Any component that is harmful to the survival of cells and a foreign matter that causes cell impure in a cell culture environment can be considered as contamination. Cellular contamination can be divided into three major categories: microbial contamination, intercellular contamination, and chemical contamination.

Microbial contamination: including fungal, bacterial, mycoplasmal and viral contamination.

Inter-cell interaction pollution: refers to other cell contamination of non-same species

Chemical contamination: refers to the chemical components required for non-cells that affect cell survival.

First, microbial contamination

Bacterial and fungal contamination is relatively easy to detect, and contamination of viruses, mycoplasmas, and other cell lines is not readily detectable.

1. When the bacteria is contaminated, the pH of the culture solution changes and the solution becomes cloudy. The massive proliferation of bacteria leads to a large consumption of nutrients in the cell fluid, and the production of toxins inhibits the growth of cells, eventually leading to cell collapse and death. In the presence of antibiotics, it is easy to cause hidden pollution.

2. Viral contamination is the most difficult to detect and remove, and is also a potential risk factor for the experimenter, but the virus has strict host and self-limiting.

3. Mycoplasma contamination is a relatively serious cell contamination that is difficult to find and difficult to remove. This kind of contamination is not visible under the microscope and does not cause turbidity and pH change of the culture solution. Due to the high nutritional requirements of mycoplasma, it is not easy to detect by traditional microbial culture methods. In addition, mycoplasma cannot be removed by filtration and most antibiotics do not work for it!

4. Fungal contamination is mostly caused by mucor, spore mold, Candida albicans, yeast, etc., and is easily transmitted by spores. After mold contamination, most of the white or pale yellow floating objects are visible in the culture solution, and the culture solution is not turbid in a short period of time. Microscopic observation revealed filamentous, tubular and dendritic hyphae interspersed between cells. Conventional antibiotics, ultraviolet light and alcohol have a poor sterilization effect on fungi and are difficult to eliminate. Most of the fungal contamination is caused by humans, or by the air environment.

Second, cell line cross-contamination

Cell line cross-contamination is difficult to detect, and when the growth rate of the passaged cells is abnormal, the contamination can be suspected. To prevent this type of contamination, the operator should only pass one cell at a time, each cell fluid should have a separate culture medium, and a cell bank should be established, and the cells should be replaced every three months.

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