Electrospinning is a fast-emerging technique highly applicable in tissue engineering (TE), since it allows the production of nanofibers meshes resembling the physical dimensions of native extracellular matrix (ECM). One of the most employed synthetic polymers in biomedical field is poly(?-caprolactone) (PCL). This polymer has been widely used to electrospun nanostructures, owing to it low cost, tunable degradability, great electro spinnability and good mechanical properties. However, PCL lacks instructive cues essential for cell attachment and proliferation, such as hydrophilicity and bioactivity, and the formation of blood vessels in implants. The limiting properties can be overcome by incorporating bioactive glass (BG), a recognized material advantageous in improving bioactivity and angiogenesis. The integration of certain elements, such as calcium (Ca) and boron (B) ions, in the inorganic material act as therapeutic agents. In this way, nanocomposite biomaterials based on the combination of a biodegradable polymer and BG are potential candidates for TE. The combination of these components at the nanoscale allows the integration of multiple properties, such as mechanical strength, hydrophilicity, biocompatibility, as well as controlled degradation behavior. Sol-gel is a viable approach to combine the polymer and inorganic components at the nanoscale and/or molecular level. However, the complex chemistry involved is still a challenge, and, for the case of PCL, its hydrophobic nature and poor solubility may be challenging when introduced into the sol while the network is being formed, especially, using a multicomponent inorganic system. Additionally, the integration of Ca and B in hybrid system via sol-gel and its homogeneous distribution into the network, at low temperatures is a challenge and has limited success, due to the calcium segregation.
The present work aims to develop and characterize multicomponent nanofibrous meshes, produced by electrospinning, using a synthetic polymeric matrix combined with boron and calcium silicate glass, formed via in situ sol-gel, and based on a green fabrication route. PCL was dissolved in green solvents, acetic acid (AA) and formic acid (FA); where inorganic part was prepared based on tetraethyl orthosilicate (TEOS), trimethyl borate (TMB) and calcium acetate (CaAc) as silica, boron, and calcium precursors, respectively. Thus, PCL and PCL/SiO2-B2O3-CaO compositions were prepared, electrospun and the membranes characterized. ATR-FTIR spectroscopy confirmed the presence of siloxane (Si-O-Si) bonds of silica and carbonyl (C=O) bonds characteristic of PCL as well as intermolecular hydrogen-bonding interactions between the carbonyls of PCL and the hydroxyls (Si-OH) of silica networks. The linkage between boron and silica was confirmed by solid state 11B NMR technique, where peaks assigned to the trigonal BO3 and tetrahedral BO4 groups were found. Thermal analysis revealed a change in the crystallinity of PCL with the incorporation of inorganic domain, confirming the formation of chemical interactions between the polymer and the inorganic components. Morphological analysis, by SEM/EDS, showed a homogenous distribution of Ca and Si elements into the fibers. 
Concluding, PCL/boron and calcium-containing silicate compositions were suitable for electrospinning into fibrous meshes, demonstrating potential for further design into multicomponent nanofibrous microstructures closer to the structure of the extracellular matrix.