Rapid non-laboratory screening of plants for pathogenic viruses crucially influences crop yields in modern agricultural technologies. The aim of this study was to develop a highly-sensitive lateral flow immunoassay (LFIA) for rapid detection of potato leafroll virus (PLRV), an infectious agent of one of the most widespread potato diseases. The proposed LFIA combines the formation of sandwich immune complexes with gold nanoparticles (GNP) as labels and silver enhancement. The enhancement stage was realized using mixture of silver lactate and hydroquinone and subsequent addition of chloride-containing buffer to stop silver reduction. LFIA with silver enhancement was 15 times more sensitive (detection limit 0.2 ng/mL; 15 min) compared with conventional LFIA (detection limit 3 ng/mL; 10 min). The enhanced LFIA detected PLRV in leaves’ extracts of infected potato in dilutions higher than enzyme-linked immunosorbent assay.

Lateral flow immunoassay (LFIA) is a convenient tool for rapid field-based control of various bacterial targets. However, for many applications, the detection limits obtained by LFIA are not sufficient. In this paper, we propose enlarging gold nanoparticles’ (GNPs) size to develop a sensitive lateral flow immunoassay to detect Ralstonia solanacearum. This bacterium is a quarantine organism that causes potato brown rot. We fabricated lateral flow test strips using gold nanoparticles (17.4 ± 1.0 nm) as a label and their conjugates with antibodies specific to R. solanacearum. We proposed a signal enhancement in the test strips’ test zone due to the tetrachloroauric (III) anion reduction on the GNP surface, and the increase in size of the gold nanoparticles on the test strips was approximately up to 100 nm, as confirmed by scanning electron microscopy. Overall, the gold enhancement approach decreased the detection limit of R. solanacearum by 33 times, to as low as 3 × 10⁴ cells∙mL^–1 in the potato tuber extract. The achieved detection limit allows the diagnosis of latent infection in potato tubers. The developed approach based on gold enhancement does not complicate analyses and requires only 3 min. The developed assay together with the sample preparation and gold enlargement requires 15 min. Thus, the developed approach is promising for the development of lateral flow test strips and their subsequent introduction into diagnostic practice.