Enhanced Mechanical Properties of Injectable Chitosan-Guar Gum Hydrogel Reinforced with Bacterial Cellulose Nanofibers for Tissue Engineering Applications

Abstract

Demand is increasing for devices capable of regenerating or replacing damaged tissues, highlighting the need for advanced biomaterials. Hydrogels are promising for regenerative medicine, but often lack mechanical strength. To overcome this, a novel nanocomposite hydrogel based on N-succinyl chitosan (NSC) and oxidized guar gum (OxGG) reinforced with bacterial cellulose nanofibers (BCFs) is developed. These hydrogels are produced through a simple and safe Schiff-base reaction and hydrogen bonding, avoiding potentially toxic cross-linker or external stimuli. Chemical characterization is performed using Fourier transform infrared, X-ray photoelectron spectroscopy, and thermogravimetric analysis. Scanning electron microscopy reveals significant changes in the hydrogel’s internal structure after BCF incorporation, resulting in a more compact and organized porous matrix. This modification also reduces phosphate buffer solution uptake, modifying the swelling behavior of the hydrogel, due to the formation of a rigid polymeric network. Both hydrogels exhibit fast gelation times (<30 s), ensuring injectability for minimally invasive therapy. NSC/OxGG/BCF hydrogels exhibit enhanced mechanical properties, with storage and Young's moduli of 3.97 and 197.1 kPa, respectively—more than double the values observed for NSC/OxGG hydrogels. Additionally, hydrogels are noncytotoxic to neonatal human dermal fibroblast cells (cell viability > 70%). These results suggest that NSC/OxGG/BCF hydrogels demonstrate promising potential for tissue engineering applications.

Stress-Relaxation Assay

Stress-relaxation unconfined compression tests were performed on the hydrogels using a MACH-1 Mechanical Tester System (Biomomentum Inc., QC, Canada). Cylindrical test specimens (10 mm in diameter, and 6–7 mm in height) were carefully prepared to ensure uniformity.[49] The stress–relaxation test parameters were as follows: ramp amplitude was set to 10% of the initial sample thickness, ramp velocity was set to 5% of the initial sample thickness per second and three ramps. The tests were performed in a water bath containing PBS solution (0.01m, pH 7.4) at room temperature. The fixed relaxation time was 15 000 s. Load and deformation, measured in Newtons and millimeters, respectively, were recorded at 10 ms intervals.