Perfusion Bioreactor Structured Surface Spheroid Formation
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Solution Overview
Problem
Bioreactors face challenges in maintaining high viable cell density due to shear forces and difficulties in harvesting attachment-dependent cells, particularly for therapeutic protein production, where unstable expression levels occur over time.
Innovation Solution
A cell culture apparatus with stacked plates featuring structured surfaces and spacers to promote spheroid cell cluster formation, allowing for high cell density growth, enhanced stability, and ease of harvesting through non-adherent wells and passive diffusion of metabolic gases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If impeller velocities are increased to accommodate elevated nutrient and gas exchange requirements, then productivity is improved, but shear force on cells increases causing cell damage
Solution Approach 1:
The bioreactor is segmented into multiple stacked plates with individual flow channels, allowing distributed nutrient and gas exchange across many small channels rather than requiring high velocity in a single large impeller system. This segmentation enables adequate mass transfer at lower shear forces.
Solution Approach 2:
The patent replaces the traditional mechanical impeller system with a passive diffusion-based gas exchange system through plate membranes, and uses gravity-driven or low-pressure perfusion for media flow. This substitution eliminates high-speed mechanical agitation that generates harmful shear forces while maintaining adequate nutrient and gas exchange.
2Productivity
If bags are rocked faster to increase mixing and exchange, then productivity is improved, but shear force on cells increases causing cell damage
Solution Approach 1:
The patent replaces mechanical rocking or agitation systems with passive convection and diffusion mechanisms. Media flow through the stacked plates is driven by pressure gradients or gravity rather than mechanical motion, eliminating the shear forces associated with rapid rocking while maintaining adequate mixing and exchange through the distributed channel network.
3Reliability
If cells are made attachment-dependent for therapeutic production, then product quality is improved, but harvesting difficulty increases
Solution Approach 1:
The plate surfaces are engineered with specific local properties: the flow channels provide a non-adherent environment for easy cell release, while the stacked plate structure creates localized attachment zones that support stable protein expression. This spatial differentiation of surface properties allows simultaneous achievement of stable expression and easy harvesting.
Solution Approach 2:
Instead of making the culture surface highly adhesive to prevent cell detachment, the patent inverts the approach by using controlled non-adherent surfaces in the flow channels. Cells are retained through the structured plate architecture rather than adhesion, allowing easy harvesting while maintaining expression stability through the controlled culture environment.
4Productivity
If continuous perfusion is used to maintain high cell density, then productivity is improved, but expression stability deteriorates over time
Solution Approach 1:
The patent optimizes perfusion flow rates through the stacked plates to maintain adequate nutrient supply and waste removal while minimizing selective pressure for rapid growth over expression stability. The distributed channel architecture allows lower flow velocities that reduce shear stress and prevent selection of shear-resistant but low-expressing cell variants, maintaining expression stability at high cell density.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The apparatus supports high cell density growth, enhances cell stability, and facilitates easier harvesting, maintaining consistent protein expression and reducing shear forces, thereby improving productivity and cost-effectiveness in bioreactor operations.
Implementation Method 1
The wells can have dimensions on the micrometer scale and can be configured to promote formation of spheroid cell clusters
Implementation Method 2
the apparatuses are designed to allow for passive diffusion of metabolic gases
Implementation Method 3
A plurality of flow channels are formed between adjacent plates and/or rails for perfusion of cell culture media
Data Source
AI summary
A cell culture apparatus includes one or more plates having a first major surface and an opposing second major surface. The first major surface comprises a structured surface defining a plurality of wells. Each well has an interior surface defining an upper aperture and a nadir, wherein the upper aperture of each well has a diametric dimension in a range from 100 micrometers to 2000 micrometers. The apparatus also includes a plurality of spacers extending from the first major surface along a length of the bottom surface. A plurality of flow channels are defined between adjacent rails.