Rational Design of Multilayer Collagen Nanosheets with Compositional and Structural Control

Two collagen-mimetic peptides, <b>CP</b>^<b>+</b> and <b>CP</b>^<b>–</b>, are reported in which the sequences comprise a multiblock architecture having positively charged N-terminal (Pro-Arg-Gly)₃ and negatively charged C-terminal (Glu-Hyp-Gly)₃ triad extensions, respectively. <b>CP</b>^<b>+</b> rapidly self-associates into positively charged nanosheets based on a monolayer structure. In contrast, <b>CP</b>^<b>–</b> self-assembles to form negatively charged monolayer nanosheets at a much slower rate, which can be accelerated in the presence of calcium­(II) ion. A 2:1 mixture of unassociated <b>CP</b>^<b>–</b> peptide with preformed <b>CP</b>^<b>+</b> nanosheets generates structurally defined triple-layer nanosheets in which two <b>CP</b>^<b>–</b> monolayers have formed on the identical surfaces of the <b>CP</b>^<b>+</b> nanosheet template. Experimental data from electrostatic force microscopy (EFM) image analysis, zeta potential measurements, and charged nanoparticle binding assays support a negative surface charge state for the triple-layer nanosheets, which is the reverse of the positive surface charge state observed for the <b>CP</b>^<b>+</b> monolayer nanosheets. The electrostatic complementarity between the <b>CP</b>^<b>+</b> and <b>CP</b>^<b>–</b> triple helical cohesive ends at the layer interfaces promotes a (<b>CP</b>^<b>–</b>/<b>CP</b>^<b>+</b>/<b>CP</b>^<b>–</b>) compositional gradient along the <i>z</i>-direction of the nanosheet. This structurally informed approach represents an attractive strategy for the fabrication of two-dimensional nanostructures with compositional control