Abstract: An object of the present invention is to provide a method for improving a proportion of capsids containing a gene of interest GOI in a method for producing a virus, and to provide a method for improving a proportion of capsids containing a gene of interest GOI in a method for introducing a nucleic acid into cells, the method including a nucleic acid introduction step of adding a nucleic acid to a suspension containing cells. According to the present invention, there is provided a method for producing a virus, the method including a nucleic acid introduction step of adding a nucleic acid to a suspension containing cells having a density of 10×106 cells/mL or more, and a culture step of culturing the cells into which the nucleic acid has been introduced, in which the nucleic acid is added in a case where a population cell doubling time of the suspension satisfies 35.4 hours or less.

Abstract: An object of the present invention is to provide a virus production method capable of improving an amount of virus production. According to the present invention, there is provided a virus production method including a nucleic acid introduction step of introducing a nucleic acid into cells via electroporation to obtain cells into which the nucleic acid has been introduced; and a culture step of culturing the cells into which the nucleic acid has been introduced, in which a CNET product defined in the present specification in the electroporation is 1×104 or more and 1×107 or less.

Abstract: An object of the present invention is to provide a method for producing a nucleic acid-introduced cell, in which a transfection efficiency is improved, and to provide a method for producing a useful substance using the nucleic acid-introduced cell. According to the present invention, there is provided a method for producing a nucleic acid-introduced cell, including (a) a treatment step of reducing an unnecessary nucleic acid in a cell-containing solution, and (b) an introduction step of introducing a target nucleic acid into a cell by adding the target nucleic acid to the cell-containing solution.

Abstract: The producing method according to the disclosed technology is a producing method for an organism-derived material into which a bioactive substance has been introduced, the producing method comprising a step of causing a suspension containing the organism-derived material before the introduction of the bioactive substance and containing the bioactive substance to pass through a first electric field region having a first electric field intensity; and a step of causing the suspension to pass through a second electric field region having a second electric field intensity lower than the first electric field intensity after the suspension has passed through the first electric field region. The organism-derived material is a human-derived cell.