C. Ramkissoon-ganorkar et al., Effect of ionic strength on the loading efficiency of model polypeptide/protein drugs in pH-/temperature-sensitive polymers, J BIOM SC P, 11(1), 2000, pp. 45-54
In this report, the effect of ionic strength on the loading efficiency of t
hree model polypeptide/protein drugs, namely angiotensin II, insulin, and c
ytochrome c, in pH- and temperature sensitive terpolymers of poly(NIPAAm-co
-butylmethacrylate-co-acrylic acid) (poly(NIPAAm-co-BMA-ca-AA)) has been in
vestigated. Loading efficiency of polypeptides in pH-/temperature-sensitive
beads composed of poly(NIPAAm-co-BMA-co-AA) terpolymer is predominantly go
verned by hydrophobic interactions, both nonspecific surface interactions a
nd/or specific interactions (binding pockets) between the protein and the p
olymer molecules. Thus, loading efficiency increases with ionic strength. H
owever, as ionic strength increases further, polymer deswelling (collapse),
which is also controlled by hydrophobic forces, becomes more pronounced, a
nd consequently, a higher fraction of water is squeezed out during bead for
mation and the loading efficiency starts to decrease.