Cationic Nanohydrogel Particles as Potential siRNA Carriers for Cellular Delivery

Abstract

Oligonucleotides such as short, double-stranded RNA (siRNA) or plasmid DNA (pDNA) promise high potential in gene therapy. For pharmaceutical application, however, adequate drug carriers are required. Among various concepts progressing in the market or final development, nanosized hydrogel particles may serve as novel transport media especially for siRNA. In this work, a new concept of synthesizing polymeric cationic nanohydrogels was developed, which offers a promising strategy to complex and transport siRNA into cells. For this purpose, amphiphilic reactive ester block copolymers were synthesized by RAFT polymerization of pentafluorophenyl methacrylate as reactive ester monomer together with tri(ethylene glycol)methyl ether methacrylate. In polar aprotic solvents, a self-assembly of these polymers could be observed leading to the formation of nanometer-sized polymer aggregates. The resulting superstructures were used to convert the reactive precursor block copolymers with amine-containing cross-linker molecules into covalently stabilized hydrogel particles. Detailed dynamic light scattering studies showed that the structure of the self-assembled aggregates can permanently be locked-in by this process. This method offers a new possibility to synthesize precise nanohydrogels of different size starting from various block copolymers. Moreover, via reactive ester approach, further functionalities could be attached to the nanoparticle, such as fluorescent dyes, which allowed distinct tracing of the hydrogels during complexation with siRNA or cell uptake experiments. In this respect, cellular uptake of the particles themselves as well as with its payload could be detected successfully. Looking ahead, these novel cationic nanohydrogel particles may serve as a new platform for proper siRNA delivery systems.

Core/shell Protein-Reactive Nanogels Via a Combination of RAFT Polymerization and Vinyl Sulfone Postmodification

“…In analogy to earlier reports [22] In analogy to earlier reports [22], a Schlenk tube equipped with a stir bar was loaded with PFPMA (2.0 g; 7.932 mmol), CETPA (83.6 mg; 0.317 mmol) and AIBN (5.2 mg; 0.032 mmol). All compounds were dissolved in anhydrous dioxane (2.0 ml).…”

“…RAFT CTA 4-cyano-4-[(ethylsulfanylthiocarbonyl) sulfanyl]pentanoic acid (CETPA) and 4-cyano-4-(phenylcarbonothioylthio)pentanoic acid (CPTPA) and the monomers tri(ethylene glycol) methyl ether methacrylate (mTEGMA) and PFPMA were synthesized according to established procedures [22,28]. Amicon ® Ultra-15 centrifugal filters with a MWCO of 3 or 10 kDa were obtained from Merck Millipore.…”

“…After re-dissolving in few ml of dioxane, this process was repeated three times. The precipitated polymer was dried for 12 h at 40°C under 10 mbar vacuum affording pPF-PMA 46 (1) In analogy to earlier reports [22], a Schlenk tube equipped with a stir bar was loaded with mTEGMA (760 mg; 3.27 mmol), pPFPMA 33 (425 mg; 0.049 mmol) and AIBN (1.1 mg; 0.07 mmol). All compounds were dissolved in anhydrous dioxane (2.34 ml).…”

“…The PEG-like hydrophilic block was used to provide nanoparticle stability and tissue mobility as recently demonstrated by us and others [6,9,21]. The PFPMA block allowed for self-assembly into nanoparticles in polar aprotic solvents (such as DMSO) followed by functionalization and crosslinking of the PFP esters with bisamines (containing a degradable linker) [22] without facing competing hydrolysis reactions that would occur in aqueous medium [23]. Furthermore, remaining PFP esters could be converted into hydrophilic moieties to yield fully hydrated nanogels after transfer to aqueous medium.…”

Living Radical Polymerization by the RAFT Process – A Third Update

“…[267] Pressley et al [611] have reported on an improved methodology for conducting click reactions to form block and cyclic polymers. [227] PFPMA/LMA Ph AIBN 25 70 100 [225] BA Ph AIBN 30 80 ,25 [194] HA Ph ACPA 5 70 100 [240] HA Ph AHPN 5 70 100 [240] BA/NA Ph AIBN 20 80 100 [202] BA C 4 H 9 S AIBN 30 80 ,25 [194] BA C 4 H 9 S AIBN þ BPO 20 þ 2 E 80 100 [194] HPA [596] tBA Poly(tBA)S AIBN -80 100 [597] NIPAm Poly(tBA-b-NIPAm)S AIBN -80 100 [597] tBA/TBBPMA Ph AIBN (20) (80) 100 [598] DAMEA/TFEA C 12 H 25 S AIBN 20 65 100 [599] HADA [194] St Ph AIBN þ BPO 20 þ 2 E 80 100 [194] St C 4 H 9 S AIBN 30 À 100 80 ,60 [194] St C 12 H 25 S AIBN 10 95 92 [393] A Monomer unit adjacent to thiocarbonylthio group. The process makes use of commercially available copper nanoparticles and is performed with microwave irradiation.…”