1,721,185 research outputs found
Gas permeability in glassy polymers: A thermodynamic approach
No full textThe permeability of various low molecular weight species (both gases and vapors) in a series of glassy polymers has been extensively analyzed by means of a thermodynamic based approach for solubility and diffusivity, recently proposed and already applied to a few penetrant/polymer systems. The model relies on the thermodynamic description of the solubility behaviors of the solutes provided by the nonequilibrium thermodynamic model for glassy polymers (NET-GP), while the diffusivity is the product of the mobility coefficient, a purely kinetic quantity, and the thermodynamic factor, accounting for the dependence of the penetrant chemical potential on its concentration in the glassy polymer matrix.
The model is applied to permeability data of many penetrant species from very light gases, such as hydrogen or helium, to hydrocarbons and fluorocarbons, in several different glasses, including very high free volume materials, polyimides and fluoropolymers. The model proved to be effective in the representation of all types of permeability behaviors with respect to penetrant upstream pressure, which may be either decreasing, increasing, or with a nonmonotonous trend showing a minimum value at the so-called plasticization pressure
Development and Characterization of Affinity Membranes for Immunoglobulin Purification
No full textThe purification of antibodies is conventionally performed using affinity
chromatography columns, with Protein A as ligand. The development of valid alternatives to Protein A is one of the challenges of the research in downstream processing, which becomes more important as the production capability of the biopharmaceutical industry increases. The objective of this work is the characterization of affinity membranes derivatized with two different synthetic ligands that show high specificity for immunoglobulins. The affinity membranes have been prepared and characterized, in view of their application in the capture purification step
Dynamic characterization of affinity membranes for monoclonal antibodies purification
No full textDownstream processes for the purification of biological products are often the cost determining production steps. Affinity technology is widely used for the primary capture stage, based on chromatographic beads. In the last decades, significant attention has been devoted to affinity chromatography using microporous membranes as chromatographic supports. Membrane chromatography can overcome the limitation associated to conventional packed-bed columns, such as high pressure drops and slow mass transfer.
This work is focused on the purification of Immunoglobulin G (IgG) via affinity membranes. A new support, Sartoepoxy Protein A membranes (Sartorius, Göettingen, Germany) has been tested in detail in dynamic experiments, using pure solutions of polyclonal IgG as well as the supernatant of a fermentation broth containing monoclonal IgG. All the relevant parameters, namely the dynamic binding capacity, process yield and recovery have been evaluated. The influence of several operating parameters on the adsorption and elution performances has been studied to determine the optimal process conditions.
A mathematical model including convection, diffusion and multi-component adsorption is proposed to simulate the adsorption, washing and elution steps; the model also considers the possible effects of dead end volumes and flow distribution. Results of the simulation have been compared with the experimental data, giving a good description of the global process
Analysis of different affinity membranes for the primary capture step in antibody manufacturing
No full textIn this work, different new affinity membranes are considered for the capturing step of a monoclonal antibody production process. The membranes with immobilized protein A and synthetic ligands, have been extensively tested with pure IgG solutions and with a cell culture supernatant containing IgG1. The effects of flow rate and IgG concentration in the feed on the separation performances like binding capacity, selectivity and process yield have been studied in detail.
The behaviour and efficiency of the different affinity membranes will be presented and will be also compared with data available for protein A chromatography beads.
A model simulation study of the relevant kinetic and transport phenomena led to the development of a mathematical model capable to describe the separation process based on affinity membrane. Model validation has been successfully performed using the experimental data available for the different membrane tested
Modelling and simulation of affinity membrane adsorption
No full textA mathematical model for the adsorption of biomolecules on affinity membranes is presented. The model considers convection, diffusion and adsorption kinetics on the membrane module as well as the influence of dead end volumes and lag times; an analysis of flow distribution on the whole system is also included. The parameters used in the simulations were obtained from equilibrium and dynamic experimental data measured for the adsorption of human IgG on A2P-Sartoepoxy affinity membranes. The identification of a bi-Langmuir kinetic mechanisms for the experimental system investigated was paramount for a correct process description and the simulated breakthrough curves were in good agreement with the experimental data. The proposed model provides a new insight into the phenomena involved in the adsorption on affinity membranes and it is a valuable tool to assess the use of membrane adsorbers in large scale processes
Performance of a New Protein A Affinity Membrane for the Primary Recovery of Antibodies
No full textRecovery of antibodies with Protein A affinity chromatography columns has become the standard for the biotechnology industry. Membrane affinity chromatography has not yet experienced
extensive application due to the lower capacity of membrane supports compared to chromatographic beads. In this work, new affinity membranes endowed with an interesting binding capacity
for human IgG are studied in view of their application in the capturing step of a monoclonal antibody production process. The membranes have been extensively tested with pure IgG solutions
and with a cell culture supernatant containing IgG1. The effects of feed flow rate and IgG concentration on the separation performances have been studied in detail, considering in particular
binding capacity, selectivity and recovery. These new high capacity affinity membranes appear good candidates to avoid the throughput limitations and other well-known drawbacks of traditional bead-based chromatographic columns
Evaluation of affinity membrane adsorbers for antibody purification
No full textRecent development of therapeutics based on monoclonal antibodies has lead biotech industry to look at alternatives to chromatography in view of the increased production needs and affinity membrane adsorbers are among the process considered.
A2P mimetic (Prometic Biosciences, UK) has been coupled to Sartobind epoxy (Sartorius AG, Germany) pre-activated cellulose membranes and characterised with pure polyclonal human IgG and MAbs from a cell culture supernatant.
Membrane capacity and selectivity towards the target proteins have been measured together with all the relevant kinetic parameters, which characterise adsorption and elution. The membranes were also studied with respect to stability of the stationary phase and ligand leakage and compared to affinity chromatography resins.
A2P-Sartobind epoxy affinity membranes were extensively tested in dynamic experiments. The effects of feed concentration and flow rate were investigated in order to find the better conditions for binding and elution steps.
The equilibrium and kinetic parameters measured experimentally were used in a mathematical model developed to describe the behaviour of affinity membrane systems in binding and elution steps. The influence of different adsorption kinetics as well as the effects of dead end volumes, lag times and analysis of flow distribution were used to assess the use of the model for scale-up purposes
Effect of relative humidity and temperature on gas transport in Matrimid®: Experimental study and modeling
No full textThe influence of water vapor on the gas permeability of a commercial polyimide, Matrimid® 5218, has
been extensively investigated at three different temperatures (25, 35 and 45 1C), and with four different
penetrant gases (CH 4 , N 2 , CO 2 and He), varying the relative humidity in the range 0–75%.
In all tests performed, the permeability coefficient decreases as the concentration of water vapor in
the membrane increases. In particular, the influence of the presence of water on gas permeability is very
similar for all penetrants, as the same permeability decrease is found, at a given relative humidity,
despite the different thermodynamic and kinetic characteristics of the probe gases considered.
As temperature is raised, the gas permeability is enhanced, as expected. On the other hand, its decrease
with respect to the dry polymer values, as relative humidity increases, is not affected by temperature, and it
remains substantially unaltered from 25 to 45 1C, suggesting that such phenomenon can be directly related
to the amount of water dissolved in the membrane, which is also unaffected by temperature.
Based on the experimental evidence, a simple model is proposed to describe the permeation process
under humid conditions, in the framework of the free volume theory. In particular, it has been considered
that absorbed water molecules influence gas permeability by occupying polymer free volume, reducing its
availability to other penetrants with lower condensability. The model describes accurately the experi-
mental data using only two adjustable parameters for the polymer-water-penetrant system, once the water
solubility is estimated from sorption measurements
Adsorption and elution of lectins by affinity membranes
No full textAffinity membranes suitable for the purification of lectins were prepared by chemical modifications of a cellulose matrix. As a model protein a lectin obtained by chromatographic techniques from Momordica charantia seeds was mainly used; Peanut agglutinin and Ricinus communis agglutinin were also considered. Different ligands were tested according to the different affinity towards the lectins used. Among the various ligands tested arabinogalactan and N-acetyl-D-galactosamine gave the best performances. The ligand binding reaction onto the epoxy groups of the activated matrices has been optimized with respect to concentration of ligand, temperature and reaction time. The ligand immobilized on the membrane surface is quantified indirectly by measuring the amount of protein bound to the membrane. The kinetics of adsorption and desorption of the purification process has been studied in detail for the different supports. Modified membranes have been used in separation process of lectins with good binding capacity towards the protein of interes
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