Purpose of Pluronic F-68 in media — In mammalian cell culture, Pluronic F-68 is typically added as what?

Introduction:
Mammalian cells are highly sensitive to hydrodynamic stress, particularly at gas–liquid interfaces. Pluronic F-68 (Poloxamer 188) is a standard media supplement used to mitigate such shear-related damage. The question asks for its principal role.

Given Data / Assumptions:

• Suspension culture with aeration and agitation.
• Typical F-68 concentrations in the 0.05–1.0 g/L range.
• Goal is to preserve viability and productivity.

Concept / Approach:
As a non-ionic surfactant, Pluronic F-68 adsorbs at interfaces and reduces direct cell contact with bubbles and moving interfaces, thereby lowering the damaging stresses that occur during bubble formation and bursting. It is not a nutrient and does not directly increase oxygen transfer coefficients like kLa; its benefit is protective, not nutritive or flocculating.

Step-by-Step Solution:
Identify the damage pathway (bubble attachment, surface rupture).Recognize surfactant-mediated protection via interfacial modification.Conclude the correct functional category: shear protectant.

Verification / Alternative check:
Comparative runs with and without F-68 show higher viable cell densities and reduced LDH release under identical aeration/agitation, confirming a protective effect rather than enhanced mass transfer.

Why Other Options Are Wrong:

• (a) Not a nutrient; does not supply carbon, nitrogen, or vitamins.
• (c) It may indirectly influence mass transfer by altering foam, but it does not directly raise kLa as an oxygen-transfer additive.
• (d) False because (a) and (c) are incorrect.
• (e) It is not a coagulant; aggregation would hinder oxygen and nutrient delivery.

Common Pitfalls:
Confusing F-68 with silicone antifoams or with nutrient supplements; attributing higher titers to improved kLa rather than improved survival.

Final Answer:
A shear protectant (non-ionic surfactant) to reduce bubble- and agitation-related damage