Title
Oxime cross-linked alginate hydrogels with tunable stress relaxation for immune cell encapsulation
Date of Award
2019
Document Type
Thesis
Degree Name
Master of Science in Engineering (MSE)
Department
Chemical and Materials Engineering
Committee Chair
Kyung-Ho Roh
Committee Member
Bernhard Vogler
Committee Member
Anuradha Subramanian
Subject(s)
Bioengineering--Research., Colloids.
Abstract
Sodium alginate hydrogels have served as a versatile and reliable tool for biomedical applications such as 3-D cell encapsulation, both in vitro and in vivo. In the past, these hydrogels have formed via ionic or covalent cross-linking of the alginate chains upon the modification of its functional groups. Hereby, we employ a technique to modify hydroxyl groups of the alginate backbone to alkoxyamine groups (-O-NH2), and we verify such modifications in 1D and 2D NMR. Alkoxyamine groups belong to the field of click bioorthogonal polymer cross-linking. In the presence of aldehyde-modified alginate chains, both polymers can form an oxime reversible covalent crosslinks, which have been proven to be responsive to environmental variables such as pH and temperature. Upon hydrogel formation in physiologically relevant aqueous media (pH 7.4, 37ºC), gels of a wide variety of stiffnesses (storage moduli of G’eq = 103 Pa - 12 kPa) and viscoelasticity (mean stress relaxation times 〈τ〉 = 4.2 h – 56.2 h) can be achieved. These properties are tailored by controlling the previously mentioned environmental variables, the ratio between alkoxyamine and aldehyde groups, and the degree of functionalization of the aldehyde-alginate counterpart. Furthermore, the control of design parameters inherent to the gel formation, such as the gelation time, can be utilized in order to form gels of different geometries. We employ an electrojetting assembly with which we can generate hydrogel microbeads with electrified jetting; or hydrogel microthreads with electrified extrusion; all with a diverse set of viscoelastic properties. Last, we employ such hydrogel formulations in order to study the influence of stress relaxation on the proliferation capability of immune cells.
Recommended Citation
Sanchez-Moran, Hector, "Oxime cross-linked alginate hydrogels with tunable stress relaxation for immune cell encapsulation" (2019). Theses. 281.
https://louis.uah.edu/uah-theses/281