Table 2.

Variable properties of alginate-based materials to be considered and highlighted in corneal TERM applications.

Properties	Noteworthy Considerations
Strength and stiffness	Mechanical properties may be tunable as a function of the intended aim. The blend with electrospun fibers of both synthetic and natural polymers reinforce alginate-based materials, without compromising their transparency [147,148]. The use of oxidized alginate can lead to softer matrices [155]. The natural shape of the cornea has to be maintained for constructs [149].
Degradation time	The degradation rate of alginate composites can be modulated from three days to around two weeks by changing the molar ratios between alginate and chelating agents (e.g., sodium citrate) [153]. Hydrogels of oxidized alginate can be degraded in vivo after 30 days [154]. The rate of degradation seems to be directly proportional to the corneal epithelial cell viability [155].
Crosslinking methods	Ionic crosslinking (with CaCl2) is the most-common method, but it can slow down the degradation rate [150,153,166]. The chemical crosslinking of gel blends (with EDC-NHS) allows the finer control of the hydrogels’ physical characteristics, but it could affect cell survival [148]. Blending with photo-crosslinkable polymers ensures transparency but requires a long time for dialysis [151]. The self-crosslinking of oxidized alginate is obtainable according to the functional group of the other blending components [152]

CaCl₂ = calcium chloride; Gel = gelatin; EDC = 1-ethyl-3-(dimethyl-aminopropyl)carbodiimide hydrochloride; NHS = N-hydroxyl succinimide.