*2.5. Acellular Bioactivity*

The acellular bioactivity of PLLA-SBA2 fibres, related to the surface deposition of HCA layers, was evaluated by immersing the samples inserted in scaffold holders (CellCrownTM 24, Scaffdex, Sigma Aldrich, Munich, Germany) in simulated body fluid (SBF) solution [43] for 1, 7, 14 and 21 days at 37 ◦C, on an oscillating tray in an incubator. A falcon tube with only SBF was used as control. After each time point, samples were washed with distilled water, dried at room temperature before SEM-EDS characterization and Fourier Transform Infrared Spectroscopy (FTIR) analysis in attenuated total reflectance (ATR) mode. PLLA neat fibres were considered as control. FTIR spectra were recorded by a spectrometer (IRAffinity-1S, Shimadzu, Kyoto, Japan), repeating 32 scans over the wavenumber range 4000–500 cm<sup>−</sup>1, with a resolution of 4 cm−1.
