How to Design Catechol-Containing Hydrogels for Cell Encapsulation Despite Catechol Toxicity.

Area of Science:

• Biomaterials Science
• Polymer Chemistry
• Cell Biology

Background:

• Catechol (cat) grafting enhances chitosan (CH) polymer adhesion.
• Catechol-containing materials exhibit variable in vitro toxicity, often attributed to quinone oxidation and reactive oxygen species (ROS) release.
• The precise mechanisms underlying catechol-induced cytotoxicity remain unclear.

Purpose of the Study:

• To investigate the relationship between oxidation levels, cross-linking methods, and the in vitro cytotoxicity of catechol-chitosan (cat-CH) hydrogels.
• To elucidate the primary mechanisms of cytotoxicity, focusing on leaching profiles, hydrogen peroxide (H2O2) production, and quinone release.

Main Methods:

• Synthesized cat-CH hydrogels by grafting hydrocaffeic acid (HCA) or dihydrobenzoic acid (DHBA) to chitosan.
• Employed oxidative cross-linking with sodium periodate (NaIO4) or physical cross-linking with sodium bicarbonate (SHC).
• Assessed hydrogel oxidation levels, leaching of catechol and quinone, H2O2 production, and in vitro cytotoxicity.

Main Results:

• NaIO4 cross-linking increased hydrogel oxidation but significantly reduced cytotoxicity, H2O2 production, and leaching of catechol and quinones.
• Cytotoxicity correlated directly with quinone release, independent of H2O2 production or catechol leaching.
• Oxidative stress is likely not the primary driver of catechol cytotoxicity; other quinone toxicity pathways are implicated.

Conclusions:

• Reducing indirect cytotoxicity of cat-CH hydrogels is achievable by chemically immobilizing catechol groups or using oxidation-resistant catechol derivatives.
• Optimizing cross-linking chemistry and purification methods are crucial for developing cytocompatible catechol-containing scaffolds.
• These findings offer strategies for engineering safer and more effective adhesive biomaterials.