Relevance of bi-functionalized polyelectrolyte multilayers for cell transfection

In an effort to develop new biomaterial coatings, it was shown that polyelectrolyte multilayers constitute a very powerful tool to render surfaces biologically active. The challenge is to multi-functionalize surfaces in a controlled way. We show here, for the first time, that it is possible to functionalize multilayer films simultaneously with two molecules acting in totally different ways on cells, namely plasmid DNA (pDNA), pre-complexed with poly(ethyleneimine) (PEI), and a peptide molecule, NDPMSH. This peptide, grafted to poly(l-glutamic acid) (PGA) was used as a signal molecule for melamona cells B16-F1 and for its ability to enhance gene delivery in a receptor-independent manner. The PGA–NDPMSH chains are embedded in poly-(allylamine hydrochloride)/poly-(sodium 4-styrene sulfonate) multilayers and the pDNA–PEI complexes are deposited on top of the films. It is shown that melanoma cells (B16-F1) are efficiently transfected after 24 h of contact with functionalized films. When brought in contact with Huh-7 cells that do not express the peptide receptors, these films trigger significantly the transfection rate, showing that it is possible to enhance the transfection process by incorporating specific peptides into multilayer films. Moreover, transfected cells sorted by flow cytometry produce melanin, demonstrating both activation via the peptide signaling pathway and cell transfection.