Protein transfection reagents are tools that allow the delivery of proteins, peptides, antibodies, or other biologically active molecules into cells. This technique is useful for studying gene function and regulation, mutational analysis, and biochemical characterization of gene products, as well as for examining the effects of gene expression on cellular health and life cycle, and for large-scale protein production for purification and downstream applications.

Protein transfection reagents are typically mixtures of cationic lipids that, when complexed with proteins or peptides, bind to negatively charged cell surfaces and fuse with the membrane or are endocytosed by the cell. The complexes then release the captured proteins into the cytoplasm or nucleus, depending on the type of protein and reagent used. Since the formed complex is non-covalent, it does not interfere with the biological activity of the proteins.

Protein transfection is an innovative and promising method for fundamental and applied research in molecular and cellular biology. It offers the ability to modulate gene expression and activity without the need for DNA or RNA transfection. It also allows the delivery of functional proteins that cannot be expressed by host cells or are difficult to produce using conventional methods.