Figure 3: Controlling and predicting DO levels in HI hydrogel matrix.

Measured DO levels in HI hydrogels as a function of time: (a) effect of laccase concentration (3 wt%, DS 45, and 6.3−25.0 U ml⁻¹ laccase). (b) Effect of degree of substitution (DS) of FA (3 wt%, 25 U ml⁻¹ laccase and 13−45 μmol g⁻¹ of polymer). (c) Effect of hydrogel thickness (3 wt%, DS 45, and 25 U ml⁻¹ laccase) (d) Model prediction of DO_min at the bottom of the HI hydrogels. We compared model numerical prediction (blue symbols) to the measured values (red symbols) to confirm the reliability of the given parameters; model predictions of DO levels and gradients after 30 min of hydrogel formation (e) in the two-layer model (air-hydrogel) and (f) across HI hydrogels, depending on different thicknesses. Formation of DO gradients within HI hydrogels (3 wt%, DS 45, and 25 U ml⁻¹ laccase) as indicated by (g) measured DO levels at different hydrogel depths as a function of time and (h) model prediction of DO_min at different hydrogel depths. We compared model numerical prediction (blue symbols) to the measured values (red symbols) to confirm the reliability of the given parameters. Model predictions of DO levels and gradients after 30 min of hydrogel formation (i) in the three-layer model (air-media-hydrogel) and (j) across the HI hydrogels with the culture media. (k) DO levels of HI hydrogels encapsulated with 2 × 10⁶ cell ml⁻¹ of ECFCs as a function of hydrogel thickness (hypoxic hydrogel thickness, 2.5 mm; nonhypoxic hydrogel thickness, 1.25 mm). Results in d,h are shown as the average values±s.d. (n=3).