Encapsulation of Indocyanine Green within nano-assembled capsules changes its optical properties

摘要

Indocyanine Green (ICG) is a photosensitive dye frequently used in clinical settings for retinal imaging and measuring cardiac output function. Its low toxicity, high absorption in the near infrared region, and vascular retention have generated much interest in its utility for several therapeutic and diagnostic applications. Its potential, however, is limited by factors such as rapid circulation kinetics and lack of target specificity. Additionally, the optical properties of ICG vary significantly with a wide range of influences such as concentration, solvent, pH, and temperature. In an effort to overcome these limitations and improve ICG's effectiveness as a chromophore for photothermal treatment, we have developed a novel nanometer-sized capsule system as a delivery vehicle for ICG. In our capsules, the ICG molecules are encapsulated within a polymer-salt aggregate core coated with dextran. In this study, we report how the optical properties of ICG are affected by its entrapment within the nano-assembled complexes (NACs). The absorption profiles of both freely dissolved ICG and encapsulated ICG were recorded under various conditions to determine the effects of encapsulation on ICG's light sensitivity and stability at different temperatures. Dilute preparations of freely dissolved ICG demonstrated more rapid degradation kinetics in response to intense broadband light (360 - 1100 nm, 56 mW/ cm~2) than NACs containing ICG. Encapsulated ICG also demonstrated greater stability at room and elevated temperatures than freely dissolved ICG. The results suggest that the entrapment of ICG within the capsules influences its ability to undergo physicochemical transformations, including oligomerization and degradation to leucoforms.