12th September, 2017

Aptamer Applications: Using Aptamers in Lateral Flow Assays

There is a growing need for easy to use, point of care tests. A technology where aptamers can be used to achieve this is in lateral flow assays. A lateral flow assay is a method of detecting the presence (or absence) of an analyte without complicated sample preparation or the need for specialist equipment.

Lateral Flow Mechanism

A lateral flow assay is made from a membrane with four distinct sites on it: the sample pad, the conjugate pad, the test line and the control line. To use lateral flow, an aqueous sample is loaded onto the sample pad.  Then, through capillary action, the sample moves along the membrane. When the flow reaches the conjugate pad, labelled affinity reagents dissociate from the membrane and either bind to the analyte or remain in the flow. As the sample continues to move along the membrane, the conjugated labelled pair reaches the capture pad. Here a second binding molecule captures the analyte which is bound to the reporter. As these complexes accumulate, the presence of the analyte can be detected. Unbound reporters are captured at the control line, as a way to confirm the flow of sample through the device.

A diagram of the lateral flow mechanism

Figure 1: schematic of how an analyte in a sample is detected in a lateral flow assay using antibodies.

Challenges with Developing Lateral Flow Assays

Most lateral flow assays use antibodies as the reporter and capture molecules. Whilst antibodies have been very useful tools across various disciplines, there are drawbacks to using them in lateral flow assays.

Antibodies are highly specific affinity reagents. However, they are limited to targets which are immunogenic. Aptamers are able to bind to both small and large molecules along with viruses and whole cells, increasing the number of applications where a lateral flow assay can be used.

Another challenge with using antibodies is how they are labelled for detection. There is limited control to where any labels bind to the antibody. This can interfere with the binding capability of individual antibodies. As aptamers are made synthetically, it is easy to modify them at a specific point on the aptamer sequence. These modifications can also be accounted for during aptamer selection so that they do not affect binding.

One of the biggest draw backs to using antibodies in lateral flow assays is their stability. Antibodies have a limited shelf life and require specialist storage equipment to extend their functionality. Aptamers, on the other hand, have a much longer lifespan. This is because they are stored dry so they do not degrade easily, making them ideal for use in lateral flow assays.

If you would like to discuss how aptamers can be used for your detection devices or have other questions regarding aptamers, please get in touch using the form below.