The combination of nanostructures with biomolecules leading to the generation of functional nanosystems holds great promise for biotechnological and biomedical applications. As a naturally occurring ...biomacromolecule, DNA exhibits excellent biocompatibility and programmability. Also, scalable synthesis can be readily realized through automated instruments. Such unique properties, together with Watson-Crick base-pairing interactions, make DNA a particularly promising candidate to be used as a building block material for a wide variety of nanostructures. In the past few decades, various DNA nanostructures have been developed, including one-, two- and three-dimensional nanomaterials. Aptamers are single-stranded DNA or RNA molecules selected by Systematic Evolution of Ligands by Exponential Enrichment (SELEX), with specific recognition abilities to their targets. Therefore, integrating aptamers into DNA nanostructures results in powerful tools for biosensing and bioimaging applications. Furthermore, owing to their high loading capability, aptamer-modified DNA nanostructures have also been altered to play the role of drug nanocarriers for
in vivo
applications and targeted cancer therapy. In this review, we summarize recent progress in the design of aptamers and related DNA molecule-integrated DNA nanostructures as well as their applications in biosensing, bioimaging and cancer therapy. To begin with, we first introduce the SELEX technology. Subsequently, the methodologies for the preparation of aptamer-integrated DNA nanostructures are presented. Then, we highlight their applications in biosensing and bioimaging for various targets, as well as targeted cancer therapy applications. Finally, we discuss several challenges and further opportunities in this emerging field.
We survey advances in biosensing, bioimaging and cancer therapy applications of aptamer-integrated DNA nanostructures in this review.
Circular bivalent aptamers (cb-apt) comprise an emerging class of chemically engineered aptamers with substantially improved stability and molecular recognition ability. Its therapeutic application, ...however, is challenged by the lack of functional modules to control the interactions of cb-apt with therapeutics. We present the design of a β-cyclodextrin-modified cb-apt (cb-apt-βCD) and its supramolecular interaction with molecular therapeutics via host–guest chemistry for targeted intracellular delivery. The supramolecular ensemble exhibits high serum stability and enhanced intracellular delivery efficiency compared to a monomeric aptamer. The cb-apt-βCD ensemble delivers green fluorescent protein into targeted cells with efficiency as high as 80%, or cytotoxic saporin to efficiently inhibit tumor cell growth. The strategy of conjugating βCD to cb-apt, and subsequently modulating the supramolecular chemistry of cb-apt-βCD, provides a general platform to expand and diversify the function of aptamers, enabling new biological and therapeutic applications.
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IJS, KILJ, NUK, PNG, UL, UM
Ascorbic acid (AA) serves as a key coenzyme in many metabolic pathways, and its abnormal level is found to be associated with several diseases. Therefore, monitoring AA level in living systems is of ...great biomedical significance. In comparison with one-photon excited fluorescent probes, two-photon (TP) excited probes are more suitable for bioimaging, as they could afford higher imaging resolution with deeper imaging depth. Here, we report for the first time an efficient TP fluorescence probe for turn-on detection and imaging of AA in living cells and tissues. In this nanosystem, the negatively charged two-photon nanoparticles (TPNPs), which were prepared by modifying the silica nanoparticles with a two-photon dye, could adsorb cobalt oxyhydroxide (CoOOH) nanoflakes which carried positive charge by electrostatic force, leading to a remarkable decrease in their fluorescence intensity. However, the introduction of AA could induce the fluorescence recovery of the nanoprobe because it could reduce CoOOH into Co2+ and result in the destruction of the CoOOH nanoflakes. The nanosystem exhibits a high sensitivity toward AA, with a LOD of 170 nM observed. It also shows high selectivity toward AA over common potential interfering species. The nanoprobe possessed both the advantages of TP imaging and excellent membrane-permeability and good biocompatibility of the silica nanoparticles and was successfully applied in TP-excited imaging of AA in living cells and tissues.
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As the smallest unit of life, cells attract interest due to their structural complexity and functional reliability. Protocells assembled by inanimate components are created as an artificial entity to ...mimic the structure and some essential properties of a natural cell, and artificial reaction networks are used to program the functions of protocells. Although the bottom-up construction of a protocell that can be considered truly 'alive' is still an ambitious goal, these man-made constructs with a certain degree of 'liveness' can offer effective tools to understand fundamental processes of cellular life, and have paved the new way for bionic applications. In this review, we highlight both the milestones and recent progress of protocells programmed by artificial reaction networks, including genetic circuits, enzyme-assisted non-genetic circuits, prebiotic mimicking reaction networks, and DNA dynamic circuits. Challenges and opportunities have also been discussed.
In this review, the milestones and recent progress of protocells programmed by various types of artificial reaction networks are highlighted.
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Creating new functional building blocks that expand the versatility of nanostructures depends on bottom-up self-assembly of amphiphilic biomolecules. Inspired by the unique physicochemical properties ...of hydrophobic perfluorocarbons, coupled with the powerful functions of nucleic acids, we herein report the synthesis of a series of diperfluorodecyl–DNA conjugates (PF–DNA) which can efficiently self-assemble into micelles in aqueous solution. On the basis of the micelle structure, both target binding affinity and enzymatic resistance of the DNA probe can be enhanced. In addition, based on the hydrophobic effect, the PF–DNA micelles (PFDM) can actively anchor onto the cell membrane, offering a promising tool for cell-surface engineering. Finally, the PFDM can enter cells, which is significant for designing carriers for intracellular delivery. The combined advantages of the DNA micelle structure and the unique physicochemical properties of perfluorocarbons make these PFDM promising for applications in bioimaging and biomedicine.
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Chemically engineering endogenous amino acids with a molecular tag is one of the most common routes of artificially functionalizing proteins for identification or cellular delivery. However, it is ...challenging to make conjugation efficient, facile and productive as well as avoiding a high chance of deactivation of the functional proteins. Here we present a new and straightforward design to specifically tether the distinct six polyhistidine tag, terminally expressed on protein cargoes and cellular membrane proteins by using bispecific circular aptamers (bc-apts). The anti-His tag aptamer on one end of the bc-apt can easily recognize the biorthogonal six polyhistidine tag (His tag) on functional proteins like EGFP or RNase A. Meanwhile, a cell-specific aptamer, sgc8, on the other end efficiently facilitates the targeted delivery of functional proteins, improving their overall bioactivity in the cellular milieu by around 4 fold. Therefore, the nuclease-resistant bc-apt is a promising molecular tethering reagent to enable the noncovalent crosslink between live diseased cells and His tag protein cargoes.
A bispecific circular aptamer was utilized to tether a built-in His tag to specific cells to enhance the delivery of functional proteins.
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Aptamers are powerful candidates for molecular imaging and targeted therapy of cancer based on such appealing features as high binding affinity, high specificity, site-specific modification and rapid ...tumor penetration. However, aptamers are susceptible to plasma exonucleases in vivo. This seriously affects their in vivo applications. To overcome this key limitation, we herein report the design and development of circular bivalent aptamers. Systematic studies reveal that cyclization of aptamers can improve thermal stability, nuclease resistance and binding affinity. In vivo fluorescence imaging further validates the efficient accumulation and retention of circular bivalent aptamers in tumors compared to “mono-aptamers”. Therefore, this study provides a simple and efficient strategy to boost in vivo aptamer applications in cancer diagnosis and therapy.
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DNA nanostructures assembled on living cell membranes have become powerful research tools. Synthetic lipid membranes have been used as a membrane model to study the dynamic behavior of DNA ...nanostructures on fluid soft lipid bilayers, but without the inherent complexity of natural membranes. Herein, we report the assembly and disassembly of DNA nanoprisms on cell-mimicking micrometer-scale giant membrane vesicles derived from living mammalian cells. Three-dimensional DNA nanoprisms with a DNA arm and a cholesterol anchor were efficiently localized on the membrane surface. The assembly and disassembly of DNA nanoprisms were dynamically manipulated by DNA strand hybridization and toehold-mediated strand displacement. Furthermore, the heterogeneity of reversible assembly/disassembly of DNA nanoprisms was monitored by Förster resonance energy transfer. This study suggests the feasibility of DNA-mediated functional biomolecular assembly on cell membranes for biomimetics studies and delivery systems.
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Aptamers and antibodies, as molecular recognition probes, play critical roles in cancer diagnosis and therapy. However, their recognition ability is based on target overexpression in disease cells, ...not target exclusivity, which can cause on-target off-tumor effects. To address the limitation, we herein report a novel strategy to develop a conditional aptamer conjugate which recognizes its cell surface target, but only after selective activation, as determined by characteristics of the disease microenvironment, which, in our model, involve tumor hypoxia. This conditional aptamer is the result of conjugating the aptamer with PEG5000-azobenzene-NHS, which is responsive to hypoxia, here acting as a caging moiety of conditional recognition. More specifically, the caging moiety is unresponsive in the intact conjugate and prevents target recognition. However, in the presence of sodium dithionite or hypoxia (<0.1% O2) or in the tumor microenvironment, the caging moiety responds by allowing conditional recognition of the cell-surface target, thereby reducing the chance of on-target off-tumor effects. It is also confirmed that the strategy can be used for developing a conditional antibody. Therefore, this study demonstrates an efficient strategy by which to develop aptamer/antibody-based diagnostic probes and therapeutic drugs for cancers with a unique hypoxic microenvironment.
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Aptamers are often compared with antibodies since both types of molecules function as targeting ligands for specific cancer cell recognition. However, aptamers offer several advantages, including ...small size, facile chemical modification, high chemical stability, low immunogenicity, rapid tissue penetration, and engineering simplicity. Despite these advantages, several crucial factors have delayed their clinical translation, such as concerns over inherent physicochemical stability and safety. Meanwhile, steps have been taken to make aptamer-drug conjugates, or ApDCs, a clinically practical tool. In this review, we highlight the development of ApDCs and discuss how researchers are solving some problems associated with their clinical application for targeted therapy.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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