The document discusses optical biosensors, including their components, operation, and applications. Optical biosensors consist of a biological component like proteins immobilized on a transducer surface. They can be coupled with microfluidics to introduce analytes and separate unbound molecules. Surface plasmon resonance is commonly used for detection and allows for real-time, label-free monitoring of biomolecule interactions. Optical biosensors have various medical applications and are expected to grow in healthcare, but challenges remain around issues like biomolecule immobilization, contamination, uniformity, and cost.

1. OPTICAL BIOSENSOR
Submitted by
Kannan Vasudev
@32

2. CONTENTS
 Introduction
 Types
 Advantages & Disadvantages
 Recent developments
 Future Applications
 Conclusion
 Bibliography

3.  Optical Biosensor consists of biological equipment, detector element and transducer associated with
both components.
 The biological component is generally a protein target (bio receptors) which is immobilized on the
surface of the transducer.
 The OBs are coupled with microfluidics which introduces an analyte as well as separates unbound
molecules and is a powerful biophysical tool for characterization quantitatively.

4.  Physical phenomenon for which the electrons in thin gold film can be excited into collective
oscillation by bombarding it with photons (light) of particular frequency.
 These occurs on the surface of metal at the interface of two media (usually glass and liquid) when it
is illuminated by polarized light at a specific angle.
 This generates surface Plasmon and consequently a reduction of the intensity of reflected light at a
specific angle known as the resonance angle. This effect is proportionate to the mass on the surface.
 SPR sensing is an exceedingly powerful and quantitative probe of the interactions. These interactions
of variety of biopolymers with various ligands, biopolymers and membranes including
protein:ligand,protein:protein,protein:DNA and protein: membrane.
 The SPR phenomenon enables direct, label-free and real-time changes of refractive index at the
sensor surface, which is proportionate to the biomolecule concentration.

5.  To measure a ligand–analyte interaction, one interacting molecule must be immobilized on the sensor
surface.
 The SPR chip contains a functional layer which enables the immobilization of interacting molecules.
 The first commercial SPR-based biosensor instrument was launched by Pharmacia Biosensor AB, which
was later renamed Biacore.

6.  Analytical devices in which fibre optic device serves as transduction element and it is to produce a
signal that is proportional to the concentration of chemical or biochemical to which the biological
element reacts.
 Transmits light on the basis of the principle of Total Internal Reflection(TIR).
 These are based on the transmission of light along with silica glass fibre or plastic fibre optic to the
site of analysis.
 Classified into 2 different categories:
 Intrinsic sensors: the internal property of optical fiber itself
converts the environmental changes into a modulation of
light signal. This modulation of light signal may be in form
of intensity, phase and frequency or may be polarization.

7.  Extrinsic sensors: In contrast to intrinsic sensing, in extrinsic sensing; the fiber may be used as
information carriers that lead to a black box and that will generate a light signal depending on the
information arrived at black box. This black box may be made of mirrors, gas, liquid cell, or many
other mechanisms that will proceed to generate an optical signal.

8.  Low technology
 Colorimetric test strips
 Cellulose pads embedded with enzymes and reagents
 Used in diabetes regulation:
glucose oxidase
1 glucose + O2-----------------------gluconic acid +H2O2
peroxidase
2 chromogen(2H) + H2O2 ---------------dye + 2H2O
 Strip includes: glucose oxidase, horseradish peroxidase, and a chromogen When oxidized, the
chromogen will be colored

9.  Luminescence-light that is not primarily generated from heat.
 Light output from a biochemical reaction.
 Can be used in detection of bacteria
--Uses Firefly luciferase(from the tails of wild fireflies).
--Bacteria is lysed and yellow light is given off.
ATP + Luciferin + O2 --- AMP + PPi + Oxyluciferin +
CO2 + hγ

10.  Small
 Flexible
 Fast
 Safe, no electrical device interacts with the body
 Good biocompatibility (fibers are glass)

11.  High cost of some instrumentation
 May be Invasive
 Fluorescent signal may not be strong enough

12.  Optical biosensor in the last decade has developed to a great extent in every field but there is still a
long way to replace completely the conventional methods of the optical biosensor technology in many
fields and, specially, in biomedical field.
 To achieve such objective, we still need to develop optical biosensors able to detect, in a direct way
at very low levels (picomolar to femtomolar) of a great number of substances in the areas of
environmental monitoring, industrial and food process, health care, biomedical technology, clinical
analysis,etc.
 There are various technical difficulties for fabrication of optical biosensor but still more research
efforts are needed for finding out better alternatives
Some of them are as follows:
1) Immobilization of biomaterials is the hardest difficulty in the process of fabrication of optical
biosensor. Material losses are observed during the process of immobilization of biomolecules on solid
substrate.

13. 2)Contamination
There is a big problem of biomolecules and chemicals used in the biosensors leaking out of the biosensor
which may create contamination. To avoid contamination, biomolecules should be attached to the
transducer as strongly as possible.
3) Uniformity
Optical biosensors that are fabricated by different processes can be easily reproduced if they are
uniform.
4) Selection Range
The selection range should be large in order to detect a lot of variety of biomaterials.
5) Sterilization
Sensor’s biomolecules may get destroyed if nonsterile probes are used.
6) Expensive
Low-cost optical biosensors have to be developed for mass use and to have a better equipment to fight
out different medical and technological problems.

14. TEST FOR TUBERCULOSIS
 Cough into the tube and sputum is brought up.
 Give positive reading if TB is present in the lungs.

15. OPTICAL BIOPSY SENSOR
 Detects if tumor in esophagus is cancerous or Benin.
 When illuminated, normal tissue and cancerous tissue will emit light at different wavelengths.
 Diagnosis is accurate over 98 %.

16. MEDICAL TELESENSOR
 Universal sensing chip.
 Multiple bio-sensing applications.
 Measure blood-oxygen levels.
 Color of hemoglobin is transmitted
when illuminated by light.

17.  Optical Biosensors are expected to grow most in importance in the healthcare, biomedical and
biopharmaceutical sectors.
 They can provide new analytical tools with reduced size as well as successfully tested in many fields
such as medicine,pharmacy,food safety,environment ,biotechnology ,..etc
 The broad practical application of optical biosensors is still under development and is limited mostly
to academic and pharmaceutical environments.

18.  Biosensors and Bioelectronics by D.Dharaneeswara Reddy,O.M.Hussain,D.V.R Sai Gopal, D. Muralidhara
Rao ,K.S Sastry
 www.ncb.nlm.nih.gov
 www.mdpi.com