Removal of DNA from a Protein Solution with Cross‐Linked Poly(Ethyleneimine) Spherical Particles

Abstract

To remove nucleic acids from a solution of a cell product used as a drug, water‐insoluble poly(ethyleneimine) (PEI) spherical particles were prepared by suspension cross‐linking with PEI and chloromethyloxirane. The PEI content of the particles was easily adjusted by changing the PEI ratio and the CMO ratio in the cross‐linking. The cross‐linked PEI particles, which had diameters of 44 to 105 µm and PEI contents of 50 to 90 unit mol%, were used as adsorbents. The adsorption of DNA and cell products to the adsorbents was determined using a batchwise method. The larger the PEI content of the adsorbent, the larger the DNA‐adsorbing activity of the adsorbent. The apparent dissociation constant between the DNA (purified DNA from salmon spermary) and the adsorbent, decreased from 8.5 × 10−8 to 9.5 × 10−10 M with an increase in PEI ratio from 50 to 90 unit mol% under physiological conditions (ionic strength (μ) = 0.17, pH 7.2). On the other hand, the adsorbing activity of bovine serum albumin also increased with increasing PEI ratio of the adsorbent from 70 unit mol% or higher, but sharply decreased with increasing of the buffer. The adsorbing activity of γ‐globulin increased with decreasing PEI ratio to 70 unit mol% or lower. As a result, when the cross‐linked PEI particles, having a PEI ratio of 80 unit mol%, were used as the adsorbent, they only selectively removed DNA from various protein solutions at an μ = 0.17 and a pH of 7.2. The particles decreased the concentration of DNA in each protein solution to less than 10 ng mL−1, and the recovery rate of protein was more 97% in all cases.