Interpenetrating Polymer Networks as Innovative Drug Delivery Systems

Polymers have always been valuable excipients in conventional dosage forms, also have shown excellent performance into the parenteral arena, and are now capable of offering advanced and sophisticated functions such as controlled drug release and drug targeting. Advances in polymer science have led to the development of several novel drug delivery systems. Interpenetrating polymer networks (IPNs) have shown superior performances over the conventional individual polymers and, consequently, the ranges of applications have grown rapidly for such class of materials. The advanced properties of IPNs like swelling capacity, stability, biocompatibility, nontoxicity and biodegradability have attracted considerable attention in pharmaceutical field especially in delivering bioactive molecules to the target site. In the past few years various research reports on the IPN based delivery systems showed that these carriers have emerged as a novel carrier in controlled drug delivery. The present review encompasses IPNs, their types, method of synthesis, factors which affects the morphology of IPNs, extensively studied IPN based drug delivery systems, and some natural polymers widely used for IPNs. 1. Introduction In the present scenario polymers are among the largest volume chemical products in the world and the global market for polymer products is growing rapidly. Polymers have always been valuable excipients in tablet and capsule formulations [1] and also have shown excellent performance into the parenteral arena as blood circulation time enhancers [2] and are now capable of offering advanced and sophisticated functions such as controlled drug release and drug targeting [3]. In the recent decades, an ever growing demand for improved polymer properties has paved the development of the blending of polymer mixtures [4, 5]. In order to overcome the poor biological performance and to improve mechanical strength a new class of polymers has been introduced which are based on blending of either natural or synthetic polymers alone or in combinations. An interpenetrating polymer network (IPN) is defined as a blend of two or more polymers in a network with at least one of the systems synthesized in the presence of another [6]. This results in a formation of physically cross-linked network when polymer chains of the second system are entangled with or penetrate the network formed by the first polymer. Each individual network retains its individual properties so synergistic improvements in properties like strength or toughness can be seen [7]. An IPN can be distinguished from