Fabrication of Protease-Sensitive and Light-Responsive Microcapsules Encompassed with Single Layer of Gold...

A bioapplicable cargo delivery system requires the following characteristics of biocompatibility, in vivo stability, and selective cargo release at target sites. We introduce herein the microcapsules enclosed with a single-layered shell of gold nanoparticles (AuNPs) mutually connected by an amyloidogenic protein of α-synuclein (αS). The microcapsules were fabricated by producing oil(chloroform)-in-water Pickering emulsions of the αS-encapsulated AuNPs and subsequent molecular engagement of the outlying αS molecules, leading to formidable β-sheet formation in the presence of chloroform. The wrinkled skin of microcapsules obtained after evaporation of the internal chloroform also reflects robustness of the protein-protein interaction, which was experimentally confirmed by their rheological stability. For the emulsions loaded with rhodamine 6G, their dye release was demonstrated to be controlled by proteases. Along with their photothermal activity, the AuNP-containing microcapsules and their proteolyzed fragments were therefore suggested to be capable of eliminating aberrant cells in the protease-activated pathologically affected areas. Orthogonal cargo loading was also achieved by encapsulating both hydrophobic and hydrophilic substances either directly dissolved in chloroform or prepackaged in inverted micelles, respectively. Microcapsule's functionality was further expanded by localizing quantum dots, magnetic nanoparticles, and antibodies inside or on the surface of the microcapsules. Taken together, these multimodal AuNP microcapsules are suggested to be an ideal cargo carrier system, which could be employed in not only biomedical theranostic applications as they exhibit structural robustness, specific targeting, triggered release, and photothermal activity but also sensor development in general.