Deconstructing collagen piezoelectricity using alanine-hydroxyproline-glycine building blocks.

Area of Science:

• Biomaterials Science
• Materials Science
• Solid State Physics

Background:

• Collagen's piezoelectricity has been studied for decades, but its fundamental building blocks' properties remain less understood.
• Recent interest in organic crystal piezoelectricity, including amino acids, motivates investigation into collagen's components.
• Amino acid-level contributions to collagen's piezoelectric response are not well-defined.

Purpose of the Study:

• To predict and measure the piezoelectric properties of collagen subcomponents (proline, hydroxyproline) in single crystalline forms.
• To investigate the piezoelectric behavior of a collagen-like alanine-hydroxyproline-glycine trimer peptide.
• To understand how crystal symmetry and molecular size influence piezoelectric charge constants in collagen building blocks.

Main Methods:

• First principles calculations to predict piezoelectric properties.
• Experimental measurements of piezoelectric properties in single amino acid crystals and a collagen-like peptide.
• Analysis of piezoelectric charge constants as a function of crystal symmetry and molecular size.

Main Results:

• Identified amino acid-level 'barcoding' of collagen's piezoelectricity, tunable via simple chemical modifications.
• Observed a significant increase (up to two orders of magnitude) in piezoelectric constants with the addition of a hydroxyl (-OH) group, as seen in hydroxyproline crystals (d25 = 25 ± 5 pC N-1).
• Measured hydroxyproline piezoelectricity comparable to commercial polyvinylidene difluoride (PVDF) films.

Conclusions:

• Collagen's piezoelectricity can be understood and engineered through a 'block by block' approach.
• First principles calculations are valuable tools for guiding the design and modification of piezoelectric biomolecules.
• Hydroxyproline's significant piezoelectric response highlights the impact of molecular structure on biomaterial properties.