ELISA (Enzyme-Linked Immunosorbant Assay)

ELISA (Enzyme-Linked Immunosorbant Assay)

Fig. Enzyme-linked Immunosorbent Assay (ELISA)

Developed independently in 1971 by two groups: Engvall and Perlmann; Weeman  and Schurs.
Based on the ability of antibodies to couple with enzyme to produce enzymatically  active immunological conjugates. The enzyme commonly used are peroxidase and alkaline phosphatase.
Helps in the detection of the substance by immune reaction through histochemical staining techniques. Widely used in serological diagnosis of various diseases. Viruses, fungi, bacteria, hormones, mycotoxins and mycoplasma like organisms (MLO) can be detected by this test. Presence of antibodies specific to HIV in the serum of suspected AIDS patients can be detected by using HIV proteins in the ELISA.
Positive cases are confirmed by Western blotting, in which a preparation of HIV proteins is subjected to electrophoresis. Proteins are then transferred from gel onto
nitrocellulose membrane, which is then incubated in the serum of the ELISA — positive patients, and Ag-Ab is detected by ELISA. Antibodies against HIV appear after 2 to 12 weeks of  infection by the virus.

Cryopreservation

Very popular and effective method for long term storage of cells and tissues at very low temperature (–196ºC) using liquid nitrogen, e.g. cornea, kidney, heart, liver, muscle and skin, zygotic and somatic embryo can be stored for long time. Callus culture suspensions can be used as media for cryopreservation.
Cryosurgery uses freezing temperatures to destroy tissues. Liquid nitrogen is sprayed directly onto the tissues for treatment of warts, or is inserted into the tissue via a hollow probe. Cancerous tumors can be destroyed in this way.