According to the different classification standards, elisa plate can be classified differently.
(I) According to the number of holes:
Elisa plates can be divided into 96-hole elisa plates and 48-hole elisa plates. 96-hole elisa plate is the most commonly used, because most ELIASA is 96 holes now. So, the customers prefer to use 96-hole board elisa plates, and the manufacturers also mostly produce 96-hole elisa plates.
(II) According to different bottom shapes:
According to elisa plates’ different bottom shapes, they can be divided into flat-bottom plates, U-shaped bottom plates, and the V-shaped bottom plates. Flat-bottom plate’s refractive index is small, which is suitable to be used on ELIASA; U-shaped bottom plate’s refractive index is large, which is convenient for sample injection, taking samples and blending operation. And it doesn’t need ELIASA. When using it, people can visually observe the color change to detect the immunoreaction. The V-shaped bottom plates can improve the accuracy of sampling.
(III) According to the binding force:
According to the binding force of elisa plate with proteins and other molecules, elisa plates can be classified as high binding force plates, middle binding force plates and amination plates.
1) High binding force
This kind of elisa plates has surface after treatment, which can greatly enhance the protein binding capacity. The protein binding capacity can be up to 300 ~ 400ng IgG/cm2, mainly combined with the protein with molecular weight > 10kD. Using this kind of elisa plates can improve the sensitivity of the experiments, and can relatively reduce the requirement of coated protein’s concentration and dosage. However, the deficiency of it is the relatively high possibility of nonspecific reaction. After packaging the antigen or antibody, nonionic detergent cannot effectively block the non-binding parts, instead of that, the proteins are needed as blocking agent.
2) Middle binding force
This kind of elisa plates passively binds proteins by surface hydrophobic bond, which is suitable to be the solid phase carrier of macromolecular protein with molecular weight > 20kD. The protein binding capacity is 200 ~ 300ng IgG/cm2. Because this kind of elisa plate only binds with macromolecules, it is suitable for the purification of antibody or antigen. It can also reduce the possibility of potential nonspecific cross reaction. Inert protein or non-ionic detergent can be blocking agents of this kind of elisa plates.
The elisa plate’s surface has positively charged amino, after modification treatment. It contains hydrophilic groups instead of hydrophobic groups. This kind of elisa plates is suitable to be the solid phase carrier for small molecular proteins. Under the appropriate buffer and pH, its surface can bind with negatively charged small molecules by ionic bonding. Because of its hydrophilic surface and the ability to covalent binding cross-linking agent, it can be used for fixing the proteins soluble in detergents such as Triton-100 or Tween 20. The defect of this plate is that it cannot bind parts of the protein molecules due to reducing hydrophobicity. In addition, the surface must be effectively blocked. Because the surface is hydrophilic and covalent, the blocking agent must be functional with any groups in the non-reactive amino and other cross-linking agent.
(IV) According to the color:
According to the color of elisa plates, they can be divided into transparent plates, black plates, and white plates. Transparent plates are the most commonly used for most general ELISA experiment. Black and white plates are used for luminescence detection. A black elisa plate has light absorption, so its signal is relatively much lower than white board’s signal. Generally, black plate is used to detect the strong light, such as fluorescence detection. But the white elisa plate is used in weak light detection, such as general chemical luminescence detection. Besides, black elisa plate can also weaken the signal from nonspecific reaction. Some customers may ask that whether the transparent elisa plates can be used for light detection. And the answer is “no”, because the light generally emitted from chemical luminescence reaction are isotropic, that is to say that the light coming out is equal in all directions. If using transparent plate, the light will not only spread from the vertical direction, but also emanating from the horizontal direction. It is easily pass through the gaps between the hole and the walls of holes. When the light is stronger, it will largely affect the result of adjacent holes. So, you cannot use transparent elisa plates for chemical luminescence tests.
(V) Fixed elisa plates or detachable elisa plates:
Now, most elisa plates are detachable, that is, a single strip can be removed. Detachable plates actually can save a lot of money, because in this way, when you want to use a new elisa plate, you can buy the same model plates to replace the used one. In addition, a detachable elisa plate can be used for in vitro testing, and is convenient to disassemble.