LAUSR

Singlet oxygen, generated from type-II photosensitization, becomes increasing popular in bioassay developments in recent years. However, the transient nature of singlet oxygen in water (lifetime shorter than 4 μs) as well as its high activity make it easy to be inactivated by the solvent molecules and other co-existing species, thus deteriorating the analytical sensitivity. Here we proposed the use of a simple redox mediator for storing the energy of the transient singlet oxygen. To demonstrate such idea, singlet oxygen generated from photosensitization of the double strand DNA-SYBR Green I (dsDNA-SG) complex was explored as the redox donor, which can be modulated through formation and de-formation of the dsDNA structure. After screening of a series of redox mediators with luminol CL reaction as the probe, ferrocyanide (K4Fe(CN)6) was found to be the most efficient, resulting in ~30 fold intensified luminol CL. By storing the oxidative capacity of singlet oxygen with ferrocyanide, the dsDNA-SG complex was evolved in to a photosensitization-mediated chemiluminescence (PMCL) biosensing platform for DNA detection. Such PMCL sensing platform allow label- and amplification-free detection of pM-scale DNA with a limit of detection (LOD) of 1.5 pM (0.45 fmol in absolute). The excellent sensitivity of PMCL sensing confirmed that such facile storage approach of oxidative capacity would be appealing for singlet oxygen-involved biosensing.