An engineered payload-delivery system includes a target cell binding unit, covlently bound to a pore forming unit, and a payload portion adapted with a region capable of non-covalently binding to the pore forming unit. The pore forming unit is derived from a particular sub-serotype of Clostridium toxin, while the payload region is derived from a different sub-serotype of Clostridium toxin. The disclosed chimeri protein-based composition is capable of specifically delivering payload to neural cells
