Multifunctional Programmable DNA Nanotrain for Activatable Hypoxia Imaging and Mitochondrion-Targeted Enhanced Photodynamic Therapy

Abstract

Programmable DNA-based nanostructures (e.g., nanotrains, nanoflowers, and DNA dendrimers) provide new approaches for safe and effective biological imaging and tumor therapy. However, few studies have reported that DNA-based nanostructures respond to the hypoxic microenvironment for activatable imaging and organelle-targeted tumor therapy. Herein, we innovatively report an azoreductase-responsive, mitochondrion-targeted multifunctional programmable DNA nanotrain for activatable hypoxia imaging and enhanced efficacy of photodynamic therapy (PDT). Cyanine structural dye (Cy3) and black hole quencher 2 (BHQ2), which were employed as a fluorescent mitochondrion-targeted molecule and azoreductase-responsive element, respectively, covalently attached to the DNA hairpin monomers. The extended guanine (G)-rich sequence at the end of the DNA hairpin monomer served as a nanocarrier for the photosensitizer 5,10,15,20-tetrakis­(4-N-methylpyridiniumyl) porphyrin (TMPyP4). Upon initiation between the DNA hairpin monomer and initiation probe, the fluorescence of Cy3 and the singlet oxygen (1O2) generation of TMPyP4 in the programmable nanotrain were effectively quenched by BHQ2 through the fluorescence resonance energy transfer (FRET) process. Once the programmable nanotrain entered cancer cells, the azo bond in BHQ2 will be reduced to amino groups by the high expression of azoreductase under hypoxia conditions; then, the fluorescence of Cy3 and the 1O2 generation of TMPyP4 will significantly be restored. Furthermore, due to the mitochondrion-targeting characteristic endowed by Cy3, the TMPyP4-loaded nanotrain would accumulate in the mitochondria of cancer cells and then demonstrate enhanced PDT efficacy under light irradiation. We expect that this programmable DNA nanotrain-based multifunctional nanoplatform could be effectively used for activatable imaging and high performance of PDT in hypoxia-related biomedical field.

Supramolecular Assembly Based on Sulfato-β-cyclodextrin for Hypoxia Cell Imaging

“…It is very important to explore the fluorescence quenching mechanism in the noncovalent hypoxia imaging system. Currently, most of the hypoxia imaging probes are covalent systems and are based on the fluorescence quenching mechanism of ultrafast photoinduced isomerization of azo groups or Förster resonance energy transfer (FRET). ,,, Due to the noncovalent interaction other than covalent conjugation between SCD/ 1 and Rho123, it is impossible that the fluorescence quenching of Rho123 was caused by the fast conformation change of azobenzene. , As shown in Figure S6, there was no appreciable overlap between the absorption spectrum of SCD/ 1 and the fluorescence emission spectrum of Rho123, excluding the FRET quenching mechanism. We speculated that the fluorescence quenching of Rho123 may be caused by 1 through the photoinduced electron transfer (PET) mechanism .…”

Engineering a dual-responsive, exosome-surface anchored DNA nanosensor for microenvironment monitoring in vivo

“…Then, NADPH and rat liver microsomes (the specific composition and description of these rat liver microsomes are provided in Table S3, ESI †) containing AzoR were employed to mimic hypoxia conditions in vitro. 13,15 Fourier-transform infrared (FTIR) spectroscopy analysis confirmed that the NQN of BHQ2 was successfully reduced to amino groups through reduction reaction under hypoxic conditions (Fig. S5, ESI †).…”

“…When the content of O 2 in the microenvironment drops, highly-expressed AzoR gradually reduces the azo bond in BHQ2 to amino groups, followed by the diminished quenching effect of BHQ2. 15 In this case, the quenched fluorescence of Cy5 would be restored, which is suitable for monitoring O 2 levels. In the case of a drop in pH, the I-motif fragment in the nanospring would fold into a quadruple-helix structure and thus cause the nanospring to change from the relaxation to contraction state.…”

A Photosensitized Singlet Oxygen (1O2) Toolbox for Bio-Organic Applications: Tailoring 1O2 Generation for DNA and Protein Labelling, Targeting and Biosensing

“…Due to the presence of the quencher, the cyanine fluorescence and the 1 O 2 production of the PS are limited. However, when the nanoconstruct is internalized, the aza-reductase expressed by hypoxic cells cleaves off the quencher, thus restoring the properties of the dyes, enabling a selective PDT approach [ 308 ].…”