Inorganic Sol-Gel Polymerization for Hydrogel Bioprinting

Area of Science:

• Biomaterials Science
• Tissue Engineering
• Polymer Chemistry

Background:

• Three-dimensional (3D) bioprinting requires advanced bioinks for fabricating functional tissue scaffolds.
• Hydrogels offer promising biomaterial properties but often lack the mechanical stability and printability needed for complex structures.
• Developing biocompatible and tunable hydrogel systems is crucial for regenerative medicine applications.

Purpose of the Study:

• To develop a novel bioink for 3D bioprinting using an inorganic sol-gel polymerization process.
• To create a hydroxypropyl methyl cellulose (HPMC)-based hydrogel precursor for extrusion-based bioprinting.
• To investigate the physicochemical properties and functionalization capabilities of the resulting hydrogel scaffolds.

Main Methods:

• An inorganic sol-gel polymerization was employed as a cross-linking reaction for hydrogel formation.
• Hybrid hydroxypropyl methyl cellulose (HPMC) with controlled silylation was synthesized as a 3D-network precursor.
• The bioink, containing human mesenchymal stem cells, was extruded and polymerized in situ at physiological pH (7.4) using biocompatible catalysts (NaF and glycine).
• Rheological and viscosity measurements were performed to determine the printing window.
• Physicochemical properties of the hydrogels were analyzed.
• Covalent functionalization was demonstrated using a triethoxysilyl-containing fluorescent molecule.

Main Results:

• A stable, printable bioink was successfully formulated using silylated HPMC and sol-gel polymerization.
• The sol-gel process occurred under biocompatible conditions (pH 7.4, NaF/glycine catalysis), suitable for cell encapsulation.
• Rheological analysis defined the optimal printing parameters for the bioink.
• The resulting hydrogels exhibited tunable physicochemical properties.
• Covalent functionalization of the hydrogel network was achieved, demonstrated by incorporating a fluorescent molecule.

Conclusions:

• The developed HPMC-based bioink, cross-linked via inorganic sol-gel polymerization, is a promising material for 3D bioprinting of cell-laden scaffolds.
• The biocompatible and tunable nature of this system supports its potential application in tissue engineering and regenerative medicine.
• The demonstrated covalent functionalization opens avenues for creating advanced, multi-functional biomaterials.