Magnetosomes on surface: an imaging study approach

In this study, we deposited isolated magnetosomes from magnetotactic bacteria Magnetospirillum strain AMB-1 onto solid surfaces using spin coating (SC) and drop coating (DC) techniques. Four imaging techniques have been used to visualize the sample structure: scanning and transmission electron microscopy (SEM, TEM), atomic and magnetic force microscopy (AFM, MFM). Additionally, dynamic light scattering was applied to measure the hydrodynamic radius of agglomerated/aggregated magnetosomes in a liquid environment. This manuscript discusses observed differences between structures obtained by two deposition techniques, i.e. possible interactions and factors responsible for magnetosomes' formation, their morphology on surfaces as a result of agglomeration and aggregation phenomena. Moreover, topography and homogeneity of obtained structures as well as thickness of protein-based membrane were also examined and described. Using high-resolution TEM, we analyzed the size of magnetic cores, their crystal structure and quality. We found that the SC technique provides a homogenous layer of magnetosomes and hydrophilization of silicon surfaces improves the deposition of magnetosomes. However, due to strong hydrogen interaction to the hydrophilic silicone surface, the organic membrane of magnetosomes is mostly flattened. As a matter of fact, the size distributions of magnetosomes deposited by SC and DC techniques (logarithmic-normal tendency) differ from the Feret diameter distribution (normal). Furthermore, our study confirms the good crystalline quality of magnetosomes' cores. It also shows that they are magnetic in the all their volume.