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

Abstract

This paper describes a method for the selective removal of DNA from various cellular products using columns packed with polycation‐immobilized cellulose beads. Polyethyleneimine (PEI), poly‐N,N‐dimethylaminopropylacrylamide (poly(DAPA)) and poly(ϵ‐lysine) (PϵL), all of which have cationic properties, were used as the ligands on the beads. Cellufine‐GC15^® and ‐CPC^® were used as cellulose matrices. Adsorption of DNA by the beads was determined using a batchwise method or a column method. Each bead type showed high DNA adsorbing activity at pH 7.0 and ionic strengths of μ=0.05–0.8. The larger the pore size of the beads, the larger the DNA‐adsorbing activity. The DNA adsorbing capacities per wet mL of PEI‐, poly(DAPA)‐ and PϵL immobilized Cellufine‐CPC with large pore sizes, were 3.7, 3.2, and 1.8 mg, respectively. When a protein, such as bovine serum albumin (BSA) or γ‐globulin, was present in solution with the DNA under physiological conditions (pH 7.0, μ=0.2), the DNA selectivity of the PEI immobilized Cellufine‐CPC columns was unsatisfactory, because both the DNA and the protein were adsorbed into the column. In contrast, the poly(DAPA) immobilized Cellufine‐CPC column selectively removed DNA from each protein solution contaminated with DNA under similar conditions: the DNA concentration in each treated protein solution was below 10 ng mL⁻¹, and high recovery of each protein (>92%) was obtained.

Keywords:

• Nucleic acids
• DNA
• N,N‐Dimethylaminopropylacrylamide
• Poly(ethyleneimine)
• Selective removal
• pK_a
• Amino group content
• Bovine serum albumin
• γ‐Globulin

Acknowledgments

We are grateful to Kohjin Co., Ltd., Tokyo for providing DAPA. This study was supported by an Industrial Technology Research Grant Program in 2003 from the New Energy and Industrial Technology Development Organization (NEDO) of Japan.