Negative Electrets Directed Fibrinogen Assembly for Surface Enrichment of Platelets

Platelet-encapsulated growth factors are desired for rapid tissue healing and personalized regeneration; however, guided platelet enrichment on implantable biomaterial surfaces still faces challenges, undermining the clinical effects of commercial platelet concentrates on tissue integration. Here, we demonstrated that high intensity of negative charge on fluorinated ethylene propylene electrets (ranging from -1252 ± 66 V/-0.465 ± 0.025 mC∙m^-2 to -2838 ± 95 V/-1.055 ± 0.035 mC∙m^-2) can direct self-assembly of fibrinogen and guide platelet adhesion for surface enrichment. Detailed fibrinogen adsorption tests with a series of protein concentrations and incubation durations showed that the negative electrets induced fibrinogen networks quickly and were more porous compared to the positive ones. In addition, an extremely low binding energy of X-ray photoelectron spectroscopy N1s (398.2 eV) and Fermi resonance associated Amide A and Amide B bands were exclusively detected on fibrinogen-incubated negative electrets, indicating that the negative surface charge interacted with the fibrinogen via producing and accumulating orient water hydrated sodium ions, which coordinate with the γ400-401 histidine dipeptides in the γC of the absorbent fibrinogen D domains and facilitated the exposure of the γ400-411 sequences, mediating platelet adhesions on the electrets free of premature activation. Since fibrinogen is a naturally present protein in the human body, this proof-of-concept study provides new insights into advancing implantable biomaterials to orchestrate tissue integration at the protein and cellular levels.