In Situ Silication of Polymer Nanofibers to Engineer Multi-Biofunctional Composites

The critical role of silica in bone homeostasis has motivated the development of silica-based biomaterials for orthopedic applications. Whereas polymer nanofibers have emerged as promising substrates for orthopedic applications, nanoparticle agglomeration precludes the preparation of silica containing composite nanofibers by electrospinning. This work presents a facile sol-gel process to fabricate electrospun nanocomposite fibers by insitu silica gelation in poly (epsilon-caprolactone) (PCL) solution. Citric acid is shown to be more effective than acetic acid as the pH catalyst for gelation by rapidly yielding near uniform nanoparticles (150 +/- 50 nm). The composite nanofibers exhibited increased water wettability than neat PCL with sustained release of silicon ions. The composite fibers induced early apatite formation in simulated body fluid. Quantitative characterization of the tubular networks formed by human umbilical cord vascular endothelial cells revealed that the eluted silicon ions and citric acid in fibers synergistically promoted angiogenic activity, which was corroborated by increased gene and protein expressions of several known angiogenic markers. Furthermore, silicate fibers augmented osteogenesis of human mesenchymal stem cells as measured by the increased mineral deposition and increased gene and protein expression of osteogenic markers. Thus, the insitu silicated fibers are promising multi-biofunctional materials for orthopedic applications.