Schematic representation of the structure of spider silk penta-block polymer. (a) Spider silk core sequence; (b) cell specific peptides and payload sequences; (c) cell-penetrating peptide and nuclear localization sequences used in the study; (d) recombinant DNA strategy used to prepare the spider silk gene delivery systems for the study. NcoI, NheI, SpeI, XhoI are restriction enzymes (RE). A box above/below a specific RE indicates an oligonucleotide sequence recognized by this RE. Pet30a(+) plasmid is in blue, cloning linker is in yellow, spider silk monomer is in dark blue, poly-L-lysine sequence is in magenta, HAB peptide is in orange and NLS is in green.