Nanofabrication of helical peptide-shelled dendrimers

This study describes nanofabrication of helical peptide-shelled dendrimers using a Langmuir monolayer technique. Poly(amido amine) dendrimers (G3) modified with poly(gamma-benzyl-L-glutamate) [number averaged degree of polymerization, n = 12, 17, and 34 (G3-PBLGs hereafter)] were newly prepared by graft polymerization of gamma-benzyl-L-glutamate-N-carboxy anhydride initiated with amino groups of the dendrimer surface. The hydrodynamic diameters of G3-PBLGs were determined to be 6.9 +/- 0.7, 8.2 +/- 1.0, and 11.9 +/- 1.7 nm for n = 12, 17, and 34, respectively, by means of dynamic light scattering. These values were consistent with the theoretical diameters of G3-PBLGs, which were calculated by considering the alpha-helical PBLG segment length. G3-PBLGs were found to form stable monomolecular films with high collapse pressures above 40 mN m-1 at the air-water interface. In addition, these monolayers could be successfully transferred onto various solid substrates. Circular dichroism and Fourier transfer infrared spectroscopies of the deposited G3-PBLGs monolayers showed that PBLG segments took an alpha-helical conformation over a wide range of surface pressure even on solid substrates as well as in bulk solutions. Monolayer thicknesses of these Langmuir-Blodgett films, estimated by x-ray photoelectron spectroscopy and atomic force microscopy, were compatible with the hydrodynamic diameters of G3-PBLGs.