Spherical Nucleic Acid Enzyme (SNAzyme) Boosted Chemiluminescence miRNA Imaging Using a Smartphone.

As acute myocardial infarction (AMI) has now become a severe death threat to humans and may abruptly occur at home or outdoors where sophisticated equipment is not available, it is of great importance to develop facile methodologies for the point-of-care (POC) diagnosis of AMI. Toward this goal, here we build a sensing platform for chemiluminescence (CL) microRNA (miRNA) imaging with a smartphone as the portable detector, and for the first time we achieve visualization of AMI-related miRNAs in real patients' serum. We first construct a spherical nucleic acid enzyme (termed SNAzyme) derived from a dense layer of G-quadruplex (G4) DNAzyme formed on the gold nanoparticle core, which displays ∼100-fold and higher catalytic activity and improved resistance to nuclease degradation in a real blood sample as compared to those of the G4 DNAzyme itself. These unique features endow the SNAzyme-boosted CL platform with superior imaging performance for analyzing an AMI-related miRNA, miRNA-133a. This miRNA is employed to trigger the target-catalyzed hairpin assembly to produce a sticky dsDNA linker that captures the SNAzyme nanolabel onto the substrate. In this way, miRNA-133a is successfully detected, with a limit of detection of 0.3 pM (S/N = 3) and a high selectivity over other miRNA analogs in patients' blood. Given its unique features in physiological environments, our SNAzyme-boosted imaging platform holds great promise for use in the POC diagnosis of AMI.