Caspase 3/7 activity as an indicator of apoptosis in (A) 3K cells/spheroid, (B) 10K cells/spheroid, and (C) 15K cells/spheroid; n=4. (D) Representative live/dead staining of 15K spheroids preconditioned for 0, 1, or 3 days and entrapped in RGD-modified alginate for 1 and 4 days. PCn indicates n days of hypoxic preconditioning and IND denotes individual (non-aggregated) cells. Live/dead images at 10× magnification; scale bar represents 200 μm. Different letters above bars indicate significance of at least p<0.05. Significance is denoted by alphabetical letterings; groups with no significance are linked by the same letters, while groups with significance do not share the same letters.