Cell Harvesting Sees Benefits from Automated Processes

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Cell harvesting is the start of the downstream separation process to recover the therapeutic biologic product from the bioreactor, following cell culture and cell lysis. Over the years, improvements in upstream cell culturing processes have resulted in significant increases in product titer that tend to create a bottleneck at the point of harvest.

Fortunately, improvements in harvesting technologies, such as centrifugation, depth filtration, and membranes have aided in easing this bottleneck. Further innovations to answer the drive for increased automation in bioprocessing are also leading to enhancements in how cell harvesting technologies can be streamlined and increase product recovery.

Harvesting challenges

Technical, equipment, or processing issues continue to pose challenges for cell harvesting. Most bottlenecks arise from manual processes during cell harvesting, says Charlie Duncheon, CEO, co-founder, and chairman of the board at Celltrio, a manufacturer of automation-based solutions for the life sciences industry. Duncheon says that manual processes are often still a concern in systems defined in semi-automated systems. He points out the following bottlenecks associated with manual steps:

Exposure of samples to changes in temperature when manually moving from one process to the next (e.g., refrigerated centrifuging to keep samples chilled when processing)

• Manual processes that increase opportunities for contamination
• Integrating protocol process knowledge beyond knowledge of one senior scientist
• Lack of organized and compiled data to ensure experiments are reproducible
• Limited variety of labware in one system for broader range of protocols
• Running samples only during “day” shifts while scientists are on site.

The size of the system required to process cell harvest also requires a large hardware footprint (e.g., 2–3 m2), adds Anil Kumar, associate director, Product Management, Repligen. The cell harvesting process also requires pre-flushing of depth filters (which are the typical workhorse of cell harvesting) to bring the total organic carbon (TOC) values down to acceptable values, Kumar says.

“Significant time is spent in installation of multiple depth filter modules and then removal of process solution-soaked depth filter modules, which are typically heavy and messy at 20–25 lbs each,” Kumar states.

Overcoming challenges

Biomanufacturers have traditionally overcome cell harvesting challenges with extensive manual labor from both scientists and technicians, says Duncheon. “This [approach] is expensive and subject to human error resulting in delayed timelines. We have seen a trend in the lab where some of the steps are automated combined with manual steps,” he states.

“We believe the real opportunity is to integrate all cell line processes using one automated, contained platform that maintains the digital record, with automatic data logging, data import/export, traceability, and reporting,” Duncheon adds.

Kumar notes that companies are taking multiple approaches to address the challenges posed by cell harvesting. He points out a new technology introduced by Repligen, a novel tangential flow depth filtration (TFDF) technology that offers a significant reduction in filter sizing and eliminates the need for pre/post flush treatment. In addition, the TFDF technology enables closed processing using a single-use filter assembly that replaces the primary clarification, Kumar says.

“Depth filter suppliers are working on developing new depth filters that will reduce the number of filter modules required to process batches. There are also new single-use centrifuges designed to provide for closed, single-use processing,” Kumar adds.

Automation as an asset

Automation is an asset to overcome bottlenecking at the cell harvest step. For instance, by providing 24 hour/7-days-a-week operation, automation can be scheduled in an optimum manner after scientists (remotely) download protocols and allows them to run the process as well as to connect every step of the cell harvesting process, Duncheon explains.

“Using robots to transfer samples from one process to the next, and automatically sharing process data and setup information, accelerates knowledge transfer and ensures consistency and uniformity,” Duncheon states. “More efficient transfers reduce exposure to open air and sample exposure to temperature.”

Duncheon also says that the greatest gains in efficiency will come from fully automating the entire process of cell culturing and harvesting, which will establish a standard platform that will provide a digital footprint. For example, Celltrio’s automation platform, RoboCell, is built on the company’s standard task modules, and this design provides flexibility and scalability, which can allow easy integration of all cell line development processes into one solution. Duncheon lists the various standard task modules in Celltrio’s portfolio, which include the following:

• Liquid handling (Robo-LH)
• Incubation and cell culturing (Robo-I)
• Cell counting, confluence, and viability inspection (RoboReader)
• Centrifuge harvesting (Robo-C)
• Cryogenic storage and retrieval of samples (RoboStor).

Because the cell harvesting process typically involves operations comprising multiple steps (e.g., pre-flush, harvest processing, and post-use product recovery steps) that are performed in manual and semi-automated mode, there is a desire to automate, which will enable faster processing and less operator dependance, Kumar comments.

Automated processing

In a 2015 study that compared automated versus manual downstream processing, the performance of automated harvesting and tandem purification was compared to those of manual processing, including manual harvesting and two-step purification. The results indicated that recovery of product was significantly higher using automated processes compared to manual, and product quality was consistent the quality seen in manual processes (1).

The researchers noted that, by setting up an automated system for in-line cell harvesting and purification, they were able to reduce their downstream bottlenecks. The researchers concluded that automated processes eliminate subjective user decisions, which in turn minimized waste and potential contamination while improving process yields and process reproducibility (1).

Transition to automation

Today, the transition to automated cell harvesting remains an growing trend, says Duncheon. He also notes that automated cell harvesting is gaining more interest because of process efficiency gains and attractive payback.

As the transition continues, the cell harvesting process is currently carried out with a mix of manual and automated systems, notes Kumar. “Currently there are limited processes that utilize automated processes. There is a desire to go more toward automated processes and minimize the manual operation, and new technology such as TFDF is designed to have thatautomated processing concept in mind,” he states.

“We believe two-dimensional cell growth and cell harvest are fully developed from companies [such as] Celltrio,” adds Duncheon. “We are committed to further innovating the cell harvesting process as we continue to examine 3D cell growth, microfiltration and depth filtration, [and other processes].”

Reference

1. F. Holenstein, et al., Journal of Chromatography A 1418, 103–109 (2015).

About the author

Feliza Mirasol is the science editor for BioPharm International.

Article Details

BioPharm International
Vol. 34, No. 8
August 2021
Pages: 28–29

Citation

When referring to this article, please cite it as F. Mirasol, “Cell Harvesting Sees Benefits from Automated Processes,” BioPharm International 34 (8) 28–29 (2021).