A first aspect of the invention relates to the use of a saponin in the in vitro delivery of a nucleic acid into a cell. Typically, the nucleic acid is plasmid DNA, e.g. with a relatively large size of at least 5.5 kbp. In embodiments, the nucleic acid is transfected into cells in the presence of saponin GE1741 and/or saponin SO1861. A second aspect of the invention relates to a method for delivering a nucleic acid encoding for a CRISPR/Cas construct into a cell in vitro. Typically, the nucleic acid is plasmid DNA, e.g. with a relatively large size of at least 5.5 kbp. In embodiments, the nucleic acid is transfected into cells in the presence of saponin GE1741 and/or saponin SO1861. In embodiments, the nucleic acid is combined with poly-lysine, forming nanoplexes for transfection of the nucleic acid into a In cell. A third aspect of the invention relates to a kit of parts for delivering a nucleic acid encoding for a CRISPR/Cas construct into a cell in vitro. In addition, the invention also relates to a nanoparticle suitable for in vitro delivery of a nucleic acid into a cell, the nanoparticle comprising or consisting of a nucleic acid encoding for a CRISPR/Cas construct, a poly-lysine peptide and optionally a saponin.