Fig. 1

Preparation and characterization of injectable composite hydrogel with rapid hemostatic function. a Speculation mechanism of Eosin Y/NPG system-initiated polymerization reaction. b UV–visible absorption spectra of Eosin Y and emission spectrum of the white light LED. c and d Evaluation of the initiating efficiency of Eosin Y/NPG system. e Direct contact cytotoxicity assay of Eosin Y, NPG, and Eosin Y/NPG photoinitiator system (n = 3). f Photopolymerization kinetic experiment of various photoinitiators. g Schematic illustration of the composition of AEC. h Digital photographs of AE and AEC gelling transition upon white light irradiation (90 s). i SEM images of AE and AEC. Scale bar = 200 μm. j Viscosity versus shear rate for AE and AEC. k Dynamic time-sweep rheological analysis showing the gelation kinetics of AE and AEC. l Dynamic frequency-sweep rheological analysis of AE and AEC. m Macroscopic view of the injectability of AE and AEC. n Representative stress–strain curves of compression test. o Relative cell viability of NIH/3T3 fibroblasts after incubation with leaching solution of AE or AEC for 24, 48 and 72 h (n = 3). p Macroscopic view and statistical results of in vitro hemolysis assay (n = 3). q HE staining of explanted AE and AEC after 1, 3 and 5 weeks of subcutaneous implantation in mice. The red arrows represented migrated tissue cells. Scale bar = 20 μm. r Macroscopic view of explanted AE and AEC. The red dashed line indicated the diameter of the residual hydrogel in each group. s Macroscopic view of BCI test and BCI value-time curves of different samples (n = 3). t Macroscopic view of whole blood clotting test and the results showing a relatively shorter clotting time of AEC (n = 3). u SEM morphology of the clotting blood on AEC and cellulose gauze at 1000 × (left) and 2000 × (right) magnification. The yellow arrows represented fibrin network and the red arrows represented deformed red blood cells. Scale bar = 20 μm. v Immunofluorescence staining of CD62p (red) showing the platelet activation under the stimulation of different samples. Scale bar = 200 μm. w Schematic illustration of the surgical procedure of hemostasis experiments in mouse liver trauma model. x Photographs of the hemostatic effect of different treatments in mouse liver trauma model. Total blood loss (y) and clotting time (z) of different samples in mouse liver trauma model (n = 5). All statistical data are represented as mean ± SD. ^*P < 0.05, ^**P < 0.01, ^***P < 0.001, ^****P < 0.0001, One-Way analysis of variance, ANOVA, Tukey’s post hoc test. LED light emitting diode, DBC double bond conversion, NPG N-phenylglycine, AE Alg-AEMA hydrogel initiated by Eosin Y/NPG, CMC sodium carboxymethyl cellulose, PVP polyvinylpyrrolidone, Ru tris-bipyridyl ruthenium hexahydrate, SPS sodium persulfate, TEOA triethanolamine, NVP N-vinyrrolidone, AEC Alg-AEMA-based Eosin Y/NPG-initiated composite hydrogel, G' storage modulus, G'' loss modulus, BCI blood clotting index, NIH National Institutes of Health