Signal enhancement on gold nanoparticle-based lateral flow tests using cellulose nanofibers

Lateral flow paper-based biosensors merge as powerful tools in point-of-care diagnostics since they are cheap, portable, robust, selective, fast and easy to use. However, the sensitivity of this type of biosensors is not always as high as required, often not permitting a clear quantification. To improve the colorimetric response of standard lateral flow strips (LFs), we have applied a new enhancement strategy that increases the sensitivity of LFs based on the use of cellulose nanofibers (CNF). CNF penetrate inside the pores of LFs nitrocellulose paper, compacting the pore size only in the test line, particularly near the surface of the strip. This modification retains the bioreceptors (antibodies) close to the surface of the strips, and thus further increasing the density of selectively attached gold nanoparticles (AuNPs) in the top part of the membrane, in the test line area, only when the sample is positive. This effect boosts in average a 36.6% the sensitivity of the LFs. The optical measurements of the LFs were carried out with a mobile phone camera whose imaging resolution was improved by attaching microscopic lens on the camera objective. The characterization of CNF into paper and their effect was analyzed using atomic force microscope (AFM) and scanning electron microscope (SEM) imaging techniques.The ICN2 is funded by the CERCA Programme / Generalitat de Catalunya. The ICN2 is supported by the Severo Ochoa program of the Spanish Ministry of Economy, Industry and Competitiveness (MINECO, grant No. SEV-2017-0706). Financial support was obtained under MAT2017-87202-P, funded by Agencia Estatal de Investigación and Fondo Europeo de Desarrollo Regional, and MINECO project FIS2015-73932-JIN. This work was partially funded by 2017-SGR-579 project from the Generalitat de Catalunya. D.Q.G. acknowledges Universitat Autònoma de Barcelona for the possibility of carrying out this work inside the framework of its PhD Programme in Chemistry. Ch.S. thanks the BIST for a preBIST Grant (No. 754558).Peer reviewe