ELISA Kits: Overview, Types, & More

What Are ELISA Kits?

ELISA, short for enzyme-linked immunosorbent assay, is a routine method performed in molecular biology and life sciences labs for quantitative analysis of a range of molecules. It includes hormones, peptides, proteins, and some other small molecules in a cell lysate or other samples.

Other than these, the assay is also used to detect growth factors, cytokines, chemokines, and SARS-CoV-2-related proteins. The ELISA assay also often goes by enzyme immunoassay (EIA).

The four common types of ELISA assay include:

• Direct ELISA: In this assay, the antigens are immobilized on the surface of the well plate. Then, the microplate is incubated with a primary antibody conjugated with substrates like AP or HRP, which forms an antigen-antibody complex. The assay does not involve a secondary antibody which reduces the chances of cross-reactivity between two antibodies.

• Indirect ELISA: This assay involves two antibodies: an antigen-specific primary antibody and an enzyme-conjugated, primary antibody-specific secondary antibody. When an antigen is immobilized on the ELISA plate surface, an antigen-specific primary antibody is added followed by incubation with enzyme-conjugates secondary antibody.  

This assay has high sensitivity and is less expensive compared to other ELISA assays.

• Sandwich ELISA: In this ELISA assay, a capture antibody is immobilized on the well plate surface, which binds to the analyte after incubation. Then, the plate is incubated with an antigen-specific antibody, also known as a primary antibody or detection antibody, which binds to the antigen. This is followed by incubation with a conjugated secondary antibody for the visualization and detection of the antigen-antibody complex.

• Competitive ELISA: In this ELISA format, the antibody present in the sample and enzyme-conjugated antibody, both compete for a common antigen. The assay is commonly used to study the presence of antigen-specific antibodies in any sample type, such as cell cultures, serum, blood, or saliva.

Figure: An illustration of the four types of ELISA assay.

In this article, we will cover more about the steps involved in ELISA assay and the reagents required to perform this high-throughput assay in labs. Further, we will also learn the types of ELISA kits available today in the market to make your lab life easier.

What are the Types of ELISA Kits?

Although different ELISA formats are available today to assist in lab workflows, they all have these common steps:

1. Capture antibody immobilization: The capture antibody is immobilized on the surface of the well plate and a sample containing antigen is added to it.
2. Washing: ELISA plates are washed with a washing buffer to remove unbound materials.
3. Incubation with Detection antibody: A detection antibody is added to the plate for the visualization of antigen-antibody interaction.
4. Washing: Microplates are washed to remove unbound antibodies.
5. Detection: Antigen-antibody complex is visualized using detection methods, such as colorimetric, chromogenic, chemiluminescent, and fluorescent assay.
6. Plate reading: A plate reader is used to detect the antigen-antibody reaction.  

Figure: An illustration of ELISA assay.

Scientists perform ELISA either by creating their own ELISA kit using individual reagents, based on their workflow or research goals, or by purchasing commercially available ELISA assay kits. The kits are either available based on the types of ELISA plates or ELISA formats, such as sandwich ELISA kit and competitive ELISA kit.

In addition to reliability testing, some manufacturers also test the kits for fit-for-purpose validation and stability. This ensures their precision, sensitivity, accuracy, specificity, and reproducibility for the assay.

PreCoated Kits

The kit includes ELISA plates precoated with an antigen-specific antibody. It also contains a biotinylated detection antibody, recombinant protein standard, and buffers and reagents for colorimetric detection. The kit is fast, easy to use, and tested by companies for validation and plate variability.

Uncoated Kits

The kit contains reagents and materials to coat your own ELISA plates and run the assay. It’s suitable if you have a limited budget in hand and are not concerned with inter- and intra-assay variance. It’s flexible, affordable, and optimized for different ELISA assays.

Some other ELISA development kits available in the market include Chemiluminescent ELISA Kits which are used to detect key biomarkers during research and ProQuantum Kits which are high-sensitivity kits and work on proximity-based amplification technology.

What are ELISA Kits Used For?

ELISA kits are used for the detection and quantification of a range of molecules in different sample types, such as:

• Growth factors
• Hormones
• Cytokines
• Chemokines
• Drugs and small molecules
• Biomarkers for tumors, diabetes, and other infectious diseases

Though some scientists prefer to prepare their own reagents and materials to perform ELISA assay, some labs prefer the kits because they are:

• Easy to use
• Convenient
• Quick
• Tested for validated performance
• Save time and money

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Procure Your R&D Lab Needs with Excedr

ELISA is a biochemical technique used in life sciences labs to detect and quantify a range of molecules, including peptides, proteins, and hormones. To make the workflow faster and more convenient for labs, a spectrum of ELISA kits are available in the market.

You can either find them based on the ELISA formats, such as sandwich ELISA format and competitive ELISA format, or types of molecules you need to study, such as Protein A ELISA Kit, Human ICAM4 PicoKine ELISA Kit, and Human CD51 PicoKine ELISA Kit. Other than these, ELISA kits based on the types of microplates are also available, which include Precoated Instant Kits and Unocated Antibody Pair Kits.

It is crucial to use high-quality kits and chemicals for performing assays that have been thoroughly tested for their performance. Additionally, high-throughput instruments should be used in combination with these reagents to ensure the acquisition of reliable and validated assay outcomes.

If you are a lab just starting and have limited financial resources, the cost of conducting certain assays can be prohibitively expensive. This can stall your research progress and make it challenging to achieve your desired outcomes.

At Excedr, as a team of scientists, we understand the challenges of research and researchers.

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There are no expensive upfront payments and no repair and maintenance costs involved. We cover everything under our leasing program. The range of equipment you can lease from Excedr includes analytical equipment, biotech and life science equipment, clinical equipment, and other general biology equipment.

Excedr’s leasing solution not only allows you to procure your desired equipment without depleting cash at hand but also helps you to redirect your energy and time to your research work. Thus, enabling you to meet your goals on time and make breakthrough discoveries that positively impact the world.