Electrochemistry and surface-enhanced Raman spectroscopy of CTAB modulated interactions of magnetic nanoparticles with biomolecules

In this study, we use cyclic voltammetry (CV) to depict the association of magnetic iron oxide nanoparticles (MNPs) with two different coating materials namely, bovine serum albumin (BSA) and dextran. The role of a cationic surfactant, hexadecyltrimethylammonium bromide (CTAB) in stabilizing the MNPs and augmenting the association with BSA and dextran is also investigated. CV of the MNPs/CTAB systems shows a diffusion-controlled mechanism on interaction with BSA and dextran. In the presence of CTAB, the reduction potential of MNPs shifted to a higher value indicating hindrance in the electron transfer process. Raman spectroscopy is used to study the structural change of MNPs during the associations. Surface-enhanced Raman spectroscopy (SERS) provides an insight into the mode of interaction by enhancing the otherwise weak signals arising due to Raman active carbon skeletal modes in organic coating materials. BSA tends to associate with the MNPs by diffusing through the CTAB molecule by hydrophobic interactions, while dextran is attached with the hydrophilic head groups of CTAB. Zeta potential and saturation magnetization of the nanoparticles show good colloidal stability and retention of magnetic properties, respectively after coating.