Gold-platinum nanoflowers as colored and catalytic labels for ultrasensitive lateral flow MicroRNA-21 assay

MicroRNAs (miRNAs) have grown up to be an important potential biomarker for clinical examination and disease diagnosis. The rapid, sensitive, selective and low-cost detection of miRNA is significant for the diagnosis and treatment of diseases. In this work, gold-platinum nanoflowers (AuPt NFs) were first used as colored and catalytic labels for ultrasensitive lateral flow miRNA-21 assay. AuPt NFs with diameter of 35 nm were gotten ready by loading Pt nanowires on the outer layer of gold nanoparticles (AuNPs). A single-strand DNA probe, which is complementary with target miRNA-21, was conjugated with AuPt NFs. AuPt NFs were used as both colored and catalytic labels in the lateral flow assay for qualitative and quantitative miRNA-21. The captured AuPt NFs in the test line presented a black band (colored label) and the addition of chromogenic substrate generated numerous red catalytic products on the test line (catalytic label). The color signal of the test line was thus enhanced significantly. Benefiting from the dual functionalities of AuPt NFs, we could detect the lowest concentration of 0.3 pM miRNA-21, which is 200 times lower than that obtained with a traditional AuNP-based lateral flow miRNA method. The method was used for the detection miRNA-21 directly in cell lysates with satisfactory results. Therefore, the AuPt NFs emerges great development prospects of ultrasensitive lateral flow nucleic acid biosensors for on-site testing and biomedical diagnosis.