Protease Responsive Essential Amino-Acid Based Nanocarriers for Near-Infrared Imaging

Delivery of the theranostic agents with effective concentration to the desired sites inside the body is a major challenge in disease management. Nanotechnology has gained attention for the delivery of theranostic agents to the targeted location. The use of essential amino-acid based homopolymers for the synthesis of biocompatible and biodegradable nanoparticles (NPs) could serve as a nanocarrier for delivery applications. In this study, poly-l-lysine (PLL) and salts were used to fabricate the NPs for the delivery of exogenous contrast agents. Here, indocyanine green (ICG) was encapsulated within these NPs, and a simple two-step green chemistry-based self-assembly process was used for the fabrication. The morphological and biochemical characterizations confirm the formation of ICG encapsulating spherical PLL NPs with an average diameter of ~225 nm. Further, a detailed study has been carried out to understand the role of constituents in the assembly mechanism of PLL NPs. Our results show a controlled release of the ICG from PLL NPs in the presence of the proteolytic enzyme. In-vitro cellular studies suggest that the PLL NPs were readily taken up by the cells showing their superior delivery efficiency of ICG in comparison to the free-form of the ICG.