Selective Heavy Atom Effect Forming Photosensitizing Hot Spots in Double-Stranded DNA Matrix

Abstract

Triplet exciton formation is essential for photosensitization-based photochemistry and photobiology. The heavy atom effect (HAE), in the form of either external or internal mode, is a basic mechanism for increasing the triplet exciton yield of photosensitizers. Herein, we report a new HAE mode by noncovalent cohosting of heavy atoms and photosensitizers in a double-stranded DNA (dsDNA) matrix. With dsDNA bearing several thymine (T) or cytosine (C) mismatches, heavy atoms (e.g., Hg2+ or Ag+) and dsDNA-staining dyes (photosensitizers) were spatially adjoined in close proximity, thus resulting in enhanced phosphorescence and 1O2 generation from the photosensitizers. The dsDNA-hosted HAE provides highly selective recognition for the heavy atoms, which is not applicable in either the external or the internal mode. Considering the simpleness and efficiency of the spatially adjoined HAE, as well as the functionality of DNA, the proposed HAE mode is appealing for various singlet oxygen- and phosphorescence-related applications.

Selective Heavy Atom Effect-Promoted Photosensitization Colorimetric Detection of Ag+ in Silver Ore Samples

“…Upon titration of hairpin DNA-EB with Ag + , both the fluorescence intensity and lifetime of EB experienced an initial enhancement and then quenching (Figure B and Figure S4). Such phenomenon is different from the case of normal dsDNA (no fluorescence quenching), , but in fact very similar to the previous case of Hg 2+ -selective HAE . Control investigations indicated that without the hairpin DNA, Ag + caused no significant perturbation to the EB fluorescence (Figure S5).…”

“…As indicated in our previous studies, − here TMB oxidation could be ascribed to 1 O 2 generated from the photosensitizers (nucleic acid dyes) after binding with dsDNA (Figure S3). Besides, the difference in photosensitizer performance may be ascribed to the different binding modes of dyes with dsDNA as well as the size of the dyes, which resulted in varied distances between the photosensitizer and heavy atom (Ag + ) and thus different activation stages for the photosensitizer. For Ru­(bpy) 3 2+ , since it is already efficient in photosensitized 1 O 2 generation, the activation by Ag + may be minimal for such a photosensitizer.…”

“…Herein, a simple and sensitive photosensitization colorimetric assay was developed for facile screening of Ag + in ore samples. Previously, a selective heavy atom effect (HAE) mode was identified by spatially adjoining heavy atoms and dsDNA-staining dyes in a dsDNA matrix, resulting in boosted 1 O 2 generation from the photosensitizers. Coupling with photochemical oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) with the photosensitized generation of singlet oxygen, − highly sensitive colorimetric sensing of the heavy atoms (exemplified with Hg 2+ ) was achieved .…”

Universal “Three-in-One” Matrix to Maximize Reactive Oxygen Species Generation from Food and Drug Administration-Approved Photosensitizers for Photodynamic Inactivation of Biofilms

“…To prove the heavy atom and paramagnetic effects of the matrix, Ce 6@CNs with different Ln 3+ were prepared, including Y 3+ ( Z = 39, 4d 0 , diamagnetic), Gd 3+ ( Z = 64, 4f 7 , paramagnetic), and Lu 3+ ( Z = 71, 4f 14 , diamagnetic) (Figure a). Compared with the Y 3+ CNs (lower atomic number), Gd 3+ CNs exhibited a shorter fluorescence lifetime (Figure b) and stronger 1 O 2 boosting (Figure c), confirming the HAE of Gd 3+ in the matrix. , Besides, although the atomic number of Lu 3+ is larger than that of Gd 3+ , the fluorescence lifetime of Gd 3+ CNs was still lower than that of Lu 3+ CNs (Figure b), while 1 O 2 generation was higher (Figure c), thereby highlighting the potential role of the paramagnetic effect of Gd 3+ …”

“…Compared with the Y 3+ CNs (lower atomic number), Gd 3+ CNs exhibited a shorter fluorescence lifetime (Figure 2b) and stronger 1 O 2 boosting (Figure 2c), confirming the HAE of Gd 3+ in the matrix. 36,37 Besides, although the atomic number of Lu 3+ is larger than that of Gd 3+ , the fluorescence lifetime of Gd 3+ CNs was still lower than that of Lu 3+ CNs (Figure 2b), while 1 O 2 generation was higher (Figure 2c), thereby highlighting the potential role of the paramagnetic effect of Gd 3+ . 16 To better probe the inhibition of non-radiative transitions by the matrix, ThT, a famous molecular motor (with twisted intramolecular charge transfer, Figure 3a) 38 was studied here.…”