DNA-Decorated Two-Dimensional Crystalline Nanosheets

DNA-amphiphilic nanostructures: synthesis, characterization and applications

DNA's extraordinary potential reaches far beyond its role as a carrier of genetic information. It serves as a remarkably adaptable structural foundation for constructing intricate nanostructures with a diverse range of functionalities. This inherent programmability sets DNA apart from other biomolecules like peptides, proteins, and small molecules. By covalently attaching DNA to synthetic hydrophobic moieties, researchers create DNA amphiphiles capable of interacting with artificial lipid bilayers and cell membranes. These hybrid structures have rapidly gained prominence due to their promising potential in the medical field. This review provides a comprehensive overview of the latest advancements in the synthesis of DNA amphiphiles and their assembly into well-defined nanostructures. It explores the diverse applications of these nanostructures across various medical domains, including targeted drug delivery, innovative immunotherapies, and gene-silencing techniques. Moreover, the review delves into the current challenges and prospects of this rapidly evolving field, highlighting the potential of DNA hybrid materials to revolutionize medical treatments and diagnostics. By addressing the limitations and exploring new avenues of research, scientists aim to unlock the full potential of DNA nanotechnology for the benefit of human health.

Esterase-Responsive Floxuridine-Tethered Multifunctional Nanoparticles for Targeted Cancer Therapy

Floxuridine is a potential clinical anticancer drug for the treatment of various cancers. However, floxuridine typically causes unfavorable side effects due to its very poor tumor selectivity, and, hence, there is a high demand for the development of novel approaches that permit the targeted delivery of floxuridine into cancerous cells. Herein, the design and synthesis of an esterase-responsive multifunctional nanoformulation for the targeted delivery of floxuridine in esterase-overexpressed cancer cells is reported. Photopolymerization of floxuridine-tethered lipoic acid results in the formation of amphiphilic floxuridine-tethered poly(disulfide). Self-assembly of the amphiphilic polymer results in the formation of nanoparticles with floxuridine decorated on the surfaces of the particles. Integration of aptamer DNA for nucleolin onto the surface of the nanoparticle is demonstrated by exploring the base-pairing interaction of floxuridine with adenine. Targeted internalization of the aptamer-decorated nanoparticle into nucleolin-expressed cancer cells is demonstrated. Esterase triggered cleavage of the ester bond connecting floxuridine with the polymer backbone, and the subsequent targeted delivery of floxuridine into cancer cells is also shown. Excellent therapeutic efficacy is observed both in vitro and also in the 3D tumor spheroid model. This noncovalent strategy provides a simple yet effective strategy for the targeted delivery of floxuridine into cancer cells in a less laborious fashion.

Bimetallic DNAsome Decorated with G4-DNA as a Nanozyme for Targeted and Enhanced Chemo/Chemodynamic Cancer Therapy

Cancer is indisputably one of the major threats to mankind, and hence the design of new approaches for the improvement of existing therapeutic strategies is always wanted. Herein, the design of a tumor microenvironment-responsive, DNA-based chemodynamic therapy (CDT) nanoagent with dual Fenton reaction centers for targeted cancer therapy is reported. Self-assembly of DNA amphiphile containing copper complex as the hydrophobic Fenton reaction center results in the formation of CDT-active DNAsome with Cu2+-based Fenton catalytic site as the hydrophobic core and hydrophilic ssDNA protrude on the surface. DNA-based surface addressability of the DNAsome is then used for the integration of second Fenton reaction center, which is a peroxidase-mimicking DNAzyme noncovalently loaded with Hemin and Doxorubicin, via DNA hybridization to give a CDT agent having dual Fenton reaction centers. Targeted internalization of the CDT nanoagent and selective generation of •OH inside HeLa cell are also shown. Excellent therapeutic efficiency is observed for the CDT nanoagent both in vitro and in vivo, and the enhanced efficacy is attributed to the combined and synergetic action of CDT and chemotherapy.

Multi-Responsive Peptide-Based Ultrathin Nanosheets Prepared by a Horizontal Monolayer Assembly

In this study, peptide-based self-assembled nanosheets with a thickness of approximately 1 nm were prepared using a hierarchical covalent physical fabrication strategy. The covalent alternating polymerization of helical peptide E3 with an azobenzene (AZO) structure yielded copolymers CoP(E3-AZO), which physically self-assembled into ultrathin nanosheets in an unanticipated two-dimensional horizontal monolayer arrangement. This special monolayer arrangement enabled the thickness of the nanosheets to be equal to the cross-sectional diameter of a single linear copolymer, which is a rare phenomenon. Molecular dynamics simulations suggested that the synergistic effect of multiple molecular interactions drives the self-assembly of CoP(E3-AZO) into nanosheets and that various methods, including phototreatment, pH adjustment, the addition of additives, and introduction of cosolvents, can alter the molecular interactions and modulate the self-assembly of CoP(E3-AZO), yielding diverse nanostructures. Remarkably, the ultrathin nanosheets selectively inhibited cancer cells at certain concentrations.

Light-regulated morphology control in supramolecular polymers

Stimuli-responsive materials have gained significant recent interest owing to their versatility and wide applications in fields ranging from materials science to biology. In the majority of examples, external stimuli, including light, act as a remote source of energy to depolymerize/deconstruct certain nanostructures or provide energy for exploring their functional features. However, there is little emphasis on the creation and precise control of these materials. Although significant progress has been made in the last few decades in understanding the pros and cons of various directional non-covalent interactions and their specific molecular recognition ability, it is only in the recent past that the focus has shifted toward controlling the dimension, dispersity, and other macroscopic properties of supramolecular assemblies. Control over the morphology of supramolecular polymers is extremely crucial not only for material properties they manifest but also for effective interactions with biological systems for their potential application in the field of biomedicine. This could effectively be achieved using photoirradiation which has been demonstrated by some recent reports. The concept as such offers a broad scope for designing versatile stimuli-responsive supramolecular materials with precise structure-property control. However, there has not yet been a compilation that focuses on the present subject of employing light to impact and regulate the morphology of supramolecular polymers or categorize the functional motif for easy understanding. In this review, we have collated recent examples of how light irradiation can tune the morphology and nanostructures of supramolecular polymers and categorized them based on their chemical transformation such as cis-trans isomerization, cycloaddition, and photo-cleavage. We have also established a direct correlation among the structures of the building blocks, mesoscopic properties and functional behavior of such materials and suggested future directions.

Cascade Energy Transfer and White-Light Emission in Chirality-Controlled Crystallization-Driven Two-Dimensional Co-assemblies from Donor and Acceptor Dye-Conjugated Polylactides

Achieving predictable and programmable two-dimensional (2D) structures with specific functions from exclusively organic soft materials remains a scientific challenge. This article unravels stereocomplex crystallization-driven self-assembly as a facile method for producing thermally robust discrete 2D-platelets of diamond shape from biodegradable semicrystalline polylactide (PLA) scaffolds. The method involves co-assembling two PLA stereoisomers, namely, PY-PDLA and NMI-PLLA, which form stereocomplex (SC)-crystals in isopropanol. By conjugating a well-known Förster resonance energy transfer (FRET) donor and acceptor dye, namely, pyrene (PY) and naphthalene monoimide (NMI), respectively, to the chain termini of these two interacting stereoisomers, a thermally robust FRET process can be stimulated from the 2D array of the co-assembled dyes on the thermally resilient SC-PLA crystal surfaces. Uniquely, by decorating the surface of the SC-PLA crystals with an externally immobilized guest dye, Rhodamine-B, similar diamond-shaped structures could be produced that exhibit pure white-light emission through a surface-induced two-step cascade energy transfer process. The FRET response in these systems displays remarkable dependence on the intrinsic crystalline packing, which could be modulated by the chirality of the co-assembling PLA chains. This is supported by comparing the properties of similar 2D platelets generated from two homochiral PLLAs (PY-PLLA and NMI-PLLA) labeled with the same FRET pair.

Two-Dimensional Supramolecular Polymerization of DNA Amphiphiles is Driven by Sequence-Dependent DNA-Chromophore Interactions

Two-dimensional (2D) assemblies of water-soluble block copolymers have been limited by a dearth of systematic studies that relate polymer structure to pathway mechanism and supramolecular morphology. Here, we employ sequence-defined triblock DNA amphiphiles for the supramolecular polymerization of free-standing DNA nanosheets in water. Our systematic modulation of amphiphile sequence shows the alkyl chain core forming a cell membrane-like structure and the distal π-stacking chromophore block folding back to interact with the hydrophilic DNA block on the nanosheet surface. This interaction is crucial to sheet formation, marked by a chiral "signature", and sensitive to DNA sequence, where nanosheets form with a mixed sequence, but not with a homogeneous poly(thymine) sequence. This work opens the possibility of forming well-ordered, bilayer-like assemblies using a single DNA amphiphile for applications in cell sensing, nucleic acid therapeutic delivery and enzyme arrays.

Solution-Phase Synthesis of DNA Amphiphiles for DNA Micellar Assembly

Hydrophobic moieties of amphiphilic DNAs can help DNAs penetrate cell membranes, but the conjugation of hydrophobic moieties to DNAs in solution phase remains challenging. Herein we report a solution-phase synthesis method to conjugate hydrophobic molecules to DNAs. This method is simple and efficient. The resulted amphiphilic DNAs can spontaneously assemble into micelles, which may serve as nanocarriers for cellular delivery of nucleic acids and water-insoluble drugs.

Self-assembly of alkyl-perylenebisdiimide-DNA amphiphiles and control of their morphology through cyclodextrin-based host-guest interaction

Amphiphilic alkyl-perylenebisdiimide-DNA hybrids self-assemble into spherical micelles and transform into nanofibers upon the addition of β-cyclodextrins due to host-guest interaction. A competitive guest can induce the nanofibers to reversibly change back to spherical micelles. Both spherical micelles and nanofibers can anchor functional molecules at the corona through DNA hybridization.

Electrostatically Directed Long-Range Self-Assembly of Nucleotides with Cationic Nanoparticles To Form Multifunctional Bioplasmonic Networks

Precise control over interparticle interactions is essential to retain the functions of individual components in a self-assembled superstructure. Here, we report the design of a multifunctional bioplasmonic network via an electrostatically directed self-assembly process involving adenosine 5'-triphosphate (ATP). The present study unveils the ability of ATP to undergo a long-range self-assembly in the presence of cations and gold nanoparticles (AuNP). Modelling and NMR studies gave a qualitative insight into the major interactions driving the bioplasmonic network formation. ATP-Ca²⁺ coordination helps in regulating the electrostatic interaction, which is crucial in transforming an uncontrolled precipitation into a kinetically controlled aggregation process. Remarkably, ATP and AuNP retained their inherent properties in the multifunctional bioplasmonic network. The generality of electrostatically directed self-assembly process was extended to different nucleotide-nanoparticle systems.

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.

DNA condensation and formation of ultrathin nanosheets via DNA assisted self-assembly of an amphiphilic fullerene derivative

DNA nanotechnology propose various assembly strategies to develop novel functional nanostructures utilizing unique interactions of DNA with small molecules, nanoparticles, polymers, and other biomolecules. Although, well defined nanostructures of DNA and amphiphilic small molecules were achieved through hybridization of covalently modified DNA, attaining precise organization of functional moieties through non-covalent interactions remain as a challenging task. Herein, we report mutually assisted assembly of an amphiphilic fullerene derivative and various DNA structures through non-covalent interactions, which leads to initial DNA condensation and subsequent assembly yielding ordered fullerene-DNA nanosheets. The molecular design of the cationic, amphiphilic fullerene derivative (FPy) ensures molecular solubility in the 10% DMSO-PBS buffer system and facile interactions with DNA through groove binding and electrostatic interactions of fullerene moiety and positively charged pyridinium moiety, respectively. The formation of FPy/DNA nanostructures were thoroughly investigated in the presence of λ-DNA, pBR322 plasmid DNA, and single and double stranded 20-mer oligonucleotides using UV-visible spectroscopy, AFM and TEM analysis. λ-DNA and pBR322 plasmid DNA readily condense in presence of FPy leading to micrometer sized few layer nanosheets with significant crystallinity due to ordered arrangement of fullerenes. Similarly, single and double stranded 20-mer oligonucleotides also interact efficiently with FPy and form highly crystalline nanosheets, signifying the role of electrostatic interaction and subsequent charge neutralization in the condensation triggered assembly. However, there is significant differences in the crystallinity and ordered arrangements of fullerenes between these two cases, where longer DNA form condensed structures and less ordered nanosheets while short oligonucleotides lead to more ordered and highly crystalline nanosheets, which could be attributed to the differential DNA condensation. Finally, we have demonstrated the addressability of the assembly using a cyanine modified single strand DNA, which also forms highly crystalline nanosheets and exhibit efficient quenching of the cyanine fluorescence upon self-assembly. These results open up new prospects in the development of functional DNA nanostructures through non-covalent interactions and hence have potential applications in the context of DNA nanotechnology.

Diels-Alder Cycloaddition with CO, CO2, SO2, or N2 Extrusion: A Powerful Tool for Material Chemistry

Phenyl, naphthyl, polyarylphenyl, coronene, and other aromatic and polyaromatic moieties primarily influence the final materials' properties. One of the synthetic tools used to implement (hetero)aromatic moieties into final structures is Diels-Alder cycloaddition (DAC), typically combined with Scholl dehydrocondensation. Substituted 2-pyranones, 1,1-dioxothiophenes, and, especially, 1,3-cyclopentadienones are valuable substrates for [4 + 2] cycloaddition, leading to multisubstituted derivatives of benzene, naphthalene, and other aromatics. Cycloadditions of dienes can be carried out with extrusion of carbon dioxide, carbon oxide, or sulphur dioxide. When pyranones, dioxothiophenes, or cyclopentadienones and DA cycloaddition are aided with acetylenes including masked ones, conjugated or isolated diynes, or polyynes and arynes, aromatic systems are obtained. This review covers the development and the current state of knowledge regarding thermal DA cycloaddition of dienes mentioned above and dienophiles leading to (hetero)aromatics via CO, CO2, or SO2 extrusion. Particular attention was paid to the role that introduced aromatic moieties play in designing molecular structures with expected properties. Undoubtedly, the DAC variants described in this review, combined with other modern synthetic tools, constitute a convenient and efficient way of obtaining functionalized nanomaterials, continually showing the potential to impact materials sciences and new technologies in the nearest future.

Thermodynamic Insights into Protein Adsorption on Supramolecular Assemblies of π-Amphiphiles

Nonspecific adsorption of proteins on the surface of nanocarriers plays a critical role in their cellular uptake and other biological functions. This article reports vesicular assemblies of two π-amphiphiles (NDI-1 and NDI-2) and thermodynamic aspects of their interaction with bovine serum albumin (BSA). Both contain a hydrophobic naphthalene-diimide (NDI) core and two oligo-oxyethylene (OE) wedges but differ by the presence of the hydrazide group in NDI-1. NDI-2 exhibits a constricted π-stacking and enthalpy-driven adsorption of BSA. In contrast, NDI-1 exhibits a stronger interaction due to enhanced entropy contribution. It is postulated that a tight packing of NDI chromophores in NDI-2 results in an inadequate space in the corona, leading to the dehydration of OE chains, which contributes to the observed enthalpy-driven binding. On the other hand, due to H-bonding along the direction of π-stacking in NDI-1, an enhanced interchromophoric distance provides more space in the shell, resulting in less dehydration of the OE chains, which results in an entropy gain from the BSA binding-induced release of water from the OE chains. Intercalation of an electron-rich pyrene in the electron-deficient NDI-1 stack further reduces the grafting density of the OE chains, resulting in negligible BSA adsorption, similar to a stealth polymer. A correlation can be seen between the thermodynamic landscape of the protein adsorption and the trend of their lower critical solution temperature (LCST), which follows the order NDI-1 + Py < NDI-1 < NDI-2.

Temperature- and Composition-Induced Multiarchitectural Transitions in the Catanionic System of a Conventional Surfactant and a Surface-Active Ionic Liquid

The mixture of the cationic surfactant, cetyltrimethylammonium bromide (CTAB), and anionic surface-active ionic liquid, 1-butyl-3-methylimidazoliumdodecyl sulfate (bmimDS), has been studied as a function of the mole fraction of CTAB, X _CTAB, with the total surfactant concentration fixed at 50 mM using turbidity measurements, rheology, dynamic light scattering, differential scanning calorimetry, small-angle neutron scattering, and small-angle X-ray scattering techniques. The catanionic mixture has been found to exhibit phase transitions from vesicles to micelles as a function of temperature, with some mole fractions of CTAB showing dual transitions. Solutions of X _CTAB = 0.2 to 0.5 exhibited a single transition from vesicles to cylindrical micelles at 45 °C. With an increase in the mole fraction of CTAB from 0.55 to 0.65, dual structural transitions at 30 and 45 °C were observed. The microstructural transition at 30 °C is ascribed to the vesicle aggregation process with smaller vesicles fusing into bigger ones, whereas the transition at 45 °C was evaluated to be the vesicle-to-cylindrical micelle transition. However, at higher mole fractions of CTAB, X _CTAB from 0.65 to 0.90, a single transition from vesicles to small cylindrical/spherical micelles was observed in the solutions, at a lower temperature of 30 °C. To the best of our knowledge, such a microstructural transitions as a function of temperature in a single mixture of cationic and anionic surfactants without any additive has not been reported so far.

Biotin-decorated NIR-absorbing nanosheets for targeted photodynamic cancer therapy

Targeted photodynamic therapy (PDT) is one of the promising approaches for the selective killing of cancerous cells without affecting the normal cells, and hence designing new strategies for targeted PDT is extremely important. Herein we report the design and synthesis of a new class of nanosheets derived from the self-assembly of the iodo-BODIPY-biotin conjugate as a photosensitizer for targeted PDT applications. The nanosheet exhibits a high extinction coefficient in the NIR region, high singlet oxygen efficiency, no toxicity in the dark and cell targeting ligands (biotin) on the surface, which are necessary features required for an ideal photosensitizer. Overexpression of sodium-dependent multivitamin transporters (SMVTs) in HeLa and A549 (biotin receptor positive cell lines) is explored for the selective uptake of the nanophotosensitizer through receptor mediated endocytosis (interaction between biotin and SMVT). Control experiments using a biotin receptor negative cell line (WI-38) are also carried out to confirm that the specific interaction between the SMVTs and biotin is mainly responsible for the selective uptake of the photosensitizer. Efficient killing of cancerous cells is demonstrated upon light irradiation through the generation of singlet oxygen and other reactive oxygen species around the cellular environment.

Janus Nanosheets with Face-Selective Molecular Recognition Properties from DNA-Peptide Conjugates

Chemical and functional anisotropy in Janus materials offer intriguing possibilities for constructing complex nanostructures and regulating chemical and biological reactions. Here, the authors report the fabrication of Janus nanosheets from molecular building blocks composed of two information-carrying biopolymers, DNA and peptides. Experimental and structural modeling studies reveal that DNA-peptide diblock conjugates assemble into Janus nanosheets with distinct DNA and peptide faces. The surprising level of structural control is attributed to the exclusive parallel β-sheet formation of phenylalanine-rich peptides. This approach is extended to triblock DNA1-peptide-DNA2 conjugates, which assemble into nanosheets presenting two different DNA on opposite faces. The Janus nanosheets with independently addressable faces are utilized to organize an enzyme pair for concerted enzymatic reactions, where enhanced catalytic activities are observed. These results demonstrate that the predictable and designable peptide interaction is a promising tool for creating Janus nanostructures with regio-selective and sequence-specific molecular recognition properties.

Active Bicomponent Nanoparticle Assembly with Temporal, Microstructural, and Functional Control

Transient supramolecular self-assembly has evolved as a tool to create temporally programmable smart materials. Yet, so far single-component self-assembly has been mostly explored. In contrast, multicomponent self-assembly provides an opportunity to create unique nanostructures exhibiting complex functional outcomes, newer and different than individual components. Even two-component can result in multiple organizations, such as self-sorted domains or co-assembled heterostructures, can occur, thus making it highly complex to predict and reversibly modulate these microstructures. In this study, we attempted to create active bicomponent nanoparticle assemblies of orthogonally pH-responsive-group-functionalized gold and cadmium selenide nanoparticles with temporal microstructural control on their composition (self-sorted or co-assembly) in order to harvest their emergent transient photocatalytic activity by coupling to temporal changes in pH. Moving towards multicomponent systems can deliver next level control in terms of structural and functional outcomes of supramolecular systems.

Combination of DNA with polymers

The preparation and applications of DNA containing polymers are comprehensively reviewed, and they are in the form of DNA−polymer covalent conjugators, supramolecular assemblies and hydrogels for advanced materials with promising features.

Assembly and functionalization of supramolecular polymers from DNA-conjugated squaraine oligomers

DNA conjugated oligomers of organic molecules are candidates for applications in the materials and medical sciences, in diagnostics, in optical devices, for delivery or for the design of complex molecular architectures. Herein, we describe the synthesis and properties of DNA-conjugated squaraine (Sq) oligomers. The oligomers self-assemble into supramolecular polymers that are amenable to further functionalization via DNA hybridization, as shown by the attachment of gold nanoparticles (AuNPs).

The assembly of supramolecular polymers of DNA-linked squaraine oligomers and their subsequent derivatization is described.

Supramolecular Two-Dimensional Systems and Their Biological Applications

Various biological systems rely on the supramolecular assembly of biomolecules through noncovalent bonds for performing sophisticated functions. In particular, cell membranes, which are 2D structures in biological systems, have various characteristics such as a large surface, flexibility, and molecule-recognition ability. Supramolecular 2D materials based on biological systems provide a novel perspective for the development of functional 2D materials. The physical and chemical properties of 2D structures, attributed to their large surface area, can enhance the sensitivity of the detection of target molecules, molecular loading, and bioconjugation efficiency, suggesting the potential utility of functional 2D materials as candidates for biological systems. Although several types of studies on supramolecular 2D materials have been reported, supramolecular biofunctional 2D materials have not been reviewed previously. In this regard, the current advances in 2D material development using molecular assembly are discussed with respect to the rational design of self-assembling aromatic amphiphiles, the formation of 2D structures, and the biological applications of functional 2D materials.

DNA Nanostructures and DNA-Functionalized Nanoparticles for Cancer Theranostics

In the last two decades, DNA has attracted significant attention toward the development of materials at the nanoscale for emerging applications due to the unparalleled versatility and programmability of DNA building blocks. DNA-based artificial nanomaterials can be broadly classified into two categories: DNA nanostructures (DNA-NSs) and DNA-functionalized nanoparticles (DNA-NPs). More importantly, their use in nanotheranostics, a field that combines diagnostics with therapy via drug or gene delivery in an all-in-one platform, has been applied extensively in recent years to provide personalized cancer treatments. Conveniently, the ease of attachment of both imaging and therapeutic moieties to DNA-NSs or DNA-NPs enables high biostability, biocompatibility, and drug loading capabilities, and as a consequence, has markedly catalyzed the rapid growth of this field. This review aims to provide an overview of the recent progress of DNA-NSs and DNA-NPs as theranostic agents, the use of DNA-NSs and DNA-NPs as gene and drug delivery platforms, and a perspective on their clinical translation in the realm of oncology.

DNA-π Amphiphiles: A Unique Building Block for the Crafting of DNA-Decorated Unilamellar Nanostructures

The unparalleled ability of DNA to recognize its complementary strand through Watson and Crick base pairing is one of the most reliable molecular recognition events found in natural systems. This highly specific sequence information encoded in DNA enables it to be a versatile building block for bottom-up self-assembly. Hence, the decoration of functional nanostructures with information-rich DNA is extremely important as this allows the integration of other functional molecules onto the surface of the nanostructures through DNA hybridization in a highly predictable manner. DNA amphiphiles are a class of molecular hybrids where a short hydrophilic DNA is conjugated to a hydrophobic moiety. Since DNA amphiphiles comprise DNA as the hydrophilic segment, their self-assembly in aqueous medium always results in the formation of nanostructures with shell made of DNA. This clearly suggests that self-assembly of DNA amphiphiles is a straightforward strategy for the ultradense decoration of a nanostructure with DNA. However, initial attempts toward the design of DNA amphiphiles were primarily focused on long flexible hydrocarbon chains as the hydrophobic moiety, and it has been demonstrated in several examples that they typically self-assemble into DNA-decorated micelles (spherical or cylindrical). Hence, molecular level control over the self-assembly of DNA amphiphiles and achieving diverse morphologies was extremely challenging and unrealized until recently.In this Account, we summarize our recent efforts in the area of self-assembly of DNA amphiphiles and narrate the remarkable effect of the incorporation of a large π-surface as the hydrophobic domain in the self-assembly of DNA amphiphiles. Self-assembly of DNA amphiphiles with flexible hydrocarbon chains as the hydrophobic moiety is primarily driven by the hydrophobic effect. The morphology of such nanostructures is typically predicted based on the volume ratio of hydrophobic to hydrophilic segments. However, control over the self-assembly and prediction of the morphology become increasingly challenging when the hydrophobic moieties can interact with each other through other noncovalent interactions. In this Account, the unique self-assembly behaviors of DNA-π amphiphiles, where a large π-surface acts as the hydrophobe, are described. Due to the extremely strong π-π stacking in aqueous medium, the assembly of the amphiphile is found to preferably proceed in a lamellar fashion (bilayer) and hence the morphology of the nanostructures can easily be tuned by the structural modification of the π-surface. Design principles for crafting various DNA-decorated lamellar nanostructures including unilamellar vesicles, two-dimensional (2D) nanosheets, and helically twisted nanoribbons by selecting suitable π-surfaces are discussed. Unilamellar vesicular nanostructures were achieved by using linear oligo(phenylene ethynylene) (OPE) as the hydrophobic segment, where lamellar assembly undergoes folding to form unilamellar vesicles. The replacement of OPE with a strongly π-stacking hydrophobe such as hexabenzocoronene (HBC) or tetraphenylethylene (TPE) provides extremely strong π-stacking compared to OPE, which efficiently directed the 2D growth for the lamellar assembly and led to the formation of 2D nanosheets. A helical twist in the lamella was achieved by the replacement of HBC with hexaphenylbenzene (HPB), which is the twisted analogue of HBC, directing the assembly into helically twisted nanoribbons. The most beneficial structural feature of this kind of nanostructure is the extremely dense decoration of their surface with ssDNA, which can further be used for DNA-directed organization of other functional nanomaterials. By exploring this, their potential as a nanoscaffold for predefined assembly of plasmonic nanomaterials into various plasmonic 1D, 2D, and 3D nanostructures through DNA hybridization is discussed. Moreover, the design of pH-responsive DNA-based vesicles and their application as a nanocarrier for payload delivery is also demonstrated.

Redox responsive activity regulation in exceptionally stable supramolecular assembly and co-assembly of a protein

Supramolecular assembly of biomolecules/macromolecules stems from the desire to mimic complex biological structures and functions of living organisms. While DNA nanotechnology is already in an advanced stage, protein assembly is still in its infancy as it is a significantly difficult task due to their large molecular weight, conformational complexity and structural instability towards variation in temperature, pH or ionic strength. This article reports highly stable redox-responsive supramolecular assembly of a protein Bovine serum albumin (BSA) which is functionalized with a supramolecular structure directing unit (SSDU). The SSDU consists of a benzamide functionalized naphthalene-diimide (NDI) chromophore which is attached with the protein by a bio-reducible disulfide linker. The SSDU attached protein (NDI-BSA) exhibits spontaneous supramolecular assembly in water by off-set π-stacking among the NDI chromophores, leading to the formation of spherical nanoparticles (diameter: 150-200 nm). The same SSDU when connected with a small hydrophilic wedge (NDI-1) instead of the large globular protein, exhibits a different π-stacking mode with relatively less longitudinal displacement which results in a fibrillar network and hydrogelation. Supramolecular co-assembly of NDI-BSA and NDI-1 (3 : 7) produces similar π-stacking and an entangled 1D morphology. Both the spherical assembly of NDI-BSA or the fibrillar co-assembly of NDI-BSA + NDI-1 (3 : 7) provide sufficient thermal stability to the protein as its thermal denaturation could be completely surpassed while the secondary structure remained intact. However, the esterase like activity of the protein reduced significantly as a result of such supramolecular assembly indicating limited access by the substrate to the active site of the enzyme located in the confined environment. In the presence of glutathione (GSH), a biologically important tri-peptide, due to the cleavage of the disulfide bond, the protein became free and was released, resulting in fully regaining its enzymatic activity. Such supramolecular assembly provided excellent protection to the protein against enzymatic hydrolysis as the relative hydrolysis was estimated to be <30% for the co-assembled protein with respect to the free protein under identical conditions. Similar to bioactivity, the enzymatic hydrolysis also became prominent after GSH-treatment, confirming that the lack of hydrolysis in the supramolecularly assembled state is indeed related to the confinement of the protein in the nanostructure assembly.

Ultrathin Two Dimensional (2D) Supramolecular Assembly and Anisotropic Conductivity of an Amphiphilic Naphthalene-Diimide

Two-dimensional (2D)-supramolecular assemblies of π-conjugated chromophores are relatively less common compared to a large number of recent examples on their low dimensional (0D or 1D) assemblies or 3D architectures. This article reports a rational design for the 2D supramolecular assembly of an amphiphilic core-substituted naphthalene-diimide derivative (cNDI-1). The building block contains a naphthalene-diimide (NDI) chromophore, symmetrically substituted with two dodecyl chains from the aromatic core while the imide positions are functionalized with two hydrophilic wedges containing oligo-oxyethylene chains. In water, it exhibits entropically favorable self-assembly with a critical aggregation concentration of 1.5 × 10^-5 M and a lower critical solution temperature of 55 °C. The UV/vis absorption spectrum in water shows bathochromically shifted absorption bands compared to that of the monomeric dye in THF, indicating offset π-stacking among the NDI chromophores. C-H symmetric and asymmetric stretching frequencies in the FT-IR spectrum support the presence of organized hydrocarbon chains in trans conformation in the self-assembled state, similar to that in the crystalline n-alkanes, which is further supported by studying the general polarization (GP) values of a noncovalently entrapped Laurdan dye. The atomic force microscopy (AFM) image shows the formation of ultrathin (height < 2.0 nm) ribbons for the spontaneously assembled sample which eventually produces a large-area 2D nanosheet by the lateral organization. The powder X-ray diffraction pattern of the drop-casted film, prepared from the preformed aggregates, reveals sharp peaks that indicate a crystalline lamellar packing along the direction of the 2D growth. Differential scanning calorimetry trace shows the melting of the crystalline alkyl chain domain at T > 75 °C, which destroys the 2D assembly. Local-scale photoconductivity of the ordered 2D assembly, studied by the flash-photolysis time-resolved microwave conductivity (FP-TRMC) technique, reveals an anisotropic conductivity with ∼3 times larger conductivity along the parallel direction compared to that along the perpendicular one.

From spin-labelled fused polyaromatic compounds to magnetically active graphene nanostructures

Molecular design of magnetically active graphene nanoscale structures is an emerging field of research. The key goal of this research is to produce graphene nanoribbons and graphene quantum dots with specified electronic, optical and magnetic properties. The review considers methods for the synthesis of spin-labelled polycyclic aromatic hydrocarbons, which are homologous precursors of graphene nanostructures, and discusses the advances and prospects of the design of magnetically active graphene materials.

The bibliography includes 134 references.

Phototheranostic DNA micelles from the self-assembly of DNA-BODIPY amphiphiles for the thermal ablation of cancer cells

Design of phototheranostic agents in a single step approach is one of the challenges in cancer therapy. Herein, a one-step strategy based on amphiphilicity-driven self-assembly of DNA-BODIPY amphiphiles for the design of a new class of micelles, which offer all three phototheranostic functions, is reported. These include (i) strong emission at NIR (φf = 30%) for imaging, (ii) high photothermal conversion (η = 52%) for PTT and (iii) an ssDNA-based shell for the integration of cell targeting moieties. Selective uptake of DNA micelles into a target cancer cell and its killing by laser irradiation (635 nm) are also demonstrated. Furthermore, the excellent biocompatibility, ultrasmall nanosize and high stability of DNA micelles are promising for in vivo applications.

DNA-Programmed Bimodal 2D Assembly of Differently Sized Nanoparticles via Folding of Precursory Circular Chains

Gold nanoparticle (AuNP) assemblies in two-dimensions (2D) exhibit collective physical/chemical properties that are useful for various devices. However, technical issues still impede the efficient ordering of differently sized AuNPs on solid supports while avoiding phase separation. This paper describes a method to construct binary 2D assemblies by folding precursory circular chains composed of small and large AuNPs. The structural change is caused by a spontaneous, non-cross-linking assembly of fully matched double-stranded DNA-modified AuNPs (dsDNA-AuNPs) at a high ionic strength. Since larger dsDNA-AuNPs have a lower critical coagulation concentration of the supporting electrolyte, the spontaneous assembly of large AuNPs precedes that of small AuNPs in the precursory chain during evaporation. Transmission electron microscopy reveals that alternate-type AuNP chains are folded into a binary 2D structure in a mixed mode, whereas block-type chains are transformed into a binary 2D structure in a core-shell mode. The methodology could potentially be harnessed for the fabrication of binary AuNP arrays for various devices.

Self-Assembly of Supramolecular DNA Amphiphiles through Host-Guest Interaction and Their Stimuli-Responsiveness

Smart DNA nanostructures have found potential application in material science and biomedicine. Most building blocks are DNA amphiphiles covalently synthesized from DNA and hydrophobic molecules. Here, the noncovalent approach based on the host-guest interaction between cucurbit[7]uril (CB[7]) and two hydrophobic guests with different topologies is utilized to modularly construct supramolecular DNA amphiphiles including DNA-CB[7]/ferrocene derivative and DNA-CB[7]/adamantine derivative. Both of the supramolecular DNA amphiphiles assemble into uniform spherical micelles, which can encapsulate hydrophobic Nile Red molecules and anchor gold nanoparticles through DNA hybridization. In addition, 1-adamantanamine hydrochloride, a competitive guest with a strong binding constant with CB[7], induces the dissociation of DNA-CB[7]/ferrocene derivative micelles. More importantly, the redox properties of ferrocene induce reversible morphology changes between the spherical micelles and the dissociated state. These stimuli-responsive DNA supra-amphiphilic micelles, as novel vehicles, expand the family of smart DNA nanostructures.

Peptide-Driven Shape Control of Low-Dimensional DNA Nanostructures

We report the rational design and fabrication of unusual low-dimensional DNA nanostructures through programmable and sequence-specific peptide interactions. Dual-bioactive block copolymers composed of DNA and amino acid-based polymers (DNA-b-poly(amino acid)) were synthesized by coupling oligonucleotides to phenylalanine (Phe)-based polymers. Unlike prototypical DNA block copolymers, which typically form simple spherical micelles, DNA-b-poly(amino acid) assemble into various low-dimensional structures such as nanofibers, ribbons, and sheets through controllable amino acid interactions. Moreover, DNA-b-poly(amino acid) assemblies can undergo protease-induced fiber-to-sheet shape transformations, where the morphology change is dictated by the type of enzymes and amino acid sequences. The peptide-based self-assembly reported here provides a programmable approach to fabricate dynamic DNA assemblies with diverse and unusual low-dimensional structures.

Galactose-Grafted 2D Nanosheets from the Self-Assembly of Amphiphilic Janus Dendrimers for the Capture and Agglutination of Escherichia coli

High aspect ratio, sugar-decorated 2D nanosheets are ideal candidates for the capture and agglutination of bacteria. Herein, the design and synthesis of two carbohydrate-based Janus amphiphiles that spontaneously self-assemble into high aspect ratio 2D sheets are reported. The unique structural features of the sheets include the extremely high aspect ratio and dense display of galactose on the surface. These structural characteristics allow the sheet to act as a supramolecular 2D platform for the capture and agglutination of E. coli through specific multivalent noncovalent interactions, which significantly reduces the mobility of the bacteria and leads to the inhibition of their proliferation. Our results suggest that the design strategy demonstrated here can be applied as a general approach for the crafting of biomolecule-decorated 2D nanosheets, which can perform as 2D platforms for their interaction with specific targets.

Nanosheets and 2D-nanonetworks by mutually assisted self-assembly of fullerene clusters and DNA three-way junctions

Programmable construction of two dimensional (2D) nanoarchitectures using short DNA strands is of utmost interest in the context of DNA nanotechnology. Previously, we have demonstrated fullerene-cluster assisted self-assembly of short oligonucleotide duplexes into micrometer long, semiconducting nanowires. This report demonstrates the construction of micrometer-sized nanosheets and 2D-nanonetworks from the mutual self-assembly of fullerene nanoclusters with three way junction DNA (3WJ-DNA) and 3WJ-DNA with a 12-mer overhang (3WJ-OH), respectively. The interaction of unique sized fullerene clusters prepared from an aniline appended fullerene derivative, F-An, with two 3WJ-DNAs, namely, 3WJ-20 and 3WJ-30, having 20 and 30 nucleobases, respectively at each strand was characterized using UV-visible absorption, circular dichroism and fluorescence techniques. The morphological characterization of nanosheets embedded with F-An clusters was performed via AFM, TEM and DLS analyses. The programmability and structural tunability of the resultant nanostructures were further demonstrated using 3WJ-OH containing a cytosine rich, single stranded DNA 12-mer overhang, which forms entangled 2D-nanonetwork structures instead of nanosheets due to the differential interaction of F-An nanoclusters with single and duplex strands of 3WJ-OH. Moreover, the selective modification of the cytosine rich sequence present in 3WJ-OH with silver nanoclusters (AgNCs) resulted in significant enhancement in silver nanocluster fluorescence (∼40%) compared to 3WJ-OH/AgNCs owing to the additional stability of AgNCs embedded in 2D nanostructures. This unique strategy of constructing DNA based 2D nanomaterials and their utilization in the integration of functional motifs could find application in the area of DNA nanotechnology and bio-molecular sensing.

DNA-Decorated, Helically Twisted Nanoribbons: A Scaffold for the Fabrication of One-Dimensional, Chiral, Plasmonic Nanostructures

Crafting of chiral plasmonic nanostructures is extremely important and challenging. DNA-directed organization of nanoparticle on a chiral template is the most appealing strategy for this purpose. Herein, we report a supramolecular approach for the design of DNA-decorated, helically twisted nanoribbons through the amphiphilicity-driven self-assembly of a new class of amphiphiles derived from DNA and hexaphenylbenzene (HPB). The ribbons are self-assembled in a lamellar fashion through the hydrophobic interactions of HPB. The transfer of molecular chirality of ssDNA into the HPB core results in the bias of one of the chiral propeller conformations for HPB and induces a helical twist into the lamellar packing, and leads to the formation of DNA-wrapped nanoribbons with M-helicity. The potential of the ribbon to act as a reversible template for the 1D chiral organization of plasmonic nanomaterials through DNA hybridization is demonstrated.

DNA-inspired oligomers: from oligophosphates to functional materials

Replacement of the natural nucleotides in DNA by non-nucleosidic building blocks leads to phosphodiester-linked oligomers with a high functional diversity.

Pressure-dependent guest binding and release on a supramolecular polymer

Pressurization on a supramolecular host–guest system induces the compression of binding pockets, discharging the guest molecules.

Reversible morphological tuning of DNA–perylenebisdiimide assemblies through host–guest interaction

A new supramolecular host–guest strategy is developed to reversibly control the morphology of DNA–perylenebisdiimide assemblies in aqueous solution.

Self-assembly of DNA-tetraphenylethylene amphiphiles into DNA-grafted nanosheets as a support for the immobilization of gold nanoparticles: a recyclable catalyst with enhanced activity

Preventing the aggregation of NPs and their recovery are the two major hurdles in NP based catalysis. Immobilization of NPs on a support has proven to be a promising strategy to overcome these difficulties. Herein we report the design of high aspect ratio two-dimensional (2D) crystalline DNA nanosheets formed from the amphiphilicity-driven self-assembly of DNA-tetraphenylethylene amphiphiles and also demonstrate the potential of DNA nanosheets for the immobilization of catalytically active NPs. The most remarkable feature of this approach is the high loading of NPs in a non-aggregated manner, and hence exhibiting enhanced catalytic activity. Recycling of NP loaded nanosheets for several cycles without reduction in catalytic efficiency by simple ultrafiltration is also demonstrated.

Free-Floating 2D Nanosheets with a Superlattice Assembled from Fe3O4 Nanoparticles for Peroxidase-Mimicking Activity

The organization of nanoparticles (NPs) with controlled chemical composition and size distribution into well-defined sheets will find many practical applications, but the chemistry remains problematic. Therefore, we report a facile method to assemble NPs to free-floating two-dimensional (2D) nanosheets with a superlattice and thicknesses reaching 22.8 nm. The ligand oleic acid is critical in the formation of nanosheets. As assembled, these free-floating 2D nanosheets remain intact in both polar and nonpolar solvents, e.g., deionized water, ethanol, N,N-dimethylformamide, dimethyl sulfoxide, toluene, hexane, and chloroform, without any disassembly. Compared to Fe₃O₄ NP building blocks, these 2D nanosheets show more favorable catalytic properties and enhanced catalytic reactivity, which can be exploited to mimic natural enzymes. Our work is expected to open up a new avenue for synthesizing free-floating 2D supersheets by NP assembly, leading to a new generation of materials with enriched functions and broader applications.