Cationic versus Anionic Surfactant in Tuning the Structure and Interaction of Nanoparticle, Protein and Surfactant Complexes.

Langmuir : the ACS journal of surfaces and colloids

PubMedID: 25079825

Mehan S, Aswal VK, Kohlbrecher J. Cationic versus Anionic Surfactant in Tuning the Structure and Interaction of Nanoparticle, Protein and Surfactant Complexes. Langmuir. 2014;.
The structure and interaction in complexes of anionic Ludox HS40 silica nanoparticle, anionic bovine serum albumin (BSA) protein and cationic dodecyl trimethyl ammonium bromide (DTAB) surfactant have been studied using small-angle neutron scattering (SANS). The results are compared with the similar complexes having anionic sodium dodecyl sulphate (SDS) surfactant (Mehan, S; Chinchalikar, A. J.; Kumar, S.; Aswal, V. K.; Schweins, R. Langmuir 2013, 29, 11290). In both the cases (DTAB and SDS), the structure in nanoparticle-protein-surfactant complexes is predominantly determined by the interactions of individual two components. The nanoparticle-surfactant (mediated through protein-surfactant complex) and protein-surfactant interactions for DTAB, whereas nanoparticle-protein (mediated through protein-surfactant complex) and protein-surfactant for SDS, are found to be responsible for the resultant structure of nanoparticle-protein-surfactant complexes. Irrespective of the charge on the surfactant, the cooperative binding of surfactant with protein leads to micelle-like clusters of surfactant formed along the unfolded protein chain. The adsorption of these protein-surfactant complexes for DTAB on oppositely charged nanoparticles gives rise to the protein-surfactant complex mediated aggregation of nanoparticles (similar to that of DTAB surfactant). It is unlike to that of depletion induced aggregation of nanoparticles with non-adsorption of protein-surfactant complexes for SDS in similarly charged nanoparticle systems (similar to that of protein alone). The modifications in nanoparticle aggregation as well as unfolding of protein in these systems as compared to the corresponding two-component systems have also been examined by selectively contrast matching the constituents.