Cell counting is performed at numerous points during cell therapy manufacturing, and is normally performed on stand-alone devices requiring several manual preparation steps. Hence non-contact cell counting methods that can be implemented in-line are a key innovation to free up operator time and reduce measurement variability. We spoke to TTP Project Leader, James Stein, on work he’s been doing to implement imaging as an in-line cell counting method.

Stuart: Why is it important to get an accurate measure of cell count for CGT manufacturing? 

James: Accurate measurement of cell count is critical for both process monitoring and quality control, and for establishing correct doses for cell therapy patients. 

Stuart: What challenges do developers face in determining cell count? 

James: Current methods for determining cell count are not fit-for-purpose in this context: they are often labour intensive, requiring manually transferring samples to a stand-alone device. This can introduce measurement variability due to manual sample prep steps and labelling.  

Stuart: What benefits might non-contact cell counting methods bring? 

James: The ability to count cell numbers in-line and in real time, rather than periodic extraction of samples for offline analysis, has a number of key benefits: 

  • Real time data gives a live and continuous assessment of the process quality and cell concentration, rather than periodic and delayed values. 
  • Removing the need to make an external connection for sample extraction avoids the risk of process contamination introduced by sampling and offline processing. 
  • Non-contact cell counting methods have no influence on the cells or process quality, and can provide more information beyond a cell count, particularly if imaging is used. 

Stuart: What work have you done at TTP to address the challenges of reliable cell counting? 

James: At TTP, we have addressed the challenge of reliable cell counting in live fluidic and microfluidic cell processes using implementations of scattering optics, imaging optics, impedance or capacitance sensing for different systems.  

Stuart: What has your experience been using scattering, impedance and capacitance sensing? 

James: Scattering, impedance and capacitance sensing options can be simple and robust, but they usually only have ‘single point’ resolution and are limited to detecting that a cell-sized object is passing by, while requiring tightly constrained fluidic channels to align cells with sensors. 

Stuart: How about imaging? 

James: Imaging optics, although more challenging to implement successfully, offers a number of exciting advantages, including: 

  • Positive confirmation that cells are being counted, rather than cell-sized objects or other ‘false targets’ 
  • Ability to store individual cell images at high resolution for later QC processing or analysis 
  • Potential to classify different cell types if a mixture of cells is expected, or not expected but a potential failure mode of the system that must be detected 
  • Ability to integrate with and measure fluorescence markers or assays, or other optically active methods, if they are being used in the system. 

Stuart: Have you been involved in implementing imaging optics in projects you have delivered for clients? 

James: Yes, in delivering effective cell counting systems for client systems, we regularly solve the key implementation and performance challenges, which include: 

  • Optical design and part selection to achieve the required spectrum coverage and sensitivity 
  • Electro-optical design and processing to manage calibration and component variation over lifetime 
  • Custom mechanical designs to implement highly compact optical systems and to achieve repeatable and accurate alignment and focussing 
  • Fluid geometries and control to control flow and cell positioning for counting 
  • Rapid image acquisition and processing to normalise images for further processing 
  • On-line and off-line image processing to identify, count and classify cells 
  • Control software and electronics to enable fully autonomous cell counting operation 

Stuart: What do you think is the key to successfully delivering this type of project? 

James: We have a great team of multi-disciplinary experts working on these projects so that we can deliver systems of this size and complexity to our clients. We bring our accumulated knowledge and experience to bear on these challenge and working on non-contact cell counting has been one of the highlights of the past decade for me! 

Struggling with accurate cell counting in cell therapy manufacturing? TTP’s innovative non-contact methods provide real-time, high-resolution counts, eliminating manual steps and contamination risks. Our expert team delivers tailored solutions with advanced imaging optics, enhancing process reliability and quality control.

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Contact TTP to revolutionise your cell counting process today.
Stuart Lowe
Head of Biotech, Cell and Gene