Culture Systems and Incubation Conditions
Core concepts
Culture systems rely on balanced salt solutions, energy substrates (pyruvate, lactate, glucose), amino acids, and protein supplementation. Sequential media change composition to match embryo metabolism; single-step media aim for stability. Know the role of bicarbonate-CO2 buffering, which requires a CO2-enriched atmosphere (commonly 5–6%) and a temperature near 37°C.
Atmosphere and environment
Reduced oxygen (around 5%) is often used to lower oxidative stress. Humidity, oil overlay, and gas recovery time after door opening all affect outcomes. Incubators must be monitored continuously with independent alarms and validated sensors.
Traps
- Confusing pH buffering (bicarbonate/CO2) with osmolality control.
- Assuming higher oxygen is always better; reduced oxygen is common practice.
- Forgetting that oil quality and lot variability can affect outcomes.
- Overlooking that incubator recovery time matters after frequent door openings.
Worked example
If a lab reports drifting pH, check CO2 concentration and gas supply first, then verify media equilibration and oil overlay integrity. If pH is correct but osmolality is off, suspect evaporation from inadequate oil coverage or improper dish preparation.