The analysis of proteins and small molecules based on sterically tunable nucleic acid hyperbranched rolling circle amplification

In this work, we succeeded in establishing a new method for proteins and small molecules analysis based on the small molecule-linked DNA and nucleic acid hyperbranched rolling circle amplification (HRCA). Small molecule linked DNA by chemical modification was used as a flexible tool to study protein-small molecule interactions. The HRCA reaction which would produce signal amplification was regulated by the steric effect depending on whether the target proteins were present. In the implement of the proposed strategy, streptavidin (SA)-biotin and anti-digoxin antibody (anti-Dig)-digoxin were chosen as two model partners. Experimental results showed that the quantitative detection of SA and anti-Dig was realized both with nanomolar detection limits. The small molecules biotin and digoxin were also detected at nanomolar levels in a wide range of 1 nM~100 µM and 1 nM~10 µM, respectively. Meanwhile, the results indicated that the method had a favorable specificity in analyzing proteins or small molecules. Thus, it may be expected to quantitatively analyze some protein markers and small molecular drugs in complex biological samples.