In this study we present the use of co-axial electrospinning to produce core-shell composite micro-/nano fibers of polyurethane (PU) and cellulose acetate phthalate (CAP). The designed fibers possess enhanced mechanical properties with a tensile strength of 13.27 +/- 2.32 MPa, which is a clear improvement over the existing CAP fibers that suffer from a poor mechanical strength (0.2 +/- 0.03 MPa). The CAP imparts pH responsiveness to the core-shell structure giving the fibers potential for "semen sensitive" (intravaginal) drug delivery. (C) 2016 Elsevier Ltd. All rights reserved.