Tailoring the delivery of therapeutic ions from bioactive scaffolds while inhibiting their apatite nucleation: a coaxial electrospinning strategy for soft tissue regeneration

The delivery of therapeutic ions, as a key element for the regeneration of soft tissue, represents a viable alternative to conventional drugs. Primarily designed for the regeneration of hard tissue, degradable bioactive inorganic matrices are a carrier of choice for the delivery of ionic chemical cues. However, they nucleate calcium-phosphate crystal on their surface, which could be undesired for most soft tissue regeneration. Here, a coaxial electrospinning process was engineered, generating core–shell fibres with inorganic particles enclosed within a bio-inert polymeric shell. Silicon doped vaterite (SiV) dispersed in poly(L-lactic acid) was selected as an inorganic composite core and poly(D,L-lactide-co-glycolide) (PLGA) as a shell. By careful selection of the electrospinning parameters, fibres of constant diameter (≈10 μm) with controllable shell thickness (from 1.3 to 4.2 μm) were obtained. The release of calcium and silica followed the Weibull model, showing a purely diffusive release after hydration of the PLGA layer. The rate of release could be controlled with the shell thickness. The nucleation of calcium-phosphate crystals was inhibited. In addition, with the presence of a PLGA shell layer, the mechanical properties of the fibermats were greatly improved with, for instance, an increase of the Young's modulus up to 536% as compared to original composite. These non-woven porous materials are an affordable investigation platform to study the effect of local ionic release onto the surrounding cell metabolism.