Fig. 2: Synthesis and physiochemical analysis of each layer in trilayer hydrogels.

a Overview and structure of the D-H/Zein/BP hydrogel scaffold. Elements were created in BioRender. Ming, Y. (2025). b Chemical synthesis reaction formula of D-H and BP. c FTIR spectra of DEAm, HEAm, and D-H hydrogel; and d FTIR spectra of NIPAm, BIS, BP and BPV. e Scanning electron microscopy (SEM) images of D-H hydrogel, Zein and Bis-PNIPAm (BP) hydrogels; and f Cross-sectional SEM of D-H/Zein/BP trilayer hydrogels in a hydrated state via Cryo-SEM, more than three experiments were conducted, and the results were repeatable. g Temperature-correlated rheological assay of upper Bis-PNIPAm (BP) hydrogels layer. D-H hydrogel; h Detection of the change in heat flow under varying temperatures in BP hydrogel using Differential Scanning Calorimetry (DSC). i–k Time-correlated rheological assay of upper Bis-PNIPAm (i) and bottom D-H (k); and j Stress-strain curves during compression testing of D-H and BP hydrogels. l Volume expansion curves for D-H, Zein and BP; and m expansion rate after 24 h (n = 3 independent samples). n Values in Depth-Sensing Indentation (DSI) testing (n = 6 independent samples), Er: Reduced Young’s Modulus, H: Nanoscale Hardness of Indentation, Pmax: Maximum Load; o Water contact angle testing for hydrated D-H hydrogels. p Time-dependent degradation rates of D-H, BP and Zein hydrogels in urine environment under static conditions (n = 3 independent samples); and q Residual mass of of D-H, BP, Zein and D-H/Zein/BP hydrogels after 60 days in urine environment (n = 3 independent samples). Data are expressed as mean ± standard error of the mean (SEM). Source data is provided as a Source Data file.