According to the study; finding that cellulose nanofibers to improve the sensitivity of lateral flow tests. They included cellulose nanofibers in the test area, producing an average increase of 36.6% of the colorimetric signal on positive tests. The proposing modification can be easily applying to any kind of lateral flow strip; enabling its use in point of care applications.
Lateral flow tests are used across a wide range of sectors, including human health and pharma, environmental testing, animal health, food and feed testing, and plant and crop health. They are paper based biosensors that fulfill the demands of the World Health Organization’s ASSURED criteria for devices, requiring them to be affordable, sensitive, selective, user friendly, rapid and robust, and derivable to the end-user. Paradoxically, sensitivity is not always assuring.
Cellulose nanofibers improve the sensitivity
But by an fluid sample, with or without a specific analyte, is applying to one end of the strip. Certain particles (transducers) preparing to attach to that analyte are dragging along by the fluid. Antibodies in large amounts are applied to the test line to retain the analyte marked with the transducers. If the analyte is present in the sample, the test line will be coloring because of the transducers. Otherwise, the particles will continue their journey to the end of the strip.
One way to enhance the sensitivity of the strips has to do with their porosity. If the pores are big enough, the transducers may go through them instead of stopping in the test line; decreasing sensitivity. If the pores are too small, sensitivity increases, but the sample will flow more slowly. The new research proposes to decrease the pore size only on the test area by including cellulose nanofibers in that zone.
Biocompatible with antibodies
They are biocompatible with antibodies, thus increasing the areas; where they can be placed on the surface of the strip, where the color of the transducer particles is best appreciating. As the study have also demonstratng that this retention is only due to the interaction of the analytes with the antibodies; not because of any interactions of the transducers with cellulose nanofibers, which avoids false positives.
This strategy could be using to discriminate better between similar concentrations of a giving analyte; which is useful, especially on diagnostic applications. The higher level of sensitivity allowing a quantitative analysis of the samples; using a simple camera device like the ones integrating in smartphones. The proposing modification is cheap and can be easily applied, enabling its use in point of care applications.