Heating Drives DNA to Hydrophobic Regions While Freezing Drives DNA to Hydrophilic Regions of Graphene Oxide for Highly Robust Biosensors

Bioconjugation is often performed at ambient temperatures, while freezing and heating may allow different interfacial and inter-/intramolecular interactions. Herein, we report that both freezing and heating allowed more stable DNA adsorption on graphene oxide. Freezing stretched DNA oligonucleotides and drove them to the more oxidized hydrophilic regions on graphene oxide. Heating enhanced hydrophobic interactions and drove DNA to the carbon-rich regions. With a mixture of low-affinity T-15 DNA and high-affinity C-15 DNA, heating drove the high-affinity DNA to high-affinity regions, achieving ultrahigh adsorption stability, leaving the low-affinity DNA to the remaining low-affinity regions. Using a diblock DNA containing a high-affinity polycytosine block and heating, the nanoflare type of sensor achieved highly sensitive DNA detection in serum with 100-fold improved signal to background ratio, solving a longstanding biosensing problem for robust detection using physisorbed DNA probes.