Star Polymers from Single-Chain Cyclized/Knotted Nanoparticles as a Core

Recent progress of non-linear topological structure polymers: synthesis, and gene delivery

Currently, many types of non-linear topological structure polymers, such as brush-shaped, star, branched and dendritic structures, have captured much attention in the field of gene delivery and nanomedicine. Compared with linear polymers, non-linear topological structural polymers offer many advantages, including multiple terminal groups, broad and complicated spatial architecture and multi-functionality sites to enhance gene delivery efficiency and targeting capabilities. Nevertheless, the complexity of their synthesis process severely hampers the development and applications of nonlinear topological polymers. This review aims to highlight various synthetic approaches of non-linear topological architecture polymers, including reversible-deactivation radical polymerization (RDRP) including atom-transfer radical polymerization (ATRP), nitroxide-mediated polymerization (NMP), reversible addition-fragmentation chain transfer (RAFT) polymerization, click chemistry reactions and Michael addition, and thoroughly discuss their advantages and disadvantages, as well as analyze their further application potential. Finally, we comprehensively discuss and summarize different non-linear topological structure polymers for genetic materials delivering performance both in vitro and in vivo, which indicated that topological effects and nonlinear topologies play a crucial role in enhancing the transfection performance of polymeric vectors. This review offered a promising guideline for the design and development of novel nonlinear polymers and facilitated the development of a new generation of polymer-based gene vectors.

3D Macrocyclic Structure Boosted Gene Delivery: Multi-Cyclic Poly(β-Amino Ester)s from Step Growth Polymerization

The topological structures of polymers play a critical role in determining their gene delivery efficiency. Exploring novel polymeric structures as gene delivery vectors is thus of great interest. In this work, a new generation of multi-cyclic poly(β-amino ester)s (CPAEs) with unique topology structure was synthesized for the first time via step growth polymerization. Through controlling the occurrence stage of cyclization, three types of CPAEs with rings of different sizes and topologies were obtained. In vitro experiments demonstrated that the CPAEs with macro rings (MCPAEs) significantly boosted the transgene expression comparing to their branched counterparts. Moreover, the MCPAE vector with optimized terminal group efficiently delivered the CRISPR plasmid coding both Staphylococcus aureus Cas9 nuclease and dual guide sgRNAs for gene editing therapy.

(Controlled) Free radical (co)polymerization of multivinyl monomers: strategies, topological structures and biomedical applications

Free radical (co)polymerization (FRP/FRcP) of multivinyl monomers (MVMs) has emerged as a powerful strategy for the synthesis of chemically and topologically complex polymers due to its unique reaction kinetics, which enables the preparation of polymers with multiple functional groups and novel macromolecular structures. However, conventional FRP/FRcP of MVMs inevitably leads to insoluble crosslinked materials. Therefore, the development of advanced strategies for the controlled polymerization of MVMs is essential for the preparation of chemically and topologically complex polymers. In this review, we introduce the gelation mechanism of conventional FRP of MVMs and present the strategies of controlled polymerization of MVMs for the preparation of chemically and topologically complex polymers. We also discuss polymers with unique topologies synthesized by controlled polymerization of MVMs, such as crosslinked networks, (hyper)branched, star, cyclic, and single-chain cyclized/knotted structures. Finally, biomedical applications of various advanced polymeric materials prepared by controlled polymerization of MVMs are highlighted and the challenges is this field are discussed.

Hyperbranched Poly(β-amino ester)s (HPAEs) Structure Optimisation for Enhanced Gene Delivery: Non-Ideal Termination Elimination

Many polymeric gene delivery nano-vectors with hyperbranched structures have been demonstrated to be superior to their linear counterparts. The higher delivery efficacy is commonly attributed to the abundant terminal groups of branched polymers, which play critical roles in cargo entrapment, material-cell interaction, and endosome escape. Hyperbranched poly(β-amino ester)s (HPAEs) have developed as a class of safe and efficient gene delivery vectors. Although numerous research has been conducted to optimise the HPAE structure for gene delivery, the effect of the secondary amine residue on its backbone monomer, which is considered the non-ideal termination, has never been optimised. In this work, the effect of the non-ideal termination was carefully evaluated. Moreover, a series of HPAEs with only ideal terminations were synthesised by adjusting the backbone synthesis strategy to further explore the merits of hyperbranched structures. The HPAE obtained from modified synthesis methods exhibited more than twice the amounts of the ideal terminal groups compared to the conventional ones, determined by NMR. Their transfection performance enhanced significantly, where the optimal HPAE candidates developed in this study outperformed leading commercial benchmarks for DNA delivery, including Lipofectamine 3000, jetPEI, and jetOPTIMUS.