Temperature-Responsive Polymers

Chapter 13Thermogel Polymers for Injectable Drug Delivery Systems

Vidhi M. Shah¹, Duc X. Nguyen¹, Deepa A. Rao², Raid G. Alany³, and Adam W.G. Alani¹

¹College of Pharmacy, Oregon State University, Portland 97201, USA

²School of Pharmacy, Pacific University, Hillsboro 97123, USA

³School of Pharmacy and Chemistry, Drug Discovery, Delivery and Patient Care (DDDPC) Theme, Kingston University London, Surrey KT1 2EE, UK

13.1 Introduction

Gels are three‐dimensional (3D) networks made from natural and/or synthetic polymers. They have the ability to swell in a solvent depending on their compatibility with the solvent. Hydrogels are gels that as the name suggests can swell in water. They are a 3D network of natural and/or synthetic polymers capable of absorbing and retaining significant amounts of water [1]. As such these gels offer the ability to release drugs solubilized in the gel network in a controlled manner [2]. Thermogels are a subset of hydrogels that are temperature sensitive and undergo sol–gel transition at a specific temperature. Therefore, unlike non‐temperature‐responsive hydrogels, which form gels in a concentration‐dependent manner, thermogels can undergo sol–gel transition in response to temperature and not only in response to polymer concentration [1, 2]. Thermogel polymers capable of undergoing sol–gel transition are composed of hydrophobic and hydrophilic segments, and the molecular weight of each segment as well as the temperature dictates the sol–gel transition process. ...