Pharmaceutical Polymer Gels in Drug Delivery

Abstract

Polymer gels are being developed at prolific pace as prominent delivery systems to circumvent obstacles in drug delivery and impart easier application of therapeutics. A large number of molecules migrate into an elastic cross-linked network of long polymers inflated with a solvent such as water, causing the swelling of network and resulting in the formation of an aggregate known as a polymer gel. Polymer gels are utilized in different technologies, including drug delivery, biomedical devices, biosensors, tissue engineering, actuators, and even in cosmetics and food. Recently, there has been growing interest in smart polymer gels constituting a new generation of biomaterials that respond to significant changes due to little changes in the environment. The polymers that form smart gels are referred as ``smart'' polymers or ``stimuli-sensitive'' polymers or ``environmentally'' sensitive polymers, and they can be classified on the basis of their structure (superporous gels, shape memory gels, artificial protein gels) and stimuli (pH-sensitive gels, temperature-sensitive or thermoresponsive gels, analyte-sensitive gels). The gel can be prepared by covalent and non-covalent cross-linking (chemical or thermally irreversible gels and physical or thermoreversible gels, respectively), and it can be evaluated for morphology, rheological behavior, adhesion, spreadability, in vitro diffusion/permeation, in vivo behavior, and stability of the formulation. Polymer gels that are sensitive to the presence of various biomarkers have been extensively used in targeting specific disease conditions. This chapter will be organized into four separate sections: defining the concept of polymer gels; describing types, formulation, and evaluation of gels; illustrating applications especially in the context of drug delivery; and including recent advances and future perspectives.