Parabens induced spherical micelle to polymersome transition in thermo-responsive amphiphilic linear and star-shaped EO-PO block copolymers

Abstract

Micellar transition induced employing pharmaceutically-active antioxidants specifically p-hydroxy benzoic acid esters (parabens) viz., methyl paraben (MP), ethyl paraben (EP), propyl paraben (PP), butyl paraben (BP), and benzyl paraben (BzP) in ~5% w/v thermoresponsive triblock linear: Pluronic® (P84) and star-shaped: Tetronic® (T1304) copolymers was investigated in aqueous solution. The solution behavior of these block copolymers in presence of parabens is well scrutinized from cloud point (CP), relative viscosity (ηrel), spectral (FT-IR, UV–vis), computational simulation, and scattering (dynamic light scattering (DLS) and small angle neutron scattering (SANS)) study. Varied phase behavior and a dramatic change in ηrel with temperature ageing is attributed to the plausible induced micellar transition (spherical micelle to polymersomes) is accounted to the hydrophobic effect of parabens onto the block copolymers which is depicted from spectral study and further rationalized using computational simulation approach. The prominent shifts observed in the hydrodynamic diameter (Dh) of parabens loaded and unloaded copolymeric micelles was inferred from DLS while fitted SANS findings clearly depicted the micellar dimensions along with the aggregation number (Nagg). Furthermore, the performed antioxidant (free radical scavenging and reducing capacity) assay in non-micellar and micellar media trait the ability to shuttle between the reduced and oxidized forms that prevents the oxidative damage which makes this study biologically important.