Components of the cell, such as the deoxyribonucleic acids (DNA), ribonucleic acids (RNA), proteins as well as small biological molecules, are known to play a role in disease causation and progression.
Identification of these disease carrying biomarkers in the cell may thus be vital for detection of disease in early stages as well as treating it successfully.
These markers, however, are present in very low quantities for detection and may be contaminated by other non-specific compounds in a patient’s blood or body fluids.
Thus detection requires highly sensitive and specific recognition methods. Micro- and nanotechnology have open vistas in early disease detection using biosensors.
What are aptamers?
Aptamers are high affinity molecules that are derived from RNA or DNA. These are normally generated using a synthetic process called “Systematic evolution of ligands by exponential enrichment” (SELEX).
Aptamers receive their name from the Latin word aptus meaning “fit”. This means they bind to the target molecules with high specificity and high affinity.
The SELEX procedure
The SELEX procedure was first developed by Ellington and Szostak in 1990. In SELEX, the aptamers are generated against an analyte from large collections of oligonucleotides.
The process in use is by affinity partitioning and amplification by an iterative approach.
SELEX allows for synthesis and generation of unique and highly specific aptamers from large pools of random oligomers.
High affinity aptamers are usually selected against a wide range of targets including organic dyes, antibiotics, amino acids, proteins and complete cells.
These aptamers bind to the analyte with specific hydrogen bonding and target binding-induced folding forming complex conformational changes.
With such binding the aptamers can incorporate small molecules into their nucleic acid structure or themselves get integrated into the larger molecules like proteins to form secondary structures.
Aptoprecipitation (AP)/Co-aptoprecipitation (Co-AP) Kits
These are aptamer kits available for rapid protein precipitation. Their advantages include:-
Aptamers do not interfere with analysis downstream, because of their high specificity.
The kits are complete and do not require the conjugation step. The kit contains the aptamer as covalently conjugated to magnetic bead.
Unlike antibodies, the aptamer recognises only the native form of the target proteins and does not bind to the denatured form.
Aptamer kits generate non-denatured proteins that can be used for further study.
The Aptamer beads that are used are highly stable, covalently immobilized and possess mild elution condition. This allows the prepared AP resin to be reused and cuts costs.
The Aptamer conjugated magnetic beads are stable even at high temperatures and have a shelf life of nearly 1 year at room temperature.
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