method of biological signalling
(a) Antibody/antigen:
Image 1
The high specificity between an antibody and an antigen can be utilized in this type of sensor technology. Biosensors utilizing this specificity must ensure that binding occurs under conditions where nonspecific interactions are minimized. Binding can be detected either through fluorescent labeling or by observing a refractive index or reflectivity change
(Image ref 1- http://www.tms.org/pubs/journals/JOM/0010/Kumar/Kumar-0010.html)
(Image ref 1- http://www.tms.org/pubs/journals/JOM/0010/Kumar/Kumar-0010.html)
(b) Enzymes:
Image 2
Enzyme-based biosensors are composed of enzyme bioreceptors that use their catalytic activity and binding capabilities for specific BIOMEDICAL NANOSTRUCTURES detection. The products of reactions catalyzed by enzymes can be detected either directly or in conjunction with an indicator. The catalytic activity of the enzymes provides these types of biosensors with the ability to detect much lower limits than with normal binding techniques. This catalytic activity is related to the integrity of the native protein structure.
(Image ref 2- http://www.ysilifesciences.com/index.php?page=how-does-the-ysi-sensor-technology-work)
(Image ref 2- http://www.ysilifesciences.com/index.php?page=how-does-the-ysi-sensor-technology-work)
(c) Nucleic acids:
Image 3
The complementary relationships between adenosine and thymine and cytosine and guanosine in DNA form the basis of specificity in nucleic acid-based biosensors. These sensors are capable of detecting trace amounts of microorganism DNA by comparing it to a complementary strand of known DNA. By unwinding the target DNA strand, adding the DNA probe, and annealing the two strands, the probe will hydrolyze to the complementary sequence on the adjacent strand. If the probe is tagged with a fluorescent compound, then this annealing can be visualized under a microscope. For accurate analysis, polymerase chain reaction (PCR) is often used to create multiple copies of the sample DNA.
(Image ref 3- http://www.rsc.org/Publishing/Journals/an/article.asp?Type=Issue&Journalcode=AN&Issue=7&SubYear=2007&Volume=132&GA=on)
(Image ref 3- http://www.rsc.org/Publishing/Journals/an/article.asp?Type=Issue&Journalcode=AN&Issue=7&SubYear=2007&Volume=132&GA=on)
(d) Cells and viruses:
Image 4
Microorganisms such as bacteria and fungi can be used as biosensors to detect specific molecules or the overall ‘‘state’’ of the surrounding environment. For example, cell behavior such as cell metabolism, cell viability, cell respiration, and bioluminescence can be used as indicators for the detection of heavy metals. Furthermore, proteins that are present in cells can also be used as bioreceptors for the detection of specific analytes.
(Image ref 4- http://www.intechopen.com/books/biosensors-for-health-environment-and-biosecurity/label-free-biosensors-for-health-applications)
(Image ref 4- http://www.intechopen.com/books/biosensors-for-health-environment-and-biosecurity/label-free-biosensors-for-health-applications)
(e) Biomimetic materials based:
Image 5
A biomimetic biosensor is an artificial or synthetic sensor that mimics the function of a natural biosensor. These can include aptasensors, where aptasensors use aptamers as the biocomponent.. Aptamers are synthetic strands of nucleic acid that can be designed to recognize amino acids, oligosaccharides, peptides, and proteins.
(Image ref 5- http://www.rsc.org/Publishing/Journals/AN/article.asp?Type=Issue&Journalcode=AN&Issue=3&SubYear=2010&Volume=135&GA=on)
(Ref no 3)
(Image ref 5- http://www.rsc.org/Publishing/Journals/AN/article.asp?Type=Issue&Journalcode=AN&Issue=3&SubYear=2010&Volume=135&GA=on)
(Ref no 3)