In culturing animal cells, which factors most directly influence the sensitivity of cells to hydrodynamic shear during mixing and aeration?

Introduction:
Animal cells lack rigid walls and are therefore more susceptible to damage from shear stress, bubble interfaces, and turbulent eddies than microbial cells. Identifying the factors that modulate shear sensitivity is essential for setting impeller speeds, gas flow rates, and for choosing protective additives that reduce damage without compromising productivity.

Given Data / Assumptions:

• Suspension culture or microcarrier-based systems are considered.
• Mixing and aeration introduce shear and bubble-related stress.
• Medium composition and cell biophysics both play roles.

Concept / Approach:
Shear sensitivity increases with larger effective cell or aggregate size due to higher stress differentials. Nutrient sufficiency influences membrane composition and cytoskeletal integrity, indirectly affecting robustness. Shear protectants such as non-ionic surfactants reduce bubble coalescence and lower interfacial damage, acting as boundary modifiers that shield cells from harmful interfaces and transient stresses.

Step-by-Step Solution:

Verification / Alternative check:
Comparative runs with and without protectants typically show higher viable cell density and reduced lactate dehydrogenase release when protectants are used and nutrients are sufficient.

Why Other Options Are Wrong:

• Single-factor answers are incomplete; shear sensitivity arises from multiple interacting factors including size, nutrition, and additives.

Common Pitfalls:
Overdosing surfactants can affect downstream purification or product folding. Neglecting nutrient balance can mask the benefits of shear protection strategies.

Final Answer:
All of the above