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What Is Dead Cell Contamination?

Updated on Aug 22, 2023

Bacterial colonies culture growth on selective media.

Dead cells naturally contaminate cell samples or cultures throughout their lifespan; this contamination can occur at any time. While common, dead cells and debris negatively affect cell populations before and after separation, isolation, and application. Removing dead cells and debris before further processing plays a critical role in culture maintenance and adherence to good laboratory practices.

Cell Culturing and Dead Cells

Researchers grow cell cultures in the laboratory that can be maintained for extended periods. Throughout this time, natural apoptosis takes place and dead cells can accumulate in detrimental concentrations within a culture.

As nutrients become less available and waste products build up, the culture environment can suffer irreparable damage. Preserving a robust and healthy culture requires proper culture maintenance, including maintaining sterile conditions and monitoring the culturing process.

Why Do Dead Cells Occur in Cultures?

Several factors, such as mishandling and outside contamination, can cause an accumulation of dead cells and cell debris. Maintained over an extended period, cell cultures can experience natural cell death due to nutrient fluctuations or a suboptimal environment. Fluctuations in temperature, pH levels, and osmolarity can greatly influence culture health.

Improper aseptic technique or intense agitation can increase the rate of cell death within a cell culture. Even when taking utmost care, some dead cell accumulation will occur due to the life of the culture or exposure to other microbes.

Which Cells Are Most Susceptible?

Certain cell characteristics can make cell types more susceptible to cell death and dead cell contamination:

  • Primary cells—those taken directly from tissues—are susceptible to cell death due to their strict environmental requirements.
  • Specialized cells that require unique media and culture conditions are at an increased risk of contamination.
  • Cells suspended within their media, such as immune or stem cells, may be more susceptible to shear stress from harsh pipetting techniques used to minimize clumping.

Fragile cells like these are more sensitive to environmental changes and mishandling.

How Do Dead Cells Negatively Affect Cell Cultures?

Without removal, dead cell contamination will accumulate within a cell sample or culture exponentially, wreaking havoc in the cell environment and risking the viability of any remaining living cells. Dead cell contamination poses many challenges to cell cultures overall.

Dead cells occupy space and clump together, disrupting the media’s flow of nutrients and oxygen. Overcrowding results in decreased growth rates and viability. Dead cells also disrupt the natural spacing among living cells, causing clumps and gaps of cells, resulting in skewed culture density and homogeneity.

These clumps of dead cells expand and induce further cell death through inflammation, nutrient competition, environmental changes, and exponential contamination. Dead cell debris releases proteins, nucleic acids, and metabolites which can affect other cells in the culture. These waste components accumulate and interact with the available nutrients, depriving living cells of growth and survival factors. Cellular debris from dead cells also contains inflammatory molecules called damage-associated molecular patterns (DAMPs) that activate immune cells against the remaining living cells.

Over time, this contamination will affect the entire culture environment, changing the pH of the conditions and increasing the culture’s risk for outside contamination that thrives on dead cellular debris, such as bacteria and fungi.

How Does Dead Cell Contamination Negatively Affect Cells Downstream?

Several significant implications arise downstream if dead cells are not removed from cell samples before separation and isolation. Dead cells and debris, being a form of contamination, lead to inaccurate experimental results and compromised downstream applications. This additional and unnecessary cellular debris introduces extraneous genetic material that can interfere with and confound the results of tests recognizing nucleic acids, such as DNA and RNA sequencing assays.

Background noise, or variations in data that result from sources other than the sample, is relevant to many forms of contamination. Dead cells and debris cause non-specific and unwanted interference during flow cytometric analysis. Dead cell contamination tends to be more auto-fluorescent than live cells and can bind antibodies non-specifically, making it difficult to differentiate from live cells. Thus, auto-florescence of dead cells greatly impacts the success of flow cytometry and the accurate characterization of cells.

Viability assays determine the frequency of viable cells within a culture and are integral in determining a cell sample’s quality. Dead cell contamination can dilute or mask the signals of living cells, hampering the accuracy of determining overall cell viability.

Removing Dead Cells Using Microbubble Technology

Akadeum understands the importance of removing dead cells from a sample before separation and isolation or further downstream processing. Our Dead Cell Removal Microbubble Kit efficiently removes dead cell contamination without causing additional damage or loss of living cells. This results in a sample that yields cleaner data without the background noise that can result from high levels of dead cell debris. Experience the ease of our microbubble technology as sample contamination simply floats away.

Reach out to our team to discuss even more benefits of removing dead cell contamination with microbubbles.

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