Double-stranded DNA matrix for photosensitization switching

Photosensitization, originated from the activation of triplet states, is the basis of many photodynamic applications, but often competes with a series of nonradiative processes. Herein, we communicate a new function of double-stranded DNA (dsDNA) for label-free photosensitization switching. Up to ∼70-fold singlet oxygen generation boosting was observed for SYBR Green I (SG) upon binding with dsDNA. Detailed photophysical and theoretical studies have revealed the role of dsDNA as a matrix, which could efficiently suppress the nonradiative transitions of SG. Such photosensitization modulation is universal for a series of dsDNA-binding photo-sensitizers, including both base intercalators and minor groove binders. In conjunction with photochemical oxidation of chromogenic substrates, a simple and low-cost photosensitization-based colorimetric detection protocol has been developed, with sensitivity comparable to that of fluorescence detection. Through loop-mediated isothermal amplification (LAMP), colorimetric detection of hepatitis B virus (HBV) was achieved with a limit of detection (LOD) down to 1 aM, which is comparable with that of the standard quantitative polymerase chain reaction (PCR). To facilitate point-of-care testing, a simple and low-cost paper strip has been developed for distance-based detection of LAMP amplicons with a LOD of 100 aM for HBV DNA.