Affinity Resins: Overview, Types, & More

Affinity Resins: Overview, Types, & More

Affinity Resins: Overview

Protein purification is one essential assay performed in life sciences and biotechnology labs to study and analyze target proteins and enzymes in a lysate based on their specific properties.

Various techniques are developed that assist in conducting the process, such as:

  • Affinity chromatography
  • Hydrophobic interaction chromatography
  • Size exclusion chromatography (SEC)
  • Metal ion affinity chromatography (IMAC)

The most powerful of all the techniques mentioned above is affinity chromatography. In this technique, the target molecule is purified by using specific binding interactions between biomolecules. It’s also known as affinity purification.

During the process, a specific purification ligand is immobilized on a solid surface followed by passing a complex mixture through the column that has a high binding affinity for the bound ligand.

Figure: Immobilized antibody affinity purification on a small scale.

The column through which samples are passed is known as a matrix. The specialized matrix that is made of agarose and other materials and coupled with affinity ligands is known as affinity resins. They provide a robust platform to capture the molecule of interest.

In this article, we will review the types of affinity resins commercially present in the market, their applications, and the labs and industries that use them in routine.

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What Are the Different Types of Affinity Resins?

Affinity chromatography is a routine workflow used in the biopharmaceutical production of a range of biomolecules, including monoclonal antibodies (mAbs) and recombinant proteins. Some commonly known and used affinity resins used in such applications are:

  • Protein A Resin: These resins have a binding affinity for immunoglobulins (IgA/IgG). They can bind to a variety of mammalian species’ antibodies and are thus extensively used for antibody purification from a cell culture media.
  • Protein G Resin: This purification resin is used to purify antibody IgA/IgG from a mixture of proteins.
  • Glutathione Resin: It’s also known as GST affinity resin. It’s mainly used for the purification of GST-tagged proteins or peptides, separating them from a protein mixture.
  • Ni-NTA (nickel-nitrilotriacetic acid) Resin: These affinity chromatography resins are used to purify biomolecules with a polyhistidine (His-tag). The histidine tags on the target protein allow the purification of proteins with high specificity.
  • Biotin Resin: Biotin and iminobiotin resins enable purification through avidin-streptavidin and neutravidin interactions. They selectively bind and purify biotinylated molecules using strong affinity.
  • Lectin Resins: These resins are designed to bind to specific carbohydrate structures present in glycoproteins. Thus, they are widely used in the purification and analysis of specific glycoprotein subtypes.

How Do Affinity Resins Work?

Affinity resins are solid support used for the purification of biomolecules in chromatography applications, such as affinity chromatography. The polymer resins are usually made of sugar or acrylamide and produced in a solution as 50-150 µm diameter beads.

Because of being extremely porous, the affinity resin allows easy movement of biomolecules between and through the beads. Furthermore, due to the covalent attachment of ligands to both the outer and inner surfaces of the bead polymer, sample molecules can freely interact with a large surface area of the immobilized ligand as they flow through.

The binding capacity of resins is an essential parameter in determining the amount of biomolecules that will be purified in a single run. The dynamic binding capacity ensures optimal performance even at high flow rates, enabling efficient bioprocessing.

During the purification process, the biomolecules are immobilized on the surface of the columns through covalent interaction between the functional groups. Then, suitable elution conditions are applied to the column for the successful purification of specific biomolecules.  

When used for viral vectors, the affinity resins should be free of impurities and contaminants, enabling high flow rates to minimize purification times and associated costs. This needs to be done to prevent the loss of infectivity. Therefore, in such processes, it’s crucial to choose resins that optimize purification while preserving the desired viral properties.

What Are Affinity Resins Used For?

Affinity resins are crucial for the purification of a range of biomolecules, such as proteins, peptides, and antibodies from a sample mixture. They are efficient solutions to diverse purification challenges, such as high-capacity demands, presence of contaminants, and nucleic acid removal, observed during streamlining the process development.

After proteins are purified using these resin columns, they are used for downstream applications such as ELISA and protein analysis and characterization.

Protein Binding

Affinity resins are made of agarose or cellulose, acting as a solid support matrix for the binding and elution of target proteins.  They are modified by binding specific ligands or other agents for bioprocessing and biotech applications.

The bound ligands have the ability to interact with target molecules when the sample is passed through the column. Then, certain elution conditions are provided to break the bond between molecules and purification of the molecule of interest.

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Affinity resins are solid-support matrices used in biopharmaceuticals and biotech labs to purify a range of biomolecules. Some commonly used affinity resins in labs include lectin, GST, and Protein A/G resins. Each of them has different properties and interacts with different biomolecules.

Performing such high-tech workflows, such as affinity chromatography, requires labs to employ high-quality reagents coupled with high-throughput equipment. However, it’s not easy when your lab is low on budget and juggling many other tasks.

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