IROP: Ionic Regulation of Permeation for High-Yield AAV Purification

Abstract

Traditional filtration methods for separating host cell proteins and DNA from adeno-associated viral capsids often result in substantial yield losses. Here, we introduce a new high-yield purification strategy termed Ionic Regulation of Permeation (IROP) for removing major impurities within a single unit operation. Rather than relying on static size exclusion or binding interactions, IROP dynamically modulates AAV transport within a nanoporous membrane. At low ionic strength, AAV permeation was negligible, while high ionic strength markedly increased the sieving coefficient, revealing an electrostatic gating mechanism. AAVs retained under low-salt conditions could not be efficiently recovered by a static high-salt wash, indicating steric-electrostatic trapping within membrane pores. In contrast, high-salt filtration enabled high recovery. Leveraging this mechanism, a two-step IROP process, involving low-salt impurity clearance followed by high-salt AAV recovery, achieved greater than 90% AAV recovery with a greater than 95% reduction in HCPs and host cell DNA.