Area of Application

3D immunofiltration (3D-IF) technology combines principles from affinity chromatography and immunoassays. Initially, molecules containing receptors (such as antibodies, antigens, streptavidin, and DNA) are immobilized on porous 3-dimensional filters. Subsequently, the following reaction steps are carried out sequentially through the filters: Analyte binding, tracer binding, substrate binding and washing. This procedure offers the following fundamental advantages:

• analyte enrichment
• shorter assay time (10-30 minutes)
• pre-calibration of the assay

The basic concept is the usage of miniature flow-through columns as depicted in Fig. 1 and 2. Combining this technique with poly-HRP technology allows for ultrasensitive rapid tests. The technology may also be combined with other detection methods (fluorometry, luminometry, magnetic particles etc), or may be used for sample extraction.

Structure of 3D Filters

Key components of the 3D-IF technology are the 3-dimensional filter elements. They are made of polymer sinter or fibrous materials. Surface treatment ensures definite immobilization of proteins and other receptors. The size of the pores can then be chosen within a range of approx. 5 to 100μm. Standard materials derived from polyethylene have an average pore size of about 20μm and contain approximately 50% pores. A typical 5*5mm (h*d) cylindrical filter, such as those used in the Senova minicolumns, has an inner surface of around 40 cm².

Detection Methods

The 3D filter elements can be combined in numerous detection procedures. Quantification can be performed directly on the filter or after elution. Senova offers rapid ultrasensitive test kits under the ABICAP© trademark. These tests are based on 3D-IF technology combined with photometric detection. For ultrasensitive rapid tests PolyHRP tracers are used in combination with a precipitating enzyme substrate (TMB). Alternatively dye particle conjugates DSC (Dye Suspensoid Conjugate) can be applied to standard applications. In both cases, the detection takes place directly on the filter via an optical measurement. This type of optics is integrated in a small column photometer. Alternatively the dyes can be eluted and conventional microplates can be used for the quantification of the eluates.

Abicap© rapid beads

Abicaps© are column-based rapid tests with shorter assay times  occurring between 10 and 30 minutes. Abicap© shows sensitivity data similar to other laboratory procedures (such as Enzyme-linked immunosorbant assay, better known as ELISA). The figure below shows one example: The reference system displayed here is an ultrasensitive ELISA based on PolyHRP. If the enrichment effects of the column technology are utilized, detection limits can be greatly enhanced. In general it is possible to transfer established immunoassay reagents to the 3D-IF format to achieve better sensitivity.

Senova offers a corresponding development service (involving customised development).  The analyte spectrum is wide, ranging from low molecular substances to proteins, viral particles and entire microorganisms. 3D-IF assay protocols are comparable to ELISA protocols, with the added benefit that assay times are considerably shorter.

Accessories

For the convenient handling of ABICAP columns Senova offers racks in the standard 8x12 format. For detection, Senova offfers two types of photometers. In addition, Senova provides all the required reagents, from poly-HRP and DSC tracers, to ready-to-use substrate solutions and buffers.