Electrospun Polycaprolactone Scaffolds with Marine-Derived Biosilica Nanoparticles ( <i>Dragmacidon reticulatum</i> ) for Bone Tissue Engineering Applications

Critical bone fractures require biomaterials capable of promoting efficient regeneration, with polymeric scaffolds with a bioactive phase being a promising approach. This study investigated the effect of the incorporation of different amounts (10, 15, and 20% w/w) of biosilica nanoparticles (nBS) extracted from the sponge <i>Dragmacidon reticulatum</i> within biodegradable polymer matrices based on poly-(ε-caprolactone) (PCL), with and without alkaline surface modification to increase polarity. Composites were processed by electrospun and casting, and the effect of the interconnected porosity on the structure, surface functionalization, and bioactivity was evaluated by comparison with the nonporous films' counterparts. Electrospinning generated nanofibrous membranes with better nBS dispersion, while the films exhibited filler agglomeration. SEM-EDS analyses revealed the best homogeneous distribution of Si and Ca in the surface-modified nanofibers containing 15% nBS. Contact angle measurements, X-ray diffraction, and thermogravimetric analysis revealed that the morphological modifications and property enhancements achieved both through biosilica particle addition and surface modification impacted the films and electrospun membranes differently. Energy dispersive spectroscopy analysis after 21 days of immersion in simulated body fluid evidenced an intense apatite deposition on the nanofibrous membranes, while maintaining an interconnected porosity. On the other side, the films with higher biosilica content exhibited mineral deposits with a Ca/P ratio ≈ 1.64, similar to that of natural hydroxyapatite. However, the Ca²⁺ release estimation by X-ray fluorescence indicated that a submicrometer porous architecture with large surface area favors more dynamic mineralization and deposition processes in time. Finally, tests with pre-osteoblasts confirmed cytocompatibility of the surface-modified electrospun composites with the most promising behavior. It is concluded that the compositional design combined with electrospun and surface modification resulted in scaffolds with biomimetic microarchitecture, better nBS dispersion, effective surface functionalization, and superior bioactive response to the films. This strategy represents an advance in the engineering of biomaterials aimed at critical bone regeneration.