Smart Hydrogels: Therapeutic Advancements in Hydrogel Technology for Smart Drug Delivery Applications

Hydrogels are three-dimensional cross-linked polymeric networks capable of imbibing substantial amounts of water or biological fluids and are widely used in biomedical applications, especially in pharmaceutical industry as drug delivery systems. Although their solvent content can be over 99%, hydrogels still retain the appearance and properties of solid materials, and the structural response can include a smart response to environmental stimuli (pH, temp, ionic strength, electric field, presence of enzyme, etc.) These responses can include shrinkage or swelling. Cellulose-based hydrogels are one of the most commonly used materials and extensively investigated due to the widespread availability of cellulose in nature. Cellulose is the most abundant renewable resource on earth that is intrinsically degradable. Additionally, the presence of hydroxyl groups results in fascinating structures and properties. Also, cellulose-based hydrogels with specific properties can be obtained by combining it with synthetic or natural polymers. This chapter surveys different characterization for cellulose hydrogels and the structure-response relationship. As such we would describe the techniques involved for characterizing cellulose-based hydrogels and their response in terms of their morphology such as polarized optical microscopy (POM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), their stability by thermal properties (often with differential scanning calorimetry, DSC), and structure response such as Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). In addition, we give a focus on measuring the mechanical properties of superabsorbent hydrogels giving examples with cellulose where applicable. Finally, we describe the techniques for analyzing biological techniques and the applications with cellulose.