Accurate and efficient quantitative and qualitative analysis of target molecules is crucial in the fields of life sciences, clinical diagnosis, and biopharmaceuticals. Among them, enzyme-linked immunosorbent assay (ELISA) has become an indispensable gold standard technology in the laboratory due to its outstanding sensitivity, specificity, and high-throughput capability. The emergence of ELISA kits has standardized and simplified the operation process of this complex technology, enabling researchers and clinical laboratory technicians to easily obtain reliable results.

1、 The core principle of ELISA: specific binding of antigen and antibody

The basic principle of ELISA is to utilize highly specific immune reactions between antigens and antibodies, and to amplify and detect signals through enzyme labeled substances. Simply put, just like a key can only open one lock, an antibody typically only recognizes and binds to a specific antigen.

According to different detection targets and methods, ELISA mainly has the following types:

1. Direct ELISA

Principle: The test antigen is directly adsorbed onto a solid-phase carrier (such as a 96 well plate), and then enzyme labeled specific primary antibody is added to bind to it. After washing away unbound antibodies, add enzyme substrate to generate a signal.

Characteristics: Less operation steps, fast speed, but the signal may be weak, and each test substance requires specific enzyme-linked antibodies.

2. Indirect ELISA

Principle: Coat the antigen onto a plate, first add unlabeled primary antibody to bind with the antigen, and then add enzyme labeled secondary antibody (antibody that recognizes the primary antibody) for binding. Finally, add the substrate for color development.

Characteristics: The signal amplification effect is significant (one primary antibody can bind multiple secondary antibodies), with high sensitivity and strong universality (primary antibodies of the same genus can be detected using the same enzyme-linked immunosorbent assay secondary antibody), making it one of the most commonly used methods.

3. Sandwich ELISA

Principle: This is the most sensitive and specific method for detecting protein antigens. Firstly, a "capture antibody" coated enzyme-linked immunosorbent assay (ELISA) plate is used to capture the target antigen in the sample. Then, another "detection antibody" is added to bind to another epitope of the antigen, forming a sandwich structure of "antibody antigen antibody". The detection of antibodies can be done through enzyme-linked immunosorbent assay (direct method) or through enzyme-linked immunosorbent assay (indirect method).

Features: High sensitivity, strong specificity, suitable for detecting low concentration antigens in complex samples such as serum and cell culture supernatants. The vast majority of commercial ELISA kits use this format.

4. Competitive ELISA

Principle: Mainly used for detecting small molecule antigens (haptens). The antigen to be tested in the sample competes with a known amount of enzyme-linked antigen for limited binding of antibodies. The higher the concentration of the antigen to be tested in the sample, the fewer enzyme-linked antigens bind to the antibody, and the weaker the final signal produced.

Characteristics: The signal strength is inversely proportional to the concentration of the analyte, suitable for the detection of small molecule substances such as hormones and drugs.

Signal detection: Regardless of the form, enzyme substrates need to be added in the end. The commonly used enzymes are horseradish peroxidase (HRP) and alkaline phosphatase (AP). The substrate reacts under the catalysis of enzymes to produce colored products. The depth of color is directly proportional to the concentration of target molecules in the sample. By measuring the absorbance value with an enzyme-linked immunosorbent assay (ELISA) reader, a standard curve can be drawn and the precise concentration of the sample can be calculated.

2、 The wide application scenarios of ELISA kits

The universality of ELISA kits has made them shine in many fields:

Clinical diagnosis:

Infectious disease detection: detection of viral antibodies (such as HIV, hepatitis B, hepatitis C) or antigens.

Hormone level monitoring: measuring insulin, thyroid hormones, sex hormones, etc.

Tumor marker screening: detecting AFP (alpha fetoprotein), CEA (carcinoembryonic antigen), PSA (prostate-specific antigen), etc.

Diagnosis of autoimmune diseases: detection of rheumatoid factors, autoantibodies, etc.

Life Science Research:

Cytokine and signaling pathway research: quantitative analysis of cytokine expression levels such as IL-6, TNF - α, IFN - γ, etc.

Protein expression and interaction research.

Drug development and efficacy evaluation: detecting the concentration of drugs in the body and their impact on biomarkers.

Food Safety and Animal Quarantine:

Allergen testing: detecting allergens such as peanuts and gluten in food.

Toxicity testing: such as aflatoxin.

Detection of veterinary drug residues.

Diagnosis of animal and plant diseases.

3、 Standard operating procedures for ELISA kit (using sandwich method as an example)

Commercialized ELISA kits provide all necessary reagents and optimized protocols, typically including the following key steps:

Preparation before the experiment:

Remove the reagent kit from the refrigerator and restore all reagents to room temperature (approximately 30 minutes).

Prepare the test samples, standards, and quality control materials.

Prepare the required washing solution, antibody detection working solution, etc.

Operation process:

1. Packaging and sealing: (Some test kits have been pre packaged, this step can be skipped)

Coating: Add capture antibodies to the wells of the enzyme-linked immunosorbent assay (ELISA) plate, incubate under suitable conditions, and allow the antibodies to adsorb onto the well walls.

Washing: Discard the liquid and clean the well plate several times with washing solution to remove unbound antibodies.

Sealing: Add sealing solution (such as BSA, skim milk), fill the wells that are not occupied by antibodies, prevent non-specific adsorption in subsequent steps, and reduce background.

2. Sample addition and incubation:

Add a series of standard samples, test samples, and quality control samples with known concentrations to the wells.

Seal the orifice plate and incubate at a specified temperature for a certain period of time to allow the target antigen to be captured by the antibody.

3. Washing:

Discard the liquid in the holes, fill each hole with detergent, let it stand for a moment, then discard, repeat 3-5 times. This step is crucial as it can completely remove unbound substances, which is the key to achieving low background and high signal-to-noise ratio.

4. Add detection antibodies:

Add enzyme labeled detection antibodies to each well. The antibody will bind to another epitope of the captured target antigen, forming a sandwich structure.

Incubate again, then wash to remove unbound detection antibodies.

5. Add substrate solution:

Add fresh enzyme substrate solution (such as TMB) to each well. Incubate in the dark and avoid light, and the enzyme will catalyze the substrate to react, producing blue (for TMB) products.

6. Termination reaction and reading:

Add termination solution (such as sulfuric acid), the reaction immediately stops, and the color of the solution changes from blue to yellow.

Within a short period of time after the reaction stops (usually within 30 minutes), measure the absorbance (OD value) of each well using an enzyme-linked immunosorbent assay (ELISA) reader at a specific wavelength (such as TMB at 450nm).

7. Data analysis:

Draw a standard curve with the concentration of the standard substance as the horizontal axis and the corresponding OD value as the vertical axis.

By substituting the OD value of the test sample into the standard curve, the accurate concentration of the target antigen in the sample can be calculated.

4、 Why choose our ELISA kit?

High sensitivity and wide dynamic range: capable of detecting concentrations as low as pg/mL and covering a wide linear range.

Zhuoyue's specificity: rigorously validated high-quality antibodies ensure extremely low cross reactivity.

Excellent repeatability: Small intra - and inter batch differences ensure stable and reliable experimental results.

Easy and fast operation: Provides pre packaged plates, ready to use reagents, and detailed instructions, greatly reducing experimental time.

Complete product line: covering multiple genera and targets, meeting your diverse research needs.

The ELISA kit, as a mature, efficient, and sensitive biological detection tool, has become the cornerstone of protein quantification and analysis in modern laboratories. Whether used for cutting-edge scientific research or precise clinical diagnosis, it can provide reliable data support. Choosing a high-quality ELISA kit is the first step towards a successful experiment.

Welcome to browse our company and search for ELISA kits that are suitable for your research objectives. If you have any technical issues, please feel free to contact our technical support team at any time.