Light-Responsive and pH-Responsive DNA Microcapsules for Controlled Release of Loads

MercuryII-mediated construction of DNA capsules for turn-on fluorescence detection of melamine

Researchers have shown significant interest in three-dimensional DNA building blocks due to their potential applications in biomedicine and biosensing. This study focuses on the synthesis of an HgII ion-stabilized DNA capsule with T-HgII-T pairs for the purpose of detecting melamine (MA). MA reacts with HgII to form a MA-HgII-MA complex, which causes HgII to leave the capsule shell, ultimately leading to capsule collapse and release of fluorescent cargo as output signal. Density functional theory (DFT) calculations and X-ray absorption spectroscopy (XAS) were used to demonstrate the ability of MA to extract HgII from the T-HgII-T adducts. The DNA capsules were characterized using TEM, SEM, DLS, zeta-potential, and melting curve analysis, which indicated the successful construction of the HgII-intercalated DNA shell. The MA-triggered destruction of the DNA capsules was visualized by confocal microscopy, and the dynamics of decapsulation were evaluated through fluorescent cargo release. The HgII-stabilized DNA capsules enable MA detection with a detection limit of 0.037 µM and are insensitive to potential interfering ions and amino acids. The tests conducted using MA spiked milk solution resulted in recoveries ranging from 109 to 113% (0.1 µM) and 94.5 to 96% (0.5 µM). These results suggest that the system is promising for highly accurate and reproducible monitoring of MA adulteration.

DNA Tetrahedra as Functional Nanostructures: From Basic Principles to Applications

Self-assembled supramolecular DNA tetrahedra composed of programmed sequence-engineered complementary base-paired strands represent elusive nanostructures having key contributions to the development and diverse applications of DNA nanotechnology. By appropriate engineering of the strands, DNA tetrahedra of tuneable sizes and chemical functionalities were designed. Programmed functionalities for diverse applications were integrated into tetrahedra structures including sequence-specific recognition strands (aptamers), catalytic DNAzymes, nanoparticles, proteins, or fluorophore. The article presents a comprehensive review addressing methods to assemble and characterize the DNA tetrahedra nanostructures, and diverse applications of DNA tetrahedra framework are discussed. Topics being addressed include the application of structurally functionalized DNA tetrahedra nanostructure for the assembly of diverse optical or electrochemical sensing platforms and functionalized intracellular sensing and imaging modules. In addition, the triggered reconfiguration of DNA tetrahedra nanostructures and dynamic networks and circuits emulating biological transformations are introduced. Moreover, the functionalization of DNA tetrahedra frameworks with nanoparticles provides building units for the assembly of optical devices and for the programmed crystallization of nanoparticle superlattices. Finally, diverse applications of DNA tetrahedra in the field of nanomedicine are addressed. These include the DNA tetrahedra-assisted permeation of nanocarriers into cells for imaging, controlled drug release, active chemodynamic/photodynamic treatment of target tissues, and regenerative medicine.

pH-responsive persistent luminescence nanoprobes biosensor for autofluorescence-free determination of glucose level in human samples and fingerprint encryption

Glucose level is an important indicator of diabetes, and maintaining an appropriate physiological concentration of glucose is important for human health. However, traditional optical sensors are interfered by the interference of strong background autofluorescence and natural responsive luminescence, which severely limits their application in complex biological samples. Herein, as a novel glucose biosensing probe, green-emitting Zn2GeO4:Mn2+, Eu3+ (ZGME) persistent luminescence nanoparticles (PLNPs) with pH stimulus-responsive was prepared by a facile one-pot hydrothermal method. We also investigated the pH stimulus-responsive luminescence behaviour of ZGME over a range of pH values from 2.8 to 8.0. Taking advantage of the interesting property that ZGME photoluminescence intensity has a pH response, within an extraordinarily narrow pH range of 5.0-6.5 for highly selectivity and sensitive determination of glucose level in human samples by acid-responsive quenching and persistent luminescent performance. The detection results show high accuracy of the measured values of glucose in serum with a wide detection range (2.5 μg L-1-10 mg L-1) and low detection limit (0.5 μg L-1). Finally, the pH-responsive persistent luminescence also makes ZGME promising for high-level fingerprint information encryption. Hence, the established pH stimulation-responsive PLNPs-based biosensing probe offers excellent performance with high selective, accuracy and signal-to-noise ratio for detection of glucose level in human samples.

Light-activated CRISPR-Cas12a for amplified imaging of microRNA in cell cycle phases at single-cell levels

An ortho-nitrobenzyl phosphate ester-caged nucleic acid hairpin structure coupled to the CRISPR-Cas12a complex is introduced as a functional reaction module for the light-induced activation of the CRISPR-Cas12a (LAC12a) machinery toward the amplified fluorescence detection of microRNA-21 (miRNA-21). The LAC12a machinery is applied for the selective, in vitro sensing of miRNA-21 and for the intracellular imaging of miRNA-21 in different cell lines. The LAC12a system is used to image miRNA-21 in different cell cycle phases of MCF-7 cells. Moreover, the LAC12a machinery integrated in cells enables the two-photon laser confocal microscopy-assisted, light-stimulated spatiotemporal, selective activation of the CRISPR-Cas12a miRNA-21 imaging machinery at the single-cell level and the evaluation of relative expression levels of miRNA-21 at distinct cell cycle phases. The method is implemented to map the distribution of cell cycle phases in an array of single cells.

DNA-empowered synthetic cells as minimalistic life forms

Cells, the fundamental units of life, orchestrate intricate functions - motility, adaptation, replication, communication, and self-organization within tissues. Originating from spatiotemporally organized structures and machinery, coupled with information processing in signalling networks, cells embody the 'sensor-processor-actuator' paradigm. Can we glean insights from these processes to construct primitive artificial systems with life-like properties? Using de novo design approaches, what can we uncover about the evolutionary path of life? This Review discusses the strides made in crafting synthetic cells, utilizing the powerful toolbox of structural and dynamic DNA nanoscience. We describe how DNA can serve as a versatile tool for engineering entire synthetic cells or subcellular entities, and how DNA enables complex behaviour, including motility and information processing for adaptive and interactive processes. We chart future directions for DNA-empowered synthetic cells, envisioning interactive systems wherein synthetic cells communicate within communities and with living cells.

Dual stimuli-responsive upconversion nanoparticle-poly-N-isopropylacrylamide/DNA core-shell microgels

Stimuli-responsive upconversion nanoparticle (UCNP)-poly-N-isopropylacrylamide (pNIPAM)/DNA core-shell microgels with tunable sizes and programmable functions have been prepared. Thanks to the near-infrared (NIR)-responsive UCNP cores and thermosensitive polymeric shells, functional DNA-incorporated microgels with high DNA activity and loading efficiency are obtained, and the activity of the loaded DNA structures can be smartly regulated by NIR illumination and temperature simultaneously.

Light Responsive DNA Nanomaterials and Their Biomedical Applications

DNA nanomaterials have been widely employed for various biomedical applications. With rapid development of chemical modification of nucleic acid, serials of stimuli-responsive elements are included in the multifunctional DNA nanomaterials. In this review, we summarize the recent advances in light responsive DNA nanomaterials based on photocleavage/photodecage, photoisomerization, and photocrosslinking for efficient bioimaging (including imaging of small molecule, microRNA, and protein) and drug delivery (including delivery of small molecule, nucleic acid, and gene editing system). We also discuss the remaining challenges and future perspectives of the light responsive DNA nanomaterials in biomedical applications.

Programming the Assembly of Oligo-Adenine with Coralyne into a pH-Responsive DNA Hydrogel

External stimuli-responsive DNA hydrogels present interesting platforms for drug loading and triggered release. Typically, drug molecules are encapsulated within three-dimensionally hybridized DNA networks. However, the utilization of drug molecules as cofactors to facilitate the directed assembly of DNA strands into hydrogel frameworks and their subsequent controlled release remains to be explored. Herein, we introduce the guided assembly of oligo-adenine (A-strand) into an acidic pH-responsive DNA hydrogel using an anticancer drug, coralyne (COR), as a low-molecular-weight cofactor. At pH 7, COR orchestrates the assembly of A-strand into an antiparallel duplex configuration cross-linked by A-COR-A units at a stoichiometric ratio of one COR cofactor per four adenine bases, resulting in a DNA hydrogel characterized by A-COR-A duplex bridges. At pH 4-5, the instability of A-COR-A units results in the disintegration of the duplex into its constituent components, leading to the release of COR and simultaneous dissociation of the DNA hydrogel matrix. This study introduces a method by which drug molecules, exemplified here by COR, facilitate the direct formation of a supramolecular cofactor-DNA complex, subsequently leading to the creation of a stimuli-responsive DNA hydrogel. This approach may inspire future investigations into DNA hydrogels tailored for controlled drug encapsulation and release applications.

Revolutionizing targeting precision: microfluidics-enabled smart microcapsules for tailored delivery and controlled release

As promising delivery systems, smart microcapsules have garnered significant attention owing to their targeted delivery loaded with diverse active materials. By precisely manipulating fluids on the micrometer scale, microfluidic has emerged as a powerful tool for tailoring delivery systems based on potential applications. The desirable characteristics of smart microcapsules are associated with encapsulation capacity, targeted delivery capability, and controlled release of encapsulants. In this review, we briefly describe the principles of droplet-based microfluidics for smart microcapsules. Subsequently, we summarize smart microcapsules as delivery systems for efficient encapsulation and focus on target delivery patterns, including passive targets, active targets, and microfluidics-assisted targets. Additionally, based on release mechanisms, we review controlled release modes adjusted by smart membranes and on/off gates. Finally, we discuss existing challenges and potential implications associated with smart microcapsules.

Stimuli-Responsive Hydrogel Microcapsules Harnessing the COVID-19 Immune Response for Cancer Therapeutics

The combination of gene therapy and immunotherapy concepts, along recent advances in DNA nanotechnology, have the potential to provide important tools for cancer therapies. We present the development of stimuli-responsive microcapsules, loaded with a viral immunogenetic agent, harnessing the immune response against the Coronavirus Disease 2019, COVID-19, to selectively attack liver cancer cells (hepatoma) or recognize breast cancer or hepatoma, by expression of green fluorescence protein, GFP. The pH-responsive microcapsules, modified with DNA-tetrahedra nanostructures, increased hepatoma permeation by 50 %. Incorporation of a GFP-encoding lentivirus vector inside the tumor-targeting pH-stimulated miRNA-triggered and Alpha-fetoprotein-dictated microcapsules enables the demonstration of neoplasm selectivity, with approximately 5,000-, 8,000- and 50,000-fold more expression in the cancerous cells, respectively. The incorporation of the SARS-CoV-2 spike protein in the gene vector promotes specific recognition of the immune-evading hepatoma by the COVID-19-analogous immune response, which leads to cytotoxic and inflammatory activity, mediated by serum components taken from vaccinated or recovered COVID-19 patients, resulting in effective elimination of the hepatoma (>85 % yield).

Stimuli-responsive (nano)architectures for phytochemical delivery in cancer therapy

The use of phytochemicals for purpose of cancer therapy has been accelerated due to resistance of tumor cells to conventional chemotherapy drugs and therefore, monotherapy does not cause significant improvement in the prognosis and survival of patients. Therefore, administration of natural products alone or in combination with chemotherapy drugs due to various mechanisms of action has been suggested. However, cancer therapy using phytochemicals requires more attention because of poor bioavailability of compounds and lack of specific accumulation at tumor site. Hence, nanocarriers for specific delivery of phytochemicals in tumor therapy has been suggested. The pharmacokinetic profile of natural products and their therapeutic indices can be improved. The nanocarriers can improve potential of natural products in crossing over BBB and also, promote internalization in cancer cells through endocytosis. Moreover, (nano)platforms can deliver both natural and synthetic anti-cancer drugs in combination cancer therapy. The surface functionalization of nanostructures with ligands improves ability in internalization in tumor cells and improving cytotoxicity of natural compounds. Interestingly, stimuli-responsive nanostructures that respond to endogenous and exogenous stimuli have been employed for delivery of natural compounds in cancer therapy. The decrease in pH in tumor microenvironment causes degradation of bonds in nanostructures to release cargo and when changes in GSH levels occur, it also mediates drug release from nanocarriers. Moreover, enzymes in the tumor microenvironment such as MMP-2 can mediate drug release from nanocarriers and more progresses in targeted drug delivery obtained by application of nanoparticles that are responsive to exogenous stimulus including light.

Advancements in Nanogels for Enhanced Ocular Drug Delivery: Cutting-Edge Strategies to Overcome Eye Barriers

Nanomedicine in gel or particle formation holds considerable potential for enhancing passive and active targeting within ocular drug delivery systems. The complex barriers of the eye, exemplified by the intricate network of closely connected tissue structures, pose significant challenges for drug administration. Leveraging the capability of engineered nanomedicine offers a promising approach to enhance drug penetration, particularly through active targeting agents such as protein peptides and aptamers, which facilitate targeted release and heightened bioavailability. Simultaneously, DNA carriers have emerged as a cutting-edge class of active-targeting structures, connecting active targeting agents and illustrating their potential in ocular drug delivery applications. This review aims to consolidate recent findings regarding the optimization of various nanoparticles, i.e., hydrogel-based systems, incorporating both passive and active targeting agents for ocular drug delivery, thereby identifying novel mechanisms and strategies. Furthermore, the review delves into the potential application of DNA nanostructures, exploring their role in the development of targeted drug delivery approaches within the field of ocular therapy.

Ethylene Glycol-Manipulated Syntheses of Calcium Carbonate Particles and DNA Capsules toward Efficient ATP-Responsive Cargo Release

Cargo molecule-encapsulated DNA capsules synthesized with a solid sacrificial template have elicited significant interest in the last decade and have been used for active materials in applications ranging from biosensors to drug delivery. However, the correlation between template properties and the subsequent assembly and triggered release behavior of the resultant carriers remain uninvestigated. In this study, ethylene glycol (EG) was added during the CaCO3 precipitation synthesis to yield particles of various sizes and surface properties, and the adenosine triphosphate (ATP)-responsive release characteristics of the fabricated DNA capsules affected by these particle properties were investigated. The geometry, crystallization, and surface morphology of the CaCO3 particles co-precipitated at various EG concentrations were characterized. We discuss the integrity of cross-linking hybridization, fluorescent molecule internalization, degree of leakage, and release efficiency of the resulting DNA capsules and their relevance brought by particle properties. To achieve efficient encapsulation and cargo release, the surface roughness of the CaCO3 particles was explored and was deemed a key determinant of the compactness of the DNA shell after template removal. This effect was particularly strong in CaCO3 particles in connection with high EG concentrations. The DNA capsules fabricated using 83% EG exhibited low leakage, high loading, and moderate release efficiencies as well as a greater apparent association constant with ATP due to their small particle size and the high-integrity DNA shells.

Stimuli-Responsive DNA-Based Hydrogels on Surfaces for Switchable Bioelectrocatalysis and Controlled Release of Loads

The assembly of enzyme [glucose oxidase (GOx)]-loaded stimuli-responsive DNA-based hydrogels on electrode surfaces, and the triggered control over the stiffness of the hydrogels, provides a means to switch the bioelectrocatalytic functions of the hydrogels. One system includes the assembly of GOx-loaded, pH-responsive, hydrogel matrices cross-linked by two cooperative nucleic acid motives comprising permanent duplex nucleic acids and "caged" i-motif pH-responsive duplexes. Bioelectrocatalyzed oxidation of glucose leads to the formation of gluconic acid that acidifies the hydrogel resulting in the separation of the i-motif constituents and lowering the hydrogel stiffness. Loading of the hydrogel matrices with insulin results in the potential-triggered, glucose concentration-controlled, switchable release of insulin from the hydrogel-modified electrodes. The switchable bioelectrocatalyzed release of insulin is demonstrated in the presence of ferrocenemethanol as a diffusional electron mediator or by applying an electrically wired integrated matrix that includes ferrocenyl-modified GOx embedded in the hydrogel. The second GOx-loaded, stimuli-responsive, DNA-based hydrogel matrix associated with the electrode includes a polyacrylamide hydrogel cooperatively cross-linked by duplex nucleic acids and "caged" G-quadruplex-responsive duplexes. The hydrogel matrix undergoes K+-ions/crown ether-triggered stiffness changes by the cyclic K+-ion-stimulated formation of G-quadruplexes (lower stiffness) and the crown ether-induced separation of the G-quadruplexes (higher stiffness). The hydrogel matrices demonstrate switchable bioelectrocatalytic functions guided by the stiffness properties of the hydrogels.

Marine-origin polysaccharides-based free-standing multilayered membranes as sustainable nanoreservoirs for controlled drug delivery

The layer-by-layer (LbL) assembly technology has been widely used to functionalise surfaces and precisely engineer robust multilayered bioarchitectures with tunable structures, compositions, properties, and functions at the nanoscale by resorting to a myriad of building blocks exhibiting complementary interactions. Among them, marine-origin polysaccharides are a sustainable renewable resource for the fabrication of nanostructured biomaterials for biomedical applications owing to their wide bioavailability, biocompatibility, biodegradability, non-cytotoxicity, and non-immunogenic properties. Chitosan (CHT) and alginate (ALG) have been widely employed as LbL ingredients to shape a wide repertoire of size- and shape-tunable electrostatic-driven multilayered assemblies by exploring their opposite charge nature. However, the insolubility of CHT in physiological conditions intrinsically limits the range of bioapplications of the as-developed CHT-based LbL structures. Herein, we report the preparation of free-standing (FS) multilayered membranes made of water-soluble quaternised CHT and ALG biopolymers for controlled release of model drug molecules. The influence of the film structure in the drug release rate is studied by assembling two distinct set-ups of FS membranes, having the model hydrophilic drug fluorescein isothiocyanate-labelled bovine serum albumin (FITC-BSA) either as an intrinsic building block or added as an outer layer after the LbL assembly process. Both FS membranes are characterised for their thickness, morphology, in vitro cytocompatibility, and release profile, with those having FITC-BSA as an intrinsic LbL ingredient denoting a more sustained release rate. This work opens up new avenues for the design and development of a wide array of CHT-based devices for biomedical applications, overcoming the limitations associated with the insolubility of native CHT under physiological conditions.

Photocleavable Ortho-Nitrobenzyl-Protected DNA Architectures and Their Applications

This review article introduces mechanistic aspects and applications of photochemically deprotected ortho-nitrobenzyl (ONB)-functionalized nucleic acids and their impact on diverse research fields including DNA nanotechnology and materials chemistry, biological chemistry, and systems chemistry. Specific topics addressed include the synthesis of the ONB-modified nucleic acids, the mechanisms involved in the photochemical deprotection of the ONB units, and the photophysical and chemical means to tune the irradiation wavelength required for the photodeprotection process. Principles to activate ONB-caged nanostructures, ONB-protected DNAzymes and aptamer frameworks are introduced. Specifically, the use of ONB-protected nucleic acids for the phototriggered spatiotemporal amplified sensing and imaging of intracellular mRNAs at the single-cell level are addressed, and control over transcription machineries, protein translation and spatiotemporal silencing of gene expression by ONB-deprotected nucleic acids are demonstrated. In addition, photodeprotection of ONB-modified nucleic acids finds important applications in controlling material properties and functions. These are introduced by the phototriggered fusion of ONB nucleic acid functionalized liposomes as models for cell-cell fusion, the light-stimulated fusion of ONB nucleic acid functionalized drug-loaded liposomes with cells for therapeutic applications, and the photolithographic patterning of ONB nucleic acid-modified interfaces. Particularly, the photolithographic control of the stiffness of membrane-like interfaces for the guided patterned growth of cells is realized. Moreover, ONB-functionalized microcapsules act as light-responsive carriers for the controlled release of drugs, and ONB-modified DNA origami frameworks act as mechanical devices or stimuli-responsive containments for the operation of DNA machineries such as the CRISPR-Cas9 system. The future challenges and potential applications of photoprotected DNA structures are discussed.

Crystallinity-tuned ultrasoft polymeric DNA networks for controlled release of anticancer drugs

Despite the vast interest in utilizing rolling circle amplification (RCA)-based DNA networks for bioapplications, precise control of the mechanical and physicochemical properties is highly challenging. To address this concern, we aimed to develop ultrasoft self-supporting polymerized DNA networks (pDNets) of variable crystallinities to manipulate sequence-mediated drug release efficiency. A controlled ratio of the inorganic magnesium pyrophosphate (MgPPi) crystal to the organic polymeric DNA resulted in the synthesis of pDNets of various nanoporosities. The number of crystal microstructures influencing drug localization and release pattern and the tunable mechanical properties influencing injectability and structural stability under physiological conditions were investigated. The pDNets exhibited ultrasoft properties with Young's moduli of 0.06-0.54 Pa; approximately 9-fold differences in mechanical properties were obtained by varying the degree of crystallinity. With functional DNA sequences, the developed platforms showed pH stimuli-responsive drug release profiles of the dynamic DNA structures and aptamer-specific cell target adhesion efficiency. Analyses of controlled delivery of anticancer therapeutics in vitro and in vivo revealed crystallinity-dependent antitumor efficacy without side effects. This strategy provides an effective one-pot enzymatic polymerization methodology and a favorable microenvironment for a three-dimensional DNA network based on demand-localized drug delivery.

DNA-Tetrahedra Corona-Modified Hydrogel Microcapsules: "Smart" ATP- or microRNA-Responsive Drug Carriers

The assembly of adenosine triphosphate (ATP)-responsive and miRNA-responsive DNA tetrahedra-functionalized carboxymethyl cellulose hydrogel microcapsules is presented. The microcapsules are loaded with the doxorubicin-dextran drug or with CdSe/ZnS quantum dots as a drug model. Selective unlocking of the respective microcapsules and the release of the loads in the presence of ATP or miRNA-141 are demonstrated. Functionalization of the hydrogel microcapsules a with corona of DNA tetrahedra nanostructures yields microcarriers that revealed superior permeation into cells. This is demonstrated by the effective permeation of the DNA tetrahedra-functionalized microcapsules into MDA-MB-231 breast cancer cells, as compared to epithelial MCF-10A nonmalignant breast cells. The superior permeation of the tetrahedra-functionalized microcapsules into MDA-MB-231 breast cancer cells, as compared to analog control hydrogel microcapsules modified with a corona of nucleic acid duplexes. The effective permeation of the stimuli-responsive, drug-loaded, DNA tetrahedra-modified microcapsules yields drug carriers of superior and selective cytotoxicity toward cancer cells.

Harnessing DNA for immunotherapy: Cancer, infectious diseases, and beyond

Despite the rapid development of immunotherapy, low response rates, poor therapeutic outcomes and severe side effects still limit their implementation, making the augmentation of immunotherapy an important goal for current research. DNA, which has principally been recognized for its functions of encoding genetic information, has recently attracted research interest due to its emerging role in immune modulation. Inspired by the intrinsic DNA-sensing signaling that triggers the host defense in response to foreign DNA, DNA or nucleic acid-based immune stimulators have been used in the prevention and treatment of various diseases. Besides that, DNA vaccines allow the synthesis of target proteins in host cells, subsequently inducing recognition of these antigens to provoke immune responses. On this basis, researchers have designed numerous vehicles for DNA and nucleic acid delivery to regulate immune systems. Additionally, DNA nanostructures have also been implemented as vaccine delivery systems to elicit strong immune responses against pathogens and diseased cells. This review will introduce the mechanism of harnessing DNA-mediated immunity for the prevention and treatment of diseases, summarize recent progress, and envisage their future applications and challenges.

Functionalized-DNA nanostructures as potential targeted drug delivery systems for cancer therapy

Seeman's pioneer idea has led to the foundation of DNA nanostructures, resulting in a remarkable advancement in DNA nanotechnology. Over the last few decades, remarkable advances in drug delivery techniques have resulted in the self-assembly of DNA for encapsulating candidate drug molecules. The nuclear targeting capability of DNA nanostructures is lies within their high spatial addressability and tremendous potential for active targeting. However, effective programming and assembling those DNA molecules remains a challenge, making the path to DNA nanostructures for real-world applications difficult. Because of their small size, most nanostructures are self-capable of infiltrating into the tumor cellular environment. Furthermore, to enable controlled and site-specific delivery of encapsulated drug molecules, DNA nanostructures are functionalized with special moieties that allow them to bind specific targets and release cargo only at targeted sites rather than non-specific sites, resulting in the prevention/limitation of cellular toxicity. In light of this, the current review seeks to shed light on the versatility of the DNA molecule as a targeting and encapsulating moiety for active drugs in order to achieve controlled and specific drug release with spatial and temporal precision. Furthermore, this review focused on the challenges associated with the construction of DNA nanostructures as well as the most recent advances in the functionalization of DNA nanostructures using various materials for controlled and targeted delivery of medications for cancer therapy.

Switchable and dynamic G-quadruplexes and their applications

G-Quadruplexes attract growing interest as functional constituents in biology, chemistry, nanotechnology, and material science. In particular, the reversible dynamic reconfiguration of G-quadruplexes provides versatile means to switch DNA nanostructures, reversibly control catalytic functions of DNA assemblies, and switch material properties and functions. The present review article discusses the switchable dynamic reconfiguration of G-quadruplexes as central functional and structural motifs that enable diverse applications in DNA nanotechnology and material science. The dynamic reconfiguration of G-quadruplexes has a major impact on the development of DNA switches and DNA machines. The integration of G-quadruplexes with enzymes yields supramolecular assemblies exhibiting switchable catalytic functions guided by dynamic G-quadruplex topologies. In addition, G-quadruplexes act as important building blocks to operate constitutional dynamic networks and transient dissipative networks mimicking complex biological dynamic circuitries. Furthermore, the integration of G-quadruplexes with DNA nanostructures, such as origami tiles, introduces dynamic and mechanical features into these static frameworks. Beyond the dynamic operation of G-quadruplex structures in solution, the assembly of G-quadruplexes on bulk surfaces such as electrodes or nanoparticles provides versatile means to engineer diverse electrochemical and photoelectrochemical devices and to switch the dynamic aggregation/deaggregation of nanoparticles, leading to nanoparticle assemblies that reveal switchable optical properties. Finally, the functionalization of hydrogels, hydrogel microcapsules, or nanoparticle carriers, such as SiO₂ nanoparticles or metal-organic framework nanoparticles, yields stimuli-responsive materials exhibiting shape-memory, self-healing, and controlled drug release properties. Indeed, G-quadruplex-modified nanomaterials find growing interest in the area of nanomedicine. Beyond the impressive G-quadruplex-based scientific advances achieved to date, exciting future developments are still anticipated. The review addresses these goals by identifying the potential opportunities and challenges ahead of the field in the coming years.

DNA-Liposome Hybrid Carriers for Triggered Cargo Release

The design of simple and versatile synthetic routes to accomplish triggered-release properties in carriers is of particular interest for drug delivery purposes. In this context, the programmability and adaptability of DNA nanoarchitectures in combination with liposomes have great potential to render biocompatible hybrid carriers for triggered cargo release. We present an approach to form a DNA mesh on large unilamellar liposomes incorporating a stimuli-responsive DNA building block. Upon incubation with a single-stranded DNA trigger sequence, a hairpin closes, and the DNA building block is allowed to self-contract. We demonstrate the actuation of this building block by single-molecule Förster resonance energy transfer (FRET), fluorescence recovery after photobleaching, and fluorescence quenching measurements. By triggering this process, we demonstrate the elevated release of the dye calcein from the DNA–liposome hybrid carriers. Interestingly, the incubation of the doxorubicin-laden active hybrid carrier with HEK293T cells suggests increased cytotoxicity relative to a control carrier without the triggered-release mechanism. In the future, the trigger could be provided by peritumoral nucleic acid sequences and lead to site-selective release of encapsulated chemotherapeutics.

Multiple Responsiveness of Polymer Actuators

To improve photosensitivity of polymer materials, an effective protocol is to increase the content of photosensitive moieties. However, most of photosensitive units are toxic. The high content is not acceptable for real-world applications. Therefore, achievement of photosensitive polymers with low content of photosensitive moieties but maintaining their photosensitivity remains a challenge. We herein report a protocol to address this challenge by combination of photosensitive monomers with hygroscopic monomers, where the synergistic action of two types of functional moieties can improve the photosensitivity of polymer network. Upon exposure to light irradiation, the polymer can be driven by not only the structural isomerization of photosensitive units but also the photothermal effects. This synergistic effect results in the polymer-based soft actuators capable of showing rapid response to light even at the extremely-low content of photosensitive moieties of 2.6 mol%. Importantly, the combination of hygroscopic and photosensitive moieties provides polymer with multiple responsiveness including acidochromism, humidity responsiveness, photo-hardening, shape memory, photochromism and in-situ swelling, making it useful in sensing systems, information transmission and artificial muscles. This article is protected by copyright. All rights reserved.

All-In-One Second Near-Infrared Light-Responsive Drug Delivery System for Synergistic Chemo-Photothermal Therapy

Light-responsive nanocarrier-based drug delivery systems (NDDSs), due to their unique advantages such as safety, minimal cross-reaction, and spatiotemporal precision, have received wide attention. Notably, second near-infrared (NIR-II) light, which has a high penetration depth for manipulating NDDSs to release drugs, is in high demand. Herein, polyethylene glycol (PEG)-modified hollow Cu_xS nanoparticles (NPs) are developed as an all-in-one NIR-II light-responsive NDDS for synergistic chemo-photothermal therapy. First, Cu_xS-PEG NPs were prepared under mild conditions by using Cu₂O NPs as sacrificial templates. The morphology, photothermal effect, drug loading/releasing abilities, and synergistic chemo-photothermal therapy of Cu_xS-PEG NPs have been investigated. The Cu_xS-PEG NPs with hollow structures showed a high drug loading capacity (∼255 μg Dox per mg of Cu_xS NPs) and stimuli-responsive drug release triggered by NIR-II laser irradiation. The synergistic chemo-photothermal therapy based on the Dox/Cu_xS-PEG NPs showed 98.5% tumor elimination. Our study emphasizes the great potential of Cu_xS-PEG NPs as an all-in-one NIR-II light-responsive NDDS for applications in biomedicine.

One stone, many birds: Recent advances in functional nanogels for cancer nanotheranostics

Inspired by the development of nanomedicine and nanotechnology, more and more possibilities in cancer theranostic have been provided in the last few years. Emerging therapeutic modalities like starvation therapy, chemodynamic therapy, and tumor oxygenation have been integrated with diagnosis, giving a plethora of theranostic nanoagents. Among all of them, nanogels (NGs) show superiority benefiting from their unique attributes: high stability, high water-absorption, large specific surface area, mechanical strength, controlled responsiveness, and high encapsulation capacity. There have been a vast number of investigations supporting various NGs combining drug delivery and multiple bioimaging techniques, encompassing photothermal imaging, photoacoustic imaging, fluorescent imaging, ultrasound imaging, magnetic resonance imaging, and computed tomography. This review summarizes recent advances in functional NGs for theranostic nanomedicine and discusses the challenges and future perspectives of this fast-growing field. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Diagnostic Tools > In Vivo Nanodiagnostics and Imaging.

pH-Responsive Liposomes Loaded with Targeting Procoagulant Proteins as Potential Embolic Agents for Solid Tumor-Targeted Therapy

Selectively inducing tumor thrombosis and subsequent necrosis is a novel and promising antitumor strategy. We have previously designed a targeting procoagulant protein, called tTF-EG3287, which is a fusion of a truncated tissue factor (tTF) with EG3287, a short peptide against the neuropilin-1 (NRP1) binding site of vascular endothelial growth factor-A 165 (VEGF-A 165). However, off-target effects and high-dose requirements limit the further use of tTF-EG3287 in antitumor therapy. Therefore, we encapsulated tTF-EG3287 into poly(2-ethyl-2-oxazoline)-distearoyl phosphatidyl ethanolamine (PEOz-DSPE)-modified liposomes to construct pH-responsive liposomes as a novel vascular embolization agent, called tTF-EG3287@Liposomes. The liposomes had an average particle size of about 100 nm and showed considerable drug-loading capacity, encapsulation efficiency, and biocompatibility. Under the stimulation of acidic microenvironments (pH 6.5), the lipid membrane of tTF-EG3287@Liposomes collapsed, and the cumulative drug release rate within 72 h was 83 ± 1.26%. When administered to a mouse model of hepatocellular carcinoma (HCC), tTF-EG3287@Liposomes showed prolonged retention and enhanced accumulation in the tumor as well as a superior antitumor effec, compared with tTF-EG3287. This study demonstrates the potential of tTF-EG3287@Liposomes as a novel embolic agent for solid tumors and provides a new strategy for tumor-targeted infarction therapy.

Construction of a Reduction-responsive DNA Microsphere using a Reduction-cleavable Spacer based on a Nitrobenzene Scaffold

Here, we describe the design and synthesis of a new reduction-cleavable spacer (RCS) based on a nitrobenzene scaffold for constructing reduction-responsive oligonucleotides according to standard phosphoramidite chemistry. In addition, we demonstrate that the introduction of the RCS in the middle of an oligonucleotide (30 nt) enables the construction of a self-assembled microsphere capable of exhibiting a reduction-responsive disassembly.

Electrochemical pH regulation in droplet microfluidics

We report a method for electrochemical pH regulation in microdroplets generated in a microfluidic device. The key finding is that controlled quantities of reagents can be generated electrochemically in moving microdroplets confined within a microfluidic channel. Additionally, products generated at the anode and cathode can be isolated within descendant microdroplets. Specifically, ∼5 nL water-in-oil microdroplets are produced at a T-junction and then later split into two descendant droplets. During splitting, floor-patterned microelectrodes drive water electrolysis within the aqueous microdroplets to produce H⁺ and OH^-. This results in a change in the pHs of the descendant droplets. The droplet pH can be regulated over a range of 5.9 to 7.7 by injecting controlled amounts of charge into the droplets. When the injected charge is between -6.3 and 54.5 nC nL^-1, the measured pH of the resulting droplets is within ±0.1 pH units of that predicted based on the magnitude of the injected charge. This technique can likely be adapted to electrogeneration of other reagents within microdroplets.

Translating cancer exosomes detection into the color change of phenol red based on target-responsive DNA microcapsules

Emerging evidence indicates that exosomes can be used as a potential biomarker for monitoring diseases, including cancer. However, enhancing the sensing performance in terms of convenience and sensitivity remains an urgent demand for exosomes detection. In this study, a pH-sensitive colorimetric biosensing strategy was developed for exosomes detection by integrating stimuli-responsive DNA microcapsules and acetylcholinesterase to produce acetic acid. The constructed DNA microcapsules consisted of DNA shells crosslinked by anti-CD63 aptamers and loaded with acetylcholinesterase. With exosomes addition, an energetically stabilized aptamer-CD63 compound was produced and microcapsules dissociated due to the reaction of surface protein CD63 of exosomes and aptamer of CD63, resulting in the release of encapsulated AChE. Through a simple centrifugation separation, unreacted DNA microcapsules were removed and the supernatant containing released acetylcholinesterase collected, which was then used for colorimetric exosomes detection through the ability of acetylcholinesterase to hydrolyze acetylcholine to release acetic acid. The resulting decreased solution pH was detected with phenol red indicator, with the sharp color transition conveniently by naked eye. Exosomes quantification was also achieved using the solution's absorption intensity ratio of 558 vs. 432 nm. The linear range was from 2.0 × 10³ to 5.0 × 10⁵ particles/μL, and the limit of detection and limit of quantification were 1.2 × 10³ particles/μL and 2.2 × 10³ particles/μL, respectively. In addition, this proposed strategy for exosomes detection showed a relative standard deviation of 3.1% and high recovery efficiency (>94%), exhibiting a bright application future in exsomes analysis.

Photoresponsive DNA materials and their applications

Photoresponsive nucleic acids attract growing interest as functional constituents in materials science. Integration of photoisomerizable units into DNA strands provides an ideal handle for the reversible reconfiguration of nucleic acid architectures by light irradiation, triggering changes in the chemical and structural properties of the nanostructures that can be exploited in the development of photoresponsive functional devices such as machines, origami structures and ion channels, as well as environmentally adaptable 'smart' materials including nanoparticle aggregates and hydrogels. Moreover, photoresponsive DNA components allow control over the composition of dynamic supramolecular ensembles that mimic native networks. Beyond this, the modification of nucleic acids with photosensitizer functionality enables these biopolymers to act as scaffolds for spatial organization of electron transfer reactions mimicking natural photosynthesis. This review provides a comprehensive overview of these exciting developments in the design of photoresponsive DNA materials, and showcases a range of applications in catalysis, sensing and drug delivery/release. The key challenges facing the development of the field in the coming years are addressed, and exciting emergent research directions are identified.

Supramolecular grafting of stimuli-responsive, carrier-free, self-deliverable nanoparticles of camptothecin and antisense DNA for combination cancer therapy

A supramolecular approach for the crafting of self-deliverable nanoparticles of antisense DNA and camptothecin for combination cancer therapy is reported.

Biocatalytic cascades and intercommunicated biocatalytic cascades in microcapsule systems

Dynamic dimerization of GOx-loaded microcapsules with β-gal//hemin/G-quadruplex-bridged T1/T2-loaded microcapsules guides the bi-directional intercommunication of the three catalysts cascade.

Photoactivated DNA Walker Based on DNA Nanoflares for Signal-Amplified MicroRNA Imaging in Single Living Cells

Specific and sensitive detection and imaging of cancer-related miRNA in living cells are desirable for cancer diagnosis and treatment. Because of the spatiotemporal variability of miRNA expression level during different cell cycles, signal amplification strategies that can be activated by external stimuli are required to image miRNAs on demand at desired times and selected locations. Herein, we develop a signal amplification strategy termed as the photoactivated DNA walker based on DNA nanoflares, which enables photocontrollable signal amplification imaging of cancer-related miRNA in single living cells. The developed method is achieved via combining photoactivated nucleic acid displacement reaction with the traditional exonuclease III (EXO III)-assisted DNA walker based on DNA nanoflares. This method is capable of on-demand activation of the DNA walker for dictated signal amplification imaging of cancer-related miRNA in single living cells. The developed method was demonstrated as a proof of concept to achieve photoactivated signal amplification imaging of miRNA-21 in single living HeLa cells via selective two-photon irradiation (λ = 740 nm) of single living HeLa cells by using confocal microscopy equipped with a femtosecond laser.

Stimuli-responsive hydrogel microcapsules for the amplified detection of microRNAs

A method for the synthesis of DNA-based acrylamide hydrogel microcapsules loaded with quantum dots as a readout signal is introduced. The shell of DNA-acrylamide hydrogel microcapsules is encoded with microRNA-responsive functionalities, being capable of the detection of cancer-associated microRNA. The microRNA-141 (miR-141), a potential biomarker in prostate cancer, was employed as a model target in the microcapsular biosensor. The sensing principle of the microcapsular biosensor is based on the competitive sequence displacement of target miR-141 with the bridging DNA in the microcapsule's shell, leading to the unlocking of DNA-acrylamide hydrogel microcapsules and the release of the readout signal provided by fluorescent quantum dots. The readout signal is intensified as the concentration of miR-141 increases. While miR-141 was directly measured by DNA-acrylamide hydrogel microcapsules, the linear range for the detection of miR-141 is 2.5 to 50 μM and the limit of detection is 1.69 μM. To improve the sensitivity of the microcapsular biosensor for clinical needs, the isothermal strand displacement polymerization/nicking amplification machinery (SDP/NA) process was coupled to the DNA-acrylamide hydrogel microcapsule sensor for the microRNA detection. The linear range for the detection of miR-141 is improved to the range of 10² to 10⁵ pM and the limit of detection is 44.9 pM. Compared to direct microcapsular biosensing, the detection limit for miR-141 by microcapsules coupled with strand-displacement amplification is enhanced by four orders of magnitude.

Modulation of liquid structure and controlling molecular diffusion using supramolecular constructs

The non-equilibrium liquid structure was achieved by interfacial jamming of pillar[5]arene carboxylic acid (P[5]AA) mediated by hydrogen bonding interactions. The assembly was reversibly modulated via jamming to unjamming transition thus dynamically shaping the liquid droplets. Interestingly, these supramolecular constructs showed pH-switchable gated diffusion of encapsulants, hence showcasing a next generation smart release system.

Prospective Cancer Therapies Using Stimuli-Responsive DNA Nanostructures

Nanostructures based on DNA self-assembly present an innovative way to address the increasing need for target-specific delivery of therapeutic molecules. Currently, most of the chemotherapeutics being used in clinical practice have undesired and exceedingly high off-target toxicity. This is a challenge in particular for small molecules, and hence, developing robust and effective methods to lower these side effects and enhance the antitumor activity is of paramount importance. Prospectively, these issues could be tackled with the help of DNA nanotechnology, which provides a route for the fabrication of custom, biocompatible, and multimodal structures, which can, to some extent, resist nuclease degradation and survive in the cellular environment. Similar to widely employed liposomal products, the DNA nanostructures (DNs) are loaded with selected drugs, and then by employing a specific stimulus, the payload can be released at its target region. This review explores several strategies and triggers to achieve targeted delivery of DNs. Notably, different modalities are explained through which DNs can interact with their respective targets as well as how structural changes triggered by external stimuli can be used to achieve the display or release of the cargo. Furthermore, the prospects and challenges of this technology are highlighted.

From Passive Signal Output to Intelligent Response: "On-Demand" Precise Imaging Controlled by Near-Infrared Light

"On-demand" accurate imaging of multiple intracellular miRNAs will significantly improve the detection reliability and accuracy. However, the "always-active" design of traditional multicomponent detection probes enables them to passively recognize and output signals as soon as they encounter targets, which will inevitably impair the detection accuracy and, inevitably, result in false-positive signals. To address this scientific problem, in this work, we developed a near-infrared (NIR) light-activated multicomponent detection intelligent nanoprobe for spatially and temporally controlled on-demand accurate imaging of multiple intracellular miRNAs. The proposed intelligent nanoprobe is composed of a rationally designed UV light-responsive triangular DNA nano sucker (TDS) and upconversion nanoparticles (UCNPs), named UCNPs@TDS (UTDS), which can enter cells autonomously through endocytosis and enable remote regulation of on-demand accurate imaging for multiple intracellular miRNAs using NIR light illumination at a chosen time and place. It is worth noting that the most important highlight of the UTDS we designed in this work is that it can resist nonspecific activation as well as effectively avoid false-positive signals and improve the accuracy of imaging of multiple intracellular miRNAs. Moreover, distinguishing different kinds of cell lines with different miRNA expressions levels can be also achieved through this NIR light-activated intelligent UTDS, showing feasible prospects in precise imaging and disease diagnosis.

Photoactivated Biosensing Process for Dictated ATP Detection in Single Living Cells

The subcellular distribution of adenosine 5'-triphosphate (ATP) and the concentration of ATP in living cells dynamically fluctuate with time during different cell cycles. The dictated activation of the biosensing process in living cells enables the spatiotemporal target detection in single living cells. Herein, a kind of o-nitrobenzylphosphate ester hairpin nucleic acid was introduced as a photoresponsive DNA probe for light-activated ATP detection in single living cells. Two methods to spatiotemporally activate the probe in single living cells were discussed. One method was the usage of the micrometer-sized optical fiber (about 5 μm) to guide the UV light (λ = 365 nm) to selectively activate the photoresponsive DNA probe in single living cells. The second method involved a two-photon laser confocal scanning microscope to selectively irradiate the photoresponsive DNA probes confined in single living cells via two-photon irradiation (λ = 740 nm). ATP aptamer integrated in the activated DNA probes selectively interacted with the target ATP, resulting in dictated signal generation. Furthermore, the photoactivated biosensing process enables dictated dual-model ATP detection in single living cells with "Signal-ON" fluorescence signal and "Signal-OFF" electrochemical signal outputs. The developed photoactivated biosensor for dictated ATP detection with high spatiotemporal resolution in single living cells at a desired time and desired place suggests the possibility to monitor biomarkers during different cell cycles.

Innovative Biomaterials for the Treatment of Bone Cancer

Bone cancer is a demanding challenge for contemporary medicine due to its high frequency of presentation and significant heterogeneity of malignant lesions developing within the bone. To date, available treatments are rarely curative and are primarily aimed at prolonging patients' survival and ameliorating their quality of life. Furthermore, both pharmacological and surgical therapies are aggravated by a consistent burden of adverse events and subsequent disability due to the loss of healthy bone structural and functional properties. Therefore, great research efforts are being made to develop innovative biomaterials able to selectively inhibit bone cancer progression while reducing the loss of bone structural properties secondary to local tissue invasion. In this review, we describe the state of the art of innovative biomaterials for the treatment of bone cancer. Along with physiological bone remodeling, the development of bone metastasis and osteosarcoma will be depicted. Subsequently, recent advances on nanocarrier-based drug delivery systems, as well as the application of novel, multifunctional biomaterials for the treatment of bone cancer will be discussed. Eventually, actual limitations and promising future perspectives regarding the employment of such approaches in the clinical scenario will be debated.

DNA Assembly-Based Stimuli-Responsive Systems

Stimuli-responsive designs with exogenous stimuli enable remote and reversible control of DNA nanostructures, which break many limitations of static nanostructures and inspired development of dynamic DNA nanotechnology. Moreover, the introduction of various types of organic molecules, polymers, chemical bonds, and chemical reactions with stimuli-responsive properties development has greatly expand the application scope of dynamic DNA nanotechnology. Here, DNA assembly-based stimuli-responsive systems are reviewed, with the focus on response units and mechanisms that depend on different exogenous stimuli (DNA strand, pH, light, temperature, electricity, metal ions, etc.), and their applications in fields of nanofabrication (DNA architectures, hybrid architectures, nanomachines, and constitutional dynamic networks) and biomedical research (biosensing, bioimaging, therapeutics, and theranostics) are discussed. Finally, the opportunities and challenges for DNA assembly-based stimuli-responsive systems are overviewed and discussed.

Self-Assembled Growing DNA Tree Mediated by Exosomes for Amplified Imaging of Messenger RNA in Living Cells

Sensitive, accurate, and nondestructive probing of endogenous messenger RNA (mRNA) in living cells places extremely high demands on nanocarriers and probes and is still a challenge. In the present study, we describe a target-triggered self-assembled DNA tree for amplified analysis of mRNA in intact living cells. The probes assembled into a DNA tree are transported into cells by exosomes, which is beneficial for reducing cell damage and realizing nondestructive analysis. The probes are l-configured single-stranded DNAs (LDNAs) that can resist the degradation of exonuclease and endonuclease, thus laying the foundation for accurate analysis. Under the induction of the target mRNA, the probes in the cells assemble into a small plantlet and eventually grow into a tree after a few rounds of self-cycling, achieving the exponential amplification of fluorescence signals. Compared with the signal amplification based on one-dimensional DNA trunk self-assembly, the three-dimensional DNA tree shows an excellent sensitivity both ex situ and in situ. In this way, favorable sensitivity, accuracy, and nondestructive analysis are integrated into one system. This DNA tree expands the analysis platform for analyzing more biomarkers on a genetic level in an intracellular, nondestructive, and hypersensitive manner and holds great potential in clinical diagnostic and research applications.