STRUCTURE AND PROTEIN SEPARATION EFFICIENCY OF POLY(N-ISOPROPYLACRYLAMIDE) GELS - EFFECT OF SYNTHESIS CONDITIONS

Crosslinked poly(N-isopropylacrylamide) (PNIPA) gels with different cr osslink densities in the form of rods and beads were prepared by free- radical crosslinking copolymerization. Solution and inverse suspension polymerization techniques were used for the gel synthesis. The gels w ere utilized to concentrate dilute aqueous solutions of penicillin G a cylase (PGA), bovine serum albumin (BSA), and 6-aminopenicillanic acid (6-APA). The discontinuous volume transition at 34 degrees C observed in the gel swelling was used as the basis of concentrating dilute aqu eous protein solutions. PNIPA gels formed below 18 degrees C were homo geneous, whereas those formed at higher temperatures exhibited heterog eneous structures. The water absorption capacity of PNIPA gels in the form of beads was much higher, and their rate of swelling was much fas ter than the rod-shaped PNIPA gels. It was also found that the polymer ization techniques used significantly affect the properties of PNIPA g els. The separation efficiency decreased when the protein molecules PG A or BSA in the external solution were replaced with small-molecular-w eight compounds, such as 6-APA. The protein separation efficiency by t he gel beads increased to 100% after coating the bead surfaces with BS A. (C) 1998 John Wiley & Sons, Inc.