Applications of biotechnology in medicine
- The recombinant DNA technological processes have made immense impact in the area of healthcare by enabling mass production of genetically engineered medicines such as insulin, by creating methods like gene therapy, recombinant DNA technology, polymerase Chain Reaction (PCR) and Enzyme Linked Immuno-sorbent Assay (ELISA).
- About 30 recombinant therapeutics have been approved for human-use over the world.
Genetically Engineered Insulin
- Insulin used for diabetes was earlier extracted from pancreas of slaughtered cattle and pigs which caused some patients to develop allergy.
- Insulin consists of two short polypeptide chains: chain A and chain B that are linked together by disulphide bridges.
- In mammals, including humans, insulin is synthesized as a pro-hormone which contains an extra stretch called the C peptide and the C peptide is not present in the mature insulin which is removed during maturation into insulin.
- Two DNA sequences were prepared corresponding to A and B, chains of human insulin and introduced them in plasmids of E. coli to produce insulin chains.
- Chains A and B were produced separately, which were extracted and combined by creating disulfide bond to form human insulin.
- Gene therapy is a collection of methods that allows correction of a faulty gene by a healthy and functional gene.
- Correction of a genetic defect involves delivery of a normal gene into the cells or tissues to take over the function of and compensate for the non-functional gene.
- The first clinical gene therapy was given in 1990 to a 4-year old girl with adenosine deaminase (ADA) deficiency which is caused due to the deletion of the gene for adenosine deaminase.
- ADA enzyme is crucial for the immune system to function.
- Lymphocytes from the blood of the patient are grown in a culture outside the body and a functional ADA cDNA (using a retroviral vector) is then introduced into these lymphocytes using a retroviral vector which are returned to the patient.
- In some children, ADA deficiency can be cured by bone marrow transplantation or by enzyme replacement therapy in which functional ADA is given to the patient by injection.
Fig. lymphocyte culture
- Recombinant DNA technology, Polymerase Chain Reaction (PCR) and Enzyme Linked Immuno-sorbent Assay (ELISA) are some of the molecular diagnosis that serve the purpose of early diagnosis to understand the pathophysiology of the disease.
- PCR is used to detect HIV in suspected AIDS patients, to detect mutations in genes in suspected cancer patients too.
- Very low concentration of a bacteria or virus can be detected by amplification of their nucleic acid by PCR.
- A single stranded DNA or RNA, tagged with a radioactive molecule (probe) is allowed to hybridize to its complementary DNA in a clone of cells followed by detection using autoradiography where the clone having the mutated gene will hence not appear on the photographic film, because the probe will not have complementarity with the mutated gene.
- ELISA is performed based on the principle of antigen-antibody interaction, infection by pathogen can be detected by the presence of antigens or by detecting the antibodies synthesized against the pathogen.
Fig. PCR technique