EtoxiClear®
Product Code: 3250

INTRODUCTION
Endotoxin are lipopolysaccharides (LPS) derived from the cell membrane of Gram negative bacteria and are often found as impurities in final pharmaceutical products.
Endotoxin elicit a variety of pathophysiological effects when administeredsystemically and the removal of residual endotoxin to below the threshold level forrecombinant proteins produced in E.coli continues to be a major challenge for thebiopharmaceutical industry.
According to pharmacopoeia the maximum permitted level of endotoxin for intravenous
products is 5 EU (endotoxin units) per kg adult per hour, where 1 EU is equivalent toapproximately 0.1 – 0.2 ng of endotoxin.
The removal of endotoxin is more challenging when associated with large protein molecules.
While several methods adapted for specific products have been described for the removal ofendotoxin from proteins, the methods based on selective adsorption are the most effective
for the removal of LPS from final product.
EtoxiClear® provides cost effective and efficient endotoxin removal, using a high performancesynthetic ligand affinity chromatography adsorbent, providing superior endotoxin removalfrom processing solutions and final products.
The adsorbent has a high dynamic binding capacity (> 1 x 10 6 EU/mL packed adsorbent); it
has low protein binding (typical recoveries of the product > 90%) and this allows for up to 4
log clearance of the residual endotoxin present in the sample.
The affinity ligand is covalently coupled to 6% cross-linked, near monodisperse agarose beads(PuraBead® 6XL) to provide a sodium hydroxide stable adsorbent with excellent selectivity forendotoxin.

EtoxiClear® PC3250 User Guide-v5

Properties of EtoxiClear®:
LIGAND:

Synthetic chemical ligand (proprietary)

ADSORBENT APPEARANCE:White

MEAN PARTICLE SIZE (µM):

100 ± 10 µm

MATRIX:DYNAMIC BINDING CAPACITY:
RECOMMENDED OPERATIONAL FLOW RATE:CHEMICAL STABILITY:

Highly cross-linked 6% near monodisperse agarose(PuraBead® 6XL)
>1,000,000 EU/mL of adsorbent*
Up to 200 cm/hr (dependent on column size)
All commonly used aqueous buffers and co-solvents

OPERATING PH:

pH 4.0 to pH 8.0 (intermittent)

PH STABILITY:Long term (3 months) pH 3 to pH 12

CLEANING / SANITIZATION:
RECOMMENDED STORAGE CONDITION†:

0.5 - 1.0 M NaOH, 25°C
2-30°C, 20% ethanol : 80% 0.1 M NaCl (v/v)* Loading at 120 cm/h, 5-minute residence time (EtoxiClear® 5 mL Column)

EtoxiClear® PC3250 User Guide-v5

Important Notes• It is good practice to filter all protein samples and chromatography buffers prior to use.
• Removal of residual endotoxin from the final protein product solution may require processoptimization to identify optimal buffer conditions.
• EtoxiClear® can be operated across a wide pH range (pH 4.0 – pH 8.0) for endotoxin
binding applications.
• It is recommended that the endotoxin removal is carried out using aseptic techniques andfor fraction collection use pyrogen free tubes/containers.
• The final protein solution should not be frozen before endotoxin removal. Freeze-thawing
increases the formation of endotoxin micelles which can be more difficult to remove.
• For optimum performance of EtoxiClear® it is recommended that a maximum bed height of
10cm and a minimum residence time of 5 minutes are used.
• Below the pH of the isoelectric point (pI) of the target protein the net charge on theprotein is positive and polyanionic (negatively charged) endotoxin molecules will interact
strongly with the protein molecule. Consequently, the effective removal of endotoxin fromthe final product could be impaired at pH values below the pI of the target protein.
• Although EtoxiClear® has low non-specific binding, it does have a anionic functional groupwhich may act as a very weak ion exchanger. This could lead to a slight binding of target
protein which can be minimized by increasing the ionic strength of the buffer by theaddition of salt (up to 0.3 M NaCl).
• Do not use ammonium or Tris based buffers. These buffers have shown to reduce theefficiency of endotoxin clearance with EtoxiClear®. Other buffers to avoid include MES andHEPES.
• Increasing the concentration of the buffer salt (i.e. from 10 mM to 100 mM sodiumphosphate) can improve the target protein recovery without having a detrimental effecton endotoxin clearance.
• If required, endotoxin clearance can be optimized by decreasing the flow rate (increasingresidence time) used during sample loading.
There are many commercially available endotoxin detection tests/kits available, however, if
a chromogenic based (LAL) test is used (e.g. Associates of Cape Cod) it is recommended toinclude Glucashield® buffer. This renders the reagent insensitive to (1→3)-β-D-glucan
interference, which may be present in the sample, by effectively blocking the Factor G
pathway of the endotoxin clotting cascade.

EtoxiClear® PC3250 User Guide-v5

COLUMN PACKING
EtoxiClear ® is supplied in 20% ethanol : 80% 0.1 M NaCl (v/v). The adsorbent can bepacked using a saline solution (e.g. 0.1 M NaCl) or an equilibration buffer (e.g. 50mM
sodium phosphate, 0.1 M NaCl, pH 7.2). Before commencing the column pack, consult
the relevant manufacturer’s instructions for the selected column. The method
described below describes the packing of EtoxiClear ® into axial columns.
Please note: it is recommended that the bed height of the column pack should be ~10 cm for
optimum performance, as taller bed heights have shown to significantly add back pressure
and shorter bed heights can affect the optimum performance of EtoxiClear ®.
1. Assemble the column and remove air from the dead spaces by flushing the end piece andadaptor with packing solution (0.1 M NaCl solution) then close the column outlet.
2. Allow all materials to equilibrate to the temperature at which the chromatography process
is to be performed.
3. If required to obtain a fixed bed height (i.e. for larger column packs), it is recommended
to determine the slurry percentage. For example, weigh a sample of the complete slurry,drain away the preservative and re-weigh the adsorbent. The final weight over the total
weight will determine the slurry percentage.
4. Carefully pour the adsorbent slurry into the column in a single continuous step. Pouring
the adsorbent down the side of the column helps to prevent air becoming trapped within
the adsorbent bed.
5. Allow the adsorbent to settle in the column leaving a dead volume of packing solution
above the adsorbent bed.
6. Ensure the top adaptor is free from air by pumping the packing solution through. Attachthe (open) top adaptor to the top of the column and adjust the adaptor to just above thebed, tighten the adaptor (seal) and attach to the workstation. Open the column outlet andapply a flow to the bed.
7. EtoxiClear® should be packed in the column until a pressure spike is observed, but notexceeding 3 bar (0.3 MPa) across the column. This should be achieved by incrementally
increasing the flow rate (i.e. commence flow at ~ 0.5 bar then 0.5 bar pressure increments
every 0.5 CV; for smaller columns, or if pressure cannot be accurately determined,
commence flow at 100 cm/h then increase the flow rate by 100 cm/h increments).
8. Mark where the adsorbent has compressed to under the last pressure / flow condition,then lower the top adaptor to that mark.
9. The column is now packed and ready to use.

EtoxiClear® PC3250 User Guide-v5

COLUMN EFFICIENCY TEST
1. Test the column at a flow rate of 100 cm/h.
2. Attach the column to an equilibrated workstation.
3. Commence flow for 1 CV (i.e. to equilibrate and obtain baseline).
4. Inject 2% to 5% CV of a 2% acetone or 2 M NaCl solution.
5. Continue flow until a UV (or conductivity) peak is observed and the trace has returned tobaseline (1 to 1.5 CV).
6. End run and determine the asymmetry factor:

7. EtoxiClear® is an affinity adsorbent, therefore an asymmetry factor for an acceptable packis between 0.8 and 1.6. The recommended plate count for an acceptable pack is ≥ 2000
N/m.

EtoxiClear® PC3250 User Guide-v5

OPERATING INSTRUCTIONS
Note: The following recommendations are not prescriptive and thorough investigation ofthese parameters at small-scale is recommended for process optimisation, including flow rate
optimisation to improve binding capacity/ resolution or decrease processing times.
1. Attach the column directly to the liquid chromatography system, ensuring that the tubing
connecting the system to the column is primed with equilibration buffer. Recommended
equilibration buffers are PBS or 50mM sodium phosphate, 0.1M NaCl, pH 7.2. Other
equilibration buffers are as follows (including 0.1M NaCl):• sodium acetate• sodium citrate
2. Note: Although the adsorbent has been manufactured in a controlled environment, werecommend that the column is treated with a depyrogenation step prior to use.
3. Clean by flushing the liquid chromatography system and column with 0.5M NaOH at 60
cm/hr. Stop the flow and hold in 0.5M NaOH for ≥16 hours (overnight) at room
temperature. Flush the NaOH out of the system and column using depyrogenatedequilibration buffer (e.g. PBS or 50mM sodium phosphate, 0.1M NaCl, pH 7.2) at 60 cm/hruntil the eluent pH is equivalent to the equilibration buffer entering the column.
4. Apply the protein solution/sample onto the column at the recommended operational flowrate of 120 cm/hr (≥ 5 minute residence time is recommended) and collect the flow
through in endotoxin free collection vessels.
5. If required, wash the column with equilibration buffer at 120 cm/h to flush out andrecover the remaining target protein with at least 1 CV or until a UV baseline is achieved.
6. The EtoxiClear® column can be regenerated by passing 2 CV of 0.5 M NaOH through thecolumn, followed by an overnight hold in 0.5 M NaOH (> 16 hours). Note: EtoxiClear ® isstable to exposure of sodium hydroxide 0.5 M to 1 M NaOH, though regeneration and reuse of the adsorbent is dependent on the nature of the sample applied to the column andwill require validation by the end-user.
7. Post overnight hold, flush the column with a further 1 CV of 0.5 M NaOH.
8. Wash out the sodium hydroxide solution with equilibration buffer (50 mM sodium
phosphate, 0.1 M NaCl, pH 7.2) until the eluent matches the pH of the equilibration buffer
entering the column.
9. For storage, place the column into 20% ethanol: 80% 0.1 M NaCl solution and store at 2 –30°C.

EtoxiClear® PC3250 User Guide-v5

ORDER INFORMATION
Gel Slurry
CodeDescription

Pack Size

3250-00010

EtoxiClear®

10 mL

3250-00025

EtoxiClear®

25 mL

3250-00100

EtoxiClear®

100 mL

3250-00500

EtoxiClear®

500 mL

3250-01000

EtoxiClear®

1000 mL

We also offer a range of larger pack sizes for supply of bulk resins into cGMP development andmanufacturing scale processes.
EtoxiClear® is available in a carefully selected range of disposable columns sizes with bed
volumes of 5 mL and 50 mL both with a standard bed height of 10 cm, suitable for processdevelopment applications and polishing steps.

Disposable Column Format
CodeDescription

4251-00005

EtoxiClear® 5 mL Column

4251-00050

EtoxiClear® 50 mL Column

In addition, Astrea Bioseparations can offer column packing services. For more information on
this or any other supply related matters, please do not hesitate to contact us at sales@astreabio.com

EtoxiClear® PC3250 User Guide-v5

Issue Date: 13 Dec 2022
CCR Number: N/A – trademarks updated
Author Name: T Hayward
QA Reviewer Name: R Hawkins
All trademarks, trade names, trade dress, product names and logos
appearing in this Technical User Guide are the property of Astrea UKServices Ltd.
Copyright © 2022 Astrea Bioseparations Ltd. All rights reserved.