Scheme 1 Schematic of fathoming the evolving dynamic degradation-associated cytocompatibilities of Zn bio-metal

Fig. 1 Transient electrochemical test of pure Zn in Hank’s and Hank’s + BSA solutions. a OCP vs. time curves. b PDP curves. c icorr and corresponding corrosion rate obtained by the Stern Geary method. d Nyquist plots with fitted lines, along with the EEC diagram. e and f Bode-impedance and bode-phase angle spectra, respectively

Fig. 2 Electrochemical measurements, including OCP vs. time curves, PDP curves, and Nyquist plots with fitted lines of pure Zn at static and dynamic conditions in Hank’s and Hank’s + BSA solutions at 37 ± 0.5 °C after 1, 7, 14, and 21 days of immersion. a-d OCP vs. time curves of pure Zn in Hank’s and Hank’s + BSA solutions at static and dynamic condition, respectively. e-h PDP curves of pure Zn in Hank’s and Hank’s + BSA solutions at static and dynamic condition, respectively. i-l Nyquist plots as well as EEC diagrams of pure Zn in Hank’s and Hank’s + BSA solutions at static and dynamic condition, respectively

Fig. 3 Parameters of fitting results from the electrochemical measurements of pure Zn immersed in Hank’s and Hank’s + BSA solutions for 1, 7, 14, and 21 days. a The icorr. b Corrosion rate calculated by icorr value. c and d Rp and Rct values, respectively

Fig. 4 Representative surface SEM images of pure Zn after 1, 7, 14, and 21 days of immersion in Hank’s a-h and Hank’s + BSA i-p solutions at static and dynamic conditions, respectively

Fig. 5 Characterization of the chemical compositions on the corrosion product of pure Zn after 21 days of immersion in Hank’s and Hank’s + BSA solutions under static and dynamic conditions. a FTIR spectra. b XPS survey spectra. c-f High-resolution XPS spectra of Ca 2p, P 2p, Zn 2p, and O 1s

Fig. 6 a XRD patterns of pure Zn after 21 days of immersion in Hank’s and Hank’s + BSA solutions at static and dynamic conditions, respectively. b pH of the media during the immersion process. c and d Weight loss changes and corrosion rate (calculated from weight loss) of pure Zn immersed in Hank’s and Hank’s + BSA solutions at static and dynamic conditions, respectively

Fig. 7 Representative surface SEM images of pure Zn after 1, 7, 14, and 21 days of immersion in Hank’s a-h and Hank’s + BSA i-p solutions at static and dynamic conditions after removing surface corrosion products, respectively

Fig. 8 HUVECs cytocompatibility of the pure Zn after 1, 7, 14, and 21 days of immersion in Hank’s and Hank’s + BSA solutions. a Representative TRITC (red) and DAPI (blue) fluorescent images of HUVECs direct culture on sample surfaces. b Quantitative HUVECs cells counting. c Live (green) and dead (red) staining of HUVECs in the sample extracts of the immersed samples. d CCK-8 of HUVECs. Data are displayed as mean ± standard deviation (SD) (n = 4). *p < 0.05, **p < 0.01, ***p < 0.001

Fig. 9 BMSCs cytocompatibility of the pure Zn after 1, 7, 14, and 21 days of immersion in Hank’s and Hank’s + BSA solutions. a Representative TRITC (red) and DAPI (blue) fluorescent images of BMSCs direct culture on sample surfaces. b Quantitative HUVECs cells counting. c Live (green) and dead (red) staining of BMSCs in the sample extracts of the immersed samples. d CCK-8 of BMSCs. Data are expressed as mean ± standard deviation (SD) (n = 4). (*p < 0.05, **p < 0.01, ***p < 0.001)

Fig. 10 Illustration of the mechanism of the dynamic corrosion evolution associated with cell compatibility of pure Zn corrosion in Hank’s and Hank’s + BSA solutions under static and fluid immersion environments