Sensitive detection of microRNA-21 in cancer cells and human serum with Au@Si nanocomposite and lateral flow assay.

We report a highly sensitive approach for detecting microRNA-21 (miR-21) in cancer cells and human serum by using Au@Si nanocomposite labeled lateral flow assay. The Au@Si nanocomposite was prepared by coating numerous 3–5 nm gold nanoparticles (GNP) on a silica nanoparticle (SiNP) with a diameter of 150 nm and used as colored label on the lateral flow assay for signal amplification. TEM results show there are around 1000 GNPs coated on the SiNP surface. The principle of miR-21 detection is based on on-strip DNA-microRNA hybridization reactions to form DNA-miR-21-DNA-Au@Si complexes, which are captured on the test zone of the lateral flow test strip and produce a visible red band. A thiol-modified detecting DNA probe (Det-DNA) and a biotin-modified capturing DNA probe (Cap-DNA), which are complementary to miR-21, were used to prepare the lateral flow test strips. After systematic optimization, the method can detect a minimum concentration of 1.0 pM miR-21, which is 60 times lower than that of the GNP-based lateral flow assay (Gao et al. Biosens & Bioelectro, 2014, 54, 578–584). The method was applied to detect miR-21 in cancer cells and spiked human serum with satisfactory results. Gold nanoparticles coated silica nanosphere as colored label for sensitive lateral flow microRNA-21 assay. Image 1 • Gold@Silica nanocomposite was prepared by loading around one thousand 3–5 nm gold nanoparticles on a silica nanosphere with a diameter of 150 nm. • Lateral flow microRNA-21 assay was developed by using the gold@Silica nanocomposite as colored tag for signal amplification. • A minimum concentration of 1.0 pM microRNA-21 can be detected visually within 20 min. • The detection limit is 60 folds lower than that of gold nanoparticle based lateral flow microRNA assay. • The assay was applied to detect microRNA-21 in cancer cells and human serum with satisfied results. [ABSTRACT FROM AUTHOR]