Methods for introducing a linear nucleic acid molecule of interest into a cell comprising a cell wall include use of nanoparticles coated with polyethylene glycol. In some embodiments, the cell comprising a cell wall is a plant cell. Methods include genetically or otherwise modifying plants and for treating or preventing disease in plant cells comprising a cell wall. Transgenic plants include a nucleic acid molecule of interest produced by regeneration of whole plants from plant cells transformed with linear nucleic acid molecules.