Name two common methods for delivering CRISPR components into cells.

• A. Viral vectors and electroporation
• B. Plasmid-based transfection and ribonucleoprotein (RNP) complex delivery
• C. Lipid-free delivery and heat shock
• D. Direct DNA sequencing and cloning

Answer: (B)

Delivering CRISPR components into cells can be done in a few practical ways, with two approaches standing out for broad use. Plasmid-based transfection introduces a DNA plasmid that encodes both the Cas9 enzyme and the guide RNA. Once inside the cell, the plasmid is transcribed and translated, producing Cas9 and the guide RNA to direct cutting at the target site. This method is easy to implement, scalable, and cost-effective, making it a go-to choice in many labs. However, because Cas9 expression can be prolonged, there’s a higher chance of off-target activity and, in some contexts, unintended DNA integration of the plasmid.

Ribonucleoprotein delivery is the other widely used route, where pre-assembled Cas9 protein complexed with the guide RNA is delivered directly into cells. Editing starts quickly, and because the complex is degraded over time, the window for off-target effects is shorter and there’s no risk of DNA integration. This approach often provides better control over editing and is especially useful when working with primary cells or when minimizing genomic integration is important. It does require handling and purification of the Cas9–gRNA complex and can need optimization for different cell types.

Other listed options represent real techniques in biology, like viral delivery or physical methods such as electroporation, but the combination of plasmid-based transfection and RNP delivery best captures the most common, versatile, non-viral strategies used to introduce CRISPR components into cells.