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RapidAssays' focus is to deliver reagents, materials and methods that allow for the development of both qualitative and
quantitative rapid assays without the need to invest in expensive LFA production equipment. This is achieved
through the use of generic RapidAssay Devices (gRAD). A gRAD does not contain analyte-specific reagents.
The analyte-specific reagents are mixed with the sample before application to the gRAD as part of the specific assay protocol.
In most cases this will involve adding the sample to a vial containing the preserved specific reagents. The result can be read
visually or with one of the available reader options.
RapidAssays provides all the materials and equipment you require to develop and produce your own rapid assay. You decide
on the assay format, for example a sandwich assay using an established antibody pair. The capture reagent is
produced by biotinylating the capture antibody using standard laboratory procedures. The detection conjugate is
produced by means of a supplied kit. The amounts of capture and detection conjugates are optimized and the test reagent is
divided into aliquots and preserved. A calibration curve for that batch of test reagent is made and used to determine
the concentration of the unknown sample.
RapidAssays has developed methods of improving the precision of LFA by means of its gRAD technology.
Using gRAD, you can achieve a precision comparable to that of ELISA in a procedure that takes only 10 minutes.
In addition, gRAD only requires minimal training and is fully portable, allowing tests to be carried out
in the field. gRAD is suited to both research and monitoring applications and allows you to develop your own spot tests
without the delay and expense associated with specific LFA development with a production partner.
A major disadvantage of LFA has been its poor precision, with CV values well above 20%. A prime reason for this is that the mixing
of the capture and detection antibodies takes place in a state of flux within the LFA device. When the sample is added to a
conventional LFA, it migrates via capillary forces to the conjugate release pad (CRP) which contains preserved detection conjugate
(DC). The DC is then dissolved by and migrates with the sample to the test line. During this time it is able to bind to the
analyte present in the sample, in accordance with the efficiency of DC release and sample contact. The rate of DC release by the CRP
is the main source of variability in LFA and variations in both sample and environmental conditions have a marked effect on the result.
In gRAD, both the capture and detection conjugates are mixed with the sample before it is applied to the device, so that contact
with the analyte takes place in a controlled manner. However, the immobilization of the capture conjugate at the test line still
takes place in a flow system and is vulnerable to variations in the flow of the sample through the device. To overcome this,
a sufficient excess of the biotinylated capture antibody is used so as to saturate the streptavidin immobilized at the
test line. Once the immobilized streptavidin is saturated with the capture antibody the result is independent of the variation in
the amount of sample mixture that passes over the test line.
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