Structure-Activity Relationships of Hydroxyapatite-Binding Peptides.

Area of Science:

• Biomaterials Science
• Biomineralization
• Peptide Chemistry

Background:

• Understanding biomolecule-hydroxyapatite (HAP) interactions is crucial for bone mineralization, HAP-based implants, and drug delivery.
• Phage display identified four model HAP-binding peptides (HBPs) to investigate structure-activity relationships.

Purpose of the Study:

• To examine how primary sequence, phosphorylation, charged residues, and net charge affect HBP binding affinity, conformation, and influence on HAP nucleation and growth.
• To establish a benchmark for molecular dynamics simulations of HBP-HAP interactions.

Main Methods:

• HAP-binding affinities were quantified using adsorption isotherms via mass depletion.
• Peptide secondary conformations in solution and bound states were analyzed using circular dichroism.
• Transmission electron microscopy (TEM) was employed to observe effects on calcium phosphate nucleation and crystal growth.

Main Results:

• Peptide net charge was the primary determinant of HAP-binding affinity, with minimal influence from other sequence features.
• Observed binding affinities and conformations correlated well with prior molecular dynamics simulation results.
• HBPs demonstrated the ability to inhibit calcium phosphate nanoparticle nucleation and phase transition to HAP, and modulated crystal growth rates, resulting in biomimetic plate-like HAP morphologies instead of needle-like ones.

Conclusions:

• The net charge of a peptide is the dominant factor governing its interaction with hydroxyapatite.
• HAP-binding peptides can significantly influence the process of biomineralization, controlling nucleation, growth, and morphology of HAP crystals.
• These findings provide valuable insights for designing biomimetic materials and improving HAP-based biomedical applications.