Molecular Diagnostics Services, Inc.
A Contract Research Organization

Master and Working Cell Banks

When a cell line is to be used over many manufacturing cycles, a two-tiered cell banking system consisting of a master cell bank (MCB) and a working cell bank (WCB) is recommended. If not provided by the customer, a cell line is established from a single clone and this cell line is used to make-up the MCB. This MCB must be characterized and extensively tested for contaminants such as bacteria, fungi, and mycoplasmas. Most cell lines also require sterility and PCR testing for viruses.

Cells from the MCB are expanded to form the WCB, which is characterized for cell viability prior to use in the manufacturing process. It is recommended that production cell banks be stored in two or more widely separated areas within a production facility as well as at a distant site in order to avoid loss of the cell line. Dual-site storage of all cells is accomplished with on-site storage and off-site storage. Once your project is completed, any unused cells can either be returned to you or destroyed at your option.

For master cell banks, MDS determines the integrity of the gene expression plasmid for the bulk of the cell mass and for a statistically significant number of clones. This method of analysis is dictated by the ability of certain cells to overgrow the bulk of the culture during the amplification process that occurs as the master cell bank is expanded to working cell bank and production scale processes.

The analysis process starts with the isolation of a sufficient number of clones to adequately sample the population of cells in the culture. The characterization of single clone isolates insures that there are no significant numbers of cells with missing or mutated genetic elements present in the cell bank. For the master cell bank, working cell bank and end of production cells, restriction mapping, Southern blot analysis and sequencing are performed on DNA prepared from the bulk of the cells.

MDS provides sequence verification by direct analysis of RT-PCR fragments targeting the appropriate mRNA for the master cell bank as well as the working cell bank and end of production cells. Southern blot analysis is also performed to confirm the stability of chromosome-inserted expression cassettes.

Gene Therapy Products: MDS provides nucleic acid analysis of viral and non-viral gene therapy constructs, including Southern blot analysis/restriction mapping; 100% accurate sequence verification of DNA or RNA from viral or plasmid constructs; and quantitative PCR of DNA or RNA.

Plant Analysis: MDS provides services for identification and characterization of genetically modified crops and plants, including Southern blot analysis; PCR analysis and sequence verification of the expression cassette.
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