Explain the construction of a mass based biosensor giving suitable analyte and compare the same with optical based biosensor?

 Introduction 

What are biosensors? It is an analytical device that detects changes in Biological processes and converts them into an electrical signal which can be then measured or analyze.


The biological material is usually in the form of an enzyme, with the help of a process known as electroenzymatic approach, which is a chemical process of converting the enzymes into corresponding electrical signals (usually current) with the help of a transducer. 

The combination of biological element and a transducer will convert the biological material into a corresponding electrical signal. Depending on the type of enzyme, the output of the transducer will be either current or voltage. Biosensors are based on the method of the transduction, which is classified into three category:-
  • Mass based biosensors
  • Optical based biosensors
  • Electrochemical biosensors


Mass based biosensors

The mass based biosensors, also known as gravimetric biosensors apply the basic principle of a response to a change in mass. Most gravimetric biosensors use piezoelectric quartz crystals, which can either be in the form of resonating crystals (quartz crystal microbalance, QCM), or as surface acoustic wave (SAW) devices. 

When a mechanical force is applied on a piezoelectric biosensor, they produce an electrical signal. The biological elements are attached to the surface of the piezoelectric biosensor, which is essentially a mass to frequency converter, converts the mechanical vibrations of the sensing molecules into proportional electrical signals.


Optical based biosensors

Optical biosensors work on the interaction of optical fields. The optical fibers allow detection of the sensing elements based on the different properties of light like absorption, scattering and fluorescence. The reaction causes changes in either properties as a result of the change in the refractive index of the interacting surface. For example, if the biological elements are antibodies and are bound with a metal layer, the refractive index of the medium which comes in contact with this layer will be varied.

One of the main advantages of using optical biosensors is their non-electrical nature. This allows them to analyze multiple elements on a single layer just by varying the wavelength of the light. They are one of the most commonly used biosensors because of their sensitivity, specificity, and small footprints.






Done by,
D_2062025_K S Gyanesh Gupta




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