Engineering Lacl for Self Assembly of Inorganic Nanoparticles on DNA Scaffold through the Understanding of Lacl Binding to Solid Surfaces

The potential of utilizing the DNA binding protein lac repressor (Lacl) to organize inorganic nanoparticles (NPs) is explored in this study. A peptide cognitive of both SiO2 and TiO2 simultaneously (STB1, -CHKKPSKSC-) is genetically engineered into the C-terminus of Lacl-STB1, and the inserted STB1 peptides in the context of Lacl-STB1 molecules are shown to actively interact with both SiO2 and TiO2. Wild-type Lacl is found to interact with the two surfaces at its flexible N-terminal DNA binding domain, and Lacl-STB1 exhibits much stronger binding affinity to both surfaces by harnessing a second binding region (STB1 peptide) fused at its C-terminus. The quantitative analysis of binding kinetics reveals that, compared to wild-type Lacl with one binding region (N-terminus), two remote bindings regions (N-terminus and C-terminus) in Lacl-STB1 do not lead to faster adsorption rates to the two surfaces, but remarkably slow down the desorption rates. Finally, using Lacl-STB1 as a linker, the successful assembly of a sandwich nanostructure of DNA/Lacl-STB1/TiO2 NPs is demonstrated using surface plasmon resonance (SPR) measurements and TEM. The demonstrated Lacl-STB1-mediated assembly of TiO2 NPs on DNA scaffold may provide a generic platform for controlled spatial arrangement of various nanoparticles of engineering interest.