Agarose

• Research over the past three decades has established agarose as a useful matrix for a number of biochemical techniques including gel electrophoresis, chromatography, and support matrix to immobilize enzymes (Zucca et al., 2016) and cells.
• These techniques utilize agarose for various molecular biology and biochemistry applications including nucleic acid analysis and purification, protein analysis and purification, immunodiffusion, gel filtration of viruses and subcellular particles, etc.
• In addition, agarose can be used to culture cells. It can be used in place of agar to prepare bacterial culture medium and also for animal cell culture (e.g., soft agar assay).
• Agarose forms an inert matrix that makes it suitable for separation techniques.
• Agarose is present in high amounts in agar which is extracted from seaweeds. Gelling property of agar is due to agarose.
• Agarose is insoluble in water but when agarose suspension in water is boiled, it melts and forms a clear transparent solution. When the melton agarose cools down, it forms a translucent gel that has sieving properties.
• Agarose is the least electrically charged subcomponent of agar (Serwer, 1983) and forms an inert matrix with sieving properties upon gelation, thus suitable for separation techniques, especially electrophoresis-based techniques.
• Agarose is a linear polysaccharide polymer of monomeric subunits agarobiose (alternating D-galactose and 3,6-anhydro-L-galactopyranose linked by α-(1→3) and β-(1→4) glycosidic bonds). The average molecular weight of an agarose molecule is ≈ 120 kDa which corresponds to 392 agarobiose units (molecular weight of the agarobiose: 306.3) in each agarose molecule (Hickson & Polson, 1968). In addition, charged (most notably ester, pyruvate, and sulfate) and uncharged (methyl) groups can also be attached to agarose polymers which influence agarose properties such as gelling temperature and electroosmosis. Therefore, the agarose purified from different sources may have very different properties due to the presence of impurities and changed & uncharged side groups in agarose polymer. Batch-to-batch variation in agarose purified even from the same raw material can also be observed.
  
• Agarose is available in a variety of forms, which differ in physical properties. The suitability of agarose for an application depends on its properties. The following parameters are considered while choosing agarose for an application:
  • Purity of agarose (primarily defined as the presence of sulfate content)
  • Melting/gelling point of agarose
  • Gel strength of the gel
  • Electroendosmosis (EEO)
• Lower-grade agarose may be contaminated with other polysaccharides, as well as salts and proteins, and often have high EEO, making them unsuitable for sensitive assays. Although ultra-purified agaroses are a better choice for most assays, they are costly that restrict their use. Often the quality of agarose and its suitability for the different assays are described in the supplier’s catalog, which can be used as a reference to choose agarose for a particular application.
• Agarose is considered safe and has no hazardous effect on health. However, agarose powder can cause itching in the eyes and coughing or sneezing if inhaled in large amounts.

REFERENCES:

• Zucca et al., 2016. Agarose and Its Derivatives as Supports for Enzyme Immobilization. Molecules. 21(11), 1577. PMID-27869778; Full-Text Link: mdpi, PMC6273708
• Hickson & Polson, 1968. Some physical characteristics of the agarose molecule. Biochim Biophys Acta. 165(1), 43-58. PMID-5672843; Full Text Link: sciencedirect, booksc
• Serwer, 1983. Agarose gels: Properties and use for electrophoresis. Electrophoresis. 4, 375. Full Text Links: wiley, ggfwzs, https://doi.org/10.1002/elps.1150040602