Fig. 2

A 1H-NMR spectra of HA and OHA, showing the existence of aldehyde groups in modified HA. B FT-IR spectrum of HA and OHA. C 11B NMR spectra of borax and OHA/borax complex, revealing the formation of borate–diol complexation. D FT-IR spectra of gelatin and OBG for demonstrating the hydrogel formation. E Raman (black) and FT-IR (red) spectrometry analysis of OBG hydrogel. F Oscillatory strain − sweep test of the PBNPs@OBG hydrogel at 37 °C (ω = 10 rad s^− 1). G Frequency dependent rheology of the PBNPs@OBG hydrogel at 37 °C (ε = 1%). H Step − strain test of the PBNPs@OBG hydrogel at low (1%) and high (400%) strains to illustrate the self-healing properties at 37 °C (ω = 10 rad s^− 1). I Shear-thinning behavior of the PBNPs@OBG hydrogel indicated by steady-shear rheology. J Oscillatory time sweep of the PBNPs@OBG hydrogel between 37 and 20 °C. K Oscillatory temperature sweep of the PBNPs@OBG hydrogel. L Swelling ratios of the PBNPs@OBG hydrogel varied with time (n = 3)