**2.3 Drug delivery**

In the past years, drug delivery carriers draw huge interest because of large biomacromolecules like genes and proteins as well as low-molecule weight drugs

**115**

hydrogel structures.

**2.4 Bone regeneration**

result in allowing cells in their natural phenotypes.

*Importance of Alginate Bioink for 3D Bioprinting in Tissue Engineering and Regenerative…*

which can be delivered in a targeted or a localized manner [36, 37]. Because of its biodegradable and biocompatible nature, alginate is used as a carrier for encapsulating and immobilizing drugs, cells, proteins, and bioactive molecules [38, 39]. Currently, alginate-based carriers like colloidal particles, polyelectrolyte, and hydrogels are under examination; few of them are practically used. Many researchers have examined the alginate-based hydrogel blends, microspheres, and porous scaffolds for precise drug delivery in various tissue engineering fields [40, 41]. Hollow microsphere of alginate-based hollow microsphere has huge applications as drug delivery carrier, micro-reactor, and biosensor [42]. The construction of the hollow microcapsules can be created by successive self-assembly of positively and negatively charged polyelectrolytes by layer-by-layer (LbL) technique. The alginate microcapsule is studied well with respect to precise releasing and loading parameters. The attempt to fabricate microcapsule biopolymer has been made by dropping alginate/chitosan in a decomposable colloid particle after removal of its core is done in an appropriate pathway. For the production of hollow microcapsule, chitosan and alginate are interchangeably deposited in CaCO3 with electrostatic biocompatibility [43]. The chitosan/alginate microcapsule functionalities and properties can be preciously adjusted by changing the microcapsule composition, exterior stimuli introduction, and thickness. Immersing alginate microcapsule in various pH solutions helps in the degradation of the microcapsules which also determines the material role and encapsulation layers for keeping microcapsule stability in various pH conditions. The addition of PEG to the microcapsule allows protection against acidic conditions, whereas the coating layer number only affects the swelling properties, not the microcapsule Young's modulus which was revealed by Wong's study [9]. For surface micro-patternings and microarray systems, 3D platform alginate hydrogels are used. For in situ gelation, a few aliquots of solution of gelatin were trapped selectively on hydrophilic area by a process called dipping process. Cells with various adhesion properties were captured by gel pattern alginate on the

Various CYP450 enzymes like vascular endothelial growth factor (VEGF) and β1-integrin upregulation showed that the stage gave many in vitro conditions that

For the reconstructive surgery, bone regeneration is an important challenge. It occurs due to tumor removal and trauma. To repair the bone, a good initiative is to induce osteogenesis in situ. To complete this process, one method is by using stem cell differentiation to form bone tissue and then seeding them in an injectable scaffold [44, 45]. As of now there are numerous investigations and studies on alginate-based injectable scaffolds for the bone regeneration. By using MSCs and alginate scaffolds, satisfactory bone tissue formation was noticed [46, 47]. For this reason the application of alginate for gel tissue generation is commonly used which displays angiogenic and osteogenic properties. Many researchers showed bone regeneration by means of injectable constructs by joining microspheres or alginatebased hydrogels that were combined with interchangeable ASCs or MSCs [48]. These studies demonstrated the potential of bone morphogenetic protein (BMP) and TGF-β delivery to induce osteogenic differentiation to mature osteocytes from MSCs and ASCs. Kolambkar et al. presented a growth factor hybrid system of delivery that comprises of a nanofiber mesh tube *which is electrospun* for directing regeneration of bone along with alginate hydrogel peptide modified in the tube for fixed recombination BMP-2 (rhBMP-2) release [49]. The discharge of fixed transport of rhBMP-2 through alginate hydrogel was important for significant regeneration to

*DOI: http://dx.doi.org/10.5772/intechopen.90426*

#### *Importance of Alginate Bioink for 3D Bioprinting in Tissue Engineering and Regenerative… DOI: http://dx.doi.org/10.5772/intechopen.90426*

which can be delivered in a targeted or a localized manner [36, 37]. Because of its biodegradable and biocompatible nature, alginate is used as a carrier for encapsulating and immobilizing drugs, cells, proteins, and bioactive molecules [38, 39]. Currently, alginate-based carriers like colloidal particles, polyelectrolyte, and hydrogels are under examination; few of them are practically used. Many researchers have examined the alginate-based hydrogel blends, microspheres, and porous scaffolds for precise drug delivery in various tissue engineering fields [40, 41]. Hollow microsphere of alginate-based hollow microsphere has huge applications as drug delivery carrier, micro-reactor, and biosensor [42]. The construction of the hollow microcapsules can be created by successive self-assembly of positively and negatively charged polyelectrolytes by layer-by-layer (LbL) technique. The alginate microcapsule is studied well with respect to precise releasing and loading parameters. The attempt to fabricate microcapsule biopolymer has been made by dropping alginate/chitosan in a decomposable colloid particle after removal of its core is done in an appropriate pathway. For the production of hollow microcapsule, chitosan and alginate are interchangeably deposited in CaCO3 with electrostatic biocompatibility [43]. The chitosan/alginate microcapsule functionalities and properties can be preciously adjusted by changing the microcapsule composition, exterior stimuli introduction, and thickness. Immersing alginate microcapsule in various pH solutions helps in the degradation of the microcapsules which also determines the material role and encapsulation layers for keeping microcapsule stability in various pH conditions. The addition of PEG to the microcapsule allows protection against acidic conditions, whereas the coating layer number only affects the swelling properties, not the microcapsule Young's modulus which was revealed by Wong's study [9]. For surface micro-patternings and microarray systems, 3D platform alginate hydrogels are used. For in situ gelation, a few aliquots of solution of gelatin were trapped selectively on hydrophilic area by a process called dipping process. Cells with various adhesion properties were captured by gel pattern alginate on the hydrogel structures.

Various CYP450 enzymes like vascular endothelial growth factor (VEGF) and β1-integrin upregulation showed that the stage gave many in vitro conditions that result in allowing cells in their natural phenotypes.
