Path-Dependent Anisotropic Colloidal Assembly of Magnetic Nanocomposite-Protein Complexes

Anisotropic self-assembly of nanoparticles (NPs) stems from the fine-tuning of their surface functionality and NP interaction. Strategies involving ligand interaction, protein interaction, and external stimulus have been developed. However, robust construction of monodispersed magnetic NPs to tens of microns of anisotropically aligned colloidal assembly triggered by adsorbed protein intermolecular interaction is yet to be elucidated. Here, we present the NP-protein interaction, magnetic force, and protein corona intermolecular interaction serially but independently induced path-dependent self-assembly of 100 nm Fe₃O₄@SiO₂ nanocomposites. Dynamic formation of the micron-sized anisotropic magnetic assembly was reproducibly realized in a continuous medium in a controllable manner. Formation of the primary globular clusters upon the unique NP-protein complexes with the help of ions acts as the prerequisite for the anisotropic colloidal assembly, followed by the magnetic force-driven pre-organization and protein intermolecular electrostatic interaction-mediated elongation. The protein concentration rather than the protein original structure plays a more pivotal role in the NP-protein interaction and subsequent colloidal assembly process. Two typical serum proteins fibrinogen and bovine serum albumin enable formation of the anisotropic colloidal assembly but with a different subtle morphology. Furthermore, the obtained micron-sized magnetic colloidal assembly can be dissociated rapidly by adding a negative electrolyte in the medium due to the interference in the NP-protein interaction. However, the self-assembly process can be recycled based on the dissociated colloidal assembly.