Radioisotope

Dr. Arvind Kumar

Introduction 

  • Radioisotopes are unstable isotopes that emit alpha, beta, or gamma radiation during decay.

  • They are widely used in medical biochemistry laboratories as tracers to study metabolic and biochemical processes.

  • Common examples include Iodine-131, Carbon-14, Phosphorus-32, and Technetium-99m.

  • Radioisotopes help in detecting and quantifying biological molecules with high sensitivity and accuracy.

  • They are essential in diagnostic techniques such as Radioimmunoassay (RIA) and thyroid function tests.

  • In research, they are used to study DNA replication, enzyme activity, and protein metabolism.

  • The radiation emitted allows visualization and measurement of molecular movement or reaction rates.

  • Handling requires strict radiation safety measures, including shielding and contamination control.

  • Proper disposal of radioactive waste is vital to prevent environmental and health hazards.

  • Radioisotopes have revolutionized diagnosis, therapy, and biochemical research, linking biochemistry with nuclear medicine.

Common Radioisotopes in Biochemistry

  1. Iodine-131 (¹³¹I)

    • Type: Beta and gamma emitter

    • Use: Thyroid function tests, thyroid cancer diagnosis, and therapy

  2. Carbon-14 (¹⁴C)

    • Type: Beta emitter

    • Use: Tracer in metabolic and enzymatic studies, carbon cycle research

  3. Phosphorus-32 (³²P)

    • Type: Beta emitter

    • Use: Labeling of DNA, RNA, and nucleotides in molecular biology experiments

  4. Sulfur-35 (³⁵S)

    • Type: Beta emitter

    • Use: Protein and amino acid labeling, study of sulfur metabolism

  5. Tritium (³H)

    • Type: Low-energy beta emitter

    • Use: Labeling of hormones, drugs, and lipids in biochemical assays

  6. Technetium-99m (⁹⁹ᵐTc)

    • Type: Gamma emitter

    • Use: Diagnostic imaging in nuclear medicine (liver, kidney, heart scans)

  7. Cobalt-60 (⁶⁰Co)

    • Type: Gamma emitter

    • Use: Radiation source for sterilization and radiotherapy; enzyme activity studies

  8. Calcium-45 (⁴⁵Ca)

    • Type: Beta emitter

    • Use: Study of calcium metabolism and bone mineralization

  9. Iron-59 (⁵⁹Fe)

    • Type: Beta and gamma emitter

    • Use: Study of iron absorption, transport, and metabolism in the body

  10. Chromium-51 (⁵¹Cr)

Uses of Radioisotopes in Biochemistry

  1. Tracer Studies:

    • Radioisotopes act as tracers to track the movement of elements or compounds in biochemical reactions and metabolic pathways.

  2. Metabolic Studies:

    • Used to measure rates of synthesis and degradation of biomolecules like carbohydrates, lipids, and proteins.

  3. Enzyme Kinetics:

    • Help in determining enzyme activity, substrate turnover, and reaction mechanisms by labeling specific molecules.

  4. DNA and RNA Research:

    • Isotopes like ³²P and ³H are used to label nucleotides for studying DNA replication, transcription, and hybridization.

  5. Protein and Amino Acid Studies:

    • ³⁵S and ¹⁴C are used for labeling proteins or amino acids to study protein synthesis and degradation.

  6. Hormone and Drug Assays:

    • Radioimmunoassay (RIA) uses radioisotopes to measure hormone levels, vitamins, and drugs with high sensitivity.

  7. Diagnostic Applications:

    • Iodine-131 is used in thyroid function tests and imaging; Technetium-99m is used in organ scans (heart, liver, kidney).

  8. Therapeutic Uses:

    • Radioisotopes like Iodine-131 and Phosphorus-32 are used to treat certain cancers and hyperthyroidism.

  9. Sterilization and Radiation Source:

    • Cobalt-60 is used for sterilizing medical instruments and as a gamma radiation source for radiotherapy.

  10. Study of Mineral Metabolism:

    • Calcium-45 and Iron-59 are used to study bone formation, calcium absorption, and iron transport in the body.

 

Safety Considerations in Biochemistry Labs

  1. Personal Protective Equipment (PPE):

    • Always wear lab coat, gloves, goggles, and closed footwear to protect against chemical splashes and biological hazards.

  2. Proper Labelling:

    • Clearly label all reagents, samples, and containers with name, concentration, hazard symbols, and date to prevent mix-ups.

  3. Chemical Handling:

    • Handle acids, bases, and solvents carefully; always add acid to water, not water to acid.

    • Avoid inhaling fumes and use fume hoods for volatile or toxic chemicals.

  4. Biological Safety:

    • Treat all biological materials as potentially infectious; use biosafety cabinets when handling pathogens or body fluids.

  5. Glassware and Equipment:

    • Inspect glassware for cracks and handle with care to prevent breakage and injury.

    • Turn off burners and electrical equipment after use.

  6. Radioisotope Safety:

    • Use shielding materials (lead or acrylic) as appropriate.

    • Wear dosimeter badges to monitor radiation exposure.

    • Dispose of radioactive waste separately and securely.

  7. Waste Disposal:

    • Segregate chemical, biological, and sharps waste.

    • Follow proper neutralization or autoclaving procedures before disposal.

  8. Emergency Preparedness:

    • Know the location of fire extinguishers, eyewash stations, first-aid kits, and safety showers.

    • Report all spills, accidents, or injuries immediately to the lab supervisor.

  9. Good Laboratory Practices (GLP):

    • Do not eat, drink, or apply cosmetics in the lab.

    • Keep the workspace clean, organized, and free of clutter.

  10. Training and Supervision:

  • Ensure all personnel receive regular safety training and understand emergency procedures before working independently.

MCQs 

  1. Radioisotopes are:
    A. Stable isotopes
    B. Unstable isotopes emitting radiation
    C. Isotopes without electrons
    D. Non-radioactive elements

  2. The radiations emitted by radioisotopes include:
    A. X-rays only
    B. Alpha, beta, and gamma rays
    C. UV and IR rays
    D. Only beta rays

  3. Radioisotopes are widely used as:
    A. Catalysts
    B. Tracers in biochemical processes
    C. Nutrients
    D. Buffers

  4. Which isotope is commonly used for thyroid diagnosis and therapy?
    A. Carbon-14
    B. Phosphorus-32
    C. Iodine-131
    D. Sulfur-35

  5. The isotope used for labeling nucleotides in DNA studies is:
    A. Calcium-45
    B. Phosphorus-32
    C. Cobalt-60
    D. Iron-59

  6. Technetium-99m is mainly used for:
    A. Protein synthesis studies
    B. Diagnostic imaging in nuclear medicine
    C. Enzyme kinetics
    D. DNA labeling

  7. The isotope Carbon-14 is used for:
    A. Protein labeling
    B. Studying metabolic and enzymatic reactions
    C. Imaging
    D. Radiation therapy

  8. Which isotope is a gamma emitter used in radiotherapy and sterilization?
    A. Cobalt-60
    B. Phosphorus-32
    C. Tritium
    D. Carbon-14

  9. Sulfur-35 is used for studying:
    A. DNA synthesis
    B. Sulfur metabolism and protein labeling
    C. Lipid oxidation
    D. Carbohydrate metabolism

  10. The isotope used to study iron absorption and metabolism is:
    A. Iron-59
    B. Carbon-14
    C. Phosphorus-32
    D. Calcium-45

  11. Radioimmunoassay (RIA) uses radioisotopes for:
    A. Measuring temperature
    B. Determining hormone and drug levels
    C. Checking pH
    D. Measuring enzyme size

  12. In therapeutic use, Iodine-131 is employed for treating:
    A. Anemia
    B. Hyperthyroidism and thyroid cancer
    C. Diabetes
    D. Obesity

  13. The isotope Calcium-45 is used for studying:
    A. Glucose metabolism
    B. Calcium absorption and bone formation
    C. Protein synthesis
    D. Fat metabolism

  14. The isotope Tritium (³H) emits:
    A. Gamma rays
    B. Low-energy beta particles
    C. Alpha particles
    D. X-rays

  15. Which of the following is a beta and gamma emitter?
    A. Carbon-14
    B. Iron-59
    C. Sulfur-35
    D. Calcium-45

  16. The radioactive isotope Phosphorus-32 is used in:
    A. Lipid studies
    B. Nucleic acid labeling
    C. Hormone assay
    D. Blood cell tagging

  17. The main advantage of radioisotopes in biochemistry is:
    A. High visibility and sensitivity in tracing molecules
    B. Cheap cost
    C. No safety concern
    D. Non-hazardous use

  18. Which of the following is a gamma emitter used for diagnostic imaging?
    A. Sulfur-35
    B. Technetium-99m
    C. Phosphorus-32
    D. Carbon-14

  19. Handling of radioisotopes requires:
    A. Ordinary lab gloves
    B. Strict safety measures, shielding, and contamination control
    C. No special care
    D. Direct contact with hand

  20. Radioactive waste must be disposed of:
    A. In normal trash bins
    B. As per radiation safety guidelines
    C. By pouring into sink
    D. By burning in open air

  21. Which safety device is used to monitor radiation exposure in lab personnel?
    A. Fire alarm
    B. Dosimeter badge
    C. Barometer
    D. Fume hood

  22. The use of lead shields or acrylic barriers is to:
    A. Reduce noise
    B. Protect from radiation exposure
    C. Store reagents
    D. Increase reaction speed

  23. What is the major health risk associated with poor radioisotope handling?
    A. Allergies
    B. Radiation burns and internal contamination
    C. Dehydration
    D. Eye strain

  24. Which radioisotope is used for studying enzyme activity and sterilization?
    A. Cobalt-60
    B. Carbon-14
    C. Tritium
    D. Sulfur-35

  25. Radioisotopes have revolutionized medical biochemistry by:
    A. Reducing lab work
    B. Linking biochemistry with nuclear medicine and improving diagnosis
    C. Eliminating chemical use
    D. Replacing all lab instruments

Answer Key

  1. B

  2. B

  3. B

  4. C

  5. B

  6. B

  7. B

  8. A

  9. B

  10. A

  11. B

  12. B

  13. B

  14. B

  15. B

  16. B

  17. A

  18. B

  19. B

  20. B

  21. B

  22. B

  23. B

  24. A

  25. B