See: Marciniak, Anja, et al. "Mouse Pancreas Tissue Slice Culture Facilitates Long-Term Studies of Exocrine and Endocrine Cell Physiology in situ." PloS one 8.11 (2013): e78706.
DRAQ7 is uniquely suited for such applications due to its verified ultra-low toxicity (as validated in Akagi, et al., 2013).