A novel anion replaced gemini surfactant: Investigation on the primary interaction between gemini surfactant and BSA

Gemini surfactants (GS) could serve as the drug carrier agents for the delivery of macromolecules due to the excellent properties and tuneable structures. Little attention has been paid to the impact of counterion change on GS and the interaction between GS and protein. In this work, ibuprofen (Ibu) replaced quaternary ammonium ion GS (GS-Ibu) with the hydrophobic chain length of 8, 10, 12, 14 and 16 carbon atoms were prepared for the first-time using extraction technology. The prepared GS-Ibu has stronger electrostatic interaction compared to traditional gemini surfactants with bromide anions (GS-Br). GS were further incubated with the model macromolecule, bovine serum albumin (BSA), to form BSA/GS complexes. The colloid stability of BSA could be affected by the concentration of GS, the length of hydrophobic chain and the type of anion. GS-Ibu exhibited better ability to prevent BSA from aggregating based the result of PAGE test. The molecular level change of BSA after the introduction of GS was first reflected by UV-Visible absorption spectrum. CD spectrum results further revealed that the primary interaction leading to the change in the secondary structure of BSA is electrostatic interaction. Molecular docking and molecular dynamic simulations confirmed the presence of hydrophobic and electrostatic interaction between BSA and GS. In conclusion, the anion replaced GS could be a promising strategy to stabilize the proteins.