Particle-attachment crystallization facilitates the occlusion of micrometer-sized Escherichia coli in calcium carbonate crystals with stable fluorescence

Inspired from the occlusion of macromolecules in mineral crystals during the biomineralization process, the occlusion mechanism of functional guest species into a host matrix is gradually revealed in artificial systems. However, the guest species within calcite crystals are limited to the nanometer scale. Herein, using amorphous calcium carbonate (ACC) as a precursor and taking advantage of the crystallization of vaterite by the attachment of ACC nanoparticles, micrometer-sized modified Escherichia coli (E. coli) was incorporated into vaterite crystals. The occlusion content of bacteria within the vaterite crystal could reach up to 16 wt%. On the contrary, the occlusion of E. coli into calcite crystals, which proceeded via ion-by-ion addition growth, was only confined to the surface layer. Through modifying the surface structure or chemical composition of bacteria, the strong interaction between the surface of the bacteria and calcium carbonate has proved to be the key factor for successful occlusion. Interestingly, the genetically modified green fluorescent protein (GFP)-E. coli/vaterite composites exhibited stable fluorescence for more than six months with little attenuation and the lifetime could be more than 1.2 μs. It was demonstrated that a combination of the amorphous precursor crystallization pathway and a suitable surface structure of the foreign species can significantly enhance the occlusion efficiency of micrometer-sized species in crystals.

Hierarchical CaCO3 particles self-assembled from metastable vaterite and stable calcite during the decomposition of Ca(HCO3)2

When Ca(HCO₃)₂ solution is put at 80 °C, ACC initially formed grow into calcite, aragonite and vaterite particles. The trunk of snow-shaped particles are self-assembled from hexagonal vaterite particles by one or more steps, followed by the filling in the pores of snow-shaped particles by small crystals.

Crystallization of calcium carbonate under the influences of casein and magnesium ions

The significant morphological changes of calcium carbonate crystals were investigated and observed in the presence of casein and magnesium ions.

Confinement controlled mineralization of calcium carbonate within collagen fibrils

The amorphous calcium carbonate infiltrates into collagen fibrils and transforms into a co-oriented crystalline phase under the function of confinement.

Controlled synthesis of mesoporous nanostructured anatase TiO2 on a genetically modified Escherichia coli surface for high reversible capacity and long-life lithium-ion batteries

Deposition and mineralization of TiO₂ on genetically modified Escherichia coli surface has been achieved, leading to formation of a nanostructured anatase TiO₂ with enhanced electrochemical performance as anode electrodes of lithium-ion batteries.