Fig. 2.

Physical characterizations of PEGDA, PEGDA/TA, AP, PTF, Alg-NHS/PEGDA hydrogel treated with TA (APT) and APTF hydrogel. (a) Macroscopic images of PEGDA hydrogels crosslinked with TA (40%), and TA/Fe³⁺ with varied Fe³⁺ concentrations (3%, 6%). (b) Releasing profile of TA from PEGDA/TA or PTF hydrogels with varied Fe³⁺ concentrations. (c) UV–Vis of released TA from PEGDA/TA or PTF hydrogels. (d) Representative SEM images of the (i) PEGDA, (ii) AP, (iii) PEGDA/TA, (iv) PTF and (v) APTF hydrogel. Scar bar = 10 μm.