Tuning hydrogen bonds and electrostatics with convection for purifying mRNA: A paradigm shift.

The increasing clinical trials of single-stranded mRNA (ss-mRNA) therapeutics highlight the urgent need to develop efficient, scalable, and economic purification methods. Current diffusion-driven, resin-based purification techniques constrain productivity and rely on expensive oligo(dT) ligands for target ss-mRNA poly(A) tail hybridization. To overcome these challenges, we use interfacial molecular forces, such as charge and hydrogen bonds, between nucleic acid variants and a positively charged synthetic microporous membrane to purify ss-mRNA, a desirable therapeutic, from an undesirable impurity, immunogenic double-stranded RNA (dsRNA). Membranes achieved high binding capacities (1.28 mg/m) and up to 100% ss-mRNA recovery at ~pH 9.0, with optimized surface density (4000 to 10,000 nmol/m). Purification was operated at rapid flow rates (1.5 ml/min,1000 MV/min) with reusability (>10 trials) and negligible ligand leaching. The key discovery of this cost-effective ligand-less multimodal surface-modified approach is that the addition of the polyamine spermine, which selectively neutralizes dsRNA charge at amine-to-phosphate ratios >450, enhanced separation efficiency.