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The following message was posted to: PharmPK
Dear Colleagues,
I am working with a lipophilic compound, which is also a weak base, in
side-by-side diffusion chambers. I am experiencing serious lost in
concentration which I suspect is due to non-specific binding of the
lipophilic compound to the acrylic chamber wall. I did not see much of
acknowledgement and solution to this problem from literature. I wonder
if
there is any good solution that can prevent or minimize this
non-specific
adsorption, such as surface treatment or modifying the properties of
transport medium (which I use Krebs Ring's bicarb buffer).
I'd appreciate your comments and suggestions.
Thank you.
Li Zhu
Dept of Biopharmaceutical Sciences,
College of Pharmacy
University of Illinois at Chicago
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Hi Zhu,
I used siliconised stainless steel cells to study tacrolimus protein
binding (Zahir H, Nand RA, et al. J Pharm Toxicol Methods 2001; 46: 27
- 35). Earlier, in our lab this method was also used by Dr Akhlaghi to
study protein binding of cyclosporine (Akhlaghi F, Ashley J, et al.
Ther Drug Monit 1999; 21: 8 - 16). In fact we siliconised all surfaces
(including test tubes, centrifugation tubes, pipette tips, vials etc)
which might possibly come in contact with these drugs. Aquasil and
Surfasil were used as siliconising solution and this substantially
increased the recovery.
Hope this helps.
Hamim
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The following message was posted to: PharmPK
Dear Li,
I am working with equilibrium dialysis for determination of plasma
protein
binding of a lipophilic insulin analogue, so I think I know your
problems. I
did use coating of container surfaces, two-three times, before adding my
final solutions. If possible You should ss HSA to buffers, of tween,
which
also may reduce adhesion.
Regards Anne plum,
Pharmacokinetics
Novo Nordisk, Denmark.
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The following message was posted to: PharmPK
Li Zhu,
Use of appropriate pH would solve the issue sometimes. I suppose you are
working at pH7.4. If possible, try using lower pH as the solubility of
your
weak base might improve and thereby reduce the non-specific adsorption.
Good Luck,
Kasiram.
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The following message was posted to: PharmPK
Li Zhu,
I am not sure about your experimental set-up but the problem of
non-specific adsorption is not unusual although a serious one to deal
with. Hydrophobic coating with silica can be tried, I think Sigma
supplies some coating solution and that it is used to coat glassware but
not sure about acrylic chambers. Can you shift to glass as it may not
adsorb your compound.
Hope this helps
Manoj Khurana
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