Design of Printable Gelatin Composite-PVA Bioink for Self-Supported Fabrication of 3D Thick Porous Constructs.

The development of thick, permeable, three-dimensional (3D) constructs is essential for advancing tissue engineering applications that require efficient mass transport and prolonged cell viability. In this study, a printable gelatin composite-poly(vinyl alcohol) (PVA) bioink is designed and evaluated for the self-supported fabrication of 3D thick porous constructs with satisfactory permeability. The proposed bioink incorporates gelatin solution, gelatin microgels, and PVA, which is utilized as a sacrificial porogen to facilitate postprinting pore formation. The rheological properties of the bioink (the PVA-to-gelatin composite v/w ratio of 1:5) demonstrate suitable shear-thinning behavior and yield-stress fluid property for extrusion-based 3D printing, and the latter enables the jamming-based physical cross-linking mechanism during printing, which works with the thermal cross-linking of gelatin solution to retain the print shape for permanent enzymatic cross-linking. Printed constructs exhibit good print fidelity and structural integrity across both two-dimensional (2D) lattice and 3D tubular geometries. After PVA removal, the freeze-dried samples show large pores formed by removed PVA, as confirmed by scanning electron microscopy and pore size analysis. Permeability tests reveal that constructs fabricated with PVA porogen removal achieve a higher permeation rate of 1.39 mm/h. NIH 3T3 fibroblast-based cell viability studies demonstrate sustained cell survival in the 10.00 mm-thick porous constructs with cell viability above 75% over 7 days with the 2D cell viability control effect considered. Despite residual PVA detected postremoval, the porous network formed by PVA removal remains effective in supporting permeability and cellular function. These findings demonstrate the potential of the printable gelatin composite-PVA bioink for fabricating thick, permeable constructs suitable for cell culture and tissue engineering applications.