Fig. 2

Characterization of SSAD and SSAD/HA hydrogels. A Scanning electron microscope (SEM) images of the skin secretion of Andrias davidianus (SSAD) and SSAD/hydroxyapatite (HA) hydrogels at different ratios. Scale bar, 10 μm. B Energy-dispersive spectroscopy mapping of the SSAD/HA hydrogel. Scale bar, 5 μm. (C) Pore size distribution of the corresponding hydrogels in (A) based on random measurements of at least 100 pores. D Energy dispersive spectroscopy analysis of the SSAD hydrogel, including C, N, O, S, Cl, and K. E Fourier-transform infrared spectrometry (FTIR) spectra of the SSAD hydrogel with or without polyvinylamine (PVAm). F Rheological behavior of SSAD and SSAD/HA hydrogels. Hollow indicates G”. Solid indicates G′. G Rheological behavior of the SSAD/HA hydrogels formed by deionized water, PVAm, and PVAm/NA separately. The deionized water group data are consistent with the SSAD/HA group data in Fig. 1F. Hollow indicates G”. Solid indicates G′. H Validation of the slow-release of small-molecule drugs by SSAD and SSAD/HA hydrogels. I Verification of the slow-release of nucleic acids (FAM-NC) by SSAD/HA hydrogels in the presence or absence of PVAm. All quantitative data are presented as mean values ± standard deviation (n = 3, * p < 0.05, ** p < 0.01, *** p < 0.001, ns: no significance).