Fig. 1.

Fabrication and characterization of PDA-HP hydrogel. (A) Schematic illustration of PDA nanoparticle synthesis via oxidative self-polymerization of dopamine. (B) SEM image of PDA. Scale bar is 0.5 μm. (C) The changes in particle size and polydispersity index (PDI) of PDA over 21 days by nanoparticle size analyzer. (D) Schematic representation of HP hydrogel synthesis via EDC/NHS-mediated heparin conjugation to poloxamer. (E) ¹H NMR spectra confirming the chemical composition of HP hydrogel. (F) SEM images of HP hydrogel and PDA-HP hydrogel after freeze-drying following in situ gelation. White dashed circles indicate representative regions containing PDA nanoparticles embedded within the HP matrix; the nanoparticles are uniformly distributed throughout the hydrogel. Scale bars are 50 μm. (G) Photographs of HP and PDA-HP hydrogels at 4 °C (sol state) and 37 °C (gel state). (H) Steady-state viscosity profiles of HP and PDA-HP hydrogels as a function of temperature (20–50 °C). Both hydrogels maintained stable viscosity between 37 °C and 43 °C, confirming good structural stability under mild photothermal conditions.