Size-Dependent Knockdown Potential of siRNA-Loaded Cationic Nanohydrogel Particles

Abstract

To overcome the poor pharmacokinetic conditions of short double-stranded RNA molecules in RNA interference therapies, cationic nanohydrogel particles can be considered as alternative safe and stable carriers for oligonucleotide delivery. For understanding key parameters during this process, two different types of well-defined cationic nanohydrogel particles were synthesized, which provided nearly identical physicochemical properties with regards to their material composition and resulting siRNA loading characteristics. Yet, according to the manufacturing process using amphiphilic reactive ester block copolymers of pentafluorophenyl methacrylate (PFPMA) and tri(ethylene glycol)methyl ether methacrylate (MEO3MA) with similar compositions but different molecular weights, the resulting nanohydrogel particles differed in size after cross-linking with spermine (average diameter 40 vs 100 nm). This affected their knockdown potential significantly. Only the 40 nm sized cationic nanogel particles were able to generate moderate gene knockdown levels, which lasted, however, up to 3 days. Interestingly, primary cell uptake and colocalization studies with lysosomal compartments revealed that only these small sized nanogels were able to avoid acidic compartments of endolysosomal uptake pathways, which may contribute to their knockdown ability exclusively. To that respect, this size-dependent intracellular distribution behavior may be considered as an essential key parameter for tuning the knockdown potential of siRNA nanohydrogel particles, which may further contribute to the development of advanced siRNA carrier systems with improved knockdown potential.

Degradable Cationic Nanohydrogel Particles for Stimuli‐Responsive Release of siRNA

“…We have recently developed a new concept to synthesize cationic nanohydrogel particles for cellular delivery [ 19 ] and could demonstrate that these carriers provide suffi cient stability under physiologically relevant conditions [ 20 ] as well as sizedependent transfection effi ciency in vitro. [ 21 ] In this work, the synthetic concept for generating such well-defi ned nanohydrogel particles was extended to integrate redox-degradable moieties into the network for stimuli-responsive release to the oligonucleotide payload as well as nanoparticle degradation. For that purpose, a disulfi de-modifi ed spermine cross-linker was designed by extending the primary spermine amine functionalities with an amine-functionalized disulfi de spacer for reactive ester conversion during nanohydrogel synthesis.…”

Nanogels: An overview of properties, biomedical applications and obstacles to clinical translation

“…For example, it is essential for the nanogels to undergo endosomal/lysosomal escape so that the encapsulated siRNA or oligonucleotides can be released in their active form in the cytosol where they are supposed to show their therapeutic effect [11]. This has brought growing interest in the use of nanogels made of bioresponsive polymers to promote escape by osmotic effects, membrane binding or membrane fusion or using pH-sensitive or reducible crosslinkers to facilitate nanogel destabilization following internalization and enhance delivery efficiency [78-81]. Degradability of the nanogels is also essential to minimize toxicities associated with the accumulation of the carrier in the body.…”

“…Chemical modifications of siRNA may also be used to enhance the transfection efficiency of these nanocarriers and to impart greater stability to their nucleic acid cargoes. The recent report by Zentel group [78] also emphasized that size-dependent uptake and intracellular distribution mechanism of siRNA-loaded cationic nanogels may be essential for tuning their knockdown potential. The authors used two sets of well-defined nanogels based on amphiphilic block copolymers of pentafluorophenyl methacrylate and tri(ethylene glycol) methyl ether methacrylate crosslinked by spermine with diameters of 40 nm and 100 nm.…”

Not Just for Tumor Targeting: Unmet Medical Needs and Opportunities for Nanomedicine

“…Here again, multifunctional nanoparticles can be designed that further co-deliver additional immuno-activation signals, for example, toll-like receptor (TLR) ligands. For these purposes, well-defined cationic nanohydrogel particles, originally engineered for siRNA delivery [23,[36][37][38], could also be loaded with unmethylated cytidine-phosphate-guanosine (CpG) oligonucleotides that activate the intracellular TLR9. This could develop into a potent route for immunoactivation toward cancer [39].…”