The present technology relates to the field of
drug delivery and provides a molecule comprising or consisting of at least one
protein-based carrier
building unit, wherein the
protein-based carrier
building unit comprises at least one, preferably at least two attachment points or conjugation sites. In particular, the present technology provides a molecule comprising at least one
protein-based
building unit, wherein the at least one protein-based building unit: a) comprises at least one conjugation site or attachment point; b) has a molecular weight of 2.5 to 70 kDa; c) has a globular three-dimensional (3D) structure; d) has a
solubility of 10 mg / mL or more, measured in
aqueous solution at
room temperature; and does not specifically bind to any human protein or binds to one or more
human proteins with a K D value of more than 5 x 10 ‑4 mol /
liter, wherein the molecule further comprises at least one
nuclear localization sequence (NLS) covalently linked to the at least one conjugation site or attachment point comprised in the protein-based carrier building unit, directly or via a
linker, wherein the NLS preferably comprises or consists of SEQ ID NO: 221.