Monitoring hydrogel degradation in real time using noninvasive imaging techniques is of great interest for designing a scaffold in tissue engineering. We report the preparation of gadolinium (Gd)-labeled and injectable hyaluronic acid (HA) hydrogels that can be visualized using T₁- and T₂-weighted magnetic resonance imaging (MRI). An HA derivative functionalized with thiol and hydrazide was labeled using a diethylenetriaminepentaacetate complex modified with “clickable” dithiopyridyl functionalities (degree of modification was 3.77% with respect to HA repeat units). The HA derivative modified with cross-linkable groups and Gd complex exhibited relaxivities r₁ = 3.78 mM^-1s^-1 and r₂ = 56.3 mM^-1s^-1. A hydrazone hydrogel network was obtained by mixing Gd-labeled HA-hydrazide and HA-aldehyde derivatives. Enzymatic hydrogel degradation could be followed using MRI because the MR images showed great correlation with the hydrogel mass loss. Ex vivo MRI of injected Gd-labeled hydrogels demonstrated that they show a significant contrast difference (SNR_coronal = 456; SNR_axial = 459) from the surrounding tissues. These results indicate that our Gd-labeled HA hydrogel has great potential as an injectable biocompatible hydrogel that can be used for longitudinal tracking in vivo using MRI.

使用无创成像技术实时监测水凝胶降解对于设计组织工程中的支架非常重要。我们报告了the（Gd）标记和可注射的透明质酸（HA）水凝胶的制备，可以使用T ₁和T ₂加权磁共振成像（MRI）进行可视化。使用经“可点击的”二硫代吡啶基官能团修饰的二亚乙基三胺五乙酸酯络合物（相对于HA重复单元，修饰度为3.77％）标记被硫醇和酰肼官能化的HA衍生物。用可交联基团和Gd配合物修饰的HA衍生物具有弛豫度r ₁  = 3.78 mM ^-1 s ^-1和r ₂ ＝ 56.3mM ^-1 s ^-1。mixing水凝胶网络是通过将Gd标记的HA-酰肼和HA-醛衍生物混合而获得的。MRI可以追踪酶促水凝胶的降解，因为MR图像与水凝胶的质量损失密切相关。注射的Gd标记水凝胶的离体MRI显示，它们 与周围组织显示出明显的对比度差异（SNR_冠状 = 456； SNR_轴向= 459）。这些结果表明，我们的Gd标记的HA水凝胶作为可注射的生物相容性水凝胶具有巨大的潜力，可用于使用MRI在体内进行纵向跟踪。