Which delivery method describes the use of pre-assembled Cas9 protein with guide RNA?

• A. Lipid nanoparticle delivery
• B. Ribonucleoprotein complex delivery using pre-assembled Cas9 protein with guide RNA
• C. Viral transduction
• D. Plasmid-based transfection

Answer: (B)

The technique being described is delivering the Cas9 protein already bound to its guide RNA as a ribonucleoprotein complex. By pre-assembling Cas9 with the guide RNA before delivery, the editing machinery is active as soon as it enters the cell, so edits can start immediately without needing the cell to transcribe and translate anything. This makes the approach fast and transient, reducing the chance of Cas9 lingering in the cell and potentially cutting unintended sites or integrating into the genome. It’s a non-viral delivery of the active protein–RNA complex, often accomplished with methods like electroporation or lipid-based carriers, and it contrasts with delivering DNA or RNA that must first be expressed to produce Cas9 and the guide RNA.