So, this week I would lke to share with you another analyzer called the Elecsys 2010 by Roche Diagnostics, USA. Elecsys 2010 is used to perform immunological tests, mainly in vitro testings for the quantitative and qualitative determination of analytes present in the human serum.
The kind of immunoassays carried out in my lab are tumor markers such as CA 125 and CA 19-9, Free T4 and Free T3, Carcinoembryonic antigen (CEA), Hep-B surface antigen type II, Hep-A virus, HIV, Thyroid Stimulating Hormone (TSH), Luteinizing Hormone (LH), Testosterone, Follicle Stimulating Hormone (FSH), Beta-HCG, Sex hormone-binding globulin (SBHG), Rubella G, Alpha Fetal Protein (AFP), Prolactin, and many more. However, for this posting, I won't go into each test individually. I will mainly focus on the principles of the analyzer, only. Elecsys 2010 works based on 3 types of principles; competitive binding, sandwich binding and bridging binding.
Elecsys 2010 by Roche Diagnostics, USA.
Retrived 24th October 2008 from http://images.google.com.sg/imgres?imgurl=http://www.rochediagnostics.pl/content/produkty_i_uslugi/diag_scentr/immunodiagnostyka/img/elecsys_2010.jpg&imgrefurl=http://www.rochediagnostics.pl/content/produkty_i_uslugi/diag_scentr/immunodiagnostyka/elecsys2010.html&h=170&w=232&sz=17&hl=en&start=7&usg=__VI1tMedzGExoyIfrzsys6Kpc8Dg=&tbnid=BQz3cQjiytYxSM:&tbnh=80&tbnw=109&prev=/images%3Fq%3Delecsys%2B2010%2Broche%26gbv%3D2%26hl%3Den
- the analyzer uses this principle for analytes with low molecular weight (eg. Free T3)
Firstly, the antigen found in the sample (human serum) is mixed with specific anti-T3 antibody labelled with ruthenium complex. After incubation, the 2 particles will bind to one another. Another reagent is added, this time containing biotinylated T3 particles and streptavidin-coated paramagnetic microparticles. The process goes through another incubation cycle, after which immune complexes are formed. The immune complexes are transported into a measuring cell where they are magnetically entrapped onto a working electrode. The unbound particles are washed away by a washing reagent called the ProCell. The ruthenium complexes are then electrically stimulated to cause a chemiluminescent reaction to produce a light signal. The analyzer then detects the amount of light produced and calculates the concentration of antigens present in the human serum. The amount of light produced is indirently proportional to the amount of antigen present. The following is an illustration done using microsoft powerpoint of how the antibodies and antigens compete with one another for binding sites.
2) Sandwich principle
- the analyzer uses this principle for analytes with higher molecular weight (eg. TSH)
The sample (human serum) containing antigens is mixed with biotinylated TSH antibodies and ruthenium-labeled TSH-specific antibodies. The mixture is then incubated for 9 minutes to allow the particles to bind to one another, after which another reagent containing streptavidin-coated paramagnetic microparticles are added and bind to the binding site of the biotinylated antibodies. The reaction goes through another incubation cycle causing the formation of immune complexes. The immune complexes are then transported into a measuring cell where they are magnetically entrapped onto a working electrode. The unbound particles are washed away by a washing reagent called the ProCell. The ruthenium complexes are then electrically stimulated to cause a chemiluminescent reaction to produce a light signal. The analyzer then detects the amount of light produced and calculates the concentration of antigens present in the human serum. The amount of light produced is dirently proportional to the amount of antigen present. The following is an illustration done using microsoft powerpoint of how the sandwich formation is formed between the antigens and antibodies. 
3) Bridging principle
- the analyzer uses this principle when the tests require detection of antibodies and not antigens in the serum.
Firstly, the machine will detect the presence of serum antibodies in the sample. The serum antibodies are then mixed with biotinylated antigen found in the test reagent and ruthenium-labeled antigens. After a period of incubation to allow the particles to bind to specific binding sites, stretavidin-coated paramagnetic particles are added and bind to the biotinylated antigen binding site, forming immune complexes. The immune complexes with the paramagnetic particles bound to them will be magnetically attracted to a working electrode when they are transported into a measuring cell. Unbound complexes are washed away by ProCell. The ruthenium antigens are then electrically stimulated to produce light signals. The light signals are detected by the analyzer which will then calculate the antibodies concentrations in the human serum. The amount of light detected is directly proportional to the amount of antibodies present. The following is an illustration done using microsoft powerpoint, of how the bindings occur during the process. 
I guess that's all for you. Hope to see all of you soon.
2 more weeks of SIP C:C:C:C:C:C:
Nur Azeimah
0607060A
TG 02
2 comments:
October 26, 2008 at 11:21 PM
Hi Azeimah,
I would like to know why the mixture is then incubated for 9 minutes to allow the particles to bind to one another? If it was left to incubate for a shorter or longer period, would it affect the result?
And secondly, I am curious on how the machine works? As in do you serum or blood? Do you have to tranfer the specimen to another container?
Thks
Dyana
0605169B
October 31, 2008 at 11:02 PM
Hi Dyana..
i was told that 9 mins was sufficient for the machine to allow the particles to compete for binding sites. If the incubation time was shorter, some particles that could actually bind to its specific binding site might not be able to bind. It is actually impossible for the incubation time to be shorter or longer as the it is already pre-set into the machine. but yea, to answer your question, it is to allow maximum possible binding of the particles. i hope that helped C:
for most immunoassay tests, we only use the serum part of the sample. for elecsys, we are required to aliquot the serum into a tube or preferably a cup.
thank you C:
Nur Azeimah
0607060A
TG 02
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