Dental pulp extracellular matrix (DPEM), as a naturally derived scaffold material for dental pulp regeneration, exhibits excellent biocompatibility. This study aims to develop a novel photo-cross-linked hydrogel composed of methacry- lated gelatin (GelMA) loaded with DPEM for application in pulp regeneration. In vitro experiments demonstrated that the GelMA–DPEM hydrogel, fabricated by mixing a 10 mg mL − 1 DPEM solution with a 10

Hydrogels as flexible strain sensors (FSSs) have attracted tremendous interest in the area of human movement monitoring. Such an application is developing rapidly. However, it is still valuable to explore hydrogel-based FSSs with excellent mechanical properties, responsiveness to stimulus, high strain sensitivity, and reliable sta-bility. Herein, a hydrogel with triple physical cross-linking (TPC hydrogel), whose structure also included hy-drophobic association-microcrystallinity-ionic coordination, was designed and fabricated. Synthetic water-soluble polymer [poly(vinyl alcohol) (PVA)] and natural polymer [sodium alginate (SA)] were introduced into the hydrogel; PVA induced microcrystal cross-linking, while SA provided ionic conductivity for the hydrogel. TPC hydrogels exhibited high toughness (5.9 MJ/m3) and excellent deformation (2490%). The introduction of SA also endowed the hydrogels with improved capability to ionize, imparting them with excellent pH-responsive swelling behavior. Impressively, TPC hydrogel-based FSSs exhibited reasonable conductivity (0.65-2.47 S/m), high sensitivity (maximum gauge factor = 10.29), and outstanding reliability and stability. This investigation broadens the avenue for the design and fabrication of hydrogels intended as FSSs with low modulus (33-45 kPa, close to human skin), excellent stretchability, and high strain sensitivity and durability.

Hydrogels with excellent stiffness, toughness, anti-fatigue, and self-recovery properties are regarded as promising water-containing materials. In this work, a dual physically cross-linked (DPC) sodium alginate (SA)/poly[acrylamide (AAm)-acrylic acid (AAc)-octadecyl methacrylate (OMA)]-Fe3+ hydrogel is reported, which is constructed by hydrophobic association (HA) and ionic coordination (IC). The optimal DPC hydrogel demonstrates excellent mechanical performance: tensile modulus of 0.65 MPa, tensile strength of 3.31 MPa, elongation at break of 1547%, and toughness of 27.8 MJ m(-3). SA/P(AAm-AAc-OMA)-Fe3+ DPC hydrogels also exhibit prominent anti-fatigue and self-recovery performance (99.1-109.7% modulus recovery and 90.4-108.9% dissipated energy recovery after resting for 5 min without additional stimuli at ambient temperature) through the reconstruction of reversible physical cross-linking. Some of the SA/P(AAm-AAc-OMA)-Fe3+ DPC hydrogels even exhibit a stretching-induced strengthening effect, which is similar to the performance of muscle-"the more training, the more strength." Hence, the combination of HA and IC will provide an effective approach to design DPC hydrogels with desirable mechanical performances and a longer service life for wider applications of soft materials.

为提升水凝胶的综合力学力学性能,设计并研究了一种全物理交联三重互穿网络水凝胶.以自由基乳液聚合法,获得疏水缔合交联的聚丙烯酰胺网络,水凝胶一步成型,依次通过冷冻-融化循环、浸没FeCl3溶液分别形成微晶交联的聚乙烯醇网络及离子交联的海藻酸钠网络.获得P(AM-SMA)/PVA/SA三重互穿网络(HMITN)水凝胶.通过傅里叶变换红外对水凝胶结构进行了表征;通过电子万能试验机对水凝胶的力学性能进行了研究.结果表明,HMITN水凝胶具有良好的强度、韧性、抗疲劳及自恢复性能,强度0.45 MPa,断裂能2.48 MJ/m3,在200％应变下进行5次循环拉伸后仍然保持20.3％的韧性,室温下自恢复260 min后,韧性可恢复66.7％.

Shape memory hydrogels (SMHs) can fix the hydrogels in a provisional shape and restore the initial shape under external stimulation. Herein, a dual-responsive shape memory hydrogel with dual-responsive swelling and self-healing properties is presented in this work. The SMHs were fabricated by one-step emulsion copolymerization of acrylic acid (AAc), acrylamide (AAm) and stearyl methacrylate (SMA). Sodium alginate (SA) was introduced as an interpenetrating polymer in the network. With ionic cross-linking between -COO- and Fe3+ or saline-reinforced hydrophobic association, the hydrogels can be fixed in a provisional shape, which can be restored by immersing the hydrogels in vitamin C solution or pure water, respectively. When the as-prepared hydrogels were immersed in FeCl3 solutions, additional ionic cross-linking between Fe3+ and -COO- could be formed, thus constructing the dual physically cross-linked (DPC) network, which endows the hydrogels with excellent fracture stress (2.6 MPa) and toughness (5.47 MJ/m(3)). Besides, the reversible physical cross-linkings endowed the hydrogel with outstanding self-healing capability. Furthermore, the pH and saline responsive swelling properties of the SMHs are additional fantastic properties. Therefore, we believe that this simple strategy provides a great opportunity for the preparation of SMHs with multiple intellectual performances.