The robustness of polymer-based lateral flow glycoassays in medically relevant media

Lateral flow immunoassays are a commonly used tool in rapid point-of-care diagnostics, notably in the formats of pregnancy and COVID-19 tests. Their reliance on antibodies limits the adaptability of the assay however, due to complex manufacturing/development and sensitivity to biological media. Polymer-based alternatives, i.e. those that do not depend on antibody-antigen interactions, offer greater tunability and robustness, and are therefore highly desirable. Lateral flow glycoassays represent a new approach, utilising glycan-functionalised polymers as the recognition unit instead of antibodies. In this study, the effect of biologically relevant media (saliva, blood, urine), lectin concentration, and polymer length, on the performance of lateral flow and flow-through glycoassays is investigated. Poly(hydroxyethyl acrylamide) (PHEA) polymers of varying chain lengths were functionalised with galactosamine to produce glycopolymers. These were subsequently bound to gold nanoparticles. In both cases, lateral flow and flow-through, target lectins were successfully detected in a range of concentrations of biologically relevant media (saliva, blood, urine). Each system was tested using soybean agglutinin (SBA) as the target protein, a lectin with known selectivity for galactose derivatives, and bovine serum albumin (BSA) as an off-target control protein. A concentration range of 0.1 mg mL^-1 to 0.5 mg mL^-1 was explored for SBA in flow-through, and 0.1 mg mL^-1 in lateral flow. Bovine serum albumin (BSA) was used as the control throughout the study at a concentration of 0.5 mg mL^-1. The ability to modify assay performance through chain length demonstrates the inherent versatility, and more importantly tuneability, of glycopolymer based lateral flow devices. This highlights the robustness of the system in biologically relevant media and further emphasises the potential of lateral flow glycoassays (LFGAs) as adaptable, polymer-centered diagnostic platforms for improved point-of-care applications.