Agarose is one of the most commonly used substances in labs for creating gels used in electrophoresis and other scientific methods. One of the most prominent features of agarose is that it is a naturally occurring substance, making it readily accessible and safe to use. What exactly is agarose? We answer this question and more about one of the unsung heroes of science.

What is Agarose?

Agarose is a natural polysaccharide extracted from the cell walls of certain species of red algae, primarily from the genera Gelidium and Gracilaria. It is composed of repeating units of agarobiose, a disaccharide made of alternating D-galactose and 3,6-anhydro-L-galactopyranose. When dissolved in water and heated, agarose forms a gel upon cooling, creating a three-dimensional matrix with uniform pores. This gel-forming ability, combined with its high gel strength and low reactivity, makes agarose an essential material in scientific and industrial applications.

(Pictured above: Gelidium red seaweed)

Are Agarose and Agar the Same? 

Agarose and agar are related but not the same. Both are derived from red algae, primarily from the genera Gelidium and Gracilaria, and are composed of polysaccharides. However, they differ in composition, properties, and applications.

Agar is a complex mixture of two main components: agarose and agaropectin. Agaropectin contains charged sulfate and carboxyl groups, making agar more heterogeneous in structure and less pure compared to agarose. Due to its complex composition, agar has a lower gel strength and higher electroendosmosis (EEO), which can interfere with certain analytical techniques. Agar is widely used in microbiology as a solidifying agent in culture media, as well as in the food industry for products like jellies, desserts, and vegetarian gelatin substitutes.

Agarose, on the other hand, is a purified fraction of agar, primarily composed of linear agarobiose units. It lacks agaropectin, making it more chemically uniform, with higher gel strength and lower electroendosmosis. These properties make agarose ideal for laboratory applications, particularly in molecular biology, such as gel electrophoresis and chromatography, where high purity and reproducibility are required.

How is Agarose Made?

The production of agarose begins with the extraction of agar from red algae through a series of purification steps. The crude agar undergoes filtration, bleaching, and alkaline treatment to remove impurities, such as proteins, pigments, and other polysaccharides. The purified agar is then subjected to further refinement processes, such as gelation, precipitation, and freeze-drying, to isolate agarose. The final product is a white, powdery substance that dissolves in hot aqueous solutions and gels upon cooling.

What is Agarose Used For? 

Agarose is not only valued for its versatility and biocompatibility but also for its unique physical and chemical properties that make it an ideal medium. One of its key characteristics is its ability to form thermally reversible gels, meaning it liquefies when heated and solidifies upon cooling without requiring additional chemicals or crosslinking agents. This property allows for easy handling and recovery of biological samples embedded in the gel. Agarose gels exhibit low electroendosmosis (EEO), meaning they do not interfere significantly with the migration of charged molecules, making them particularly useful in electrophoresis and chromatography.

The mechanical strength of agarose gels is another important factor in its widespread use. Unlike polyacrylamide, which requires toxic reagents for polymerization, agarose gels are non-toxic and can be safely handled without special precautions. The gels also maintain structural integrity over a range of temperatures and buffer conditions, making them suitable for various molecular biology techniques. The concentration of agarose determines the gel’s pore size, which can be adjusted to optimize separation efficiency for different fragment sizes.

Agarose is widely used in molecular biology, particularly in gel electrophoresis, where it serves as a medium for separating nucleic acids (DNA and RNA) based on size. Its porous structure allows molecules to migrate under an electric field, with smaller fragments moving more quickly through the gel than larger ones. This technique is fundamental in genetic research, forensic analysis, and biotechnology. Beyond electrophoresis, agarose is used in chromatography for purifying proteins, antibodies, and nucleic acids, as well as in microbiology for culturing cells and in tissue engineering as a biocompatible scaffold.

Agarose is also used in immunodiffusion assays, where it serves as a medium for antigen-antibody interactions in diagnostic tests. In microbiology, agarose is sometimes preferred over traditional agar for culturing certain bacteria and fungi, as it lacks impurities that may interfere with microbial growth. In biomedical research, agarose hydrogels are used in cell culture studies, tissue engineering, and drug delivery systems due to their biocompatibility and ability to mimic the extracellular matrix.

(Agarose gel in a gel plate. Image courtesy: Wikipedia)

Forms of Agarose

Agarose is commercially available in several forms, each tailored to specific laboratory and industrial applications.

Agarose Powder

The most common form is powdered agarose, which is highly purified and dissolves easily in hot aqueous solutions. This form is widely used in molecular biology for gel electrophoresis, chromatography, and other analytical techniques. The powder allows researchers to prepare gels of varying concentrations to optimize pore size for the separation of different molecular weights of DNA, RNA, or proteins.

Pre-cast Gels

In addition to powder, agarose is also available in pre-cast gels, which are ready-to-use and eliminate the need for manual gel preparation. These gels are often found in electrophoresis kits for educational and rapid diagnostic applications, providing convenience and consistency in results. Another form is agarose beads or microspheres, which are used in chromatography for biomolecule purification, such as affinity or ion-exchange chromatography. These beads serve as a matrix for separating proteins, antibodies, and nucleic acids based on their biochemical properties.

Agarose Tablets

Agarose tablets, which provide a pre-measured, convenient alternative to powder, ensure consistency in gel preparation and reducing weighing errors. A great example of these are the EZ Pack Agarose LE, packaged in blister packs in individual 0.5g tablets.

Is Agarose Sustainable?

From a sustainability perspective, ongoing research is exploring ways to enhance the environmental benefits of agarose production. Scientists are investigating alternative sources of agarose from different seaweed species and developing eco-friendly extraction methods that minimize chemical waste. Additionally, efforts to cultivate red algae in controlled environments, such as aquaculture farms, are helping to reduce the impact of wild harvesting and ensure a more sustainable supply chain.

From an environmental perspective, agarose offers several benefits. As a naturally derived, biodegradable polymer, it presents a sustainable alternative to synthetic materials commonly used in laboratories. Unlike synthetic gels, agarose does not release harmful byproducts or contribute to microplastic pollution. Additionally, its production relies on renewable marine resources, and ongoing research focuses on sustainable harvesting methods to minimize ecological impact. The non-toxic nature of agarose also makes it safer for personnel and reduces hazardous waste.