This document discusses immunoassay methods and their applications in pharmaceutical analysis. It begins by defining immunoassays as tests that use antibody-antigen complexes to generate a measurable result. It then covers the basic principles, classifications, common immunoassay methods like RIA, ELISA, and advances in preparation, methodology, and instrumentation. Immunoassays are described as having wide applications in areas like disease diagnosis, therapeutic drug monitoring, and bioequivalence studies due to their ability to quantify a variety of compounds.

1. Immunoassay Methods and their Applications in
Pharmaceutical Analysis:
Basic Methodology and Recent Advances
PREPARED BY
SIBASISH DEY
M.PHARM,1ST YEAR
DEPT. OF PHARMACEUTICAL CHEMISTRY
GURU NANAK INSTITUTE OF PHARMACEUTICAL SCIENCE
AND TECHNOLOGY.

2. INTRODUCTION
•An immunoassay is a test that uses antibody and antigen
complexes as a means of generating a measurable result.
• An antibody: antigen complex is also known as an immuno-
complex.
• “Immuno” refers to an immune response that causes the
body to generate antibodies, and “assay” refers to a test. Thus,
an immunoassay is a test that utilizes immunocomplexing
when antibodies and antigens are brought together.

3. PRINCIPLE
Immunoassays methods are based on a competitive binding
reaction between a fixed amount of labelled form of an analyte and
a variable amount of unlabelled sample analyte for a limited
amount of binding sites on a highly specific antianalyte antibody.
When these immuno analytical reagents are mixed and incubated,
the analyte is bound to the antibody forming an immune complex.
This complex is separated from the unbound reagent fraction by
physical or chemical separation technique.
A standard curve, which represents the measured signal as a
function of the concentration of the unlabelled analyte in the
sample is constructed. Unknown analyte concentration is
determined from this calibration curve.(1)

4. CLASSIFICATION
• Competative immunoassay.
• Non-competative immunoassay.
• Homogenous immunoassay.
• Heterogenous immunoassay.

5. Competative immunoassays(2)

6. Non-competative immunoassays(2)

7. Homogenous immunoassay and Heterogenous immunoassay

8. IMMUNOASSAY METHODS APPLIED IN
PHARMACEUTICAL ANALYSIS
1.RIA
2.ELISA
3. Fluoroimmunoassay
4. Chemiluminescence Immunoassay
5. Liposome Immunoassay (3,4,5,6,7)
1.RIA

9. 2.ELISA
3.FIA

10. 4. Chemiluminescence Immunoassay(9)
Liposome Immunoassay(8)

11. ADVANCES IN IMMUNOASSAYS FOR
PHARMACEUTICAL ANALYSIS
1.Advances in Preparation of the Immunoanalytical Reagents.(10)
2. Advances to Involve New Categories of Compounds.(11)

12. ADVANCES IN METHODOLOGYAND INSTRUMENTAION
1.Cloned Enzyme Donor Immunoassay(12,13)

13. 2.Flow Injection Immunoassay(14)

14. 3.Capillary Electrophoresis Immunoassay(15)
1.Capillary electrophoresis immunoassay (CEIA) has been recently introduced as a
sensitive analytical technique, particularly when combined with a sensitive detection
method.
2. This technique is a combined use of the principles of the capillary electrophoresis
separation and the heterogeneous immunoassay.
3. In this technique, the antibody is attached covalently to the modified interior
surface of a microcapillary, which is used as a solid phase immuno reactor.
4.Then The analyte and labelled analyte (tracers) are mixed and the mixture is then
injected into the system.
5.Tracers are detected with on column detector. The concentration dependent peaks
produced serve as the basis for quantitation.

15. 4.Immunosensors(16)
Immunosensors can be divided, in principle, into two categories: nonlabeled and
labeled immunosensors. Nonlabeled immunosensors are designed so that
the immunocomplex (i.e., the antigen–antibody complex) is directly determined by
measuring the physical changes. In contrast, in a labeled immunosensor a sensitively
detectable label is incorporated.
In nonlabeled immunosensor Either antibody or antigen is immobilized on the solid matrix
to form a sensing device. The solid matrix should be sensitive enough in
its surface characteristics to detect the immunocomplex formation. Electrode, membrane, or
optically active material surfaces may be used to construct nonlabeled immunosensors. The
antigen or antibody to be determined is dissolved in a solution and reacts with the
complementary matrix-bound antibody or antigen to form an immunocomplex. This
formation thus alters the physical properties of the surface, such as the electrode potential,
the transmembrane potential, or the optical properties.
Labeled immunosensors are basically designed so that immunochemical complexation takes
place on the surface of the sensor matrix. There are several variations of the procedure to
form an immunocomplex on this matrix. In the final step, however, the label should be
incorporated into the immunocomplex, which can thus be determined by potentiometric,
amperometric, and optical measurements

16. Advantage and Disadvantage
Advantage:-
1.High sensitivity-Low detection limit .
2.High specificity –Detect specific compound.
3. Safe and simple .
4.Fast Tests (between 5 minutes and 1hour).
5.Cost effective .
6.Tests can yield quantitative or qualitative data.
Disadvantage:-
1.Negative results don’t always rule out the
presence of a drug .
2.May not be sensitive to be certain compounds.
3.Some chemists are reluctant to use immunoassay
due to its biological basis and their unfamiliarity
with it.

17. USE OF IMMUNOASSAY
1.These measures the presence or concentration of macromolecule or a
small molecule in a solution through the use of an antibody or an antigen.
For ex. in analyte fluids urine and serum.
2.These are used in sports anti-doping laboratories to test athletes, blood
samples for prohibited recombinant human growth hormone.
3.These are used in analysis of metabolites or biomarkers which indicate
disease diagnosis.
4.Used in measurements of very low concentrations of low molecular
weight drugs.
5. Used in therapeutic drug monitoring.
5. In clinical pharmacokinetic.
6. Used in bioequivalence studies in drug discovery and pharmaceutical
industries.

18. CONCLUSION
Easy to use.
Result obtained within short time.
No require for extraction procedure.
No hazards chemical used.
The instrumentation technology leads to automation of
immunoassays and consequently increasing their throughput.
Immunoassay methods are capable of quantifying wide variety of
compounds such as low molecular weight drugs, macromolecular
biomolecules, metabolites, and/or biomarkers which indicate
disease diagnosis.
Therefore, these methods found wide applicability in many
important areas of pharmaceutical analysis such as diagnosis of
diseases, therapeutic drug monitoring, clinical pharmacokinetic and
bioequivalence studies in drug discovery and pharmaceutical
industries.

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