Exploration and modulation of the photophysical properties of bromelain in a bioamphiphilic micellar system: comparative studies on the basis of room temperature ionic liquids, anionic surfactants, drugs and salts

Abstract

In this study, a new bioamphiphile sodium-2-decanamyde-2-methyl propanoate (SDMP) was synthesized to study the photophysical properties of bromelain (BM) in its micellar medium, and the experiment was further extended with the addition of room-temperature ionic liquids (RTILs) and a commonly used anionic surfactant sodium dodecyl sulfate (SDS), salt sodium chloride (NaCl) and a cationic drug nortriptyline (NOT) using steady-state and time-resolved spectroscopy, along with other techniques. For the modulation of the photophysical properties of BM, the interaction of BM was first studied with an SDMP micelle and then with two ILs of different chain lengths, SDS and NOT. This study reveals that micellar assemblies significantly reduce the degradation rate of bromelain owing to partitioning in the palisade layer of micelles from bulk water. The increase in average lifetime with the addition of SDMP after the micellar zone may be the result of hindrance of the excited-state intramolecular proton transfer (ESIPT) process. Furthermore, the stability and activity were compared with those of conventional imidazolium-based ionic liquids, i.e., 1-hexadecyl-3-methylimidazolium chloride (C₁₆MeImCl) and 1-decyl-3-methylimidazolium chloride (C₁₀MeImCl), using spectroscopic techniques. The present study shows that both the studied ILs interact with the functional groups of BM. Therefore, it appears that the SDMP micellar medium stabilizes BM more than an aqueous medium. The interaction between BM and amino acid surfactant (AAS) may provide new insights in the field of green technology using renewable natural resources to create eco-friendly and bio-degradable products.