition of inorganic particles onto semiconductor silicon wafers wit... more Abstract The liquid-based deposition of inorganic particles onto semiconductor silicon wafers with a native oxide layer has been investigated experimentally by exposing wafers to a variety of sample contaminants in stirred aqueous solutions. Test results clearly demonstrate the importance of electrostatic wafer/particle interactions in cleanroom-liquid particle deposition. A simple theoretical model based on Derjaguin-Laundau-Verwey-Overbeek (DLVO) theory and hydrodynamic boundary layer resistances has been found to successfully predict the observed wafer contamination levels. While deposition from bulk deionized (DI) water is often absent when an electrostatic repulsion exists between the wafer surface and the contaminant, dramatic particle contamination can occur if the forces are attractive. The solution ionic strength and the particle diameter have a controlling influence on deposition levels. The model predicts that as device dimensions shrink, it will be increasingly difficult to control wafer surface contamination by smaller particles.

Research paper thumbnail of Spin Coating of Photoresists Using Liquid Carbon Dioxide

Industrial & Engineering Chemistry Research, 2004

A novel high-pressure carbon dioxide (CO2) spin-coating apparatus was designed and constructed to... more A novel high-pressure carbon dioxide (CO2) spin-coating apparatus was designed and constructed to produce high-quality thin films of CO2-soluble photoresists based on 1H,1H-perfluorooctyl methacrylate/tert-butyl methacrylate copolymers. Film thicknesses were correlated to various process variables including rotational speed, solution viscosity, and evaporative driving force. The effects of these operating conditions on the film thickness and uniformity were compared to those of a theoretical model adapted for spin coating in CO2. Excellent correlation was found between the theoretical predictions and observed film properties, with the final films being of sufficient quality for use in photolithography. The potential of this spin-coating process in CO2 for developing a novel “dry lithography” is discussed.

Research paper thumbnail of Iminodiacetic Acid (IDA) Cation-Exchange Nonwoven Membranes for Efficient Capture of Antibodies and Antibody Fragments

Membranes, 2021

There is strong need to reduce the manufacturing costs and increase the downstream purification e... more There is strong need to reduce the manufacturing costs and increase the downstream purification efficiency of high-value therapeutic monoclonal antibodies (mAbs). This paper explores the performance of a weak cation-exchange membrane based on the coupling of IDA to poly(butylene terephthalate) (PBT) nonwoven fabrics. Uniform and conformal layers of poly(glycidyl methacrylate) (GMA) were first grafted to the surface of the nonwovens. Then IDA was coupled to the polyGMA layers under optimized conditions, resulting in membranes with very high permeability and binding capacity. This resulted in IgG dynamic binding capacities at very short residence times (0.1–2.0 min) that are much higher than those achieved by the best cation-exchange resins. Similar results were obtained in the purification of a single-chain (scFv) antibody fragment. As is customary with membrane systems, the dynamic binding capacities did not change significantly over a wide range of residence times. Finally, the exc...

Research paper thumbnail of End‐to‐end collaboration to transform biopharmaceutical development and manufacturing

Biotechnology and Bioengineering

Research paper thumbnail of Nonwoven Ion-Exchange Membranes with High Protein Binding Capacity for Bioseparations

Membranes

This study presents the preparation and characterization of UV-grafted polybutylene terepthalate ... more This study presents the preparation and characterization of UV-grafted polybutylene terepthalate (PBT) ion exchange nonwoven membranes for chromatographic purification of biomolecules. The PBT nonwoven was functionalized with sulfonate and secondary amine for cation and anion exchange (CEX and AEX), respectively. The anion exchange membrane showed an equilibrium static binding capacity of 1300 mg BSA/g of membrane, while the cationic membranes achieved a maximum equilibrium binding capacity of over 700 mg hIgG/g of membrane. The CEX and AEX membranes resulted in dynamic binding capacities under flow conditions, with a residence time of 0.1 min, of 200 mg hIgG/mL of membrane and 55 mg BSA/mL of membrane, respectively. The selectivity of the PBT-CEX membranes was demonstrated by purifying antibodies and antibody fragments (hIgG and scFv) from CHO cell culture supernatants in a bind-an-elute mode. The purity of the eluted samples exceeded 97%, with good log removal values (LRV) for bot...

Research paper thumbnail of Targeted Capture of Chinese Hamster Ovary Host Cell Proteins: Peptide Ligand Binding by Proteomic Analysis

Biotechnology and Bioengineering

Research paper thumbnail of Targeted Capture of Chinese Hamster Ovary Host Cell Proteins: Peptide Ligand Discovery

International Journal of Molecular Sciences

The growing integration of quality-by-design (QbD) concepts in biomanufacturing calls for a detai... more The growing integration of quality-by-design (QbD) concepts in biomanufacturing calls for a detailed and quantitative knowledge of the profile of impurities and their impact on the product safety and efficacy. Particularly valuable is the determination of the residual level of host cell proteins (HCPs) secreted, together with the product of interest, by the recombinant cells utilized for production. Though often referred to as a single impurity, HCPs comprise a variety of species with diverse abundance, size, function, and composition. The clearance of these impurities is a complex issue due to their cell line to cell line, product-to-product, and batch-to-batch variations. Improvements in HCP monitoring through proteomic-based methods have led to identification of a subset of “problematic” HCPs that are particularly challenging to remove, both at the product capture and product polishing steps, and compromise product stability and safety even at trace concentrations. This paper des...

Research paper thumbnail of Silica resins and peptide ligands to develop disposable affinity adsorbents for antibody purification

Biochemical Engineering Journal

Research paper thumbnail of Optimization of Sequence, Display, and Mode of Operation of IgG-Binding Peptide Ligands to Develop Robust, High-Capacity Affinity Adsorbents That Afford High IgG Product Quality

International Journal of Molecular Sciences

This work presents the use of peptide ligand HWRGWV and its cognate sequences to develop affinity... more This work presents the use of peptide ligand HWRGWV and its cognate sequences to develop affinity adsorbents that compete with Protein A in terms of binding capacity and quality of the eluted product. First, the peptide ligand was conjugated to crosslinked agarose resins (WorkBeads) at different densities and using different spacer arms. The optimization of ligand density and display resulted in values of static and dynamic binding capacity of 85 mg/mL and 65 mg/mL, respectively. A selected peptide-WorkBeads adsorbent was utilized for purifying Mabs from Chinese Hamster Ovary (CHO) cell culture supernatants. The peptide-WorkBeads adsorbent was found able to withstand sanitization with strong alkaline solutions (0.5 M NaOH). The purity of the eluted product was consistently higher than 95%, with logarithmic removal value (LRV) of 1.5 for host cell proteins (HCPs) and 4.0 for DNA. HCP clearance was significantly improved by adding a post-load washing step with either 0.1 M Tris HCl pH...

Research paper thumbnail of Longitudinal and lateral thermal dispersion in packed beds. I: Theory

Aiche Journal, 1985

A new model is developed for the transient thermal response of a packed bed. using the method of ... more A new model is developed for the transient thermal response of a packed bed. using the method of spatial averaging. Equations for the average temperature of the fluid and the solid phase are derived from the point equations for thermal energy in each phase. The new model exhibits some unusual convective and dispersive coupling between the equations for the average fluid and solid temperatures. The response of the model equations to a pulse disturbance is analyzed. It is found that after a sufficiently long time has elapsed, the temperature pulses for the fluid and solid phases will be separated by a constant distance and will spread or disperse about their centroids at an equal rate. The pulse separation predicted by the new model equations is larger than that predicted using more conventional analyses of heat transfer in packed beds. Effective thermal conductivities measured under steady state conditions can differ significantly from those observed in transient experiments due to the spread in temperature pulses caused by heat exchange between phases. Estimates are made of the magnitude of the more important terms affecting longitudinal and lateral effective thermal conductivities under flow conditions, in order to make possible a direct comparison between theory and experiment in a companion paper.

Research paper thumbnail of Transport and fate of reactive trace gases in red spruce needles. 2. Interpretations of flux experiments using gas transport theory

Environ Sci Technol, 1993

A mathematical description of the multicomponent transport of gaseous species into needles of con... more A mathematical description of the multicomponent transport of gaseous species into needles of conifer trees is presented. Detailed physiology of the stomatal zone is taken into account, and diffusion through the atmospheric boundary layer, wax-filled antechamber, stomata, and substomatal cavity are described starting from the fundamental equations for multicomponent gas diffusion. The model was used to analyze the results from two sets of exposure experiments in which red spruce saplings were exposed to gas-phase H202 or to a combination of H202, S02, and 03. Model calculations indicate that the waxfilled antechamber may provide a porous zone in which water can condense, thus protecting the sensitive inner tissues below the stomata from exposure to water-soluble, toxic, trace gases (such as SO2 and H202). The model was found to be sensitive to the accuracy of measurements of leaf temperature, dewpoint temperature of the chamber inlet and exit air, and gas flow rate and may provide some insight into the role of atmospheric pollutants in forest decline.