Described are nucleic acids encoding a polypeptide for delivery of a nanoparticle to the cytosol, the peptide comprising: (a) a nanoparticle association domain, (b) a spacer domain, (c) an uptake domain, and (d) a vesicle escape domain, wherein the domains (a) through (d) appear in the same order as listed above, and wherein the peptide, upon addition of a non-hydrolyzable lipophilic moiety to the vesicle escape domain and binding to a nanoparticle, is effective to induce uptake of a nanoparticle by a cell and delivery of the nanoparticle to the cytosol of the cell. Also described are methods of delivery of a nanoparticle to the cytosol of a cell, the method comprising providing to a cell a nanoparticle attached to such a peptide. Exemplary nanoparticles include quantum dots.