Gelatin intervened synthesis of calcite cocoon-like microparticles assembled with small rhombohedra at low temperature

Biomimetic crystallisation of calcium carbonate (CaCO3) in the presence of gelatin was investigated at room temperature (RT) and at low temperature. The presence of gelatin was found to alter the normal crystallisation of large calcite rhombohedral crystals, leading to the unique morphosynthesis of calcite microcrystals. Compared to the overgrowth of irregular calcite products synthesised in the presence of gelatin at RT, predominant cocoon-like and minor rosette-like microparticles with the typical size of 2–4 μm were obtained at low temperature (4°C). The samples showed that the cocoon-like microparticles were orderly stacked by small well faceted rhombohedra. The formation of hollow microspheres was confirmed by observing the consumption of the internal precursors, further indicative of the unique low temperature modulating effects of gelatin. The present biomimetic approach is simple and biosafe, and the obtained cocoon-like hollow microparticles could be potentially used for biomedical purposes.