Dual-Responsive Turn-On T1 Imaging-Guided Mild Photothermia for Precise Apoptotic Cancer Therapy.

Apoptosis has gained increasing attention in cancer therapy as an intrinsic signaling pathway, which leads to minimal leakage of waste products from a dying cell to neighboring normal cells. Among various stimuli to trigger apoptosis, mild hyperthermia is attractive but confronts limitations of non-specific heating and acquired resistance from elevated expression of heat shock proteins. Here, a dual-stimulation activated turn-on T1 imaging-based nanoparticulate system (DAS) is developed for mild photothermia (≈43 °C)-mediated precise apoptotic cancer therapy. In the DAS, a superparamagnetic quencher (ferroferric oxide nanoparticles, Fe3 O4 NPs) and a paramagnetic enhancer (Gd-DOTA complexes) are connected via the N6-methyladenine (m6 A)-caged, Zn2+ -dependent DNAzyme molecular device. The substrate strand of the DNAzyme contains one segment of Gd-DOTA complex-labeled sequence and another one of HSP70 antisense oligonucleotide. When the DAS is taken up by cancer cells, overexpressed fat mass and obesity-associated protein (FTO) specifically demethylates the m6 A group, thereby activating DNAzymes to cleave the substrate strand and simultaneously releasing Gd-DOTA complex-labeled oligonucleotides. The restored T1 signal from the liberated Gd-DOTA complexes lights up the tumor to guide the location and time of deploying 808 nm laser irradiation. Afterward, locally generated mild photothermia works in concert with HSP70 antisense oligonucleotides to promote apoptosis of tumor cells. This highly integrated design provides an alternative strategy for mild hyperthermia-mediated precise apoptotic cancer therapy.

A Telomerase-Activated Magnetic Resonance Imaging Probe for Consecutively Monitoring Tumor Growth Kinetics and In Situ Screening Inhibitors.

Telomerase has long been considered as a biomarker for cancer diagnosis and a therapeutic target for drug discovery. Detecting telomerase activity in vivo could provide more direct information of tumor progression and response to drug treatment, which, however, is hampered by the lack of an effective probe that can generate an output signal without a tissue penetration depth limit. In this study, using the principle of distance-dependent magnetic resonance tuning, we constructed a telomerase-activated magnetic resonance imaging probe (TAMP) by connecting superparamagnetic ferroferric oxide nanoparticles (SPFONs) and paramagnetic Gd-DOTA (Gd(III) 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) complexes via telomerase-responsive DNA motifs. Upon telomerase-catalyzed extension of the primer in TAMP, Gd-DOTA-conjugated oligonucleotides can be liberated from the surface of SPFONs through a DNA strand displacement reaction, restoring the T1 signal of the Gd-DOTA for a direct readout of the telomerase activity. Here we show that, by tracking telomerase activity, this probe provides consistent monitoring of tumor growth kinetics during progression and in response to drug treatment and enables in situ screening of telomerase inhibitors in whole-animal models. This study provides an alternative toolkit for cancer diagnosis, treatment response assessment, and anticancer drug screening.

Accelerated DNA tetrahedron-based molecular beacon for efficient microRNA imaging in living cells.

Herein, we develop an accelerated DNA tetrahedron based molecular beacon for efficient detection and imaging of miRNA in living cells. Our study provides an improved strategy for fluorescence amplified RNA imaging in early clinical diagnosis.

Light-Controlled, Toehold-Mediated Logic Circuit for Assembly of DNA Tiles.

Inspired by cytoskeletal structures that respond sensitively to environmental changes and chemical inputs, we report a strategy to trigger and finely control the assembly of stimulus-responsive DNA nanostructures with light under isothermal conditions. The strategy is achieved via integrating an upstream light-controlled, toehold-mediated DNA strand displacement circuit with a downstream DNA tile self-assembly process. By rationally designing an upstream DNA strand module, we further transform the upstream DNA strand displacement circuit to an "AND gate" circuit to control the assembly of DNA nanostructures. This example represents the demonstration of the spatial and temporal assembly of DNA nanostructures using a noninvasive chemical input. Such a light-controlled DNA logic circuit not only adds a new element to the tool box of DNA nanotechnology but also inspires us to assemble complex and responsive nanostructures.

Active Self-Assembly of Train-Shaped DNA Nanostructures via Catalytic Hairpin Assembly Reactions.

Biomolecular self-assembly is a powerful approach for fabricating supramolecular architectures. Over the past decade, a myriad of biomolecular assemblies, such as self-assembly proteins, lipids, and DNA nanostructures, have been used in a wide range of applications, from nano-optics to nanoelectronics and drug delivery. The method of controlling when and where the self-assembly starts is essential for assembly dynamics and functionalization. Here, train-shaped DNA nanostructures are actively self-assembled using DNA tiles as artificial "carriages," hairpin structures as "couplers," and initiators of catalytic hairpin assembly (CHA) reactions as "wrenches." The initiator wrench can selectively open the hairpin couplers to couple the DNA tile carriages with high product yield. As such, DNA nanotrains are actively prepared with two, three, four, or more carriages. Furthermore, by flexibly modifying the carriages with "biotin seats" (biotin-modified DNA tiles), streptavidin "passengers" are precisely arranged in corresponding seats. The applications of the CHA-triggered self-assembly mechanism are also extended for assembling the large DNA origami dimer. With the creation of 1D architectures established, it is thought that this CHA-triggered self-assembly mechanism may provide a new element of control for complex autonomous assemblies from a variety of starting materials with specific sites and times.

Spatial Regulation of Biomolecular Interactions with a Switchable Trident-Shaped DNA Nanoactuator.

DNA nanostructures with controllable motions and functions have been used as flexible scaffolds to precisely and spatially organize molecular reactions at the nanoscale. The construction of dynamic DNA nanostructures with site-specifically incorporated functional elements is a critical step toward building nanomachines. Artificial self-assembled DNA nanostructures have also been developed to mimic key biological processes like various small biomolecule- and protein-based functional biochemistry pathways. Here, we report a self-assembled dynamic trident-shaped DNA (TS DNA) nanoactuator, in which biomolecules can be tethered to the three "arms" of the TS DNA nanoactuator. The TS DNA nanoactuator is implemented as the mechanical scaffold for the reconfiguration of fluorescent/quenching molecules and the assembly of gold nanoparticles, which exhibit controlled spatial separation. Furthermore, two enzymes (glucose oxidase and horseradish peroxidase) are attached to the two outer arms of the TS DNA nanoactuator, which show an enhanced cascade reaction efficiency compared to free enzymes. The efficiency of the two-enzyme cascade reaction can be spatially regulated by switching the TS DNA nanoactuator between opened, semiopened, and closed states through adding the "thermodynamic drivers" (fuels or antifuels). This is the first report to precisely modulate the relative position of coupled enzyme with multiple states and only based on one dynamic DNA scaffold. The present TS DNA nanoactuator with multistage conformational transition functionality could be applied as a potential platform to precisely and dynamically control the multienzyme pathways and would broaden the scope of DNA nanostructures in single-molecule biology applications.