Membrane Blocking

Blocking of the membrane is sometimes used to minimize nonspecific binding of the analyte and detector particle or to improve the flow properties of the membrane (10,11). Blocking agents used in other immunoassays can be

Fig. 3. Relationship between capture line placement and sensitivity.

used successfully in lateral-flow tests, although for large-scale manufacturing an ample and consistent supply must be available. Also, application of the blocking agent represents an additional processing step in manufacturing. It is important that the blocking agent not be applied in excess, because any molecules not adsorbed to the nitrocellulose can dry down as crystals in the pores, reducing or blocking sample flow.

An excess of blocking agent can be avoided by titrating to the minimum amount required or by washing the membrane after blocking to remove any excess. Often, it is simpler to impregnate a blocking agent into the sample pad to be mobilized when the sample is applied to the test.

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