No 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.

A novel AB2 type amphiphilic miktoarm-star copolymer of alpha-methoxy-poly(ethylene glycol)-b-poly(gamma-benzyl-L-glutamate)2 was synthesized by ring-opening polymerization of gamma-benzyl-L-glutamate N-carboxyanhydride. The polymerization was initiated by the terminal amino groups of alpha-methoxy-omega-N,N-bis(aminoethyl) poly(ethylene glycol). Structural properties of the star copolymer were confirmed by IR and 1H NMR spectra. Polymeric micelles were prepared in aqueous solution by dialysis method. Spherical core/shell structure of the micelles was confirmed by transmission electron microscopy and 1H NMR spectra. Dynamic light scattering results indicated that the sizes of the micelles were mostly in the range of 20-50 nm with a narrow size distribution. With the molecular weight of each poly(gamma-benzyl-L-glutamate) block increasing from 2.0 kDa to 13.2 kDa, Tamoxifen loading content increased from 7.34% to 20.30%, corresponding to the increase of Tamoxifen entrapment efficiency from 4.11% to 29.13% and Tamoxifen solubility in water from 11.75 microg/ml to 82.23 microg/ml. In vitro release study of Tamoxifen-loaded micelles at 37 degrees C demonstrated that Tamoxifen-release from micelles at pH 5.0 was much faster than that at pH 7.4. These polymeric micelles are expected to be utilized as promising new drug carriers.

Monitoring hypoxia-related changes in subcellular organelles would provide deeper insights into hypoxia-related metabolic pathways, further helping us to recognize various diseases on subcellular level. However, there is still a lack of real-time, in situ, and controllable means for biosensing in subcellular organelles under hypoxic conditions. Herein, we report a reductase and light programmatical gated nanodevice via integrating light-responsive DNA probes into a hypoxia-responsive metal–organic framework for spatiotemporally controlled imaging of biomolecules in subcellular organelles under hypoxic conditions. A small-molecule-decorated strategy was applied to endow the nanodevice with the ability to target subcellular organelles. Dynamic changes of mitochondrial adenosine triphosphate under hypoxic conditions were chosen as a model physiological process. The assay was validated in living cells and tumor tissue slices obtained from mice models. Due to the highly integrated, easily accessible, and available for living cells and tissues, we envision that the concept and methodology can be further extended to monitor biomolecules in other subcellular organelles under hypoxic conditions with a spatiotemporal controllable approach.