A Novel Electroporation System for Living Cell Staining and Membrane Dynamics Interrogation

A live mammalian cells electroporation array for on-chip immunofluorescence

The detection of intracellular proteins in vitro is commonly realized with immunofluorescence techniques, through which antibodies or markers are delivered into fixed cells and recognize specific proteins. Many innovative techniques, however, avoid cells fixation by chemical compounds and, among the others, electroporation is widely used. Here we demonstrate that in situ electroporation on thin film SiO2 capacitive microelectrodes can be realized with high efficiency to deliver fluorescent markers and antibodies into mammalian cell lines and primary neuronal cells to detect intracellular proteins, like actin. The results presented in this work open the way to the use of this technique for the detection of potentially any target protein, even through subsequent electroporations.

Recent Advances in Microscale Electroporation

Electroporation (EP) is a commonly used strategy to increase cell permeability for intracellular cargo delivery or irreversible cell membrane disruption using electric fields. In recent years, EP performance has been improved by shrinking electrodes and device structures to the microscale. Integration with microfluidics has led to the design of devices performing static EP, where cells are fixed in a defined region, or continuous EP, where cells constantly pass through the device. Each device type performs superior to conventional, macroscale EP devices while providing additional advantages in precision manipulation (static EP) and increased throughput (continuous EP). Microscale EP is gentle on cells and has enabled more sensitive assaying of cells with novel applications. In this Review, we present the physical principles of microscale EP devices and examine design trends in recent years. In addition, we discuss the use of reversible and irreversible EP in the development of therapeutics and analysis of intracellular contents, among other noteworthy applications. This Review aims to inform and encourage scientists and engineers to expand the use of efficient and versatile microscale EP technologies.

In Situ Deployment of Engineered Extracellular Vesicles into the Tumor Niche via Myeloid-Derived Suppressor Cells

Extracellular vesicles (EVs) have emerged as a promising carrier system for the delivery of therapeutic payloads in multiple disease models, including cancer. However, effective targeting of EVs to cancerous tissue remains a challenge. Here, it is shown that nonviral transfection of myeloid-derived suppressor cells (MDSCs) can be leveraged to drive targeted release of engineered EVs that can modulate transfer and overexpression of therapeutic anticancer genes in tumor cells and tissue. MDSCs are immature immune cells that exhibit enhanced tropism toward tumor tissue and play a role in modulating tumor progression. Current MDSC research has been mostly focused on mitigating immunosuppression in the tumor niche; however, the tumor homing abilities of these cells present untapped potential to deliver EV therapeutics directly to cancerous tissue. In vivo and ex vivo studies with murine models of breast cancer show that nonviral transfection of MDSCs does not hinder their ability to home to cancerous tissue. Moreover, transfected MDSCs can release engineered EVs and mediate antitumoral responses via paracrine signaling, including decreased invasion/metastatic activity and increased apoptosis/necrosis. Altogether, these findings indicate that MDSCs can be a powerful tool for the deployment of EV-based therapeutics to tumor tissue.

Dielectric Dispersion Modulated Sensing of Yeast Suspension Electroporation

A specific pulsed electric field protocol can be used to induce electroporation. This is used in the food industry for yeast pasteurization, in laboratories for generic transfer and the medical field for cancer treatment. The sensing of electroporation can be done with simple ‘instantaneous’ voltage-current analysis. However, there are some intrinsic low-frequency phenomena superposing the electroporation current, such as electrode polarization. The biological media are non-homogeneous, giving them specific characterization in the broad frequency spectrum. For example, the cell barrier, i.e., cell membrane, causes so called β-dispersion in the frequency range of tens to thousands of kHz. Electroporation is a dynamic phenomenon characterized by altering the cell membrane permeability. In this work, we show that the impedance measurement at certain frequencies could be used to detect the occurrence of electroporation, i.e., dielectric dispersion modulated sensing. This approach may be used for the design and implementation of electroporation systems. Yeast suspension electroporation is simulated to show changes in the frequency spectrum. Moreover, the alteration depends on characteristics of the system. Three types of external buffers and their characteristics are evaluated.

In situ electroporation of mammalian cells through SiO2 thin film capacitive microelectrodes

Electroporation is a widely used non-viral technique for the delivery of molecules, including nucleic acids, into cells. Recently, electronic microsystems that miniaturize the electroporation machinery have been developed as a new tool for genetic manipulation of cells in vitro, by integrating metal microelectrodes in the culture substrate and enabling electroporation in-situ. We report that non-faradic SiO₂ thin film-insulated microelectrodes can be used for reliable and spatially selective in-situ electroporation of mammalian cells. CHO-K1 and SH-SY5Y cell lines and primary neuronal cultures were electroporated by application of short and low amplitude voltage transients leading to cell electroporation by capacitive currents. We demonstrate reliable delivery of DNA plasmids and exogenous gene expression, accompanied by high spatial selectivity and cell viability, even with differentiated neurons. Finally, we show that SiO₂ thin film-insulated microelectrodes support a double and serial transfection of the targeted cells.