OPTIMIZATION OF PRESSURE-FLOW LIMITS, STRENGTH, INTRAPARTICLE TRANSPORT AND DYNAMIC CAPACITY BY HYDROGEL SOLIDS CONTENT AND BEAD SIZE IN CELLULOSE IMMUNOSORBENTS

The design of existing beaded adsorbent materials for column-mode prot ein purification has emphasized the impact Of diffusional transport ph enomena upon adsorbent capacity. A design model is presented here that optimizes molecular accessibility of proteins relative to the mechani cal stability at low operating pressures by manipulation of size and s olids content for uncross-linked cellulose beads. Cellulose beads of s everal different sizes ranging from about 250 to 1000 mum diameter and having different solids contents were evaluated. Solids content of gr eater than about 9% cellulose greatly reduced the permeability of larg e proteins such as thyroglobulin and beta-amylase into the beaded matr ix at bead contacting times of about 5 and 50 s. Furthermore, the amou nt of permeation at 3% solids content by thyroglobulin at bead contact ing times of about 5 s was about tenfold larger than predicted by diff usion models using the binary diffusivity in a purely aqueous continuu m. The utility of a low solids content, large bead cellulose support w as shown with immobilized IgG (M(r) 155 kDa) capturing recombinant hum an Protein C (M(r) 62 kDa). A 1000 mum diameter beaded cellulose immun osorbent having 3% solids content gave equivalent capacity to a 140 mu m diameter beaded, cross-linked agarose support containing 4% solids. In contrast to the smaller diameter, cross-linked beaded agarose, the low solids content beaded cellulose benefitted from greater physical s tability due to more optimal pressure-flow characteristics imparted by large bead size.