3D-printing of shear-thinning and self-healing gelatin/starch/ halloysite-nanotube hydrogels for soft tissue engineering: An in vitro and in vivo assessment

Abstract

Shear-thinning and self-healing hydrogels are essential for various biomedical applications, specially 3D-printing. This study developed a novel shear-thinning and self-healing hydrogel based on gelatin, starch, and Halloysite-nanotubes (G-S-H) for 3D-printing soft tissues. Different G-S-H ratios and cross-linking reagents (i.e. EDC-NHS and glutaraldehyde) were employed to enhance mechanical properties and degradation rates. Characterization encompassed compression and rheological tests, degradation rates, zeta potential and Dynamic light scattering measurement, morphological analysis, and cytotoxicity assessment. The hydrogels demonstrated suitable stiffness resembling soft tissues and exhibited non-Newtonian behavior with distinct shear-thinning and self-healing properties. In vivo assessments of implanted scaffolds in rats revealed rapid degradation of the noncross-linked scaffold subcutaneously, while the EDC-NHS scaffold showed prolonged degradation over 60 days, supporting tissue ingrowth into inter-filament spaces and filament pores. Histological analysis indicated initial acute inflammatory responses followed by transition to mild immune responses by day 60. The EDC-NHS-crosslinked scaffold supported higher vascularization and collagen deposition compared to the glutaraldehyde-crosslinked scaffold. Overall, the G-S-H hydrogels showed promise for 3D-printing applications in soft tissue engineering, offering optimal mechanical properties, degradation rate and biocompatibility for long-term tissue support. This study underscores the importance of scaffold composition in governing degradation rates, tissue integration, and biocompatibility in tissue engineering applications.