Modification and cross-linking parameters in hyaluronic acid hydrogels--definitions and analytical methods

Area of Science:

• Biomaterials Science
• Polymer Chemistry
• Analytical Chemistry

Background:

• Cross-linked hyaluronic acid (HA) hydrogels are widely used in biomedical applications.
• Accurate quantification of modification and cross-linking is essential for understanding HA hydrogel properties.
• Existing methods may lack precision or applicability to diverse HA hydrogel formulations.

Purpose of the Study:

• To establish precise definitions and methods for quantifying modification and cross-linking in HA hydrogels.
• To introduce a novel analytical approach for determining key cross-linking parameters.
• To enable correlation of HA hydrogel characteristics with mechanical and biocompatibility properties.

Main Methods:

• Degradation of HA hydrogels using chondroitinase AC enzyme.
• Analysis of degradation products via Size Exclusion Chromatography coupled with Electrospray Ionization Mass Spectrometry (SEC-ESI-MS).
• Determination of degree of modification (MoD) using (1)H NMR spectroscopy and effective cross-linker ratio (CrR) via SEC-ESI-MS.

Main Results:

• A novel SEC-ESI-MS based method was successfully developed and applied to quantify cross-linking in HA hydrogels.
• The method allows for the determination of effective cross-linker ratio (CrR).
• Combined with MoD, CrR enables calculation of degree of substitution (DS) and degree of cross-linking (CrD).

Conclusions:

• The presented definitions and methods provide a robust framework for characterizing cross-linked HA hydrogels.
• This analytical approach is applicable to commercially available cross-linked HA hydrogels.
• Accurate quantification of MoD, DS, and CrD is vital for advancing HA hydrogel research and development.