Injectable Hybrid-Crosslinked Hydrogels as Fatigue-Resistant and Shape-Stable Skin Depots

Abstract

Injectable hydrogels have gained considerable attention, but they are typically mechanically weak and subject to repeated physiological stresses in the body. Herein, we prepared polyurethane diacrylate (EPC–DA) hydrogels, which are injectable and can be photocrosslinked into fatigue-resistant implants. The mechanical properties can be tuned by changing photocrosslinking conditions, and the hybrid-crosslinked EPC–DA hydrogels exhibited high stability and sustained release properties. In contrast to common injectable hydrogels, EPC–DA hydrogels exhibited excellent antifatigue properties with >90% recovery during cyclic compression tests and showed shape stability after application of force and immersion in an aqueous buffer for 35 days. The EPC–DA hydrogel formed a shape-stable hydrogel depot in an ex vivo porcine skin model, with establishment of a temporary soft gel before in situ fixing by UV crosslinking. Hybrid crosslinking using injectable polymeric micelles or nanoparticles may be a general strategy for producing hydrogel implants resistant to physiological stresses.

Interstitial Injection of Hydrogels with High‐Mechanical Conductivity Relieves Muscle Atrophy Induced by Nerve Injury

“…However, the maximum compressive stress of these hydrogels reduces to ≈80% of the initial value after a few dozen fatigue tests, whereas our 0.3 PMN/C+Ag hydrogel remains stable at 96.8% of the initial state after 5000 fatigue tests. [ 55–57 ] This property of 0.3 PMN/C+Ag to remain stable under large deformations allows it to withstand repeated physiological stresses in vivo without rupturing and providing mechanical support to the surrounding tissues. This ability makes it possible to inject it into the myofascial space and treat muscle atrophy effectively.…”

“…However, the maximum compressive stress of these hydrogels reduces to ≈80% of the initial value after a few dozen fatigue tests, whereas our 0.3 PMN/C+Ag hydrogel remains stable at 96.8% of the initial state after 5000 fatigue tests. [55][56][57] This property of 0.3 PMN/C+Ag to remain stable under large deformations allows it to withstand repeated physiological stresses in vivo without rupturing and providing mechanical support to the The ratio of the muscle tension of the gastrocnemius muscle on the atrophic side to that on the healthy side of rats, n = 10. g) Gene expression level of 𝛼7-integrin (Itg7a), n = 6. h) Protein expression levels of FAK and pFAK in the gastrocnemius muscles; i,j) are the corresponding statistical results, n = 6.…”

4D Printing of Single-Network Shape Memory Polyurethanes with Two-Way Actuation Properties

“…The monomers with crosslinked segments form the hard segment to provide mechanical rigidity, while PCLDA and PPDLDA oligomers form the switching segments for shape fixation and recovery. The photoinitiator (TPO) initiates a free radical polymerization process, resulting in rapid chain growth to form the crosslinked polymer matrix when exposed to UV irradiation. ,− Different resins were formulated by varying the weight percentage of monomers and oligomers to determine the ideal resin composition. PCLDA and PPDLDA were completely dissolved in the resin formulation after 1 h sonication at 40 kHz and overnight stirring at 500 rpm.…”

Electrically Conductive Polymers for Additive Manufacturing

“…The initiating species then prompt the polymerization process by reacting with monomer and/or oligomer units. , Monomers and oligomers are the basic building blocks of photosensitive resins that determine the properties of the final products. The functional groups of monomers and oligomers play a significant role in determining the types and features of the photopolymerization process (i.e., curing speed, curing rate, and cross-link density). , In particular, the degree of functionalization of monomers and oligomers has a great impact on the curing kinetics, and it is well worth consideration when formulating a photosensitive resin. Monomers and oligomers with a high degree of functionalization result in fast-curing kinetics but may cause early gelation or vitrification of the cross-linked structures, thus hindering the polymerization process.…”