Far-red light-triggered cargo release from liposomes bound to a photosensitizer-cellulose nanofiber hydrogel

Light-triggered release from liposomes has been extensively researched. In virtually all the cases the photosensitizer has been encapsulated in liposomes core or liposomal membrane. However, the light-triggered drug release system, where the photosensitizer is located outside of the liposomes has never been reported before. The central concept of our research revolves around the far-red light-induced release of cargo from liposomes embedded in anionic nanofibrillar cellulose (ANFC), wherein the photosensitizer resides in the hydrogel, outside of liposomes. Both the sensitizer and the liposomes bind strongly to the anionic cellulose nanofibers by simple mixing, making the system easy to fabricate. Upon light activation, this photosensitizer generates reactive oxygen species, which, in turn, induce the liposomal bilayer disruption, ultimately resulting in cargo release. The release mechanism is the generation of reactive oxygen species and the subsequent oxidation of unsaturated lipids in the liposomal membrane. We were able to achieve ca. 70 % release of model hydrophilic cargo molecule calcein with a relatively low dose of light (262 J/cm2) while employing straightforward fabrication techniques for the drug delivery system. Our system was remarkably responsive to the far-red light (730nm, 0.875 W/cm²), enabling deep tissue penetration. Therefore, this very promising novel cellulose-immobilized photosensitizer liposomal complex could be used as a controlled drug delivery system, which can have potential applications in externally activated coatings or implants.