4 features to look for in an ELISA kit
Enzyme-linked Immunosorbent Assay (ELISA) kits are designed to make it easier to detect substances, in most cases antigens, in a wet or liquid sample. This test is also used in various industries for quality control and plant pathology.
ELISA kits have been used widely in detecting toxins and food allergens like milk, eggs, almonds, peanuts and walnuts.
There are so many ELISA kits available in the market; therefore, it’s important to know what to look for. The most obvious feature to look out for is whether the kit detects what you are looking for. Apart from this, here are more important features;
There are different forms available in the market. Good ELISA testing kits should be able to capture an antigen by either capturing it with an antibody that is attached to the assay plate or absorbing it to the assay plate.
The most used format is the sandwich assay. This involves two antibodies, one used to capture and the other used to detect. This format is very sensitive and strong and that’s why it favored. This format is not favorable for small antigens since it’s hard to attach two big antibodies to it or an antigen that has one side for binding an antibody.
Competitive ELISA is the best for small antigens. This format uses purified, labeled and unlabeled antigens that compete to bind to the antibodies in the sample.
Antibodies that can be used in ELISA can be polyclonal or monoclonal; at times both are used together. In sandwich assay the polyclonal is used to capture and the monoclonal is used as a detector. The polyclonal captures all the antigens with the polyclonal antibody while the monoclonal will only detect subsets of antigens with a particular epitope.
It’s important to ensure that the antibodies (monoclonal and polyclonal) used are a good match. You do not want them to be competing for the same binding sites on the sample’s antigen. They should detect and capture on different epitopes of the antigens that won’t overlap.
So while buying one, get one with a matched pair that has been proven to work well together.
Interference and cross-reactivity
The results of your assay can be distorted by antibody cross-reactivity or by interference. Cross-reactivity can be brought about by the compatibility of the antibodies derived from the host animal.
You should always go for antibodies produced from the animal you need. This said, it is also important to find out whether cross-reactivity may occur.
It is also important to find out what blocking and washing buffers are present and whether they can interfere with your results.
There are different ways of detecting binding in ELISAs, so what you need to know is the detection you need and get one that works for you.
Antigens are attached to a surface, and then a precise antibody is applied over the surface to bind to the antigen. After the antibody is linked to an enzyme, anelement comprising of the enzyme’s substrate is added. The reaction then produces a detectable sign; in most cases, it’s usually a color change.
Kevin Craig is a biomedical science student by day and a writer by night. He likes discovering new technology in the medical field. After testing technologies like ELISA testing kits, he writes reviews and recommends them to his readers.