Cationic star polymer siRNA transfectants interconnected with a piperazine-based cationic cross-linker

Star polymers with acid-labile diacetal-based cores synthesized by aqueous RAFT polymerization for intracellular DNA delivery

Facile low temperature aqueous heterogeneous RAFT polymerization for preparation of novel star polymers with acid-labile diacetal-based cores for DNA delivery.

Star Polymers

Recent advances in controlled/living polymerization techniques and highly efficient coupling chemistries have enabled the facile synthesis of complex polymer architectures with controlled dimensions and functionality. As an example, star polymers consist of many linear polymers fused at a central point with a large number of chain end functionalities. Owing to this exclusive structure, star polymers exhibit some remarkable characteristics and properties unattainable by simple linear polymers. Hence, they constitute a unique class of technologically important nanomaterials that have been utilized or are currently under audition for many applications in life sciences and nanotechnologies. This article first provides a comprehensive summary of synthetic strategies towards star polymers, then reviews the latest developments in the synthesis and characterization methods of star macromolecules, and lastly outlines emerging applications and current commercial use of star-shaped polymers. The aim of this work is to promote star polymer research, generate new avenues of scientific investigation, and provide contemporary perspectives on chemical innovation that may expedite the commercialization of new star nanomaterials. We envision in the not-too-distant future star polymers will play an increasingly important role in materials science and nanotechnology in both academic and industrial settings.

Peptide-Based Star Polymers as Potential siRNA Carriers

16- and 32-arm star polymers were synthesised using poly(amido amine) (PAMAM) dendrimers as multifunctional initiators for the ring-opening polymerisation (ROP) of ϵ-Z-l-lysine N-carboxyanhydride (Lys NCA) via the core-first approach. The resulting star polymers were subsequently post-functionalised with poly(ethylene glycol) (PEG) via carbodiimide coupling, potentially improving the biodistribution of the stars in vivo. De-protection of the carboxybenzyl (Cbz)-protected star arms yielded water-soluble cationic poly(l-lysine) (PLL) star polymers with hydrodynamic radii ranging from 2.0 to 3.3 nm. Successful complexation of the PLL star polymers with double-stranded oligodeoxynucleotides (ODNs)—a mimic for small interfering RNA (siRNA)—was achieved at a nitrogen-to-phosphate (N/P) ratio of 5. Cell viability studies using HEK293T cells indicated the ‘safe’ concentration for these polymers is within a suitable window for the delivery of siRNA therapeutics.

Nanoparticulate nonviral agent for the effective delivery of pDNA and siRNA to differentiated cells and primary human T lymphocytes

Delivery of polynucleotides such as plasmid DNA (pDNA) and siRNA to nondividing and primary cells by nonviral vectors presents a considerable challenge. In this contribution, we introduce a novel type of PDMAEMA-based star-shaped nanoparticles that (i) are efficient transfection agents in clinically relevant and difficult-to-transfect human cells (Jurkat T cells, primary T lymphocytes) and (ii) can efficiently deliver siRNA to human primary T lymphocytes resulting to more than 40% silencing of the targeted gene. Transfection efficiencies achieved by the new vectors in serum-free medium are generally high and only slightly reduced in the presence of serum, while cytotoxicity and cell membrane disruptive potential at physiological pH are low. Therefore, these novel agents are expected to be promising carriers for nonviral gene transfer. Moreover, we propose a general design principle for the construction of polycationic nanoparticles capable of delivering nucleic acids to the above-mentioned cells.