Functional characterization of liver spheroids
After spheroids were cultured with functionalized MPs, levels of albumin were determined using a commercially available kit (QuantiChrom™ BCP Albumin, BioAssay Systems, cat# DIAP-250) as a measure of liver cells’ function. The experiment was performed according to the manufacturer’s instructions. Briefly, the medium was collected on days 5 and 10. A 20 µl aliquot was used to measure albumin secretion into the medium. 200 μL of working reagent was added and after 5 min incubation at room temperature, the optical density at 590-630 nm (peak absorbance at 610 nm) was read by a plate reader (Tecan Infinite M200, Tecan Austria GmbH, Austria). Urea was also measured by the QuantiChrom™ Urea Assay Kit (BioAssay Systems, cat# DIUR-100,) using a similar procedure to the albumin kit. 5 μL of sample was mixed with 200 μL of working reagent, incubated for 20 min, and absorbance was read at 520 nm by plate reader.