Lateral flow Immunochromatographic assays are the devices that are used for the purpose of detection of analytes in the given sample. Immunochromatography is the combination of chromatography and Immuno Assays. LFIAs are the most inexpensive and widely used devices for conducting different types of tests. There are different parts of the Lateral Flow immunochromatographic assays such as sample pad, conjugate par, nitrocellulose membrane, and adsorbent pad. However, there are different types of Lateral Flow Immunochromatographic assay such as the one created from the single piece or sheet of cellulose membrane which is then further manufactured from the process of laser cutting. Comparing it to the other forms of Immuno Assay such as enzyme-linked immunosorbent assay (ELISA), or western blot the LFIAs are better, reliable, and fast. Not only that but they also provide the advantages of cost-effectiveness and material reduction. Moreover, they save time and produce results within a short time span that is approximately within 20 minutes or around 20 minutes. Lateral Flow Immunochromatographic Assays are compatible with a wide range of matrices such as serum, urine, semen, blood, and saliva. The contemporary assays are used for different purposes of testing such as pregnancy tests, rapid diagnostic tests, influenza, tuberculosis (TB), and malaria. They are also used for home-testing, food safety testing, biological agent detection, and veterinary medicine.
As it's mentioned above that lateral flow immunochromatographic assays are also manufactured with a single piece of nitrocellulose membrane which yields faster and accurate results, therefore, they were tested for the detection of Plasmodium falciparum histidine-rich protein 2 (PfHRP2) that is a malaria infection's biomarker that is detectable at the low concentration of up to 4 ng mL−1 and can be seen by the naked eye. Also, there was no element of cross-reactivity with a few of the other protein biomarkers of Plasmodium. Now, when the Lateral Flow Immunochromatographic Assay created one with a sheet of nitrocellulose membrane used for testing it yielded reliable and accurate results as compared to the pre-existing LFIAs for PfHRP2 detection. Further, it can do malaria detection testing and other protein biomarkers can also be tested.
There are a few principles on which the Lateral Flow Immochrmotograhy Assay works. Firstly, the working techniques are the same as that of the ELISA sandwich technique but the difference lies in the process where the capillary action of immunological reaction is put through the chromatographic paper. Secondly, when the matrix of the specimen is dropped onto the sample pad of the LFIA device, a complex known as the immunocomplex (Ab-Ag complex) is formed due to the antigens on the sample pad with the antibody. This immunocomplex then further travels towards the other parts of the LFIA device and gets in contact with the antibodies locked on the nitrocellulose membrane of the device. When there are more complexes formed, the purple-red line starts to appear that denotes the positive result i.e. the targeted antigen is present in the sample. The immunochromatographic unit is created by attaching the sample pad to the end of the membrane.
Four steps are required for doing an Immunochromatographic test on the LFIA device. The first step is to put the specimen on the sample pad. After the sample has been through the sample pad the solubilization of the molecules starts to occur. Here the solubilization of the detector molecule is important as for the protection of the positive results they will bind with the target analyte in the sample. After these steps, the capillary action starts it working. The whole fluid mixture is taken to the nitrocellulose membrane with the help of capillary action. Now, in the nitrocellulose membrane, there would be the immobilized antigen or antibody which will further combine with the target analyte thus bringing positive results if they would be present in the sample. If the result is positive, either a pink or purple line will appear. The adsorbent pad at the end absorbs any extra unabsorbed parts of the sample.
To summarize the benefits of the Lateral Flow Immunochromatographic Assay, it is reliable, fast, accurate, and easy to use. Moreover, it is cost-effective and can be used for different diagnostic purposes. There are no limitations and obstacles to the climatic changes and reservations for different climates. It is only for one-time usage thus hygienic and assured tests. Also, they are easily available over the counter and one doesn’t have to get a prescription for it i.e. time-saving. Lastly, it requires a very small amount of sample volume for undergoing the test procedure. With benefits, there are few limitations to it as well. First, it tends towards the quality results rather than the quantitative results additionally. Lastly, it is not as sensitive as other devices for the reason that it can detect two analytes simultaneously.
There are wide applications of the Lateral Flow Immunochromatographic Assay. It is used for multiple purposes at the clinical diagnosis for the screening and detection of the various clinical markers. Moreover, it is also used for home-based testing and detecting different kinds of diseases such as Sexually transmitted diseases, malaria, TB, liver diseases, and reproductive health of both genders can also be tested. Human chorionic gonadotropin (HCG) or pregnancy test can also be detected using Lateral FLow immunochromatographic Assay. LFIA is the most preferred test method for detecting any kind of viral, bacterial, or even parasitic infections such as dengue, syphilis, filariasis, etc. It is also used in science forensics, and cancer biomarkers.
Conclusion
Lateral Flow Immunochromatographic Assay is the most preferred and easy method for doing any kind of testing. It is technologically equipped, easy to use, reliable, and an effective method. There are some limitations that don't weigh heavy as compared to the benefits of the Lateral Flow Immunochromatographic Assay. They are considered contemporary and conventional for the detection of tests and their wide usage proves their authentication and credibility. Therefore, Lateral flow immunochromatographic Assays can be used for a wide range of purposes related to any kind of medical testing.
References
https://www.onlinebiologynotes.com/immunochromatography-assay-ica-principle-components-steps-merits-limitations-and-applications/
https://pubs.rsc.org/en/content/articlelanding/2021/an/d0an02073g#!divAbstract
https://www.sciencedirect.com/topics/chemistry/immunochromatography
