3D printedβ-sheet-reinforced natural polymer hydrogel bilayer tissue engineering scaffold

It remains a significant challenge to fabricate natural polymer(NP)hydrogels with anti-swelling ability and high strengths in the physiological environment.Herein,theβ-sheet-reinforced NP hydrogel is developed by copolymerizing methacrylated gelatin(GelMA)and methacrylated silk fibroin(SFMA)in aqueous solution,followed by ethanol treatment(named GelMA-SFMAAL).Theβ-sheets formed by SFMA can act as a stable physical crosslink to enhance the mechanical properties and prolong the degradation of the GelMA network.Importantly,the chemical crosslinking in the GelMA-SFMA hydrogel prevents excessive aggregation of hydrophobicβ-sheets,thereby avoiding the formation of brittle hydrogel.The obtained GelMA-SFMA-AL hydrogels exhibit considerably enhanced mechanical properties(Young's modulus:0.89–3.68 MPa;tensile strength:0.31–0.96 MPa;toughness:0.09–0.63 MJ/m^(3);compressive modulus:0.78–2.20 MPa;compressive strength:2.65–5.93 MPa)compared with GelMA-SFMA hydrogels(Young's modulus:0.04–0.13 MPa;tensile strength:0.04–0.07 MPa;toughness:0.01–0.02 MJ/m^(3);compressive modulus:0.03–0.09 MPa;compressive strength:0.30–0.64 MPa).A bilayer osteochondral scaffold is constructed via digital light processing(DLP)three-dimensiaonl(3D)printing technology,comprising GelMA-SFMA@diclofenac sodium(DS)-AL as the top layer and GelMA-SFMA@bioactive glass(BG)-AL as the bottom layer.The bilayer hydrogel scaffold is demonstrated to support cell attachment and spreading,and facilitate osteogenic differentiation of rat bone marrow stem cells in vitro.In vivo implantation experiment suggests this bilayer scaffold is promising to be used for osteochondral tissue regeneration.

A hyperbranched polymer-based water-resistant adhesive:Durable underwater adhesion and primer for anchoring anti-fouling hydrogel coating

Direct deployment of gluing and achieving durable robust adhesion in water is challenging due to difficulty in repelling interface water.This work reports a novel hyperbranched polymer-based water-resistant adhesive(HBPBA)based on Michael addition reaction of multi-vinyl monomers with dopamine and 3-aminophenylboronic acid.Upon encountering water,the HBPBA forms coacervates whose hydrophobic chains aggregate to displace interface water,and meanwhile the catechols exposing outwards contribute to underwater adhesion.The HBPBA can strongly glue diverse substrates including PTFE,PE,PET,ceramic,Ti and stainless steel.The HBPBA can maintain stable adhesion in different environments,such as tap water,simulated sea water,PBS,and a wide range of pH solutions(pH 2 to 10)for 3 months,supposedly due to the complexation of catechol with boronic acid.Intriguingly,HBPBA film can be bonded to the titanium surface as a primer,which firmly anchors the antifouling PNAGAPCBAA hydrogel coating through copolymerization of remaining double bonds in HBPBA and NAGA plus CBAA.The PNAGA-PCBAA hydrogel-modified titanium is biocompatible and shows outstanding antifouling ability both in vitro and in vivo.This work proposes a new strategy for creating underwater deployable and water-resistant adhesives that may find promising applications in engineering and biomedical fields.