Cellufine Amino en Formyl
Activated Supports for Immobilization of Antibodies, Antigens,
Affinity Ligands and Enzymes.
The growth of process-scale affinity chromatography has
created the need for a new generation of support matrix materials and coupling
chemistries suited for the industrial environment. Classical agarose based
supports perform poorly at the large-scale for several reasons. They provide
poor flow properties in large columns. The widely used cyanogen bromide coupling
chemistry has well-documented problems with bond stability and non-specific
adsorption. Additionally, even with more modern chemistries, agarose can shed
polysaccharide chains, giving rise to significant ligand leakage under mild
operating conditions.
Cellufine activated supports provide state-of-the-art laboratory performance at
the process-scale without difficulty. The products are based on rigid spherical
cellulose beads specially optimized for affinity chromatography to provide very
large pore size and high ligand capacity together with high flow rates in large
columns. The cellulose backbone offers very low non-specific adsorption without
the ligand leakage problems of agarose.
Features:
• High flow rates in laboratory and process columns for high throughput
• Low ligand leakage due to exceptionally stable coupling chemistry and support
matrix
• Excellent mechanical, chemical and environmental resistance
• High ligand loading capacity
• Compatible with high molecular weight ligands and target proteins due to pore
size equivalency with 4 % cross-linked agarose media
• Unreacted formyl groups easily converted during reduction to neutral hydroxyls
for low non-specific adsorption
• Built in hydrophilic spacer arms for maximum ligand accessibility and low non-specific
adsorption
• No media damage or fines generation with extended mixing to allow use of
simple coupling apparatus
• Ligand coupling occurs under mild conditions in short reaction times
• Thermal stability of media allows high temperature reactions
• Long shelf-life of unreacted media
Antigen Purification:
Figure 3 illustrates the use of Cellufine Formyl coupled with an antibody for
largescale antigen purification. In this application the Cellufine affinity
column provides a significant concentration and purification of antigen at high
yield. The subject column has been used for over 30 months to process over 3,000
liters of starting plasma with no significant degradation in performance.
To produce the gel, 45 liters of horse serum containing anti-HBs Ag antibody
were first concentrated and purified by ammonium sulfate precipitation and
dialysed into 0.2M phosphate (pH 7) with 0.1 M NaCl. The resulting antibody
serum was added to 12 liters of Cellufine Formyl and reacted together with 80
grams of NaCNBH3 at 4 to 8 °C for 24 hours. The antibody gel was then washed
with buffer and packed into the column. The process stream consisted of human
plasma positive for HBs Ag which had been previously purified by freeze-thawing,
centrifugation, ammonium sulfate precipitation and gel filtration chromatography.
Sample: 1200 liters semi-purified HBs Ag-positive human plasma
Column: 140 x 780mm (12 liters) Cellufine Formyl Horse Anti-HBs Ag
Starting/Wash 0.1M NaCl, 0.2M phosphate
Buffer: (pH 7) wash volume 200 liters
Eluent: 0.2M glycine/HCl (pH 3)
Flow Rate: 20cm/hr loading/washing 26cm/hr elution
Product Volume: 14 liters (85 x concentration)
Yield: 87 %
Single Step:
Purification: 149 x
RCA, Purification:
Cellufine Formyl can be used to immobilize lectins for glycoprotein
purification, as shown in Figure 4. Con A (50mg) was immobilized on 0.5g (wet)
of Cellufine Formyl by reacting at
4 °C overnight in 1ml of 0.1M acetate (pH 6.4) containing 1mM MgCl2, 1mM MnCl2
and 1mM CaCl2 under the presence of methyl-alpha-D-mannoside and NaCNBH3. After
washing with water, the gel was suspended at 4 °C overnight in 2ml of 1 %
glutaraldehyde with NaCNBH3. After a second water wash the gel was suspended for
one hour at room temperature in 2ml of 1M Tris/HCl (pH 7.4) and rewashed.
Sample: 66ml RCA1 (30mg/ml protein)
Column: 0.9 x 9mm (0.6ml) Cellufine Formyl Con A
Starting/Wash 0.1M NaCl
Buffer: 0.2M Phosphate (pH 7.2)
Eluent: 0.2M methyl-alpha-D-mannoside
Flow Rate: 12cm/hr
Functional selection of activated supports:
The two types of Cellufine activated support media are Cellufine Formyl, and
Amino. The availability of two functional groups allows great flexibility in
selecting media for optimal reaction conditions (pH, temperature, activating
agents, reactant concentrations, etc.). Each is a high-stability, functional
packing optimized for an application group. Control of reaction chemistry and
ligand density is straightforward.
A general support for proteins:
Cellufine Formyl:
The aldehyde active group on Cellufine Formyl packings reacts with primary amine
groups on the ligand to form a Schiff’s base complex (see Figure 5). A mild
reducing agent is used to convert the Schiff’s base to a highly stable linkage.
Table 2 illustrates a general ligand coupling protocol.
Reducing Agents:
Cellufine Formyl requires a reducing agent for formation of a highly stable
linkage. A number of reducing agents are available for good results in virtually
any application. The agent should be selected to produce a reasonable reaction
rate and yet not be so strong as to damage the protein ligand (such as by
reduction of disulfide bonds) or as to reduce the aldehyde groups. Sodium
borohydride (NaBH4), sodium cyanoborohydride (NaCNBH3) and
a newer, non-toxic reducing agent, trimethylamine borane ((CH3)3NBH3)
are successful agents, depending upon the particular requirements. For any
agent, the quantity required is typically less than 10 milligrams per gram of
wet gel.
INTERMEDIATES FOR
ADVANCED CHEMISTRY:
Cellufine Amino:
Cellufine Amino and Carboxyl are convenient intermediates for use in coupling
reactions requiring greater chemical sophistication than possible with Cellufine
Formyl. Each support can be easily used with carbodiimide reagents to form a
media suitable for coupling the opposite functionality (see Figure 6). Other
reaction chemistries can also be used, such as carbodiimide in conjunction with
Cellufine Carboxyl to form an active ester group (e. g., N-hydroxysuccinimide).
The excellent mechanical and chemical stability of the Cellufine support matrix
allows effective performance over a wide range of chemistries.
Versatile coupling:
Optimization of ligand coupling chemistry is often critical to the success of an
affinity separation. Cellufine Formyl allows a broad range of coupling
conditions to be used to maximize both coupling efficiency and yield of active
protein. Cellufine Amino and Carboxyl give the user a wide range of further
options for custom chemistry in specialty applications.
Coupling with Formyl:
The reaction rate of Cellufine Formyl is rapid enough to be practical, yet slow
enough to be extremely gentle to most proteins. It also allows for a fine
measure of control. The rate may be controlled effectively with temperature to
achieve maximum protein stability. The pH of effective couplings ranges between
3 and 10.
The coupling efficiency (the ratio between amount coupled and amount offered)
and total ligand density can be varied and optimized quite easily through
changes in coupling ligand concentration, pH and temperature. A standard set of
conditions will work well for most cases, but optimization over a broad range
can be used to improve process economics for specific applications.
Coupling with Amino:
The flexibility of these media is illustrated in the use of Cellufine Amino for
the immobilization of heparin (Figure 9) and for coupling of reduced sugars.
Amino supports have often been used to couple reducing sugars directly through
the aldehyde functionality. A major problem with agarose-based supports, however,
has been the lengthy reaction time (often weeks) required. The thermal stability
of Cellufine media allows much faster reactions at high temperatures (Figure 7).
Antibody Purification:
Optimization of ligand coupling to activated gels always involves a trade-off
between efficiency of uptake (the fraction of ligand offered in the reaction
that is actually coupled) and the final ligand loading (mg of ligand coupled per
ml of gel). When purified ligand is readily available, a high loading gel can be
produced at the cost of low coupling efficiency. In the more common case,
however, purified ligand is quite precious, and good coupling efficiency is
highly desirable, even at the expense of low loading. Low ligand density may
also improve binding specificity in some cases.
The lack of competing hydrolysis reaction in the aldehyde chemistry of Cellufine
Formyl makes fine control of the loading and efficiency quite straightforward.
In this example, high purity bovine serum albumin is used as an antigen for the
purification of rabbit anti-BSA antibody. The coupling reaction was designed to
give very high efficiency (98 %) and relatively low ligand density.
Sample: 24ml precipitated rabbit antiserum
Column: 14 x 34mm Cellufine Formyl BSA (5.2ml)
Starting/Wash 0.05M Phosphate (pH 7.4)
Buffer: /0.5M NaCl
Eluent: 0.2M Glycine/HCl (pH 2.25)
Flow Rate: 27cm/hr
Yield: 27mg antibody
Single Step
Purification: 20 x
Cellufine Formyl BSA was prepared by washing 5g (wet) of media with 0.1M
phosphate (pH 7.1), adding 5ml of 4mg/ml BSA and stirring for 12 hours at 25 °C.
After washing with buffer, the media was suspended in 5ml of buffer containing
0.4M ethanola-mine. After stirring for 4 hours at 25 °C the media was washed
with buffer. The BSA coupled was about 3.0 mg/ml media.
Heparin Immobilization:
The complex carbohydrate heparin can be coupled in two ways: either through the
side chain carboxyl groups by a carbodiimide reaction; or directly through the
aldehyde group located on the terminal sugar of the molecule. Selection will
depend on performance requirements. Coupling through the carboxyl groups is
faster and produces a higher loading but the terminal aldehyde reaction normally
results in higher biological activity.
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