RNA transfection is an essential part of the CRISPR-Cas9 gene editing system. The CRISPR-Cas9 system consists of two key components: the Cas9 protein, which acts as a molecular scissors to cut DNA, and a guide RNA (gRNA) that directs Cas9 to the correct location in the genome.

To use the CRISPR-Cas9 system for gene editing, both the Cas9 protein and the gRNA need to be delivered into cells. One common approach is to transfect cells with plasmid DNA that encodes the Cas9 protein and the gRNA. However, RNA transfection can also be used, with some potential advantages:

1. Transfection of mRNA encoding Cas9: Instead of transfecting cells with plasmid DNA that encodes Cas9, cells can be transfected with mRNA that encodes Cas9. This approach can be advantageous because it avoids the potential risks associated with DNA delivery, such as integration into the genome and long-term expression of Cas9, which can lead to off-target effects.

2. Transfection of gRNA: The gRNA can also be delivered into cells by transfection. This can be done either by transfecting a plasmid that encodes the gRNA, or by directly transfecting the gRNA itself. Direct transfection of gRNA can be advantageous because it can result in faster and more predictable gRNA expression compared to plasmid-based delivery.

For both Cas9 mRNA and gRNA, transfection can be done using various methods, including lipid-based transfection, electroporation, and nucleofection. The choice of method depends on the specific needs of the experiment, including the type of cells being used and the desired efficiency and duration of gene editing.

It’s also worth noting that other RNA-based gene editing systems, such as the CRISPR-Cas13 system for RNA editing, also rely on RNA transfection for delivery of the necessary components into cells.