Formation of fibrinogen-based hydrogels using phototriggerable diplasmalogen liposomes.

We report the triggered release of Ca2+ from liposomal compartments to induce rapid gelation of protein-based hydrogels. Phototriggerable liposomes were designed by entrapping CaCl(2) within liposomes composed of 38:57:5 diplasmenylcholine (DPPlsC):disteroylphosphatidylcholine (DSPC):bacteriochlorophyll (Bchl). These liposomes release >80% of their entrapped Ca2+ within 15 min when irradiated at 800 nm (800 mW/cm2). A precursor solution, containing liposomes suspended in aqueous human fibrinogen and transglutaminase (TGase), remained fluid for several hours in the dark, but gelled rapidly when exposed to 800 nm excitation, as a result of photosensitized Ca2+ release and TG-induced fibrinogen cross-linking. TGase and hrFXIII activities, determined using a fluorimetric dansylcadaverine assay, were found to depend strongly on irradiation time and reaction temperature. SDS-PAGE of the photolyzed reaction mixture revealed that gelation arises from enzyme-catalyzed cross-linking of predominately the alpha and gamma chains of fibrinogen. This approach to the phototriggered formation of protein hydrogels creates new opportunities for biomaterials applications in drug delivery, tissue engineering, and wound healing.