Biocomputing label-free security system based on homogenous ligation chain reaction-induced dramatic change in...

The development of smart platform with accurate, inexpensive and reliable detection of single-nucleotide polymorphisms (SNPs) has long been concerned in the fields of medical diagnosis and basic research. Here, we present a ligation chain reaction (LCR)-based sensing system for the cost-effective screening of SNPs by simply conducting DNA melting analysis. No chemical modification is required and the signaling operation is accomplished in homogeneous solution, circumventing the complex modification process and possibly compromised enzymatic activity associated with heterogeneous materials, such as quantum dot (QD) and gold nanoparticle (GNP). Due to the enzymatic catalysis and high fidelity of ligase, the system is capable of executing signal amplification, providing a high sensitivity and selectivity. KRAS gene is easily recognized and the site-specific mutation of guanine (G) to adenine (A), thymine (T) or cytosine (C) is accurately screened. Moreover, the excellent reliability was demonstrated by blind test and recovery test. LCR-based signaling mechanism was further used to develop the biocomputing security system, and two logic gates consisting of four single-stranded DNAs (ssDNAs) offer a double insurance to protect the information against illegal invasion, guaranteeing the reliability of output information. Once in the absence of one essential factor, the security system was always locked regardless of target key, serving as a novel strategy to ensure the safety of output information at molecular level. As a proof-of-concept scheme, this contribution introduces new insight into the development of DNA security systems and the exploitation of powerful signal transduction strategy suitable for rapid and convenient disease diagnosis.