Coating a DNA self-assembled monolayer with a metal organic framework-based exoskeleton for improved sensing performance.

The formation of DNA self-assembled monolayers (SAMs) is one of the most popular ways to attach DNA molecules onto Au surfaces and is extensively used in many fields, especially in biosensing. However, the relatively poor stability of DNA SAMs (e.g., after long-term storage or under harsh environmental conditions) greatly limits their use in real applications. Herein, a new strategy is reported to protect the DNA SAMs by using a metal organic framework (MOF)-based exoskeleton. Taking electrochemical DNA (E-DNA) sensors as an example, we have systematically studied the stability of various DNA probes from the simple single-stranded DNA to a complex DNA nanostructure on the Au electrode surface. We have found that different DNA probes lead to various MOF profiles and the formed MOFs can be conveniently removed by simple acidic water rinse. Thanks to the exoskeleton, the stability of DNA SAMs is significantly enhanced and the DNA probes can be insulated from heat, nuclease, and varying ionic strengths, greatly extending the shelf-life of E-DNA sensors and indirectly improving their sensing performance. More importantly, the secondary structures of DNA probes can also be well preserved. The longstanding stability is of particular importance to biosensors; thus they can be facilely handled, transported, and stored in a resource-limited setting without compromising the analytical performance of biosensors.