Which method directly delivers naked DNA into cells?
Electroporation applies brief high-intensity electric fields to transiently permeabilize lipid bilayer enabling direct cytosolic entry naked nucleic acids without chemical carriers. Square-wave pulses 100-1500 V/cm for microseconds to tens milliseconds generate transmembrane potential exceeding dielectric strength 0.2-1 V causing rearrangement lipids forming aqueous pores water intrusion between headgroups. Polyanionic DNA driven electrophoretically toward anode migrates through pores reaching cytoplasm within milliseconds before rapid resealing seconds mediated lateral diffusion and calcium-dependent exocytosis. Efficiency depends buffer conductivity, osmolality, cell diameter affecting induced potential proportional radius, pulse number, DNA concentration. Nuclear entry limiting but mitosis or nuclear localization signals improve. In vivo devices needle array electrodes deliver 50-500 V intramuscularly achieving DNA vaccine uptake myofibers and dendritic cells triggering MHC I and II presentation. Ex vivo clinical-scale electroporators transfect primary human T cells CD34 stem cells with mRNA or Cas9 RNP achieving 80 percent efficiency preserving viability avoiding insertional mutagenesis and viral manufacturing complexity suitable repeated applications.
Ref: FDA Guidance Electroporation Devices 2021; Molecular Therapy Methods Electroporation Protocol; NCERT Biotechnology Ch 11 Electroporation Principles.