Gene therapy is one of the most promising medical fields which holds the potential to rapidly advance the treatment of difficult ailments such as cancer as well as inherited genetic diseases. However, clinical translation is limited by several drug delivery hurdles including renal clearance, phagocytosis, enzymatic degradation, protein absorption, as well as cellular internalization barriers. Additionally, successful treatments require sustained release of drug payloads to maintain the effective therapeutic level. As such, controlled and sustained release is a significant concern as the localization and kinetics of nucleic acid therapeutics can significantly influence the therapeutic efficacy. This is an unmet need which calls for the development of controlled-release nanoparticle (NP) technologies to further improve the gene therapy efficacy by prolonging the release of nucleic acid drug payload for sustained, long-term gene expression or silencing. Herein, we present a polymeric NP system with sustained gene delivery properties, which can be synthesized using biodegradable and biocompatible polymers via self-assembly VSports手机版. The NP delivery system is composed of a polymeric NP which acts as a drug depot encapsulating cationic polymer/nucleic acid complexes, facilitating the enhanced retention and prolonged release of the gene payload. The NPs showed excellent cellular biocompatibility and gene delivery efficacy using the green fluorescent protein (GFP) encoded DNA plasmid (pGFP) as a reporter gene. Sustained release of the pGFP payload was shown over a period of 8 days. The physicochemical properties such as morphology, particle size, zeta potential, pGFP encapsulation efficiency and biological properties such as pGFP release profile, in vitro cytotoxicity and transfection efficacy in Hek 293 cells were characterized and evaluated. Importantly, the NP-mediated sustained release of pGFP generates enhanced GFP expression over time. We expect this NP-mediated gene delivery system to provide safe and sustained release of various nucleic acid-based therapeutics with applications in both fundamental biological studies and clinical translations. .