Arben Merkoçi – Institut Català de Nanociència i Nanotecnologia (ICN2)

Lateral flow assays (LFAs) represent one of the most important point of care (POC) devices for diagnostics applications. LFAs are quick, simple and cheap assays that can be used to analyse various samples out of the laboratory making them one of the most widespread biosensors currently available. LFAs have been successfully employed for various applications that range from chemical to biochemical analytes in various kinds of samples (ex. water, blood, food or environmental samples). LFAs operation is based on the capillary flow of the sample throughout a series of sequential pads with different functionalities aiming to generate a signal to indicate the absence/presence (and, in some cases, the concentration) of the analyte of interest. To have a user-friendly operation, their development requires the optimization of multiple and interconnected parameters. This process is quite important for those who are involved in the LFA development and application. In this tutorial we provide the readers with important knowledge including procedures and results with interest for research and development of LFAs based on nanoparticles as signalling tools. Some basic knowledge to understand the principles governing an LFA and to take informed decisions during lateral flow strip design and fabrication are given first. This is followed by a roadmap for optimal LFA development independent of the specific application and step-by-step example procedure for the assembly and operation of an LF strip for the detection of human Immunoglobulin G. The tutorial also contains an extensive troubleshooting section addressing the most frequent issues in designing, assembling and using LFAs. By changing only the receptors, the provided example procedure can easily be adapted for cost-efficient detection of a broad variety of targets with interest for various applications including applications with interest for some COVID19 related biomarkers.

Parolo, Claudio; Sena-Torralba, Amadeo; Bergua, Jose Francisco; Calucho, Enric; Fuentes-Chust, Celia; Hu, Liming; Rivas, Lourdes; alvarez-Diduk, Ruslan; Nguyen, Emily P.; Cinti, Stefano; Quesada- Gonzalez, Daniel; Merkoci, Arben 2020, ‘Tutorial: design and fabrication of nanoparticle-based lateral-flow immunoassays’, Nature Protocols, 15, pages 3788–3816.