Nanobody‐Ferritin Conjugate for Targeted Photodynamic Therapy
2020
Ferritin is an iron-storage protein nanocage assembled by 24 subunits. The hollow cavity of ferritin enables its encapsulation of various therapeutic agents. Antibody-ferritin conjugate provides an effective approach for the targeted drug delivery. However, the complicated preparation and protein stability hampers wide applications of this system. Herein, we designed a novel nanobody-ferritin platform (Nb-Ftn) for targeted drug delivery. The site-specific conjugation between nanobody and ferritin is achieved by transglutaminase catalyzed protein ligation. This ligation strategy allows the Nb-conjugation after drug loading in ferritin, which avoids the deactivation of nanobody from the harsh pH required for drug encapsulation. To verify the tumor targeting of this Nb-Ftn platform, a photodynamic reagent, manganese phthalocyanine (MnPc) was loaded into the ferritin cavity, and an anti-EGFR nanobody was conjugated to the surface of ferritin. The ferritin nanocage can encapsulate about 82 MnPc molecules. This MnPc@Nb-Ftn conjugate can be efficiently internalized by EGFR positive A431 cancer cells, but not by EGFR negative MCF-7 cells. Upon 730 nm laser irradiation, MnPc@Nb-Ftn selectively killed EGFR positive A431 cells by generating ROS, whereas no obvious damage was observed on MCF-7 cells. As ferritin can be used for encapsulation of various therapeutic agents, this work provides a strategy for facile construction of nanobody-ferritin for targeted drug delivery.
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