Persistent gene silencing is crucially required for the successful therapeutics of short interfering RNA (siRNA). Here, we describe a nanoparticle based delivery system which assembled by layering siRNAs between protease degradable polypeptides to extend the therapeutic window. These tightly packed nanoparticles are efficiently taken up by cells by endocytosis, and the fabricated siRNAs are gradually released following intracellular degradation of the polypeptide layers. During cell division, the particles are distributed to the daughter cells. Due to the slow degradation through the multiple layers, the particles continuously release siRNA in all cells. Using this controlled release construct, the gene silencing effect of siRNA is consistent for an ultra-long period of time (>3 weeks) with only a single treatment.