Drug Delivery System

**85**

**Chapter 5**

Drug Delivery

*Zermina Rashid*

through different methods.

(nanogels) has increased [9, 10].

for the incorporation of therapeutic agents [12, 13].

**1. Introduction**

**Abstract**

pH-Responsive Microgels:

Promising Carriers for Controlled

The development of a new drug entity is a time-consuming and an expensive process; therefore, the design of new drug delivery systems for an existing drug molecule can significantly improve the safety and efficacy of the drug with improved patient compliance. In recent years, polymeric carriers have been widely investigated and are playing an important role in controlled drug delivery, biomedical applications, and tissue engineering. Microgels are microscopic hydrogels and have attracted much attention as vehicle for drug delivery. Stimuli-responsive MGs are smart drug delivery carriers and have the capability to incorporate and release their host molecules in response to stimuli (pH, ionic strength, and temperature), for targeted drug delivery. Of the many stimuli, alteration in pH is markedly fascinating because of the availability of pH gradients admissible for drug targeting. For example, pH gradients between normal tissues and some pathological sites between the extracellular environment and some cellular compartments, and along the gastrointestinal (GI) tract, are well characterized. Microgels can be fabricated

**Keywords:** controlled drug delivery, microgels, stimuli-responsive microgels, targeted delivery, pharmaceutical applications, types, methods of formulation

Among the available biomaterials, hydrogels, three-dimensional polymeric networks capable of imbibing large amounts of water or biological fluids, have proved their value in diverse biomedical applications [1–3]. In addition to the swelling property of the hydrogels, their biocompatibility, good mechanical properties, tunable chemical structure, and three-dimensional physical structure have made them one of the promising class of materials for tissue engineering [4, 5], pharmaceutical applications [6, 7], and biomaterials science [8]. In recent years, with the advancements in technology, interest in microscopic (microgels) and nanoscopic hydrogels

Microgels, hydrogel particles formed by physical or chemical cross-linking of polymer networks in microscale size [11], have exceptional properties like large surface area, tunable size from micrometers to nanometers, ease in synthesis, control over particle size, responsiveness to environmental factors, and an interior network
