Fig. 1.

Characteristics of different samples. (a) Illustration of surface modification of PEEK. Fe³⁺ acts as an ionic cross-linker that can interact with up to three 3,4-dihydroxy-l-phenylalanine (DOPA) catechol functionalities to promote TA crosslinking. BMSC-derived Exos were reversibly bound to TA-SPEEK via hydrogen bond formation between phosphate groups in Exos phospholipid and polyphenol groups in the TA molecule. (b) FE-SEM images of PEEK, SPEEK, TA-SPEEK and Exo-TA-SPEEK. Scale bar represents 500 nm. (c) AFM images of PEEK, SPEEK, TA-SPEEK and Exo-TA-SPEEK. (d) 3D immunofluorescence images show an even distribution of Exos on the TA-SPEEK surface. Scale bar represents 200 μm. (e) The daily Exos released from SPEEK and TA-SPEEK within 14 days (n = 3). (f) Cumulative Exos release curve of SPEEK and TA-SPEEK up to 14 days (n = 3). (g) Immunofluorescence images show PKH26 labeled Exos were phagocytized by the BMSCs. Scale bar represents 200 μm. (h) Water contact angles of each sample (n = 3). ANOVA followed by Bonferroni's multiple comparison test was used for statistical analysis (*p < 0.05, **p < 0.01, ***p < 0.001).