Lateral flow immunoassay strips are always used in point-of-care and on-field detection or other situations in which a convenient and non-instrument method is always required. However, without instrument, the signal must be strong enough for the human naked-eye to distinguish. This is one of the most important factor define the limits of detection (LOD).
Considered that enzymes (especially horseradish peroxidase, HRP) are always employed to generate colormetric signals in other formats of immuno-based assays such as western blotting and ELISA, a series of lateral flow immunoassays based on the enzyme are developed.
This assays usually include 2 steps. The first is run just like the conventional lateral flow immunoassays. After the first step, substrates was added and stronger signal will show up. And the step 2 is an optional step, that is, if the signal generated by the colloidal gold in the step 1 is strong enough, users can skip the substrate step. And whether the step 2 is needed to generate an adequate signal can also used to be a criteria to semi-quantitative detection.
It is our pleasure to hear from you, and discuss this system with you, thus please contact us if you have any idea or questions related to it.
Parolo C, de la Escosura-Muñiz A, Merkoçi A. Enhanced lateral flow immunoassay using gold nanoparticles loaded with enzymes[J]. Biosensors and Bioelectronics, 2013, 40(1): 412-416.
He Y, Zhang S, Zhang X, et al. Ultrasensitive nucleic acid biosensor based on enzyme–gold nanoparticle dual label and lateral flow strip biosensor[J]. Biosensors and Bioelectronics, 2011, 26(5): 2018-2024.