Functionalization of DNA Nanostructures for Cell Signaling Applications

Transforming growth factor ¿ (TGF-¿) is an important cytokine responsible for a wide range of different cellular functions including extracellular matrix formation, angiogenesis and epithelial-mesenchymal transition. We have sought to use selfassembling DNA nanostructures to influence TGF-¿ signaling. Functionalization of DNA nanostructures with TGF-¿ receptor binding peptides allows us to cluster TGF-¿ receptors and lower the energy barrier of TGF-¿ binding thus sensitizing the cells to cytokine stimulation. To functionalize our nanostructures we relied on biotin-streptavidin linkages. This introduces a multivalency that can pose problems in some designs. Therefore we have investigated alternative means of Functionalization such as peptide nucleic acids (PNA). PNA is a synthetic DNA analog consisting of a backbone of repeating N-(2-aminoethyl)-glycine units to which purine and pyrimidine bases are linked by amide bonds. The solid phase synthesis of PNA allows for convenient extension of the backbone into a peptide segment enabling automatic peptide functionalization of DNA nanostructures. Using AFM, we have investigated how the neutral character of the PNA backbone alters the incorporation in DNA-based nanostructures compared to a DNA. Results indicate that PNA can successfully be used to functionalize DNA nanostructures and encourage future studies combining PNA functionalization and cell receptor simulation.