title: Naked-eye detection as a universal approach to lower the limit of detection of enzyme-linked immunoassays.
abstract: Colorimetric biosensors for the detection of analytes with the naked eye are required in environmental monitoring, point-of-care diagnostics, and analyses in resources constrained settings, where detection instruments may not be available. However, instrument-based detection methods are usually more adequate for detecting small variations in the signal compared to naked-eye detection schemes, and consequently the limit of detection of the latter is usually higher than the former. Here, we demonstrate that the limit of detection of colorimetric enzyme-linked immunoassays can be decreased several orders of magnitude when using naked-eye detection instead of a spectrophotometer for detecting the signal. The key step to lower the limit of detection is adding a small volume of chromogenic substrate during the signal generation step. This generates highly colored solutions that can be easily visualized with the naked eye and recorded with the camera of a mobile phone. The proposed method does not require expensive equipment or complex protocols to enhance the signal, and therefore it is a universal approach to lower the limit of detection of colorimetric enzyme-linked immunoassays.
authors.affiliation: WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, Technology and Innovation Centre, 99 George Street, Glasgow, G1 1RD, Scotland, UK.
authors.forename: Erin F
authors.initials: EF
authors.lastname: O'Connor
authors.affiliation: WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, Technology and Innovation Centre, 99 George Street, Glasgow, G1 1RD, Scotland, UK.
authors.forename: Sureyya
authors.initials: S
authors.lastname: Paterson
authors.affiliation: WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, Technology and Innovation Centre, 99 George Street, Glasgow, G1 1RD, Scotland, UK. roberto.delarica@strath.ac.uk.
authors.forename: Roberto
authors.initials: R
authors.lastname: de la Rica
mesh_terms: D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D006801:Humans; D007074:Immunoglobulin G / Q000032:analysis; D057230:Limit of Detection
chemical_list: D007074:Immunoglobulin G
keywords: Antibody; Biosensor; ELISA; Immunosensor; Naked-eye detection; Smartphone