Target-templated molecular nano-machine for auto-catalytic recycling amplification detection of low-abundant antibody in human serum

Abstract

The development of convenient and sensitive sensing method capable of monitoring low-abundant antibody is appealing for pathogens diagnosis and vaccine immunotherapy evaluation. With regards to this, we herein constructed a simple molecular nano-machine for ultrasensitive monitoring of Anti-Digoxigenin (Anti-Dig) antibody via a target-initiated auto-cycling proximity recording (APR) amplification. One target bivalent Anti-Dig antibody can simultaneously recognize two Dig-labeled catalytic hairpin DNAs (Dig-HP1) and bring them into close distance to form the proximity catalytic probe pairs. Subsequently, the 3′-overhang of the FAM/Dabycl labeled hairpin signal probes hybridize on the exposure primer binding domain at Dig-HP1 template and initiate the APR reaction to cross open and extend Dig-HP1 to generate many elongated DNA duplexes with the help of Bst DNA polymerase. These DNA duplexes make the fluorophore and quencher away from each other and thereby produce dramatically enhanced fluorescence signal for sensitive detection of target Anti-Dig antibody down to 0.18 nM. Moreover, this method can selectively monitor Anti-Dig antibody against other interference proteins, and also be extended to detect Anti-Dig antibody in serum samples, confirming its potential for ultrasensitive detection of low-abundant antibodies for early disease therapy and vaccine evaluation.