Which sample types are considered extremely high risk and generally not recommended?

Answer:
Based on internal validation experience, the following sample types are associated with very high experimental failure risk and are generally not recommended for the SeekOne DD Multiome ATAC + RNA workflow:

• Pancreatic tissues
  Pancreatic tissues contain extremely high endogenous nuclease activity, leading to rapid degradation of both DNA and RNA after tissue collection. Even with nuclease inhibitors, degradation is often difficult to control. 
• Plant tissues
  Plant samples contain complex cell wall structures that make nuclei isolation challenging. In addition, abundant polysaccharides and polyphenols can interfere with transposase activity and downstream enzymatic reactions. 
• Fixed tissues (e.g., FFPE samples)
  Extensive crosslinking prevents efficient recovery of intact nuclei, while chromatin is often highly fragmented and inaccessible to transposase reactions. 

These sample types are not absolute technical impossibilities, but they typically require substantial workflow optimization beyond the standard validated protocol.