Effect of cationic polymer adsorbent pK a on the selective removal of endotoxin from an albumin solution

Abstract

SummaryTo obtain fundamental information about the surface-environment effect of adsorbent on the selective adsorption of endotoxin (hpopolysaccharide; LPS) from a protein solution, crosslinked poly(c-lysine)(PL) and aminated poly(7-methyl L-glutamate) (PM LG-NH 2) spherical adsorbents were prepared. The apparent pKa (pKa,app) of the PL and PMLG-NH 2 adsorbents was adjusted by controlling the ratio of poly(c-lysine), in cross-linking, and the amination conditions (time and ratio of diaminoethane in the particles), respectively.When adsorption of LPS and acidic protein, e.g. bovine serum albumin (BSA), by the particles was determined by a batchwise method at pH 7.0 and an ionic strength, ix, of 0.05, they were found to depend strongly on pKa,app but not necessarily on the amino-group content. When pKa,app was increased from 6.8 to 8.2, the LPS-adsorbing capacity was increased from 1.0 to 2.7 mg mL 1 wet adsorbent and the apparent dissociation constant for adsorbent and LPS decreased from 3.7 xl0 10 to 1.0 xl0 l~ Although PMLG-NH 2 with the highest pKa,app, 8.2, had the highest LPS-adsorbing activity, it also adsorbed BSA. The BSA-adsorbing activity was sharply reduced when pKa,app was reduced to 6.8 or lower. As a result, the cross-linked PL adsorbent of pKa,app 6.8 had the highest LPS selectivity. The adsorbent could reduce levels of natural LPS associated with acidic protein (ovalbumin or BSA) at pH 7.0 and ix = 0.05. The residual LPS concentration in each sample was > 100 pg mL 1, and recovery of the protein was >96%.

Stimuli-Sensitive Particles for Drug Delivery

“…[25][26][27][28][29][30] Unlike anionic polymers, which exhibit pH-induced transitions in their physical conformation around pH 4-6, these cationic polymers display the change in their conformation at pH 8 or higher based on their pKa values ( Figure 5) [31][32][33] Several investigations focused on modifying these cationic polymers to reduce their pKa values to match the physiologic pH to become useful in biological and pharmaceutical applications. [34] One approach is to incorporate hydrophobic monomers into the cationic polymer backbone to shift the polymer's overall pKa towards the neutral pH range.…”

Selective Removal of DNA from Bioproducts by Polycation‐Immobilized Cellulose Beads

“…Cationic adsorption is remarkably dependent on the pK a of the adsorbent, pK a of the bioproducts and ionic strength of the buffer. [15] Hydrophobic adsorption is independent of the ionic strength. [5,6] Nucleic acids (DNA and RNA) are polynucleosides with anionic regions (phosphate groups), pentoses, and purine and pyrimidine bases, and, thus, the DNA charge is anionic when the pH exceeds the pK a (,2).…”

Chromatographic Removal of DNA from Protein Solutions by Cationic Polymer Beads

“…Therefore, we considered that aminated PMLG beads may be used as selective adsorbents for DNA. The adsorption of several cellular products, such as DNA, BSA and -globulin, increased with increasing the bead's M lim [34][35][36]. A swelling size of cellular product (protein and DNA) in a solution is estimated as not its nanometer size but its molecular size.…”