Partially-hydrophobized polymer particles derived from N,N-dimethylaminopropylacrylamide for endotoxin removal from acidic protein solution.

Novel copolymeric adsorbents for the selective removal of endotoxin from an acidic protein solution were prepared. The adsorbents comprise spherical copolymers derived from N,N-dimethylaminopropylacrylamide (DMAPAA) and divinylbenzene (DVB). When the molar ratio of DMAPAA to DVB was 80/20 (amino-group content: 5.1 meq/g) and the pore size (molecular mass exclusion of polysaccharide, Mlim) was 4000 to 10000, DMAPAA/DVB showed high endotoxin-adsorbing activity at pH 5.0 to 9.0 and ionic strengths of mu = 0.05 to 0.4. The capacity of the adsorbent (Mlim: 4000) was 390 micrograms of endotoxin (lipopolysaccharide purified from E. coli O111:B4) per ml of the adsorbent using the batchwise method. The apparent dissociation constant between endotoxin and the adsorbent was 2.2 x 10(-12) M. On the other hand, the adsorption of bovine serum albumin, an acidic protein, by the adsorbent increased with an increase in Mlim from 4000 to 10000, but decreased with an increase in ionic strength (mu) from 0.05 to 0.2. As a result, DMAPAA/DVB (80/20) (Mlim: 4000) selectively removed endotoxin from various acidic protein solutions at pH 7.0 and mu = 0.05. The residual concentration of endotoxin in the protein solution always decreased to a concentration lower than 0.1 ng/ml, and recovery of the protein was more than 97%.