Development of an adaptive electroporation system for intratumoral plasmid DNA delivery.

Intratumoral electroporation of plasmid DNA encoding the proinflammatory cytokine interleukin 12 promotes innate and adaptive immune responses correlating with anti-tumor effects. Clinical electroporation conditions are fixed parameters optimized in preclinical tumors, which consist of cells implanted into skin. These conditions have little translatability to clinically relevant tumors, as implanted models cannot capture the heterogeneity encountered in genetically engineered mouse models or clinical tumors. Variables affecting treatment outcome include tumor size, degree of vascularization, fibrosis, and necrosis, which can result in suboptimal gene transfer and variable therapeutic outcomes. To address this, a feedback controlled electroporation generator was developed, which is capable of assessing the electrochemical properties of tissue in real time. Determination of these properties is accomplished by impedance spectroscopy and equivalent circuit model parameter estimation. Model parameters that estimate electrical properties of cell membranes are used to adjust electroporation parameters for each applied pulse. Studies performed in syngeneic colon carcinoma tumors (MC38) and spontaneous mammary tumors (MMTV-PyVT) demonstrated feedback-based electroporation is capable of achieving maximum expression of reporter genes with significantly less variability and applied energy. These findings represent an advancement to the practice of gene electro-transfer, as reducing variability and retaining transfected cell viability is paramount to treatment success.