Scalable Production of Transfection-Grade Plasmid DNA by Liquid-Liquid Extraction Without Chromatography: Application to CAR-T Vector Packaging.

The growing demand for high-quality plasmid DNA (pDNA) in cell and gene therapy, including chimeric antigen receptor T-cell therapy (CAR-T) manufacturing, is constrained by the limited availability of transfection-grade plasmids. This study describes a practical, scalable, and cost-effective acidic phenol extraction method based on a modified alkaline lysis protocol. This approach efficiently removes endotoxins and residual genomic DNA without requiring chromatography or ultracentrifugation. When benchmarked against CsCl density gradient ultracentrifugation and a commercial midiprep kit, the acidic phenol method delivered comparable plasmid purity and functional performance while providing superior scalability, yielding 5-10 mg of pDNA per 500 mL culture. Notably, residual endotoxin levels were negligible for downstream applications such as transfection and lentiviral vector packaging. Lentiviral vectors produced with these plasmids reached titers exceeding 5 × 106 TU/mL, with transduction efficiencies statistically indistinguishable from those obtained with CsCl-purified DNA. The acidic phenol extraction method is a robust, scalable, and cost-effective alternative to industry-standard methods, matching them in yield and purity while being readily scalable, making it a practical tool for both academic research and preparative laboratory production.