14th November 2019

Flow cytometry has gained popularity and demand in the field of biology because of its accurate analysis and high throughput. The use of multiple lasers, affinity ligands and attached fluorophores allows simultaneous analysis of several markers expressed on thousands of cells per second (Figure 1). Some of the most widely used applications include drug testing, microbiological analysis of bacteria and viruses, cell phenotyping, stem cell research and most importantly detecting cancer cells. Aptamers compete with antibodies in many such applications, in which high-affinity and specificity ligands are needed. Moreover, low specificity and inconsistent labelling of antibodies may lead to significant loss of function and reliability in detecting the target of interest. In this regard, fluorescence–tagged aptamers have shown increased use in flow and imaging cytometry for detecting cells expressing distinct antigens.

Figure 1. Schematic representation showing fluorescence–activated cell sorting (FACS) technique where a population of mixed cells is sorted into a negative sample and a positive sample containing cells of interest by the flow cytometer.

The advantage of using aptamers is that they are specifically designed and optimized for the conditions you want to use them in ensuring they bind to their target with high specificity and affinity.  For example, labeling steps (or appropriate functional groups) can be incorporated during synthesis to enable reliable site-specific labeling. This allows for easy multiplex analysis by using multiple aptamers with different dyes. Moreover, our in-vitro selection process mainly includes counter selection against negative target, which ensures higher affinity to the target and therefore lowers the limit of detection (Figure 2).

Figure 2.  An example of our FACS data showing concentration dependent binding of an individual aptamer (FITC labeled) to the target cell line,H929 (left) and negligible binding to the negative cells, K562 (right).

Beyond that, aptamers open up new possibilities to improve flow cytometry analysis by combining with nanoparticles such as quantum dots for the generation of new multivalent detector molecules with enhanced affinity and sensitivity. Moreover, decreasing costs in production with improved batch to batch consistency means aptamers are expected to be established as high quality molecular probes that can complement and substitute antibodies in flow cytometry and FACS.

If you want to explore on how aptamers can be used for your research, discovery and development projects then please contact us using the form below.

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