Delivery systems and their methods of formation are generally provided. The delivery system can protect a delivery molecule (e.g., DNA/RNA) and deliver it into a cell via serum. In one embodiment, the method can include binding a delivery molecule with polyethylenimine such that an end of the delivery molecule is exposed capping the end of the delivery molecule with a first biocompatible polymer to form a core and encapsulating the core with a second biocompatible polymer. The resulting delivery system can include a delivery molecule bonded with polyethylenimine such that an end of the delivery molecule is exposed a first biocompatible polymer electrostatically bonded to the end of the delivery molecule to form a core and a second biocompatible polymer encapsulating the core.
