The evaluation of hydroxyl ions as a nucleating agent for apatite on electrospun non-woven poly( ϵ -caprolactone) fabric.

The capacity of hydroxyl ions when used as a nucleating agent to form apatite in simulated body fluid (SBF) was investigated. A 25 wt% poly(ϵ-caprolactone) solution was prepared using 1,1,3,3-hexafluoro-2-propanol as a solvent and was electrospun under an electric field of 1 kV/cm. Subsequently, non-woven poly(ϵ-caprolactone) fabrics were dipped into 4 M NaOH solution and the experimental group was then directly air-dried (NaOH coated), while the control group was washed with deionized water and air-dried (NaOH treated) under ambient conditions. The non-woven poly(ϵ-caprolactone) fabrics that were coated and treated with NaOH were exposed to SBF for 1 week, which resulted in the deposition of a layer of apatite crystals on the non-woven poly(ϵ-caprolactone) fabric coated with NaOH only. On the other hand, when the non-woven poly(ϵ-caprolactone) fabrics were dipped into 0.05, 0.1, 1 and 4 M NaOH solutions, respectively, air-dried, and then soaked in SBF, the apatite forming capacity was gradually increased according to the concentration of NaOH solution. These results were explained in terms of the degree of apatite supersaturation in SBF induced by the release of hydroxyl ions from the coated NaOH because hydroxyl ions are one of the constituent elements of apatite. These results suggest that hydroxyl ions have a good potential for use as a nucleating agent for apatite on a previously non-bioactive polymer surface.