Method

Immunological rapid tests in the flow-thru assay format, also called 3D-immunofiltration, are based on the same biochemical function principle as lateral flow assays: They are able to recognise the analyte by receptor structures such as antibodies. The difference is that the addition of the sample, conjugate and additional washes is performed sequentially to a three-dimensional porous molding, where capture antibodys are immobilized to. All solutions and their components, analytes and detection reagents flow into the depths of the filter. Utilizing enhancement effects, it is possible to allow detection limits in an ultra sensitive range.

The structure of three-dimensional filter

The key component of the three-dimensional flow-through assays are filter elements (3D) filters. They are based on polymeric sintered or fibrous materials. They are surface-treated, so that a defined immobilization of antibodies or other receptors is possible. The pore sizes can be chosen in a wide range from about 5 microns to about 100 microns. Standard material based on Polyethylene usually has a pore radius of about 20 microns with a pore volume fraction of about 50%.

ABICAP

A particularly advantageous design of a 3D assay format, based on porous polyethylene (PE) moldings in a microcolumn, is the ABICAP system (AntiBody Immuno Column for Analytical Purpose). This micro-column method is sold by Senova with a corresponding optical evaluation system.
The assay times range between 10 to 30 minutes. The assay time is extended at enrichment of analytes from large volumes (10-100 mL). In free flow, flow rates between 1 and 5 ml per minute can be expected.
The reading is usually carried out directly on the 3D filter with an optical arrangement, the Senova photometer.

ABICAP detection method

Due to the sequential addition of assay reagents, it is possible to use a wide variety of detection methods. For example, antibody conjugates can be used on the basis of color particles of gold, latex or carbon. Furthermore, a magnetic selection procedure has been developed within the framework of a research project of Senova where magnetic particles have been used as a tracer.
A very sensitive detection technique for 3D assays is based on PolyHRP-labeled detection antibodies. They are binding to the captured analytes on the filter. In the presence of PolyHRP, a colorless substrate, 3,3 ', 5,5' - tetramethylbenzidine (TMB), is oxidized to a blue-stained TMB radical cation in a following step. In ready-for-use substrate solutions that are being utilized in 3D assays, anionic dextran sulfates are included in addition to substrate and hydrogen peroxide. Thereby the blue colored TMB radical cation precipitates in the pores of the porous molding, thus causing a coloration of the molding, depending on the amount of analyte present.

Your entry into the 3D immunofiltration

In addition to our full ABICAP test kits based on 3D immunofiltration and the ultra-sensitive technology PolyHRP, Senova offers its customers extensive development packages at a fixed price. Did you establish an Elisa and want to reduce the analysis time to <1 h gaining sensitivity at the same time? Then you should opt for the 3DIF assay transfer package. For more packages see our webshop.

For all other tasks, please contact our team.

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