ELISA, like the name of a retro and elegant girl, attracts the attention of the IVD stage.

Enzyme-Linked Immunosorbent Assay (ELISA) is a labeled immunoassay, which is hailed as the gold standard in immunoassays. This immunological test is highly sensitive and can be used to detect and quantify substances, including antibodies, antigens, proteins, glycoproteins, and hormones.

ELISA is a highly classic and time-honored assay that has been continuously applied in clinical and basic research.

Before the development of ELISA, the only option for immunoassay was radioimmunoassay. However, due to the potential health risks posed by radioactivity to experimental personnel, ELISA emerged as a safer alternative method.

The principle of ELISA is very similar to other immunoassay techniques. ELISA relies on specific antibodies binding to target antigens, and the detection system indicates the presence and quantity of antigen binding.

Antibody is a protein produced by an individual's immune system. This type of protein can bind to an antigen in a specific region. Antigen is a protein that can originate from certain foreign substances. When it binds to an antibody, it triggers a series of signals through the human immune system. This interaction is utilized in ELISA testing, which allows for the identification of specific protein antibodies and antigens with only a small amount of test sample.

ELISA

To maximize the sensitivity and accuracy of the assay, ELISA analysis typically employs 96 microplates in a single experiment for parallel analysis of numerous samples, standards, and controls.

The surface of these plates is treated with a special adsorbent, allowing antigens or antibodies to adhere correctly.

There are mainly four types of ELISA:

Direct ELISA (plate with adsorbed antigen; screening antibody)

Indirect ELISA (plate with adsorbed antigen; screening for antigen/antibody)

Sandwich ELISA (plate with adsorbed antibody; screening antigen)

Competitive ELISA (antibody screening)

Direct ELISA

In direct ELISA, protein antigens are adsorbed into the wells and washed to suppress the amount of unadsorbed antigens. Then, the antigen is directly detected by a labeled antibody.

Analysis of advantages and disadvantages

advantage

1. Fast, using only one antibody and fewer steps

2. Eliminated cross-reactivity of the second antibody

shortcoming

1 Cell smear: Adhere non-adherent cells to a coverslip through chemical bonding

2. The immunoreactivity of primary antibodies may be adversely affected by enzyme or tag labeling

3.Labeling primary antibodies for each specific ELISA system is both time-consuming and expensive

4. The low sensitivity is due to the low density of labeled antibodies

Indirect ELISA

In indirect ELISA, proteins are nonspecifically adsorbed to the wells. Since the antigen is detected indirectly by using a secondary antibody, the detection is carried out in two steps, hence the name indirect ELISA. In the first detection, an antigen-specific unlabeled antibody is added, followed by the addition of a secondary antibody that detects the first antibody.

Advantages and disadvantages analysis

advantage

1. Multiple primary antibodies can be prepared within a species, and the same labeled secondary antibodies can be used for detection

2 Due to the lack of labeling, the maximum immunoreactivity of the first antibody was retained

3 Three high labeled secondary antibody densities can achieve high sensitivity, resulting in signal amplification

shortcoming

1 Cell smear: Non adherent cells are adhered to a cover glass through chemical bonding

2 Secondary antibodies may undergo cross reactivity, leading to non-specific signals

3 An additional incubation step is required during this process

sandwich elisa

Sandwich ELISA typically requires paired antibody pairs, where each antibody has specificity for a different, non overlapping portion (epitope) of the antigen molecule. The first antibody (referred to as the capture antibody) is adsorbed into the well, and then the sample solution is added to the well. The second antibody (referred to as the detection antibody) measures the concentration of the sample after this step.

Advantages and disadvantages analysis

advantage

1 High specificity: Specific capture and detection of antigens/analytes

2. Suitable for complex or coarse/impure samples: no need to purify antigens before measurement

3 Flexibility and Sensitivity: Direct or indirect detection methods can be used However, sandwich ELISA requires two antibodies targeting different epitopes of the same antigen. Therefore, it may be necessary to develop customized antibodies. Competitive ELISA

However, sandwich ELISA requires two antibodies targeting different epitopes of the same antigen. Therefore, it may be necessary to develop customized antibodies.

Competitive ELISA

Competitive ELISA is a complex technique that is particularly suitable for small antigens. Competitive ELISA is mainly used to measure the concentration of antigens (or antibodies) in samples. The principle is to detect the signal output interference caused by the competition between the sample antigen or antibody and the labeled reference substance (antigen or antibody). Since the signal is induced by a labeled reference substance, the rule is as follows: 'The weaker the signal, the higher the concentration of the analyte in the sample'.

Competitive ELISA is a detection method based on direct, indirect, or sandwich ELISA. Therefore, the advantages and disadvantages are related to the chosen technology. ELISA application

ELISA application

ELISA has a wide range of applications, including rapid antibody screening tests for human immunodeficiency virus (HIV), COIVD-19 virus and other viruses, bacteria, fungi, autoimmune diseases, food allergens, blood types, presence of progesterone hCG, laboratory and clinical research testing, forensic toxicology, and other diagnostics.

ELISA

Due to its high sensitivity

Therefore, it is widely used for HIV screening tests.

In HIV testing, indirect detection based on ELISA is usually used to test collected blood or saliva samples. ELISA is a screening tool used for HIV testing, and due to potential false positives, the final diagnosis still requires further testing.

COIVD-19

The infectious disease virus COIVD-19 that is prevalent this year can be detected through ELISA testing. Serological diagnosis is particularly important for mild to moderate COVID-19 patients, who may be detected two weeks after onset. Serological diagnosis is also becoming an important tool for understanding the scope of COVID-19 transmission in the community and identifying potential individuals who have obtained immunization permits. The evolution of ELISA has played an important role in allergy research and diagnosis in food allergies.

Scientists have developed an ultra sensitive ELISA variant that can detect the number of Pick level allergens. Food allergies can be life-threatening within the scope of public health, therefore ELISA testing is of great significance in maintaining human medical health.

With the advancement of science, systematic innovation based on multiple disciplines and fields has accelerated the pace of updating and iterating ELISA technology.

Recently, researchers from Imperial College London published a study in the journal Nature on the successful development of a new Elisa enzyme-linked immunosorbent assay (ELISA) technology. The enzyme in this technology is used to control the accumulation of gold nanoparticles and detect ultra-low levels of proteins through color changes. The detection results can be read with the naked eye without the need for expensive instruments and cumbersome experimental steps.

The University of Michigan Ann Arbor Branch and the School of Information Technology of Fudan University published a new optical microflow laser enzyme-linked immunosorbent assay (ELISA) technology jointly developed by them recently in the journal Nature Communication. This new technology will be applied to the early detection and diagnosis of major diseases such as cancer and AIDS, as well as the research on the catalytic mechanism of single enzyme molecule.

The innovation of this technology compared to traditional ELISA technology lies in using fluorescent products as laser gain media and utilizing high-quality factor optical microcavities to generate laser output; At a fixed pump power, the threshold time for generating laser light is inversely proportional to the concentration of the target molecule being measured, and different concentrations correspond to different threshold times. Therefore, the threshold time is used as the detection signal in this technology.

The existing enzyme-linked immunosorbent assay (ELISA) devices still lack sensitivity for many clinical samples. Especially for rare samples, when the total number of target molecules of the tested protein is extremely small, improving the efficiency of molecular counting is crucial.

A diagnostic company in the United States has developed a fully automated digital ultra sensitive single-molecule protein detection method that can detect samples with fewer target molecules, improving measurement accuracy and sensitivity. This technology is an ultra sensitive research and diagnostic platform based on single-molecule immune array technology, with a sensitivity to protein concentration 1000 times higher than existing technologies.

Researchers from the University of Michigan and the diagnostic company jointly developed a portable, fast, low-cost and high-precision microfluidic ELISA device for COVID-19 antibody detection, which can obtain quantitative and accurate results in just 15 minutes by taking fingertip blood samples. This microfluidic ELISA product has a lightweight appearance, easy portability, and low cost, meeting the detection needs of operators to quickly respond to the pandemic during this outbreak.

How to make ancient technologies shine with new brilliance, so that they can still gain a place in the constantly emerging new technologies, requires innovative thinking and solid technological support. After more than 40 years of development and evolution in in vitro diagnostic technology, ITL has accumulated rich experience in product development, from the late 1980s radioactive immunology to the current hot research and design of immunoassay instruments such as chemiluminescence. In addition, the diversity and innovation of ITL's research and development projects have injected more innovative blood into the development and design of traditional IVD projects, sparking different sparks. If you also have any projects related to immune analysis that you would like to discuss with us, please feel free to contact us!