An expandable balloon for use in angioplasty procedures comprises a balloon having an outer surface layer, the outer surface layer being made from electrospun nanofibers and incorporating at least one pharmaceutically active substance, such as nitric oxide (NO). The outer surface layer may be formed on a separate flexible tubular member or sock, which is slipped over the balloon. An acidic agent, such as ascorbic acid, may be included in the balloon for enhancing NO release. A method of treating cell disorders in tubular structures of a living being comprises the steps of placing a coated balloon at a treatment site within the tubular structures, expanding the balloon at the treatment site, and releasing the pharmaceutically active substance at the treatment site. Optionally, a stent may be crimped onto the balloon prior to insertion of the balloon and stent into the tubular structures of the living being.