Aptamer Biosensor: A Comparative Analysis of Protein Detection Methods

This report provides a comprehensive overview of aptamer biosensors, focusing on their application in protein detection. It begins with an introduction to the limitations of conventional protein measurement techniques, highlighting the need for more efficient and cost-effective methods. The report then delves into the design and working principles of aptamer biosensors, emphasizing their use of RNA or ssDNA-based oligonucleotides for biorecognition. A detailed explanation of biosensor components, including the bio-recognition element (aptamer) and transducer, is provided. Furthermore, the report discusses optical aptasensors, including surface plasmon resonance (SPR) techniques. The report also compares aptamer biosensors with protein mass spectrometry, pointing out the advantages of aptamer biosensors in terms of cost and complexity. Overall, the report aims to provide a clear understanding of aptamer biosensors as a viable and advantageous solution for protein detection in the healthcare sector and beyond.

Introduction
(Aptamer Biosensor)
Measuring the level of protein using conventional methods is very expensive and
time consuming. There is a need of developing a method or an equipment that is
capable of measuring or quantifying them and have certain advantages such as less
complex, cheap and easy to use. Aptamers based Biosensor provide solution to this
complex problem. These are special RNA or ssDNA based oligonucleotides. They
have special structure that is capable of favouring bioregion part of biosensor.
These biosensors have been developed to target all types as sizes of protein. These
Aptamers based sensors provide cheap, reliable, less complex way of detecting
proteins and hence play a vital role in health sector.
Biosensor
Biosensors are sometimes also referred to as bioelectronics, these are sensors
which are made up of biological materials like cell receptors, enzymes and
antibodies to detect analyte and used with the combination of physiochemical
detectors [1] .
Figure 1
Source: Biosensors Young H. Lee and Raj Mutharasan, Department of Chemical
Engineering, Drexel University (2014)
Physiochemical detectors are basically a type of transducer that converts one type of
signal into another signal. This process may take place by physiochemical,
electrolyte or piezo electrically.
Existing technologies for protein identification
Other technologies that are capable of measuring protein is protein mass
spectrometry. This is an expensive technique as compared to Aptamer biosensor.
First the protein is ionized by using either of two techniques:
 Electrospray ionization
 Matrix assisted laser ionization
After ionization they are passed through spectrometer in which different peaks are
obtained that correspond to different mass and types of protein. These peaks are

compared to already available peaks in the library of spectrometer. This method is
time consuming and expensive.
Design of Aptamer Biosensor
How it works?
They consist of bio recognition element, Aptamers, they are very small in size. Just
like typical biosensor they are made up of variety of components antibody based
biosensor equipment [2].
 Electronic part: This is basically used for the transmission of signal which are
generated by interaction
 Biological part: This part is basically used as a sensing device. This is similar
in function to electronic sensor but it is a biological matter like enzymes.
Biosensor is a combination of bio-receptor that is attached to a transducer, there are
some electronic parts as well for display. Aptamers biosensor do not use antibodies
for bio recognition element. As mentioned above aptamers are small in size so they
provide certain flexibility and advantage when used in biosensors. This chemically
stability of DNA aptamers gives properties like stability to biosensors. In this section
Optical aptasensors will be discussed.
Bio optical transduction type of transducer is that it uses photons in order to collect
information. The detection mechanism is dependent on the type of enzyme system.
It uses plasma type resonance, evanescent wave spectroscopy. It also uses
luminance detection as well.
Plasma Resonance Technique is sometimes also called as Surface Plasma
Resonance Technique or SPR. There is an interface between the positively and
negatively charged material and the name resonance comes due to the oscillation of
electron between the interfaces when the light is fallen on the surface of the material.
Many of the color based biosensors also work on this principle.
The biological part of the biosensor is also called as bio-receptor. The main
advantage of using it in biosensor is that it is very quick to use and requires no
specialization i.e. the basic selection process depends on the requirement. For
example, some bio-receptors can measure the concentration glucose in the blood
just by dipping the sensor in the sample. Some of the examples of bio-receptors
other than enzymes are:
 Nuclei
 Anti-bodies
 Receptors
Working principle of bio-receptor is based on two basic parts working together. One
part is bio-recognition layer and the other part is physiochemical transducer. They
both work together to convert biochemical signal to an electronic or optical signal.
Due to biochemical action of the analyte, the change produced in the layer can easily
be measured by physic-transducer and is proportional to analyte.
Transducer is a device which converts the signal that can be measured in terms of
quantity. The basic working principle of transducer in case of biosensor is that it