Remote-Controlled Release of DNA in Living Cells via Simultaneous Light and Host–Guest Mediations

Azo Reductase Activated Magnetic Resonance Tuning Probe with "Switch-On" Property for Specific and Sensitive Tumor Imaging in Vivo

Cancer remains a threat to human health. However, if tumors can be detected in the early stage, then the effectiveness of cancer treatment could be significantly improved. Therefore, it is worthwhile to develop more sensitive and accurate cancer diagnostic methods. Herein, we demonstrated an azo reductase (AzoR)-activated magnetic resonance tuning (MRET) probe with a "switch-on" property for specific and sensitive tumor imaging in vivo. Specifically, Gd-labeled DNA1 (DNA1-Gd) and cyclodextrin-coated magnetic nanoparticles (MNP-CD) were employed as enhancer and quencher of MRET, respectively, while DNA2, an azobenzene (Azo) group-modified aptamer (AS1411), served as a linker between enhancer and quencher to construct the MRET probe of MNP@DNA(1-2)-Gd. In tumor tissues with high-level AzoR, the T1-weighted magnetic resonance signal of the MRET probe could be restored by intelligently regulating the switch from "OFF" to "ON" after activation with AzoR, thus accurately indicating the location of the tumor accurately. Moreover, the tumor with a 4 times smaller size than that of the normal tumor model could be imaged based on the proposed MRET probe. The as-proposed MRET-based magnetic resonance imaging strategy not only achieves tumor imaging accurately but also shows promise for early diagnosis of tumors, which might improve patients' survival rates and provide an opportunity for image-guided biomedical applications in the future.

Two-Photon Light Trigger siRNA Transfection of Cancer Cells Using Non-Toxic Porous Silicon Nanoparticles

The concept of using two-photon excitation in the NIR for the spatiotemporal control of biological processes holds great promise. However, its use for the delivery of nucleic acids has been very scarcely described and the reported procedures are not optimal as they often involve potentially toxic materials and irradiation conditions. This work prepares a simple system made of biocompatible porous silicon nanoparticles (pSiNP) for the safe siRNA photocontrolled delivery and gene silencing in cells upon two-photon excitation. PSiNP are linked to an azobenzene moiety, which possesses a lysine group (pSiNP@ICPES-azo@Lys) to efficiently complex siRNA. Non-linear excitation of the two-photon absorber system (pSiNP) followed by intermolecular energy transfer (FRET) to trans azobenzene moiety, result in the photoisomerization of the azobenzene from trans to cis and in the destabilization of the azobenzene-siRNA complex, thus inducing the delivery of the cargo siRNA to the cytoplasm of cells. Efficient silencing in MCF-7 expressing stable firefly luciferase with siRNAluc against luciferase is observed. Furthermore, siRNA against inhibitory apoptotic protein (IAP) leads to over 70% of MCF-7 cancer cell death. The developed technique using two-photon light allows a unique high spatiotemporally controlled and safe siRNA delivery in cells in few seconds of irradiation.

Visualization of O2/ATP cross-talk in living cells with a smart fluorescent nanoprobe

Herein, we propose a dual-responsive fluorescent nanoprobe to visualize the cross-talk between O2 and adenosine triphosphate (ATP) in living cells. We hope it will be a helpful tool for the further understanding of cellular metabolism and further facilitating risk warning in the process of adaptation to consistent environmental pressures in premalignant lesions.

Versatile Types of Cyclodextrin-Based Nucleic Acid Delivery Systems

Nowadays, nucleic acid therapy has become a promising way for the treatment of various malignant diseases. Cyclodextrin (CD)-based nucleic acid delivery systems have attracted widespread attention due to the favorable chemical structures and excellent biological properties of CD. Recently, a variety of CD-based nucleic acid delivery systems has been designed according to the different functions of CD for flexible gene therapies. In this review, the construction strategies and biomedical applications of CD-based nucleic acid delivery systems are mainly focused on. The review begins with an introduction to the synthesis and properties of simple CD-grafted polycations. Thereafter, CD-related supramolecular assemblies based on different guest components are discussed in detail. Finally, different CD-based organic/inorganic nanohybrids and their relevant functions are demonstrated. It is hoped that this brief review will motivate the delicate design of CD-based nucleic acid delivery systems for potential clinical applications.

Histidine-Based Reduction-Sensitive Star-Polymer Inclusion Complex as a Potential DNA Carrier: Biophysical Studies Using Time-Resolved Fluorescence as an Important Tool

An ideal DNA carrier is one that is capable of effectively condensing DNA into complexes of optimum size and shape, preventing premature decomplexation in the bloodstream and efficiently releasing the DNA into affected cells. In this context, we have developed a novel β-cyclodextrin (β-CD)-based four-arm star-shaped polymer inclusion complex (IC) with arms made of a poly(l-histidine)-based cationic polymer. The polymer was well characterized by gel permeation chromatography, NMR, and matrix-assisted laser desorption ionization time-of-flight mass spectrometry. We have also investigated its DNA complexation and release properties. Bisadamantane containing a disulfide bond was synthesized that linked two such poly(l-histidine)-containing β-CD units via guest-host interactions to prepare the presented IC. Besides using the conventional steady-state fluorescence spectroscopy, the ability of this IC to condense DNA to form polyplexes and their release behavior have been established by using the time-resolved fluorescence spectroscopy technique. Thiazole orange (TO) was used for the first time as a DNA-intercalating dye in the time-resolved fluorescence spectroscopic study. The superior DNA-condensing ability of the IC as compared to that of the precursor two-arm β-CD and linear poly(l-histidine) of a comparable molecular weight, as confirmed by dynamic light scattering, zeta potential, atomic force microscopy, and gel electrophoresis studies, could be attributed to a higher charge density. The IC-DNA polyplexes were found to be stable in a medium similar to an extracellular fluid but could efficiently release DNA in the presence of 10 mM glutathione, a concentration prevalent in the intracellular fluid of cancer cells. Hence, here, we have successfully demonstrated the synthesis of a novel biocompatible star-shaped IC with the potential to carry and release DNA in cancer cells and also established the feasibility of using the time-resolved fluorescence spectroscopic technique to study the complexation behavior of the polycation and DNA using TO as a DNA-intercalating dye.

NIR Remote-Controlled "Lock-Unlock" Nanosystem for Imaging Potassium Ions in Living Cells

Despite great achievements in sensitive and selective detection of important biomolecules in living cells, it is still challenging to develop smart and controllable sensing nanodevices for cellular studies that can be activated at desired time in target sites. To address this issue, we have constructed a remote-controlled "lock-unlock" nanosystem for visual analysis of endogenous potassium ions (K⁺), which employed a dual-stranded aptamer precursor (DSAP) as recognition molecules, SiO₂ based gold nanoshells (AuNS) as nanocarriers, and near-infrared ray (NIR) as the remotely applied stimulus. With the well-designed and activatable DSAP-AuNS, the deficiencies of traditional aptamer-based sensors have been successfully overcome, and the undesired response during transport has been avoided, especially in complex physiological microenvironments. While triggered by NIR, the increased local temperature of AuNS induced the dehybridiztion of DSAP, realized the "lock-unlock" switch of the DSAP-AuNS nanosystem, activated the binding capability of aptamer, and then monitored intracellular K⁺ via the change of fluorescence signal. This DSAP-AuNS nanosystem not only allows us to visualize endogenous ions in living cells at a desired time but also paves the way for fabricating temporal controllable nanodevices for cellular studies.

DNA-supramolecule conjugates in theranostics

The elegant properties of deoxyribonucleic acid (DNA), such as accurate recognition, programmability and addressability, make it a well-defined and promising material to develop various molecular probes, drug delivery carriers and theranostic systems for cancer diagnosis and therapy. In addition, supramolecular chemistry, also termed "chemistry beyond the molecule", is a promising research field that aims to develop functional chemical systems by bringing discrete molecular components together in a manner that invokes noncovalent intermolecular forces, such as hydrophobic interaction, hydrogen bonding, metal coordination, and shape or size matching. Thus, DNA-supramolecule conjugates (DSCs) combine accurate recognition, programmability and addressability of DNA with the greater toolbox of supramolecular chemistry. This review discusses the applications of DSCs in sensing, protein activity regulation, cell behavior manipulation, and biomedicine.

Design, synthesis, and applications of DNA-macrocyclic host conjugates

With this Feature Article we review, for the first time, the development of DNA-host conjugates-a nascent yet rapidly growing research focus within the ambit of DNA supramolecular chemistry. Synthetic hosts (such as cyclodextrins, cucurbiturils, and calixarenes) are well-suited to be partnered with DNA, since DNA assembly and host-guest binding both thrive in aqueous media, are largely orthogonal, and exhibit controllable and input-responsive properties. The covalent braiding of these two supramolecular synthons thus leads to advanced self-assemblies and nanostructures with exciting function that range from drug delivery agents to input-triggered switches. The latter class of DNA-host conjugates have been demonstrated to precisely control protein activity, and have also been used as modulable catalysts and versatile biosensors.

Bifunctional magnetic nanoparticles for efficient cholesterol detection and elimination via host-guest chemistry in real samples

Cholesterol is an essential compound for maintaining cellular homeostasis and human healthy. Sensitive detection of cholesterol and efficient elimination of excess cholesterol have become the essential manipulations in clinical diagnosis and health management. To date, it is still quite challenging that cholesterol detection and elimination tasks are carried out simultaneously. In this study, bifunctional magnetic nanoparticles (Fe₃O₄@PDA-PBA-CD) are designed and fabricated to overcome this difficulty. Taking advantages of competitive host-guest interaction and magnetic separation, highly efficient, reusable and simultaneous cholesterol detection and elimination can be achieved. The limit of detection is determined to be 4.3 nM, which is comparable or even lower than existing methods. The distinguished performance may attribute to the high loading efficiency and magnetic enrichment of nanoparticles. Besides, this efficient strategy is resistant to interfering substances, thus realizing sensitive cholesterol detection in real sample. Simultaneously, the bifunctional magnetic nanoparticles also have up to 95% cholesterol elimination efficiency, which is higher than previous reported methods. Furthermore, the nanoparticles are turned out to be reusable within 5 times without noticeable loss in cholesterol elimination efficiency. Therefore, the bifunctional magnetic nanoparticles fabricated here could hold great potential for simultaneous cholesterol detection and elimination in practical applications.

Photo-responsive hollow silica nanoparticles for light-triggered genetic and photodynamic synergistic therapy

The development of multifunctional carriers incorporating genetic and photodynamic therapy (PDT) for synergistic antitumor treatment has attracted intensive interests very recently. However, most of the currently reported systems employ passive gene release strategies depending on tumor microenvironment, which are negatively affected by the heterogeneity of cancer cells, thus resulting in limited controllability in therapeutic progress. Herein, a novel photo-responsive hollow silica nanoparticle (HNP)-based gene and photosensitizer (PS) co-delivery nanovehicle is designed for dual-wavelength light-triggered synergistic gene and PDT therapy. The resultant HNP conjugated with PDMAEMA polycation through a 405-nm light-cleavable Cou-linker, namely, HNP-Cou-PD, exhibits excellent gene condensation capacity, good biocompatibility, outstanding PS loading ability, and light-triggered gene release properties. HNP-Cou-PD with Chlorin e6 (Ce6) loaded inside the silica cavity and a plasmid encoding caspase-8 gene (CSP8) attached to the PDMAEMA outside layer (Ce6-HNP-Cou-PD/CSP8) has been proven to possess better antitumor effects under the irradiation of pre-405-nm and post-670-nm light both in vitro and in vivo because of the light-triggered intracellular gene release and reactive oxygen species (ROS) generation. Therefore, HNP-Cou-PD designed as a gene and PS co-delivery carrier might have promising applications in the future to precisely treat various types of cancers.

STATEMENT OF SIGNIFICANCE

Multifunctional carriers incorporating genetic and photodynamic therapy (PDT) have drawn intense attention very recently, ascribing to their enhanced anticancer effects. However, in the present gene and PDT synergistic system, gene release strategies passively relying on tumor microenvironment often result in no or poor controllability compared with PDT (a spatial and temporal therapeutic modal), which may hinder their synergistic efficacy, especially in an on-demand manner. To resolve this problem, we designed a hollow silica nanoparticle-based dual-wavelength light-responsive gene and photosensitizer (PS) co-delivery platform to achieve photo-triggered gene and PDT synergistic therapy. We believe that our work may have extensive application prospects in precise treatment of various cancers and be of interest to the readership.

Recent developments in reversible photoregulation of oligonucleotide structure and function

There is a growing interest in the photoregulation of biological functions, due to the high level of spatiotemporal precision achievable with light. Additionally, light is non-invasive and waste-free. In particular, the photoregulation of oligonucleotide structure and function is a rapidly developing study field with relevance to biological, physical and material sciences. Molecular photoswitches have been incorporated in oligonucleotides for 20 years, and the field has currently grown beyond fundamental studies on photochemistry of the switches and DNA duplex stability, and is moving towards applications in chemical biology, nanotechnology and material science. Moreover, the currently emerging field of photopharmacology indicates the relevance of photocontrol in future medicine. In recent years, a large number of publications has appeared on photoregulation of DNA and RNA structure and function. New strategies are evaluated and novel, exciting applications are shown. In this comprehensive review, the key strategies for photoswitch inclusion in oligonucleotides are presented and illustrated with recent examples. Additionally the applications that have emerged in recent years are discussed, including gene regulation, drug delivery and materials design. Finally, we identify the challenges that the field currently faces and look forward to future applications.

Utilizing light-triggered plasmon-driven catalysis reactions as a template for molecular delivery and release

Due to the facile manipulation and non-invasive nature of light-triggered release, it is one of the most potent ways to selectively and remotely deliver a molecular target. Among the various carrier platforms, plasmonic nanoparticles possess advantages such as enhanced cellular uptake and easy loading of "cargo" molecules. Two general strategies are currently utilized to achieve light-induced molecule release from plasmonic nanoparticles. The first uses femtosecond laser pulses to directly break the bond between the nanoparticle and the loaded target. The other requires significant photo-thermal effects to weaken the interaction between the cargo molecules and nanoparticle-attached host molecules. Different from above mechanisms, herein, we introduce a new light-controlled molecular-release method by taking advantage of a plasmon-driven catalytic reaction at the particle surface. In this strategy, we link the target to a plasmon responsive molecule, 4-aminobenzenethiol (4-ABT), through the robust and simple EDC coupling reaction and subsequently load the complex onto the particles via the strong Au-thiol interaction. Upon continuous-wave (CW) laser illumination, the excited surface plasmon catalyzes the formation of 4,4'-dimercaptoazobenzenethiol (DMAB) and simultaneously releases the loaded molecules with high efficiency. This method does not require the use of high-power pulsed lasers, nor does it rely on photo-thermal effects. We believe that plasmon-driven release strategies open a new direction for the designing of next-generation light-triggered release processes.

Understanding Resonant Light-Triggered DNA Release from Plasmonic Nanoparticles

Nanoparticle-based platforms for gene therapy and drug delivery are gaining popularity for cancer treatment. To improve therapeutic selectivity, one important strategy is to remotely trigger the release of a therapeutic cargo from a specially designed gene- or drug-laden near-infrared (NIR) absorbing gold nanoparticle complex with NIR light. While there have been multiple demonstrations of NIR nanoparticle-based release platforms, our understanding of how light-triggered release works in such complexes is still limited. Here, we investigate the specific mechanisms of DNA release from plasmonic nanoparticle complexes using continuous wave (CW) and femtosecond pulsed lasers. We find that the characteristics of nanoparticle-based DNA release vary profoundly from the same nanoparticle complex, depending on the type of laser excitation. CW laser illumination drives the photothermal release of dehybridized single-stranded DNA, while pulsed-laser excitation results in double-stranded DNA release by cleavage of the Au-S bond, with negligible local heating. This dramatic difference in DNA release from the same DNA-nanoparticle complex has very important implications in the development of NIR-triggered gene or drug delivery nanocomplexes.

Shedding PEG Palisade by Temporal Photostimulation and Intracellular Reducing Milieu for Facilitated Intracellular Trafficking and DNA Release

The dilemma of poly(ethylene glycol) surface modification (PEGylation) inspired us to develop an intracellularly sheddable PEG palisade for synthetic delivery systems. Here, we attempted to conjugate PEG to polyethylenimine (PEI) through tandem linkages of disulfide-bridge susceptible to cytoplasmic reduction and an azobenzene/cyclodextrin inclusion complex responsive to external photoirradiation. The subsequent investigations revealed that facile PEG detachment could be achieved in endosomes upon photoirradiation, consequently engendering exposure of membrane-disruptive PEI for facilitated endosome escape. The liberated formulation in the cytosol was further subjected to complete PEG detachment relying on disulfide cleavage in the reductive cytosol, thus accelerating dissociation of electrostatically assembled PEI/DNA polyplex to release DNA by means of polyion exchange reaction with intracellularly charged species, ultimately contributing to efficient gene expression.

Recent progress in ferrocene- and azobenzene-based photoelectric responsive materials

Ferrocene- and azobenzene-based derivatives are commonly used photoelectric responsive materials and possess wide range of applications.

DNA–ligand interactions gained and lost: light-induced ligand redistribution in a supramolecular cascade

Controlled DNA binding: a photoresponsive ligand is made to migrate from cyclodextrin to double-stranded DNA upon irradiation and is eventually extracted from the nucleic acid by cucurbituril.

Supramolecular polymer networks based on cucurbit[8]uril host–guest interactions as aqueous photo-rheological fluids

A low-mass fraction (≤0.75 wt%) supramolecular polymer network is fabricated as an aqueous photo-rheological fluid (PRF) via cucurbit[8]uril mediated host–guest interactions. UV irradiation can induce the transition from a highly viscous and rigid gel into a Newtonian-like fluid.