An Interfacial Dynamic Crosslinking Approach toward Catalyst-free and Mechanically Robust Elastomeric Vitrimer with a Segregated Structure

Elastomeric vitrimers with covalent adaptable networks are promising candidates to overcome the intrinsic drawbacks of conventional covalently-crosslinked elastomers;however, most elastomeric vitrimers show poor mechanical properties and require the addition of exogenous catalysts. Herein, we fabricate a catalyst-free and mechanically robust elastomeric vitrimer by constructing a segregated structure of sodium alginate (SA) in the continuous matrix of epoxidized natural rubber (ENR), and further crosslinking the composite by exchangeable hydroxyl ester bonds at the ENR-SA interfaces. The manufacturing process of the elastomeric vitrimer is facile and environmentally friendly without hazardous solvents or exogenous catalysts, as the abundant hydroxyl groups of the segregated SA phase can act as catalyst to activate the crosslinking reaction and promote the dynamic transesterification reaction. Interestingly, the segregated SA structure bears most of the load owing to its high modulus and small deformability, and thus ruptures preferentially upon deformation, leading to efficient energy dissipation.Moreover, the periodic stiffness fluctuation between rigid segregated SA phase and soft ENR matrix is beneficial to the crack-resisting. As a result,the elastomeric vitrimer manifests exceptional combination of catalyst-free, defect-tolerance, high tensile strength and toughness. In addition,the elastomeric vitrimer also exhibits multi-shape memory behavior which may further broaden its applications.

Research Article Dynamically crosslinked nanocapsules for the efficient and serumresistant cytosolic protein delivery

Intracellular protein delivery is critical to the development of protein-based biopharmaceuticals and therapies.However,current delivery vectors often suffer from complicated syntheses,low generality among various proteins,and insufficient serum stability.Herein,we developed an enlightened cytosolic protein delivery strategy by dynamically crosslinking epigallocatechin gallate(EGCG),low-molecular-weight polyethylenimine(PEI 1.8k),and 2-acetylphenylboric acid(2-APBA)on the protein surface,hence forming the EPP-protein nanocapsules(NCs).EGCG enhanced protein encapsulation via hydrogen bonding,and reduced the positive charge density of PEI to endow the NCs with high serum tolerance,thereby enabling effective cellular internalization in serum.The formation of reversible imine and boronate ester among 2-APBA,EGCG,and PEI 1.8k allowed acid-triggered dissociation of EPP-protein NCs in the endolysosomes,which triggered efficient intracellular release of the native proteins.Such strategy therefore showed high efficiency and universality for diversities of proteins with different molecular weights and isoelectric points,including enzyme,toxin,antibody,and CRISPR(clustered regularly interspaced short palindromic repeats)-Cas9 ribonucleoprotein(RNP),outperforming the commercial protein transduction reagent PULSin and RNP transfection reagent lipofectamine CMAX.Moreover,intravenously(i.v.)injected EPP-saporin NCs efficiently delivered saporin into 4T1 tumor cells to provoke robust antitumor effect.This simple,versatile,and robust cytosolic protein delivery system holds translational potentials for the development of protein-based therapeutics.

Reconfigurable and orthogonal stiffness-structure patterning of dynamically crosslinked amphigels

Patterning diversified properties and surface structure of polymer materials are of great importance toward their potential in biology,optics,and electronics.However,achieving both the patternability of stiffness and microstructure in a reconfigurable manner remains challenging.Here,we prepare amphigels crosslinked by dynamic disulfide bonds,which can be reversibly swollen by immiscible water or liquid paraffin.In the paraffingel form,the materials exhibited a high modulus of 130 MPa due to densified hydrogen bonds.Whereas swollen by water,the modulus fell over two orders of magnitude owing to the destruction of the hydrogen bonds.Via regionalized swelling of the solvents,well-controlled and rewritable soft/stiff mechanical patterns can be created.On the other hand,the dynamic exchange of the disulfide crosslinking enables mechanophoto patterning to fabricate sophisticated macrogeometries and microstructures.The reconfigurable stiffness-structure patterning can be manipulated orthogonally,which will create more application opportunities beyond conventional hydrogels and organogels.

Antibacterial conductive self-healing hydrogel wound dressing with dual dynamic bonds promotes infected wound healing

In clinical applications,there is a lack of wound dressings that combine efficient resistance to drug-resistant bacteria with good self-healing properties.In this study,a series of adhesive self-healing conductive antibacterial hydrogel dressings based on oxidized sodium alginate-grafted dopamine/carboxymethyl chitosan/Fe3+(OSD/CMC/Fe hydrogel)/polydopamine-encapsulated poly(thiophene-3-acetic acid)(OSD/CMC/Fe/PA hydrogel)were prepared for the repair of infected wound.The Schiff base and Fe3+coordination bonds of the hydrogel structure are dynamic bonds that can be repaired automatically after the hydrogel network is disrupted.Macroscopically,the hydrogel exhibits self-healing properties,allowing the hydrogel dressing to adapt to complex wound surfaces.The OSD/CMC/Fe/PA hydrogel showed good conductivity and photothermal antibacterial properties under near-infrared(NIR)light irradiation.In addition,the hydrogels exhibit tunable rheological properties,suitable mechanical properties,antioxidant properties,tissue adhesion properties and hemostatic properties.Furthermore,all hydrogel dressings improved wound healing in the infected full-thickness defect skin wound repair test in mice.The wound size repaired by OSD/CMC/Fe/PA3 hydrogel+NIR was much smaller(12%)than the control group treated with Tegaderm™film after 14 days.In conclusion,the hydrogels have high antibacterial efficiency,suitable conductivity,great self-healing properties,good biocompatibility,hemostasis and antioxidant properties,making them promising candidates for wound healing dressings for the treatment of infected skin wounds.