Sensitive dipstick assays for lectin detection, based on glycan–BSA conjugate immobilisation on gold nanoparticles

Abstract

There is an unmet need for simple, reliable, and portable devices for the early detection of pathogens and toxins. In this research work, we explored the development of a rapid carbohydrate-based assay for the detection of glycan-binding proteins, lectins, in relation to the detection of the Ricinus communis phytotoxin ricin due to its potential as a bioterrorism agent. To allow a visual read-out of the test, gold nanoparticles were applied on a paper-based diagnostic device in the format of a dipstick assay. A small collection of carbohydrates was modified with an azidopropyl tether, allowing the functionalisation of alkyne-modified bovine serum albumin through Cu(I)-catalysed alkyne–azide cycloaddition. To further understand the impact of the nanoparticle size and the presentation of glycans on the assay, ca. 150 nm gold nanoshells and ca. 40 nm gold nanoparticles covalently functionalised with glycans were investigated for their performance in the dipstick assays. The detection of a selection of lectins, including R. communis agglutinin 120, a surrogate for ricin, was carried out. The results presented in this work highlight the potential of glyconanoparticles for the development of cost-effective detection tools for pathogens and toxins bearing surface carbohydrate-binding lectins.