Development of an injectable, conductive nanocomposite hydrogel reinforced with reduced graphene oxide for potential application in electrically active tissue engineering

The development of injectable and printable conductive hydrogels is of great importance for tissue engineering, particularly for supporting the regeneration of electrically active or excitable tissues. In this study, a nanocomposite hydrogel was formulated by incorporating reduced graphene oxide (rGO) into a self-healing and<i>in situ</i>-gelling aldehyde-functionalized xanthan gum (AXG) and gelatin (Gel) matrix. The AXG-Gel hydrogels incorporated by 0, 0.5, 1, and 2% w/v rGO were synthesized using Schiff-base chemistry and evaluated for its physicochemical, mechanical, rheological, electrical, and biological properties. The 1% rGO formulation exhibited the highest mechanical modulus (0.315 ± 0.0135 MPa) and self-healing yield (93.18 ± 1.56%), compared to 0.2157 ± 0.0145 MPa and 77.16 ± 5.98% in the 2% rGO formulation. By an increase in rGO content, an increase in porosity was observed, holding values from 90.43% in rGO-free scaffolds to 97.70% in the 2% rGO group. All samples maintained high swelling capacities (>800%), with AXG-Gel-0.5rGO showing the highest (∼940%) and AXG-Gel-2rGO the lowest (∼830%). Conductivity improved significantly in the 1% rGO hydrogel, achieving 4.16 × 10²S/m which was 24% higher than the rGO-free scaffold (3.33 × 10²S m^-1). Impedance spectroscopy showed reduced resistance and higher charge transfer efficiency in rGO-loaded scaffolds. The AXG-Gel-1rGO also exhibited favourable rheological behavior, with a storage modulus of 1.7 kPa at 1 Hz and pronounced shear-thinning. The injectability and printability were confirmed by syringe injection assay and extrusion-based 3D printing of circular structure. MTT and SEM-based cytocompatibility assays confirmed an excellent viability and cell adhesion for AXG-Gel-1rGO scaffolds after 3 d. Overall, the 1% rGO scaffold achieved a balanced combination of conductivity, printability, injectability, porosity, mechanical strength, and cytocompatibility, indicating its potential as a promising candidate for future electrically active tissue engineering applications.