Hydrogels: Biomaterials for Sustained and Localized Drug Delivery
213
engineering, including biomedical relevance [8–202]. Polymeric network encapsulated with nanoparticles that aim at targeted drug delivery has proven hydrogel a
valuable biomaterial for pharmaceutics [42].
Nanocomposites take over the advantage of hydrophilicity of the polymers, versatility, biocompatibility as well as the increased surface to the volume aspect ratio
of the nanoparticles. Diverse nanomaterials such as graphene, carbon nanotubes
(CNTs) (see Sect. 4.2.1); polymeric/dendritic nanomaterial (see Sect. 4.2.2); inorganic/organic nanomaterials such as silicates, hydroxyapatite nanoparticle-based
formulations (see Sect. 4.2.3); metallic nanoparticles such as gold, silver nanoparticles (see Sect. 4.2.4) are utilized in hydrogel nanocomposite formulation. This
interdisciplinary field of research is known to have a significant effect on developing nanocomposites such as biodegradable polymeric nanoparticles, polymeric
micelles, solid lipid nanoparticle (SLN), lipid drug conjugate (LDC), nanostructured
lipid carriers (NLC), and quantum dots [12–160].
A combinatorial approach of nanotechnology and hydrogel for nanogel formulations produces three-dimensionally cross-linked submicron hydrophobic (or less
soluble) particles for drug delivery. Nanogel increases the solubility of the drug,
accumulation at the intended site of action, and stability of bioactive molecules in
physiological conditions while reducing cytotoxicity. Temperature responsive, pHtemperature dual responsive nanogels are also constructed using copolymer blocks.
Micro/nano-particles prepared by spray drying, microemulsion, phase separation
procedures are used for mucoadhesive drug delivery systems (MDDS). Mucal adhesion occurs through the surface to surface contact in the form of micro/nanospheres or
asymmetric patches. Stimuli responsive nanogels have gained considerable interest
in research for its drug delivery capabilities and controlled drug release at the intended
absorption site [19–69].
This chapter discusses the significant classifications of hydrogels based on their
polymeric source and crosslinking techniques; different parameter constraints for
hydrogel design; biomaterials for hydrogel nanocomposite formulation for biomedical applications; drug release mechanisms by diffusion to various stimuli in the physiological environment. Further, this chapter briefly emphasizes the current challenges
and future research focus of hydrogel for clinical translations.
2 Classification of Hydrogel
Hydrogels are designed to encapsulate drug and release in a sustained mode in
targeted location for prolonging the effect as well as minimizing repeated dosage.
These are promising biomaterials for their unique physicochemical properties, which
include molecular weight of the polymer, method of crosslinking and intermolecular
bonding among monomer and between the monomer and crosslinking agent [37].
The physical nature of hydrogel plays a vital role in introducing the drug-loaded
hydrogel into the target system. The ‘sol-gel’ characteristics of the prepared hydrogel
decide the route of administration of the hydrogel into the host system [109].
213
engineering, including biomedical relevance [8–202]. Polymeric network encapsulated with nanoparticles that aim at targeted drug delivery has proven hydrogel a
valuable biomaterial for pharmaceutics [42].
Nanocomposites take over the advantage of hydrophilicity of the polymers, versatility, biocompatibility as well as the increased surface to the volume aspect ratio
of the nanoparticles. Diverse nanomaterials such as graphene, carbon nanotubes
(CNTs) (see Sect. 4.2.1); polymeric/dendritic nanomaterial (see Sect. 4.2.2); inorganic/organic nanomaterials such as silicates, hydroxyapatite nanoparticle-based
formulations (see Sect. 4.2.3); metallic nanoparticles such as gold, silver nanoparticles (see Sect. 4.2.4) are utilized in hydrogel nanocomposite formulation. This
interdisciplinary field of research is known to have a significant effect on developing nanocomposites such as biodegradable polymeric nanoparticles, polymeric
micelles, solid lipid nanoparticle (SLN), lipid drug conjugate (LDC), nanostructured
lipid carriers (NLC), and quantum dots [12–160].
A combinatorial approach of nanotechnology and hydrogel for nanogel formulations produces three-dimensionally cross-linked submicron hydrophobic (or less
soluble) particles for drug delivery. Nanogel increases the solubility of the drug,
accumulation at the intended site of action, and stability of bioactive molecules in
physiological conditions while reducing cytotoxicity. Temperature responsive, pHtemperature dual responsive nanogels are also constructed using copolymer blocks.
Micro/nano-particles prepared by spray drying, microemulsion, phase separation
procedures are used for mucoadhesive drug delivery systems (MDDS). Mucal adhesion occurs through the surface to surface contact in the form of micro/nanospheres or
asymmetric patches. Stimuli responsive nanogels have gained considerable interest
in research for its drug delivery capabilities and controlled drug release at the intended
absorption site [19–69].
This chapter discusses the significant classifications of hydrogels based on their
polymeric source and crosslinking techniques; different parameter constraints for
hydrogel design; biomaterials for hydrogel nanocomposite formulation for biomedical applications; drug release mechanisms by diffusion to various stimuli in the physiological environment. Further, this chapter briefly emphasizes the current challenges
and future research focus of hydrogel for clinical translations.
2 Classification of Hydrogel
Hydrogels are designed to encapsulate drug and release in a sustained mode in
targeted location for prolonging the effect as well as minimizing repeated dosage.
These are promising biomaterials for their unique physicochemical properties, which
include molecular weight of the polymer, method of crosslinking and intermolecular
bonding among monomer and between the monomer and crosslinking agent [37].
The physical nature of hydrogel plays a vital role in introducing the drug-loaded
hydrogel into the target system. The ‘sol-gel’ characteristics of the prepared hydrogel
decide the route of administration of the hydrogel into the host system [109].