Fluorescence Spectroscopic Analysis of Sodium Cholate Induced Disaggregation of Methylene Blue

Methylene blue (MB) has been used as a staining reagent for a long time. And also it has been established as a pharmaceutical agent recently. MB in aqueous environment undergoes self-association and forms dimmers, followed by formation of larger aggregates. The absorption studies reveal presence of monomer and dimer at 665 nm and 610 nm respectively, while the higher aggregates were found at around 292 nm. MB is a well-known staining dye and also a fluorescent molecule. Even though MB has a strong fluorescence, the adaptation of MB as a fluorescent probe is not explored thoroughly. Here, we attempt to probe the micellization behavior of bile salt media by using MB monomer absorption and fluorescence. Bile salts are well known disaggregation agents and widely used as drug delivery systems. Among the various bile salts, sodium cholate (NaC), a primary unconjugated bile salt was chosen for the study. The absorption and fluorescence data indicate that there is increase in absorbance and fluorescence intensity along with increase in fluorescence anisotropy. The study reveals that NaC induces disaggregation of MB aggregates through hydrophobic interactions.