Cold sintering of vaterite microspheres incorporated with GFP-modified Escherichia coli under gigapascal-level pressure for enhanced mechanical properties and stable fluorescence

Biominerals possess the capability to encapsulate organic macromolecules or inorganic nanoparticles within their matrix crystals during the growth process. The robust interfacial interactions between guest nanoparticles and the host crystals contribute to the exceptional mechanical properties of biominerals. Inspired by this natural encapsulation process, vaterite microspheres incorporating green fluorescence protein-modified Escherichia coli (GFP- E. coli @vaterite) are synthesized. The encapsulation process involves the initial adhesion of amorphous calcium carbonate precursor onto the surface of E. coli , followed by progressive mineralization with growing vaterite crystals, thereby achieving the encapsulation of 14.6 wt% bacteria within vaterite microspheres. Subsequently, dense composite bulks are fabricated through cold sintering of the GFP- E. coli @vaterite powder at 100 °C under a pressure of 1 GPa. The resulting composites achieved flexural strength and fracture toughness of 69.9 MPa and 0.75 MPa·m 1/2 , representing 1.4-fold and 2.2-fold improvements over pure vaterite bulk (48.4 MPa and 0.34 MPa·m 1/2 ), respectively. Notably, the GFP- E. coli @vaterite composite bulks maintained stable fluorescence for more than eighteen months, with minimal signal attenuation and a fluorescence lifetime exceeding 1.1 μs. Our work provides an efficient approach to fabricate integrated structural and functional composites under low temperature conditions. This work also establishes a new direction in fluorescent marking technologies and demonstrates promising potential for practical implementation.