Facile Synthesis of Multifunctional Bioreducible Polymers for mRNA Delivery.

Bioreducible polymeric mRNA carriers are an emerging family of vectors for gene delivery and vaccine development. A few bioreducible systems have been generated through aqueous-phase ring-opening polymerization of lipoic acid derivatives, however this methodology limits hydrophobic group incorporation and functionality into resulting polymers. Herein, a poly(active ester)disulfide polymer is synthesized that can undergo facile aminolysis with amine-containing substrates under stoichiometric control and mild reaction conditions to yield a library of multifunctional polydisulfide polymers. Functionalized polydisulfide polymer species form stable mRNA-polymer nanoparticles for intracellular delivery of mRNAs in vitro. Alkyl-functionalized polydisulfide-RNA nanoparticles demonstrate rapid cellular uptake and excellent biodegradability when delivering EGFP and OVA mRNAs to cells in vitro. This streamlined polydisulfide synthesis provides a new facile methodology for accessing multifunctional bioreducible polymers as biomaterials for RNA delivery and other applications.

Multifunctional Dendronized Polypeptides for Controlled Adjuvanticity.

Vaccination has been playing an important role in treating both infectious and cancerous diseases. Nevertheless, many diseases still lack proper vaccines due to the difficulty to generate sufficient amounts of antigen-specific antibodies or T cells. Adjuvants provide an important route to improve and direct immune responses. However, there are few adjuvants approved clinically and many of them lack the clear structure/adjuvanticity relationship. Here, we synthesized and evaluated a series of dendronized polypeptides (denpols) functionalized with varying tryptophan/histidine (W/H) molar ratios of 0/100, 25/75, 50/50, 75/25, and 100/0 as tunable synthetic adjuvants. The denpols showed structure-dependent inflammasome activation in THP1 monocytic cells and structure-related activation and antigen cross-presentation in vitro in bone marrow-derived dendritic cells. We used the denpols with bacterial pathogen Coxiella burnetii antigens in vivo, which showed both high and tunable adjuvating activities, as demonstrated by the antigen-specific antibody and T cell responses. The denpols are easy to make and scalable, biodegradable, and have highly adjustable chemical structures. Taken together, denpols show great potential as a new and versatile adjuvant platform that allows us to adjust adjuvanticity based on structure-activity correlation with the aim to fine-tune the immune response, thus advancing vaccine development.

Multivalent Peptide-Functionalized Bioreducible Polymers for Cellular Delivery of Various RNAs.

RNA-based therapeutics have garnered tremendous attention due to their potential to revolutionize protein replacement therapies, immunotherapy, and treatment of genetic disorders. The lack of safe and efficient RNA delivery methods has significantly hindered the clinical translation and widespread application of RNA-based therapeutics. With differing sizes and structures of therapeutic RNA molecules, a critical challenge of the field is to develop RNA delivery systems that accommodate these variations while retaining high biocompatibility and efficacy. In this study, we developed a series of multivalent peptide-functionalized bioreducible polymers (MPBP) as a safe and efficient delivery vehicle derived from a core polymer backbone for various RNA species. The facile synthesis of MPBPs from a single polymer backbone provides access to numerous polymers with diverse architectures that enable cellular delivery of different RNA cargos. Postfunctionalization with multifunctional peptides enables strong RNA complexation, enhanced cellular uptake, and facilitates endosomal escape of cargo. The high delivery efficiency and low cytotoxicity for various RNA-MPBP nanoparticles in multiple cell lines demonstrates that the MPBP approach is a novel promising vector strategy for future RNA delivery systems.