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Immunoasaay Enhancers
for Researchers and Manufacturers
Alkaline Phosphatase CONJUGATE STABILIZERS
ALKALINE PHOSPHATASE (AP) -CONJUGATE
STABILIZER
The major advantage of a liquid AP-conjugate is it eliminates
the chance for human error when dissolving or diluting the lyophilized or
concentrated conjugate. Adding too much or not enough buffer results in assay to
assay variation. Until now, the disadvantage of this format was the inherent
instability of the liquid AP-conjugates. This problem has now been addressed!
The AP-CONJUGATE STABILIZER is formulated to allow you to provide pre-diluted,
READY-TO-USE CONJUGATES.
This product is prepared in a proprietary buffer system and contains a non
mercury containing preservative (no azide, no thimerosal).
cat#AP-Stab READY-TO-USE : This formulation was designed to reconstitute
lyophilized or concentrated AP-conjugates. Conjugates are tittered and diluted
to working concentrations with the AP-CONJUGATE STABILIZER.
Use at full strength or dilute 1:1 with 10mM MES Buffer, pH 6.0 (or 0.85%
NACL. The use of more than 10% or 1.5mM Phosphate will cause precipitation.
For additional protection, add 10% glycerol to the conjugate stabilizer solution
(if compatible with your system). Store at 4 DEG C and protect diluted material
from light.
Conjugates prepared in this manner will maintain AP activity for up to 2 years
at 4 DEG C. (actual time must be determined with your particular conjugate and
assay characteristics).
CAT# RDI-APSTAB-1X = €475.00/Liter
€444.00/Liter
for 5-9 liters
€425.00/liter
10-20 Liters
Please allow 2 weeks for delivery on multi-liter quantities (to
ensure product from same production lot!).
You should titer your conjugate with each batch. Our testing
shows you may need slightly more of your conjugate but the long term stability
of the "working conjugate" makes for a much more reproducible product. The
addition of glycerol is generally only needed for very unstable
conjugates.Minimize the number of times you open and close the bulk stabilizer
bottle. Try to maintain aseptic techniques. Ideally, sterile filter your
conjugate prior to addition to the stabilizer (or after dilution for maximum
stabilizing effect).
FOR RESEARCH OR FURTHER MANUFACTURING USE ONLY.
Technical Recommendations for
Stabilizing Solutions:
You should titer your conjugate with each batch. Our testing
shows you may need slightly more of your conjugate but the long term stability
of the "working conjugate" makes for a much more reproducible product.
Minimize the number of times you open and close the bulk
stabilizer bottle. Try to maintain aseptic techniques. Ideally, sterile filter
your conjugate prior to addition to the stabilizer (or after dilution for
maximum stabilizing effect). Package diluted conjugates in oxygen barrier
bottles (PET or brown glass lyophilization vials with stoppers and tight caps).
NOTE: Stability of HRP conjugates is prolonged by keeping conjugates cool and
reducing exposure to light and oxygen. Thorough vacuum degassing with nitrogen
flushing of all buffers, conjugates and diluents will extend diluted conjugate
stability under severe conditions as will addition of metal free glycerol.
Our primary formulation of Alk-Phos Stabilizer is a proprietary formulation
made with certified reagents under a standardized GMP production protocol. I
regret that I cannot give you any additional details on its preparation or
formulation.
As for validating an extended stability with such a product, this is also too
dependent on the product to give you much information. However, the following is
a "SAMPLE" protocol of process that must be investigated for using such a
product.
1) You should first titer your conjugate with the stabilizer (full strength ) to
obtain a working dilution. Generally, you will need approx 10% more conjugate
initially than if used with a standard buffer diluent.
2) Then , you should sterile filter the conjugate (if possible) and add it to
the stabilizer. If you have the capabilities and you have a very unstable
conjugate, you may also wish to add glycerol.
-if you conjugate is susceptible to bacterial decay, you can add
additional thimerosal or other non azide preservatives as desired (as our
microcide I).
3) Bottle the cold, diluted material with nitrogen pressure or gravity fill into
pre-chilled low oxygen transfer bottles. Ideally, brown borosilicate glass with
stopper and screw cap or tight crimp seals. Also good is PETE type cell culture
bottles (which have low O2 and CO2 transfer).
4) Stability testing: The only truly applicable method is real time studies in
various packages at your intended storage conditions 4-8 DEG C. One generally
would perform 24 hours at 37 DEG C and then 24 hours at 20 DEG C and then
regular store at 4-8 DEG C (this simulates generally shipping conditions of one
stressful day in a delivery truck, one day waiting for receiving to put kit in
refrigerator and then the remaining time for storage as needed).
5) Some initial accelerated stability testing can be performed to stress the
conjugate and see if any changes in packaging methods will have an effect. These
include the following: a) make up 16 bottles each of your conjugate ( 8 in the
stabilizer, and 8 in your regular assay buffer or diluent).
Before bottling, remove enough to run your assay (to set
baseline characteristics).
Additional bottles may be made if your decide to test different packages (ie,
glass versus plastic etc). Each bottle MUST be made up to the volume intended
for final use so that head space/void space is at actual dimensions.
b) Place Two sets in 37 DEG C bath, two at room temp, two at 4-8 DEG C and two
at -20 DEG C (to study frozen effects long term).
c) Each 24 hours, open one designated set, remove only enough to run a standard
curve . Close vial and place back in designated temp. Repeat every 48 hours
until such time that the 37 DEG C conjugate looses enough activity to make it
unsuitable for your assay. Then continue testing once per week observing the
room temp studies. At conclusion of study, check the unopened vials and compare
that activity with activity at beginning and from the last of your sampled vials
(this checks to see if some of the additional loss of activity was due to
opening and closing the vials themselves).
As you can see, this requires a comprehensive evaluation. Since there are too
many factors involved, we cannot say what effect any one item might have on the
result. The varied stability/purity of the conjugate itself will have a great
effect on the stability of any stabilizer to be of help.
