*Article* **Robocasting and Laser Micromachining of Sol-Gel Derived 3D Silica/Gelatin/**β**-TCP Scaffolds for Bone Tissue Regeneration**

**María V. Reyes-Peces <sup>1</sup> , Eduardo Félix 1,2 , Francisco J. Martínez-Vázquez <sup>3</sup> , Rafael Fernández-Montesinos 4,5 , Óscar Bomati-Miguel 1,2 , María del Mar Mesa-Díaz 2,6 , Rodrigo Alcántara 2,7 , José Ignacio Vilches-Pérez <sup>5</sup> , Mercedes Salido 4,5 , Nicolás De la Rosa-Fox 1,2 and Manuel Piñero 1,2,\***

	- **\*** Correspondence: manolo.piniero@gm.uca.es

**Abstract:** The design and synthesis of sol-gel silica-based hybrid materials and composites offer significant benefits to obtain innovative biomaterials with controlled porosity at the nanostructure level for applications in bone tissue engineering. In this work, the combination of robocasting with sol-gel ink of suitable viscosity prepared by mixing tetraethoxysilane (TEOS), gelatin and β-tricalcium phosphate (β-TCP) allowed for the manufacture of 3D scaffolds consisting of a 3D square mesh of interpenetrating rods, with macropore size of 354.0 ± 17.0 µm, without the use of chemical additives at room temperature. The silica/gelatin/β-TCP system underwent irreversible gelation, and the resulting gels were also used to fabricate different 3D structures by means of an alternative scaffolding method, involving high-resolution laser micromachining by laser ablation. By this way, 3D scaffolds made of 2 mm thick rectangular prisms presenting a parallel macropore system drilled through the whole thickness and consisting of laser micromachined holes of 350.8 ± 16.6-micrometer diameter, whose centers were spaced 1312.0 ± 23.0 µm, were created. Both sol-gel based 3D scaffold configurations combined compressive strength in the range of 2–3 MPa and the biocompatibility of the hybrid material. In addition, the observed Si, Ca and P biodegradation provided a suitable microenvironment with significant focal adhesion development, maturation and also enhanced in vitro cell growth. In conclusion, this work successfully confirmed the feasibility of both strategies for the fabrication of new sol-gel-based hybrid scaffolds with osteoconductive properties.

**Keywords:** 3D scaffold; hybrid; sol-gel ink; robocasting; laser micromachining; osteoblasts; regenerative medicine; bone tissue engineering; cytoskeleton; focal adhesion
