Target-induced self-assembly of DNA nanomachine on magnetic particle for multi-amplified biosensing of nucleic acid, protein, and cancer cell.

A biosensing system is established for the multi-amplified detection of DNA or specific substrates of aptamers under isothermal conditions, which combines nicked rolling circle amplification (N-RCA) and beacon assisted amplification (BAA) with sensitive colorimetric technique by using DNAzymes as reporter units. According to the configuration, the analysis of DNA is accomplished by recognizing the target to capture nucleic acid-functionalized magnetic particles, followed by the self-assembly of the other two nucleic acids into multicomponent DNA supramolecular structure on magnetic particles. After magnetic separation, the circularization with ligase and the fragmentation with polymerase activate N-RCA and BAA in the presence of polymerase, dNTPs, and the nicking endonuclease, successively producing horseradish peroxidase (HRP)-mimicking DNAzymes that act as colorimetric reporter to catalyze the oxidation of ABTS(2-) by H2O2 in the presence of hemin. Under the optimized conditions, we obtain a wide dynamic range for DNA analysis over 6 orders of magnitude from 1.0 × 10(-14) to 1.0 × 10(-9)M with a low limit of detection of 6.8 × 10(-15)M. In the absence of a target, neither self-assembly of nucleic acids nor amplification process can be initiated, indicating an excellent selectivity of the proposed strategy. Similarly, an analogous system is activated by cancer cells or lysozyme through cooperative self-assembly of nucleic acids on magnetic particles in the presence of respective substrates of aptamers to synthesize HRP-mimicking DNAzymes that give the readout signal for the recognition events, achieving LODs of 81 Ramos cells and 7.2 × 10(-15)M lysozyme, respectively.