Cleaning and Sanitization
Silica-based media are perceived as having limited resistance to alkaline conditions and, therefore, to typical sanitization procedures used in biomanufacturing processes.
In the case of protein A media, the alkaline resistance is limited by the intrinsic fragility of the protein A itself and by the nature of the coupling chemistry, rather than by the solid support itself (except for glass bead-based protein A media, for which the use of NaOH is prohibited by the manufacturer).
A new agarose-based protein A media was introduced to address this issue, but its improved chemical stability is correlated with lower DBC, and it obviously still suffers from the intrinsic mechanical limitations of agarose.
AbSolute is based on specially modified silica and features multiple-point epoxy-type couplings of protein A to the matrix. It is stable through alkaline cleaning and sanitization. Indeed, the modified silica-based protein A media remains stable after 150 cycles of repeated alkali washing using 50 mM NaOH with a residence time of 20 minutes.
A test was performed on a 4.6x10 mm column with a flow velocity of 300 cm/hr. A solution of 0.2 mg/mL polyclonal human IgG in PBS (pH=7.4) was loaded for 20 minutes. The elution step was performed with 0.15 M citric acid containing 0.15 M NaCl (pH=2.2).
The alkali-CIP was then applied (50 mM NaOH, 20 minutes). The overlay of chromatograms obtained during 150 cycles (not shown) illustrates the reproducibility of the tested method. After 150 cycles with repeated alkali washing, a decrease of only 13% of the DBC was measured.