Hyaluronan (HA) is a major component of the extracellular matrix and is particularly attractive for cell‐based assays; yet, common crosslinking strategies of HA hydrogels are not fully tunable and bioorthogonal, and result in gels subject to swelling, which affects their physicochemical properties. To overcome these limitations, HA hydrogels based on the inverse electron‐demand Diels–Alder (IEDDA) “click” reaction are designed. By crosslinking two modified HA components together, as opposed to using telechelic components, tunable gelation times as fast as 4.4 ± 0.4 min and as slow as 46.2 ± 1.8 min are achieved for facile use. By optimizing HA molar mass, ultralow polymer content hydrogels of 0.5% (w/v), resulting in minimal (<3–5% mass variation) to nonswelling (<1%), transparent and biodegradable hydrogels are synthesized. To demonstrate their versatility, the newly designed hydrogels are tested as matrices for 3D cell culture and retinal explant imaging where transparency is important. IEDDA hydrogels are cytocompatible with primary photoreceptors and enable multiphoton imaging of embedded retinal explants for double the time (>38 h) than agarose thermogels (<20 h). IEDDA HA hydrogels constitute a new hydrogel platform. They have low polymer content, tunable gelation time, and are stable, thereby making them suitable for a diversity of applications.

中文翻译：

---

具有可调节胶凝时间的非溶胀，超低含量反向电子需求Diels–Alder透明质酸水凝胶：合成和体外评估

透明质酸（HA）是细胞外基质的主要成分，对于基于细胞的测定法特别有吸引力；然而，HA水凝胶的常见交联策略尚不完全可调且与生物正交，导致凝胶易溶胀，从而影响其理化性质。为了克服这些限制，设计了基于逆电子需求Diels–Alder（IEDDA）“点击”反应的HA水凝胶。通过将两种改性的HA组分交联在一起（与使用遥螯剂组分相反），可轻松实现高达4.4±0.4分钟和46.2±1.8分钟的可调节胶凝时间。通过优化HA摩尔质量，可合成0.5％（w / v）的超低聚合物含量水凝胶，从而使非溶胀性（<1％）变化最小（<3-5％质量变化），从而合成出透明且可生物降解的水凝胶。为了证明其多功能性，新设计的水凝胶已作为透明性很重要的3D细胞培养和视网膜外植体成像的基质进行了测试。IEDDA水凝胶与主要的感光细胞具有细胞相容性，并且使嵌入的视网膜外植体的多光子成像时间比琼脂糖热凝胶（<20 h）长两倍（> 38 h）。IEDDA HA水凝胶构成了一个新的水凝胶平台。它们具有低的聚合物含量，可调节的胶凝时间，并且稳定，因此使其适合于多种应用。38 h）比琼脂糖热凝胶（<20 h）。IEDDA HA水凝胶构成了一个新的水凝胶平台。它们具有低的聚合物含量，可调节的胶凝时间，并且稳定，因此使其适合于多种应用。38 h）比琼脂糖热凝胶（<20 h）。IEDDA HA水凝胶构成了一个新的水凝胶平台。它们具有低的聚合物含量，可调节的胶凝时间，并且稳定，因此使其适合于多种应用。