This study implemented the application of microcomputed tomography (micro-CT) as a characterization technique for the study and investigation of the microstructure of 3D scaffold structures produced via three-dimensional bioprinting (3DBP). The study focused on the preparation, characterization, and cytotoxicity analysis of gold nanoparticles (Au-NPs) incorporated into 3DBP hydrogels for micro-CT evaluation. The Au-NPs were characterized by using various techniques, including UV-vis spectrometry, dynamic light scattering (DLS), zeta potential measurement, and transmission electron microscopy (TEM). The characterization results confirmed the successful coating of the Au-NPs with 2 kDa methoxy-PEG and revealed their spherical shape with a mean core diameter of 66 nm. Cytotoxicity analysis using live-dead fluorescent microscopy indicated that all tested Au-NP solutions were nontoxic to AC16 cardiomyocytes in both 2D and 3D culture conditions. Scanning electron microscopy (SEM) showed distinguishable differences in image contrast and intensity between samples with and without Au-NPs, with high concentrations of Au-NPs displaying nanoparticle aggregates. Micro-CT imaging demonstrated that scaffolds containing Au-NPs depicted enhanced imaging resolution and quality, allowing for visualization of the microstructure. The 3D reconstruction of scaffold structures from micro-CT imaging using Dragonfly software further supported the improved visualization. Mechanical analysis revealed that the addition of Au-NPs enhanced the mechanical properties of acellular scaffolds, including their elastic moduli and complex viscosity, but the presence of cells led to biodegradation and reduced mechanical strength. These findings highlight the successful preparation and characterization of Au-NPs, their nontoxic nature in both 2D and 3D culture conditions, their influence on imaging quality, and the impact on the mechanical properties of 3D-printed hydrogels. These results contribute to the development of functional and biocompatible materials for tissue engineering and regenerative medicine applications.
Keywords: 3D bioprinting; alginate-gelatin hydrogels; gold nanoparticles; mechanical properties; micro-CT imaging; microstructure evaluation.