| High quality magnetite crystals have previously been synthesized in a pluronic medium using a biomineralization protein, mms6, derived from magnetotactic bacteria. However, until present these studies have been conducted only in the solution phase, for which particle aggregation and movement of particles to the bottom of the pluronic medium limit characterization opportunities, including how the particles affect the pluronic structure. In this study, magnetite synthesis is completed in a solid pluronic gel phase for which magnetite particles are suspended and can be characterized using small-angle x-ray scattering (SAXS). This study has shown that the proteins alone do not affect the Pluronic structure, except slightly for the case of the highest concentration of His-mms6. In addition, mixed chlorides may act to stabilize the self-organization of the Pluronic due in electrostatic interactions. This study has shown that magnetite synthesis in Pluronic is a function of several parameters including the concentration and size of the protein used for templating, the concentration of the magnetite, and the viscosity of the Pluronic gel. Our results indicate that magnetite particle synthesis in Pluronic causes the inter-micellar distance to decrease, most notably for the case of the highest concentration of His-mms6. This may be attributed to an apparent compression in the gel because of the magnetite particles and the large size of His-mms6. Large magnetite particles can be formed in solid Pluronic gel in the absence of protein, indicating that Pluronic alone may template particle synthesis. This is in contrast to magnetite formation in the solution phase, for which either the His-mms6 or C25 protein is required for templating. Disruption in the FCC structure is observed for the case of the highest His-mms6 concentration, which is consistent with the larger size of the His-mms6 protein. Disruption of the FCC structure may eliminate the possible templating ability of the Pluronic gel, as evidenced by the lack of large particles present in the case of the highest His-mms6 concentration. The large scattering due to the magnetite particles suggests the use of a lower concentration of iron chlorides so as to be able to resolve all the higher order peaks in the gel. Compared to the solution phase experiments, the solid gel phase synthesis method results in a gel with a much higher viscosity, which is likely to impede particle growth. Thus, the viscosity of the gel may be used to control the particle size in the biomineralization synthesis platform. |
