Polyamines Promote Aragonite Nucleation and Generate Biomimetic Structures

Area of Science:

• Materials Science
• Biomineralization
• Crystallography

Background:

• Organisms precisely control calcium carbonate polymorphs (calcite, aragonite) using anionic biomacromolecules.
• Mimicking this biomineralization control synthetically with anionic molecules has proven challenging.

Purpose of the Study:

• To investigate the role of cationic polyamines in controlling calcium carbonate polymorph formation.
• To explore novel mechanisms for achieving precise control over biomineralization.

Main Methods:

• Utilized cationic polyamines of varying sizes (small molecules to polyelectrolytes).
• Investigated polyamine effects on calcium carbonate nucleation and growth.
• Developed a theoretical model to explain polyamine-mediated polymorph selectivity.
• Combined polyamines with magnesium ions to assess synergistic effects.

Main Results:

• Cationic polyamines effectively controlled calcium carbonate polymorphs, promoting aragonite nucleation at low concentrations and favoring calcite/vaterite at high concentrations.
• Aragonite formed via particle assembly, yielding nanoparticulate structures similar to biogenic aragonite.
• Subsequent growth resulted in stacked aragonite platelets resembling nacre structures.
• A theoretical model explained polymorph control via competing nucleation and growth effects, distinct from magnesium ion inhibition of calcite.

Conclusions:

• Cationic polyamines offer exceptional control over calcium carbonate polymorphism, distinct from anionic molecules and magnesium ions.
• The combination of polyamines and magnesium ions provides unprecedented control over aragonite formation.
• Organisms may utilize both amine-rich molecules and magnesium ions for biomineralization control.