Comparison of Bipolar and Unipolar Pulses in Cell Electrofusion: Simulation and Experimental Research

Influences of pulsed electric field parameters on cell electroporation and electrofusion events: Comprehensive understanding by experiments and molecular dynamics simulations

Electroporation and electrofusion are efficient methods, which have been widely used in different areas of biotechnology and medicine. Pulse strength and width, as an external condition, play an important role in the process of these methods. However, comparatively little work has been done to explore the effects of pulsed electric field parameters on electroporation and electrofusion. Herein, influences of pulse strength and width on the electroporation and electrofusion of phospholipid bilayers were systematically investigated by using experiments combined with molecular dynamics simulations. Experimental results and machine learning-based regression analysis showed that the number of pores is mainly determined by pulse strength, while the sizes of pores were enlarged by increasing the pulse widths. In addition, the formation of large-size pores is the most crucial factor that affects the fusion rate of myeloma cells. The same trend has taken place on coarse-grained and all-atom MD simulations. The result suggested that electroporation events occur only in an electric field exceeding the strength of threshold, and the unbalanced degree of electric potential between two membranes leads to pores formation during the process of electroporation. Generally, this work provides a comprehensive understanding of how pulse strength and width govern the poration event of bilayer lipid membranes, as well as guidance on the experimental design of electrofusion.

Advances in hybridoma preparation using electrofusion technology

As a rapidly developing cell engineering technique, cell electrofusion has been increasingly applied in the field of hybridoma preparation in recent years. However, it is difficult to completely replace the polyethylene glycol-mediated cell fusion using electrofusion due to the high operation requirements, high cost of electrofusion instruments, and lack of prior reference research work. The key elements limiting electrofusion in the field of hybridoma preparation also introduce practical complications, such as the use/choice of electrofusion instruments, setup/optimization of electrical parameters, and precise control of cells. This review summarizes the state of the art of cell electrofusion in hybridoma preparation based on recent published literature, mainly focusing on electrofusion instruments and their components, process control and characterization, and cell treatment. It also provides new information and insightful commentary critically important for further electrofusion development in the field of hybridoma preparation.

Artificial intelligence-accelerated high-throughput screening of antibiotic combinations on a microfluidic combinatorial droplet system

Microfluidic platforms have been employed as an effective tool for drug screening and exhibit the advantages of lower reagent consumption, higher throughput and a higher degree of automation. Despite the great advancement, it remains challenging to screen complex antibiotic combinations in a simple, high-throughput and systematic manner. Meanwhile, the large amounts of datasets generated during the screening process generally outpace the abilities of the conventional manual or semi-automatic data analysis. To address these issues, we propose an artificial intelligence-accelerated high-throughput combinatorial drug evaluation system (AI-HTCDES), which not only allows high-throughput production of antibiotic combinations with varying concentrations, but can also automatically analyze the dynamic growth of bacteria under the action of different antibiotic combinations. Based on this system, several antibiotic combinations displaying an additive effect are discovered, and the dosage regimens of each component in the combinations are determined. This strategy not only provides useful guidance in the clinical use of antibiotic combination therapy and personalized medicine, but also offers a promising tool for the combinatorial screenings of other medicines.

Substantially Improved Electrofusion Efficiency of Hybridoma Cells: Based on the Combination of Nanosecond and Microsecond Pulses

As the initial antibody technology, the preparation of hybridoma cells has been widely used in discovering antibody drugs and is still in use. Various antibody drugs obtained through this technology have been approved for treating human diseases. However, the key to producing hybridoma cells is efficient cell fusion. High-voltage microsecond pulsed electric fields (μsHVPEFs) are currently one of the most common methods used for cell electrofusion. Nevertheless, the membrane potential induced by the external microsecond pulse is proportional to the diameter of the cell, making it difficult to fuse cells of different sizes. Although nanosecond pulsed electric fields (nsPEFs) can achieve the fusion of cells of different sizes, due to the limitation of pore size, deoxyribonucleic acid (DNA) cannot efficiently pass through the cell pores produced by nsPEFs. This directly causes the significant loss of the target gene and reduces the proportion of positive cells after fusion. To achieve an electric field environment independent of cell size and enable efficient cell fusion, we propose a combination of nanosecond pulsed electric fields and low-voltage microsecond pulsed electric fields (ns/μsLVPEFs) to balance the advantages and disadvantages of the two techniques. The results of fluorescence experiments and hybridoma culture experiments showed that after lymphocytes and myeloma cells were stimulated by a pulse (ns/μsLVPEF, μsHVPEF, and control), compared with μsHVPEF, applying ns/μsLVPEF at the same energy could increase the cell fusion efficiency by 1.5–3.0 times. Thus far, we have combined nanosecond and microsecond pulses and provided a practical solution that can significantly increase cell fusion efficiency. This efficient cell fusion method may contribute to the further development of hybridoma technology in electrofusion.

Response characteristics and optimization of electroporation: simulation based on finite element method

Electroporation has been widely used in biology, medicine, and the food industry as a means to transport various molecules through the cell membrane. The phenomenon of electroporation is the result of cell membrane damage caused by the application of an electric field. In order to understand more precisely how cells function, we established a dielectric model of a spherical cell and analyzed its characteristics by the finite element method. The effects of altering different electrical parameters were determined. The results showed that the electric field strength was positively related to the transmembrane voltage (TMV) and pore density. There was a minimum electric field strength necessary to induce a critical TMV for the formation of pores. Pulse width also had to be long enough to charge the cell membrane, compared with the normal membrane charging time constant of about 1 μs. When the pulse width was shorter than the charging time constant, it was necessary to increase pulse frequency to create a high enough TMV. The rise-time of the electric pulse also affected electroporation: a fast rise-time pulse not only allowed penetration of the plasma membrane but also the organelle membrane. With slow rise-time pulse, the organelle was shielded from electroporation. This study defines the response characteristics of electrical parameters on the electric load cell and establishes the specificity of parameters for different purposes.