**1. Introduction**

Polymers are the materials that are either prepared/produced synthetically or isolated from natural sources. Polymers can respond based on their environmental conditions such as pH, temperature, ionic strength, electric field, magnetic field, chemical and biological stimuli to deliver the desired therapeutic agents. Recently, biopolymer is a biomaterial used in various delivery systems to interact with the biological system and release the therapeutic agent. These biopolymers are utilized in the various applications due to their biocompatibility, biodegradability and low immunogenicity. Among the various biopolymers, synthetic polymers

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

have well-defined structure and fine-tunable degradation kinetic and mechanical properties compared to the natural polymers. Recently, biodegradable nanoparticles have a major role in the field of health sciences especially for treating various diseases through drugs, vaccines and genes [1–7]. Nanoparticle in gene-delivery system has been utilized for treating various diseases such as cancer and haemophilia. The major challenge in the gene delivery is delivering the genetic materials such as DNA, plasmids, RNA and siRNA into the target/special cells to replace the damaged genes or expression inhibition of undesired genes or expression and production of required proteins. In gene delivery, the genetic material is either encapsulated inside the nanoparticle or conjugated to the nanoparticle. The nature, source and their physico-chemical properties of the polymers play an important role in the formation of desired properties of nanoparticles and to achieve a better therapeutic effect [8–12].
