Can the monocyte attachment step be performed overnight when using PromoCell Macrophage Generation Media?

No. An overnight attachment step is not recommended. The PromoCell Monocyte Attachment Medium is specifically formulated for short‑term attachment of monocytes and does not provide sufficient nutrients or survival factors for extended incubation.
 
Why overnight incubation should be avoided

• Induction of apoptosis: Leaving PBMCs in Monocyte Attachment Medium for longer than 1.5–2 hours will induce apoptosis of monocytes, leading to significant cell loss.
• Reduced purity due to lymphocyte attachment: Lymphocytes survive longer under these conditions. During prolonged incubation, some lymphocytes may also attach and can no longer be removed by washing, resulting in reduced monocyte purity.
• Negative impact on macrophage differentiation: The combination of monocyte loss and lymphocyte contamination compromises downstream differentiation into macrophages and affects reproducibility.

For these reasons, overnight incubation in Monocyte Attachment Medium is inappropriate.

Recommended alternatives

• Standard protocol: 1.5 hours monocyte attachment
• If timing is critical: The attachment step can be shortened to 1 hour

Best practice: 
- Pre‑equilibrate the Monocyte Attachment Medium in the incubator
- Add the appropriate amount of PBMC suspension directly
- Under these conditions, most monocytes are already attached after 1 hour