Enclosure of siRNA in Alternately Hydrophilic–Hydrophobic Double-Layered Nanoarchitectures for Promoted RNAi

To accomplish the transcellular transportation of the RNA interfering payloads, an attempt was made to electrostatically complex an anionic small interfering RNA (siRNA) with the cationic polylysine segments of both hydrophilic poly­(ethylene glycol) (PEG) and thermal-responsive poly­(N-isopropylacrylamide) (PNIPAM) containing block copolymers into nanoscaled delivery systems. Notably, the formulated PLys&siRNA complex was schemed for disulfide cross-linkages with the aim of preventing the premature release of the vulnerable siRNA payloads into the extracellular compartment. Moreover, the thermal-responsive hydrophilic–hydrophobic transition of PNIPAM segments enabled the precise fabrication of hydrophilic PEG and hydrophobic PNIPAM alternative double-layered surroundings along the formulated PLys&siRNA complex core. These unique double-layered surroundings have been validated as vital in protecting the internal vulnerable siRNA payloads, particularly those from enzymatic digestion by the environmental ribonucleases. Therefore, the proposed siRNA delivery constructs have prompted progressive endocytosis into the parathyroid cells due to their persistent retention in the biological environment. Also noteworthy was the fact that the proposed disulfide cross-linkages could be selectively cleaved in the intracellular environment due to the enriched glutathione in the cytosol (in stark contrast to the minimal presence of glutathione in the extracellular environment), thereby facilitating the selective intracellular liberation of the functional siRNA payloads in the RNAi-active cytosol. Eventually, with our proposed siRNA delivery constructs, after encapsulation of the therapeutic siRNA [siPTH: knockdown of the mRNA of parathyroid hormone (PTH) for the potential treatment of hyperparathyroidism], the potent knockdown of parathyroid hormone mRNA and consequent suppressed expression of parathyroid hormone was accomplished. Therefore, the proposed hydrophilic–hydrophobic alternative double-layered nanocapsules can be highlighted in the fabrication of a variety of nanomaterials for the protection of vulnerable payloads in harsh environments.