No abstract

Three-dimensional (3D) printing utilizing controlled polymerization systems is emerging as a powerful approach to fabricate “living” objects, which can be further modified with various functionalities. Here, we report photoinduced free radical-promoted cationic reversible addition–fragmentation chain transfer (RAFT) polymerization under broad wavelengths from ultraviolet (UV) to near-infrared (NIR) light. A commercially available iron catalyst, cyclopentadienyl iron dicarbonyl dimer (Fe2(Cp)2(CO)4), was used as the photocatalyst, and several diphenyliodonium salts were examined as oxidants. Various poly­(vinyl ether)­s with controlled molecular weights and a narrow dispersity (1.06–1.32) were prepared through this method. Relatively high chain-end fidelity can be observed and has been demonstrated by successful chain-extension experiments. In addition, benefiting from the penetrating ability of NIR light, 3D objects with different thicknesses were achieved by employing stereolithography-based 3D printing techniques. Furthermore, the postfunctionalization of these 3D printed objects with fluorescent monomers provides a facile method to build 3D objects with complex functionality and potential applications in anticounterfeiting materials.

Three-dimensional (3D) printing based on photoinduced reversible addition–fragmentation chain transfer (RAFT) polymerization is emerging as a versatile and powerful method to prepare “living” 3D objects, which can be postmodified with various functionalities. However, an additional photoinitiator or photocatalyst is necessary in these systems, which is toxic and will cause negative effects on the properties of the prepared materials. Here, we report oxygen-tolerant and rapid living 3D printing based on photoiniferter RAFT polymerization, which does not need additional photoinitiators or photocatalysts. A xanthate, O-ethyl-S-2-ethyl propionate, was chosen as both the photoinitiator and RAFT agent in this process. Various monomers and RAFT agents were screened in this system. Materials with different properties were prepared utilizing the postfunctionalization of the printed living objects. Furthermore, a polymer welding method was proposed by painting fresh monomers between two living objects for post-photocuring. This photoiniferter RAFT polymerization-based living 3D printing method was also successfully applied to a commercial digital light processing technique-based 3D printer, offering a facile method to fabricate living 3D materials with different shapes.

Nucleic acid vaccines, especially messenger RNA (mRNA) vaccines, display unique benefits in the current COVID-19 pandemic. The application of polymeric materials as delivery carriers has greatly promoted nucleic acid vaccine as a promising prophylactic and therapeutic strategy. The inherent properties of polymeric materials render nucleic acid vaccines with excellent in vivo stability, enhanced biosafety, specific cellular uptake, endolysosomal escape, and promoted antigen expression. Although polymeric delivery of nucleic acid vaccines has progressed significantly in the past decades, clinical translation of polymer-gene vaccine systems still faces insurmountable challenges. This review summarizes the diverse polymers and their characterizations and representative formulations for nucleic acid vaccine delivery. We also discussed existing problems, coping strategies, and prospect relevant to applications of nucleic acid vaccines and polymeric carriers. This review highlights the rational design and development of polymeric vaccine delivery systems towards meeting the goals of defending serious or emerging diseases.