15386_Biosensors and Biochips

Basic Biosensor Instrumentation

A biosensor is made up of two parts:

1.Physical component: Transducer, amplifier, display unit, etc. 2.Biological component: Enzymes, antibodies, nucleic acids, etc.

Figure 6 Block diagram of a biosensor. Engineering Chemistry Copyright 2013 Wiley India Pvt. Ltd. All rights reserved.

Components of a Biosensor

Detector

Types of Biosensors

Based on the type of physical change produced, the biosensors are of following types:

1.Potentiometric biosensors: Measure the electrical potential. 2.Calorimetric biosensors: Measure the heat released or absorbed by a reaction. 3.Optical biosensors: Measure the light produced or absorbed during the reaction. 4.Acoustic wave biosensors: Measure the change in the mass of the biological material during the reaction. 5.Amperometric biosensors: Measure the movement of electron during an oxidation-reduction reaction.

Engineering Chemistry Copyright 2013 Wiley India Pvt. Ltd. All rights reserved.

RECOGNITIONHow do you specifically recognize the analyte?

Antibody DNA

Complementary DNA

Antigen Other:

enzyme/substrate

PNA/DNA or PNA/RNA

Antibody Antibody

Antibodies are biological molecules that exhibit very specific binding capabilities for specific structure (antigens).

Antigen It can be recognized by antibody.

Bioreceptors

membrane

Bioreceptors

Display

Bioreceptor

Enzyme is a large protein molecule that acts as a catalyst in chemical reactions. Enzymes are often chosen as bioreceptors based on their specific binding capabilities as well as their catalytic activity

Bioreceptors EnzymeEnzyme

Bioreceptors

Bioreceptor

Display

Four chemical bases:• adenine(A), guanine (G),

• cytosine (C), and thymine (T)

Bioreceptors

DNA structure Another biorecognition mechanism involves hybridization of deoxyribonucleic acid (DNA) or ribonucleic acid (RNA), which are the building blocks of genetics.

Bioreceptors

Bioreceptor

Display

Nourishment

Product

Bioreceptors

Living Cell Living Cell

Bioreceptors

Bioreceptor

Display

The immobilization is done either by physical entrapment or chemical attachment.

Immobilizatiom

Bioreceptor (Antibody, Enzyme, Cell, …) + polymer solution → polymerization

Physical Entrapment

adsorptive interactions such as ionic, polar or hydrogen bonding and hydrophobic interaction.

Adsorption

Example of biosensors

Pregnancy test Detects the hCG protein in urine.

Glucose monitoring device (for diabetes patients)

Monitors the glucose level in the blood.

Example of biosensorsExample of biosensors

Infectous disease biosensor

Old time coal miners’ biosensor