Insights into BSA-micellar carrier-drug systems using pyrene excimer

The study investigates mixtures of bovine serum albumin (BSA) and micellar carriers with incorporated pyrene (Py). Mono-disperse hexaethyleneglycol mono n -dodecyl ether (C 12 E 6 ) and respective, poly-disperse eicosaethyleneglycol mono n -tetradecyl ether (C 14 EO 20 ) are employed to get micellar carriers with different dimension and polarity. Pyrene is used both as a probe and model drug to get insight upon the albumin-carrier association and the medicine transport. At BSA addition upon the drug-carrier system, the emissive signal and lifetime of Py excimer decrease, while the monomer lifetime increases. The results prove the transport of the probe in small micellar clusters on the polypeptide chain. Comparison of the quenching of BSA fluorescence by surfactant or/and Py unveils a hybrid process when both quenchers are present. In accord, a non-radiative fluorescence resonance energy transfer (FRET) occurs between BSA tryptophan and Py with higher donor–acceptor distance, the longer the carrier’s alkyl and ethyleneoxide chains. Pyrene predominantly forms dynamic excimers in all studied systems, which shows that the probe’s environment is fluid. The pyrene association ratio provided by UV–Vis absorption spectra indicates the transfer of some Py monomers only from the C 12 E 6 micelles to nonpolar zones of protein. Differently, the long ethyleneoxide chains of C 14 EO 20 impede the pyrene relocation. The Py-loaded micelles stabilize the secondary structure of BSA. The work sheds light on the transport of drugs with micellar carriers from alkyl-ethoxylated nonionic surfactants.