Contact Inhibition and Nutrient Depletion Cell Death (Cell Culture (Cell Death))

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Cultures exceeding 80-100% confluence show central necrosis, detachment of cell sheets, and debris accumulation. Media becomes acidic (yellow) and depleted. Common causes: 1) Cell density exceeds 80% confluence causing contact inhibition and nutrient/oxygen depletion 2) Prolonged culture (>5 days) without media change depleting glucose, glutamine, and growth factors 3) Accumulation of metabolic waste products (lactate, ammonia) reaching toxic concentrations 4) Central hypoxia in overcrowded monolayers where oxygen diffusion limited to <100 μm depth Solutions: 1) Passage adherent cells at 70-80% confluence; use split ratios of 1:3 to 1:6 for maintenance cultures 2) Change media every 2-3 days or when phenol red indicator shifts toward yellow (pH <7.0) 3) For rapidly growing lines, use higher glucose formulations (4.5 g/L DMEM) and supplement with 2-4 mM fresh L-glutamine 4) Implement automated cell counting (Scepter system) to standardize seeding density: 3-5×10³ cells/cm² 5) For high-density cultures, increase media volume to ≥0.2 mL/cm² growth surface and refresh daily