RADIOISOTOPES IN

BIOLOGY

AYESHA ZAINAB BEG

14 MBT 007

CONTENTS

INTRODUCTIONHISTORYPHENOMENON OF RADIATIONRADIOISOTOPES IN BIOLOGYSCOPEDISADVANTAGESCONCLUSION

INTRODUCTION ISOTOPES

Having same atomic number (protons in nucleus) and different atomic mass ( proton + neutron) .STABLE ISOTOPES

Stable nuclei and do not undergo radioactive decay.RADIOISOTOPES

Unstable isotopes which through the process of the radioactive decay attain stability.

RADIOACTIVE DECAY Particles or electromagnetic radiation are emitted from the

nucleus of an unstable isotope.

Wilhelm Röntgen 1895, produced and detected X-rays Henri Becquerel, 1896 discovered Radioactivity

Marie and Perrie Curie, 1898 discovery of Polonium and Radium.

HISTORY

THE ATOM• Protons(P) in nucleus indicates the atomic

number(Z) of the element.• Central nucleus is of proton (P) and

neutrons(N) where atomic mass (A) is concentrated. [A= Z+N]

Atomic stability and radiation• Ratio of neutrons to proton determine the

stability of the elements

THE PHENOMENON OF RADIOACTIVITY

ELEMENTSWith low Z

With high Z

N/P

N/P

PN

CONT.. Isotopes having high Z are unstable as nuclear binding energy decreases for the protons. Instability of isotopes leads to radioactive decay. Radiatioactive decays are classified as

• Alpha (α), Beta (β),Gamma (ϒ) and X Ray radiation.

ALPHA

Heavy Charged particle

Most ToxicConstant energy per

particle

BETA

Light Charged Particle

Less toxicNegatively charged

Energy varies particle to particle

GAMMA/ X RAY

Electromagnetic Radiation

Toxicity same as βHighly penetrating

PENETRATION DIAGRAM

TERMS AND UNITS

• Half-life Time taken for the activity to fall from any value to half of that value• Biological half-life Time taken by half the amount of radioisotopic element to leave the

body.

• Bq- One disintegration per second (dps)

• Ci- Disintegration in 1g Radium (curie - 3.7x1010 disintegration per seconds)

• Sv - Amount of radiation that gives a dose in humans equivalent to 1Gy of X-ray (1Gy=100 rad; 1 rad = .01j/kg

Radioisotopes -exquisite sensitivityRadiotracing a processCompatibility with in vivo system Assays and Probe

RADIOISOTOPES IN BIOLOGY

TRACING , DETECTION AND ASSAYRADIOTRACERS

• For metabolic pathway elucidation

• Metabolic turn over time

• Pharmacological studies

AUTORADIOGRAPHY

• Detection and localization of radiation from a given object.

• Photographic emulsion- silver halide + gel

• Ionising radiation from radioactive object acts upon photographic emulsion to give latent image.

• Radioactive event- Dark silver grains• Uses- i. Detection on chromatogramii. Tissue/organ sections iii. DNA,RNA and protein studies

RADIOIMMUNOASSAY• Radioimmunoassay (RIA) is sensitive technique used to measure

concentrations of antigens by use of antibodies

• Principle: Competitive binding of radiolabeled Ag* and unlabeled Ag to a high-affinity Ab

A STEPS IN RIA

B. Determination of Uk

C. EXAMPLE

Historical perspective of 32 P & 35S - Hershey and Chase experimentUse of 32 P and 3H

MOLECULAR BIOLOGY

Probes and Labeling

Probes20-30 ntd*

End labeling5’ or 3’

MISMATCH CLEAVAGE ASSAY Radiolabelled synthetic RNA strands

• Method used to detect point mutation and genomic variations.

• Synthetic wild type isotopic RNA forms heteroduplex with cDNA of mutated gene

• RNAse cleaves to the mismatch points in

the heteroduplex

• PAGE analysis gives insight of the point mutations.

• Used in cancer research and vaccines production. eg. P 53 gene

Isotopic RNA

cDNA from mutated mRNA

Heteroduplex

RNAse

Proc. Natl. Acad. Sci. USA Vol. 87, pp. 7555-7559,Iternational Atomic Energy Agency

NUCLEAR MEDICINE AND CLINICAL ASPECT

•THERAPEUTIC RADIOPHARMACEUTICALS

• Efficacious therapy of diseases by noninvasive manner

• Radioisotopes – 131 I , 211 At, 192Ir

• Eg. Hyperthyroidism and cancers.

DIAGNOSTIC RADIOPHARMACEUTICALS

POSITRON EMISSION TOMOGRAPHY 3D image of functional processes in the body. •Radioisotopes and radio tracers - nitrogen-13 ,oxygen 15 ,fluorine- 18 Eg.18- FDG •Positron decay produces indirect gamma rays.

•Detection- Gamma camera in the scanner•USES

• Clinical diagnosis• Neuroimaging

RADIOTHERAPY

•RADISOTOPES- 60Co , 192Ir , 137Cs

•EXTERNAL BEAM RADIATION THERAPY

•INTERNAL BEAM RADIATION THERAPY(BRACHYTHERAPY)

EBRT

IBRT

CONVENTIONAL RI• Conjugation of Ab with

radionuclide• Eg. 90 Y , 131I, 161Tb

• AUGER THERAPY• 125 I, 177Lu

• Low energy electron (Auger Electrons) emission.

• Highly accurate, less damaging and applicable with non-internalizing Abs.

RADIOIMMUNOTHERAPY

ACCR ; Institut Laue-langevin

SCOPE

• EVOLUTIONARY AND ARCHELOGICAL SCIENCE- RADIODATING

• CRIMNOLOGY AND HISTORY- NEUTRON ACTIVATION ANALYSIS

• AGRICULTURE , ENVIRONMENT & ECONOMICS

Radiolabeled pesticides Crop improvement- BARC(2010) green gram, black gram, groundnut, jute

FROM WHERE DID THE ICE MAN COMMETH ?WHO

KILLED NAPOLEAN?

• Damage to environment and disposal problems.

• High cost for production of radioisotopes.

• Radiation induced mutations or other health issues.

• In assays or detections possibility of loss of native state of sample.

DISADVANTAGES

• Radioisotopes are aiding in the developmental researches and disease profiling.

• Radio tracing opened avenues for in-vivo processes’s elucidation

• Development of Molecular Biology

• In Nuclear medicine diagnostic and therapeutics radiopharmaceuticals aiding treatments by non invasive method.

CONCLUSION

THANK YOU!