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Cell centrifugation

Overview of cell biology and its importance

The main two categories of cells are prokaryotic and eukaryotic cells. Prokaryotic cells are what make up bacteria and archaea while eukaryotic cells make up organisms of the domain eukaryota. The inside of the prokaryotic cell houses it’s genetic material, DNA, in a region called the nucleoid region. There are also ribosomes within the central region of the bacteria. The next layer is the plasma membrane, a bi-lipid layer like you will see for eukaryotic cells. Unlike eukaryotic cells, prokaryotic cells will have a cell wall and a capsule surrounding the cell membrane. The eukaryotic cell is surrounded by a lipid membrane, and has membrane-bound organelles. The genetic material, DNA, is stored in the nucleus which is a membrane bound organelle. In research, many different types of cells are used. Bacterial cells are used in protein purification to grow a plasmid to express a protein of interest. You can read about this in our article protein expression and purification. Many types of Eukaryotic cells are used to do in vivo studies. Depending on your research interests, you might use muscle cells, or skin cells, or cancer cells. 

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How does magnetic bead separation work?

Magnetic bead separation is a quick, efficient, clean process that scientists use to replace filtration and centrifugation and separation techniques. Magnetic beads and particles are functionalized with antigens, antibodies, catalyzers, proteins or nucleic acids, enabling them to bind cells, bacteria, viruses and other biological entities.

These complexes of magnetic beads and their bound materials are then separated from a complex mixture in solution with a magnetic separation rack. The result is an isolated solution of your target biological elements which can be enriched and concentrated through this process. 

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Magnetic DNA Purification: History and recent developments


Genomic sequencing and molecular analysis have become so standard to biological research that they are now all but required for work to be published in high profile journals. Outside the scientific realm, magnetic DNA purification is also fundamental to forensic analysis in the criminal justice system. Therefore, a method to rapidly extract and purify high-quality DNA and RNA from a variety of tissues is indispensable, and improvements to the technique are desired.

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Cell based assays

Cell based assays are used to quantify cellular function, measure how stimuli affect cells, or to localize an effect within the cell. The cells are live and intact, and require the use of fluorescent tags and chemiluminescent or colorimetric enzymes. The quantification is performed by flow cytometry or microscopy. This is very different from studies of protein or nucleic acid which require destruction of the cell and isolation of those components from cell lysate. A cell based assay is conducted entirely within live, intact cells. The goal is to understand a cellular process, localization of a molecule or drug to a cellular compartment, or to measure how cells react to a substance. Cell based assays are usually performed in tightly controlled cell lines to test for a wide range of behaviors:

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Mistake #5 in CLIA IVD-kit manufacturing: Inappropriate safety precautions when working with magnetic fields

The first four mistakes we described in the last weeks are related to the production process of CLIA IVD-kits. However, even if you get a perfect reproducible, high performant process, it is a last mistake you should avoid. We have frequently see IVD-manufacturers to adopt solutions implying high safety risk for the operators and the equipment.

FREE Download: Five critical mistakes in CLIA IVD-kits manufacturing
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Mistake #4 in CLIA IVD-kit manufacturing: Neglecting process scalability

When developing a CLIA IVD-kit, the initial focus is on the biomarker and how to coat the magnetic beads. Biomagnetic separation conditions usually get swept to one side.

FREE Download: Five critical mistakes in CLIA IVD-kits manufacturing
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Mistake #3 in CLIA IVD kit manufacturing: Defining the process based purely on the separation time

Not all mistakes made in CLIA-IVD kit manufacturing involve the magnetic rack itself. Besides the two mistakes we reviewed during the last weeks, the third mistake we have detected involves process validation. Biomagnetic separation processes are often validated solely by specifying a separation time.

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Mistake #1 in CLIA IVD-kit manufacturing: Blaming the magnetic beads

Product development is a time-consuming, expensive process for CLIA-IVD kit manufacturers. There are several steps involved: 

  • Selecting the biomarker
  • Choosing the right coupling 
  • Selecting the right magnetic bead 

You are well versed with the first two points but what is “the right bead”? Assuming you have the right biomarker and a perfect coupling, the ideal magnetic bead should have the following properties:

  • High recovery/fast separation, compatible with the timing of the analyzer step. It needs to be fast enough during large-scale production processes without high bead and coupled biomarker losses.
  • No aggregation problems. Beads should be easy to re-suspend. It makes no sense to separate quickly if several additional sonication steps are required, which are difficult processes to control/implement in large volumes.
  • Low kit-to-kit variability. Batch aliquots (typically less than a milliliter) of production batches (liters scale) must be consistent. If not, variability causes problems when interpreting the results in the analyzer.


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