Evaluation of Single Hydrogel Nanofiber Mechanics Using Persistence Length Analysis

Area of Science:

• Biomaterials Science
• Polymer Science
• Tissue Engineering

Background:

• Polyelectrolyte hydrogel fibers mimic the extracellular matrix for tissue scaffolding.
• Metal ions are known to tune the mechanical properties of these fibers.
• Evaluating single hydrated fiber mechanics and ion modulation remains challenging.

Purpose of the Study:

• To directly evaluate the mechanical properties of single hydrated polyelectrolyte fibers.
• To understand how ferric ions modulate the mechanical properties of poly(acrylic acid) and chitosan fibers.
• To establish persistence length analysis as a method for evaluating hydrated fiber mechanics.

Main Methods:

• Electrospinning of poly(acrylic acid) (PAA) and chitosan (CS) fibers.
• Dark-field microscopy for fiber imaging.
• Persistence length analysis to determine fiber mechanics.
• Nanoscale infrared spectroscopy to study ion-polymer interactions.

Main Results:

• Persistence length analysis is a viable method for evaluating hydrated fiber mechanics.
• Ferric ions result in shorter and stiffer nanofibers with a Young's modulus in the kilopascal range.
• Low concentrations of ferric ions reduce the Young's modulus of PAA and PAA/CS fibers by interacting with carboxylate groups.

Conclusions:

• Ferric ion concentration significantly influences the mechanical properties of PAA and PAA/CS fibers.
• The interaction between ferric ions and carboxylate groups is key to modulating fiber stiffness.
• This study provides a foundation for designing tunable hydrogel fibers for tissue engineering applications.