Table 1.
Parameters used in the mathematical model for describing protein delivery in multicellular tumor spheroids and in a microfluidic tumor-on-a-chip.
| Parameter | Value and Units | Reference |
|---|---|---|
| Void fraction tumor-on-a-chip (ε) | 0.80 | Experimental a |
| Void fraction spheroids (ε) | 0.15 | [14] |
| Re0 tumor-on-a-chip (BT-474) | HER2: 2.18 nm EpCAM: 2.45 nm |
Calculated b |
| Re0 spheroids (BT-474) | HER2: 234 nm EpCAM: 263 nm |
Calculated d |
| kon | HER2-binding DARPin 9_26: 7.38 × 104
m−1·s−1 EpCAM-binding DARPin Ec1: 3.65 × 105 m−1·s−1 |
[35,36] |
| koff | HER2-binding DARPin 9_26: 0.1 × 10−3 s−1 EpCAM-binding DARPin Ec1: 3.65 × 105 s−1 |
[35,36] |
| ke | HER2: 1.67 × 10−4 s−1 EpCAM: 3.46 × 10−5 s−1 |
[37,38] |
| Diffusion coefficient DWater (DARPin) | 164 µm2·s−1 | Estimated c |
a The void fraction was estimated by determining the cell occupancy in the chip from a threshold applied to confocal images of the cell channel (CellTrace yellow-stained BT-474 cells) and subtracting the percentage of positive pixels in the images from the total gel area. b Calculated based on quantified values for the number of receptors per cell and number of cells in the microfluidic chip or in the spheroids; c The diffusion coefficient of DARPins in water was estimated based on the Stokes–Einstein law by taking into account the hydrodynamic radius of DARPins, as reported previously [30]. d In the spheroid model, diffusion coefficients were varied and evaluated against experimental data.