Bursts of Bipolar Microsecond Pulses Inhibit Tumor Growth

Abstract

Irreversible electroporation (IRE) is an emerging focal therapy which is demonstrating utility in the treatment of unresectable tumors where thermal ablation techniques are contraindicated. IRE uses ultra-short duration, high-intensity monopolar pulsed electric fields to permanently disrupt cell membranes within a well-defined volume. Though preliminary clinical results for IRE are promising, implementing IRE can be challenging due to the heterogeneous nature of tumor tissue and the unintended induction of muscle contractions. High-frequency IRE (H-FIRE), a new treatment modality which replaces the monopolar IRE pulses with a burst of bipolar pulses, has the potential to resolve these clinical challenges. We explored the pulse-duration space between 250 ns and 100 μs and determined the lethal electric field intensity for specific H-FIRE protocols using a 3D tumor mimic. Murine tumors were exposed to 120 bursts, each energized for 100 μs, containing individual pulses 1, 2, or 5 μs in duration. Tumor growth was significantly inhibited and all protocols were able to achieve complete regressions. The H-FIRE protocol substantially reduces muscle contractions and the therapy can be delivered without the need for a neuromuscular blockade. This work shows the potential for H-FIRE to be used as a focal therapy and merits its investigation in larger pre-clinical models.

Quantification of cell membrane permeability induced by monopolar and high-frequency bipolar bursts of electrical pulses

“…applications that utilize controlled, square electrical pulses on the order of one microsecond [19,58]. The observations about PEFs with single-microsecond pulse widths from the field of PEF-based food processing do not directly provide information on the efficiency of these pulses to enhance molecular transport across mammalian cell membranes.…”

“…estimates When PI binds to nucleic acids, it undergoes a dramatic fluorescence increase, making it useful in assays for evaluating membrane integrity, such as cell death [19] or membrane permeabilization [67,66], which rely on a binary result. Continuous measurements have been performed [65] using chemical agents to calibrate fluorescence intensity measurements, though they have not been used to study the temporal evolution of membrane permeability induced by electric fields with pulse widths on the order of the characteristic membrane charging time.…”

“…In irreversible electroporation (IRE), the cellular membrane is disrupted to generate an irrecoverable homeostatic imbalance [18,19,20,21]. In gene electrotransfer (GET) [22,23] or electrochemotherapy (ECT) [24,25,26], electroporation enables therapeutic molecules to be more efficiently delivered into cells.…”

Modeling of Transmembrane Potential in Realistic Multicellular Structures before Electroporation

“…S10 and S11). It has been previously observed that H-FIRE treatment generates more homogenous lesions (2,24,(27)(28)(29)(30)(31) and in this article, we offer an explanation for that phenomenon.…”

Maximizing Local Access to Therapeutic Deliveries in Glioblastoma. Part III: Irreversible Electroporation and High-Frequency Irreversible Electroporation for the Eradication of Glioblastoma

“…The cell-killing effects of H-FIRE were later explored using 3D in vitro tumor constructs and in vivo subcutaneous murine tumors over a wide range of pulse durations (250 ns-100 µs) (41). The in vitro tumor constructs were assembled by mixing murine pancreatic tumor cells with collagen I hydrogel, injecting into cylindrical molds, and polymerizing at 37°C (42); the in vivo subcutaneous tumors were produced by injecting human GBM cells (DBTRG-05MG) into the dorsolateral flank region of athymic nude-Foxn1 nu mice.…”