additional parameters such as core to shell flow ratio, as well as interfacial tension to obtain nanofibers with core-shell structure and homogenous nanofiber production [6]. Core-shell nanofibers are of great significance to encapsulate various types of bioactive molecules including drugs, proteins, and genes for the sustained release of these molecules due to advantages summarized as follows: G possibility to obtain nanofibers from un-spinnable solutions [4,8], G preventing the burst release which might cause toxicological effects [4,9], G prolonging the time of release and exhibiting sustained release for a longer time [5,10], G controlling the release kinetics of bioactive molecules by changing the composition [11] or feed rate [12] of core and shell solutions, G encapsulating the unstable bioactive molecules in mild conditions and protecting biological activity of these molecules [9,13], and G loading more than one bioactive molecule in the same nanofiber and regulating the rate of release [10,14]. 13.2 Delivery of drugs from core-shell nanofibers 13.2.1 Delivery of hydrophilic drugs from core-shell nanofibers Prolonged release of hydrophilic drugs with the minimum release at the initial stage is a challenge because of their high solubility in aqueous medium. Using both