Drying and storage effects on poly(ethylene glycol) hydrogel mechanical properties and bioactivity

Area of Science:

• Biomaterials Science
• Polymer Chemistry
• Tissue Engineering

Background:

• Poly(ethylene glycol) (PEG) hydrogels are crucial for controlling cell-material interactions in biomedical applications.
• Assessing the stability of PEG hydrogels after drying and storage is essential for developing off-the-shelf biomaterials.
• Limited research exists on the systematic effects of drying conditions on hydrogel properties and bioactivity.

Purpose of the Study:

• To investigate the impact of various drying methods (vacuum-drying, lyophilizing) on the mechanical properties and swelling ratios of PEG-diacrylate hydrogels.
• To evaluate the retention of bioactivity (cell adhesion and spreading) in collagen- and streptococcal collagen-like protein (Scl2-2)-functionalized PEG-diacrylamide hydrogels after different storage conditions.
• To determine optimal processing and storage conditions for maintaining the functionality of PEG hydrogel scaffolds.

Main Methods:

• PEG-diacrylate hydrogels were subjected to vacuum-drying, lyophilization, and a hydration-then-vacuum-drying process.
• Mechanical properties (compressive and tensile modulus) and swelling ratios were measured for processed hydrogels.
• Cell adhesion and spreading assays were performed on functionalized PEG-diacrylamide hydrogels stored under dry conditions versus phosphate-buffered saline (PBS) for 6 weeks.

Main Results:

• Drying and processing methods induced significant changes in mechanical properties and swelling ratios only in select PEG-diacrylate hydrogel formulations, with no consistent trends observed.
• Dry storage conditions effectively preserved the bioactivity of collagen- and Scl2-2-functionalized PEG-diacrylamide hydrogels.
• Storage in PBS significantly reduced hydrogel bioactivity, attributed to ester hydrolysis of the acrylate-PEG-N-hydroxysuccinimide linker.

Conclusions:

• Specific processing methods can be employed for PEG hydrogels without compromising their essential properties.
• Dry storage is a viable strategy for preserving the bioactivity of functionalized PEG hydrogel scaffolds.
• These findings support the development of stable, off-the-shelf PEG hydrogel biomaterials with recoverable functionality.