Mechanism of Formation of Supramolecular DNA-Templated Polymer Nanowires

Functional DNA-Polymer Conjugates

DNA nanotechnology has seen large developments over the last 30 years through the combination of solid phase synthesis and the discovery of DNA nanostructures. Solid phase synthesis has facilitated the availability of short DNA sequences and the expansion of the DNA toolbox to increase the chemical functionalities afforded on DNA, which in turn enabled the conception and synthesis of sophisticated and complex 2D and 3D nanostructures. In parallel, polymer science has developed several polymerization approaches to build di- and triblock copolymers bearing hydrophilic, hydrophobic, and amphiphilic properties. By bringing together these two emerging technologies, complementary properties of both materials have been explored; for example, the synthesis of amphiphilic DNA-polymer conjugates has enabled the production of several nanostructures, such as spherical and rod-like micelles. Through both the DNA and polymer parts, stimuli-responsiveness can be instilled. Nanostructures have consequently been developed with responsive structural changes to physical properties, such as pH and temperature, as well as short DNA through competitive complementary binding. These responsive changes have enabled the application of DNA-polymer conjugates in biomedical applications including drug delivery. This review discusses the progress of DNA-polymer conjugates, exploring the synthetic routes and state-of-the-art applications afforded through the combination of nucleic acids and synthetic polymers.

DNA Transformations for Diagnosis and Therapy

Due to its unique physical and chemical characteristics, DNA, which is known only as genetic information, has been identified and utilized as a new material at an astonishing rate. The role of DNA has increased dramatically with the advent of various DNA derivatives such as DNA-RNA, DNA-metal hybrids, and PNA, which can be organized into 2D or 3D structures by exploiting their complementary recognition. Due to its intrinsic biocompatibility, self-assembly, tunable immunogenicity, structural programmability, long stability, and electron-rich nature, DNA has generated major interest in electronic and catalytic applications. Based on its advantages, DNA and its derivatives are utilized in several fields where the traditional methodologies are ineffective. Here, the present challenges and opportunities of DNA transformations are demonstrated, especially in biomedical applications that include diagnosis and therapy. Natural DNAs previously utilized and transformed into patterns are not found in nature due to lack of multiplexing, resulting in low sensitivity and high error frequency in multi-targeted therapeutics. More recently, new platforms have advanced the diagnostic ability and therapeutic efficacy of DNA in biomedicine. There is confidence that DNA will play a strong role in next-generation clinical technology and can be used in multifaceted applications.

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.

Hybrid gold/DNA nanowire circuit with sub-10 nm nanostructure arrays

We report on a simple and efficient method for the selective positioning of Au/DNA hybrid nanocircuits using a sequential combination of electron-beam lithography (EBL), plasma ashing, and a molecular patterning process. The nanostructures produced by the EBL and ashing process could be uniformly formed over a 12.6 in² substrate with sub-10 nm patterning with good pattern fidelity. In addition, DNA molecules were immobilized on the selectively nanopatterned regions by alternating surface coating procedures of 3-(aminopropyl)triethoxysilane (APS) and diamond like carbon (DLC), followed by deposition of DNA molecules into a well-defined single DNA nanowire. These single DNA nanowires were used not only for fabricating Au/DNA hybrid nanowires by the conjugation of Au nanoparticles with DNA, but also for the formation of Au/DNA hybrid nanocircuits. These nanocircuits prepared from Au/DNA hybrid nanowires demonstrate conductivities of up to 4.3 × 10⁵ S/m in stable electrical performance. This selective and precise positioning method capable of controlling the size of nanostructures may find application in making sub-10 nm DNA wires and metal/DNA hybrid nanocircuits.

Structural and Photophysical Templating of Conjugated Polyelectrolytes with Single-Stranded DNA

A promising approach to influence and control the photophysical properties of conjugated polymers is directing their molecular conformation by templating. We explore here the templating effect of single-stranded DNA oligomers (ssDNAs) on cationic polythiophenes with the goal to uncover the intermolecular interactions that direct the polymer backbone conformation. We have comprehensively characterized the optical behavior and structure of the polythiophenes in conformationally distinct complexes depending on the sequence of nucleic bases and addressed the effect on the ultrafast excited-state relaxation. This, in combination with molecular dynamics simulations, allowed us a detailed atomistic-level understanding of the structure-property correlations. We find that electrostatic and other noncovalent interactions direct the assembly with the polymer, and we identify that optimal templating is achieved with (ideally 10-20) consecutive cytosine bases through numerous π-stacking interactions with the thiophene rings and side groups of the polymer, leading to a rigid assembly with ssDNA, with highly ordered chains and unique optical signatures. Our insights are an important step forward in an effective approach to structural templating and optoelectronic control of conjugated polymers and organic materials in general.

DNA-Based Fabrication for Nanoelectronics

The bottom-up DNA-templated nanoelectronics exploits the unparalleled self-assembly properties of DNA molecules and their amenability with various types of nanomaterials. In principle, nanoelectronic devices can be bottom-up assembled with near-atomic precision, which compares favorably with well-established top-down fabrication process with nanometer precision. Over the past decade, intensive effort has been made to develop DNA-based nanoassemblies including DNA-metal, DNA-polymer, and DNA-carbon nanotube complexes. This review introduces the history of DNA-based fabrication for nanoelectronics briefly and summarizes the state-of-art advances of DNA-based nanoelectronics. In particular, the most widely applied characterization techniques to explore their unique electronic properties at the nanoscale are described and discussed, including scanning tunneling microscopy, conductive atomic force microscopy, and Kelvin probe force microscopy. We also provide a perspective on potential applications of DNA-based nanoelectronics.

From Interaction to Function in DNA-Templated Supramolecular Self-Assemblies

DNA-templated self-assembly represents a rich and growing subset of supramolecular chemistry where functional self-assemblies are programmed in a versatile manner using nucleic acids as readily-available and readily-tunable templates. In this review, we summarize the different DNA recognition modes and the basic supramolecular interactions at play in this context. We discuss the recent results that report the DNA-templated self-assembly of small molecules into complex yet precise nanoarrays, going from 1D to 3D architectures. Finally, we show their emerging functions as photonic/electronic nanowires, sensors, gene delivery vectors, and supramolecular catalysts, and their growing applications in a wide range of area from materials to biological sciences.

Multifunctional one-dimensional polymeric nanostructures for drug delivery and biosensor applications

Advances in nanotechnology in the last decades have paved the way for significant achievements in diagnosis and treatment of various diseases. Different types of functional nanostructures have been explored and utilized as tools for addressing the challenges in detection or treatment of diseases. In particular, one-dimensional nanostructures hold great promise in theranostic applications due to their increased surface area-to-volume ratios, which allow better targeting, increased loading capacity and improved sensitivity to biomolecules. Stable polymeric nanostructures that are stimuli-responsive, biocompatible and biodegradable are especially preferred for bioapplications. In this review, different synthesis techniques of polymeric one-dimensional nanostructures are explored and functionalization methods of these nanostructures for specific applications are explained. Biosensing and drug delibiovery applications of these nanostructures are presented in detail.

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.

A simple dialysis device for large DNA molecules

The potential of genomic DNA is realized when new modalities are invented that manipulate large DNAs with minimal breakage or loss of sample. Here, we describe a polydimethylsiloxane-polycarbonate membrane device to remove small molecules from a sample while retaining large DNAs. Dialysis rates dramatically change as DNA size in kb (M) increases and DNA dimensions become comparable to pore size, and chain characteristics go from rod-like to Gaussian. Consequently, we describe empirical rates of dialysis, R, as a function of M as falling into two regimes: DNAs ≤ 1 kb show R(M) ∼e ^{- t/τ} _M (t = time, τ_M = time constant), while DNAs ≥1.65 kb slowly passage with R(M) ∼M ^-1.68; such partitioning potentiates single-molecule imaging.

Chemistries for DNA Nanotechnology

The predictable nature of DNA interactions enables the programmable assembly of highly advanced 2D and 3D DNA structures of nanoscale dimensions. The access to ever larger and more complex structures has been achieved through decades of work on developing structural design principles. Concurrently, an increased focus has emerged on the applications of DNA nanostructures. In its nature, DNA is chemically inert and nanostructures based on unmodified DNA mostly lack function. However, functionality can be obtained through chemical modification of DNA nanostructures and the opportunities are endless. In this review, we discuss methodology for chemical functionalization of DNA nanostructures and provide examples of how this is being used to create functional nanodevices and make DNA nanostructures more applicable. We aim to encourage researchers to adopt chemical modifications as part of their work in DNA nanotechnology and inspire chemists to address current challenges and opportunities within the field.

Conductive Core-Shell Aramid Nanofibrils: Compromising Conductivity with Mechanical Robustness for Organic Wearable Sensing

One-dimensional organic nanomaterials with a combination of electric conductivity, flexibility, and mechanical robustness are highly in demand in a variety of flexible electronic devices. Herein, conducting polymers were combined with robust Kevlar nanofibrils (aramid nanofibrils, abbreviated as ANFs) via in situ polymerization. Owing to the strong interactions between ANFs and conjugated polymers, the resultant core-shell ANFs showed high electric conductivity in combination with flexibility, robustness, physical stability, and endurance to bending and solvents, in sharp contrast to many inorganic conductive nanomaterials. Due to their responsivity of conductivity to different stimuli (e.g., humidity and strain), their membranes were capable not only of sensing human motions and speech words, but also of showing high sensitivity to variation of environmental humidity. In such a way, these core-shell ANFs may pave the way for combining both conductivity and mechanical properties applicable for diverse wearable devices.

Surface-Guided Chemical Processes on Self-Assembled DNA Nanostructures

Solid-liquid interfaces have been of great significance in the activation of chemical reactions via restricting the conformation or orientation of the reactants. Self-assembled DNA nanostructures encoded with tremendous chemical and physical information provide an efficient platform to unravel and regulate mechanisms of surface chemical processes. In this review, we discuss the surface addressability, morphological features, and charged properties of DNA nanostructures as well as the recognition, catalytic, and dynamic properties of DNA molecules. We highlight the synergies between the surface properties of DNA nanostructures and the molecular features of DNA strands, which is a key to the synthesis of conductive polymer nanomaterials with well-defined shapes or electronic/optical properties. We also focus on the control over the substrate channeling pathways of enzyme networks or metal nucleation on DNA nanostructures toward the production of specifically emissive metal nanoclusters. In the end, we provide an outlook of future possible directions based on the rational design of DNA-based self-assembly, including dynamic energy transfer, stimuli-responsive synthesis, and programmable activation of the mechanophores on the surfaces of DNA nanostructures.

Inkjet printing and electrical characterisation of DNA-templated cadmium sulphide nanowires

Cadmium sulphide can be templated on λ-DNA molecules to form an aqueous dispersion of CdS/λ-DNA nanowires. Subsequent addition of ethylene glycol to 50% v/v is sufficient to formulate an ink suitable for printing using piezoelectric drop-on-demand technology. Printed droplet arrays show a coffee-ring morphology of individual deposits by fluorescence and Raman microscopy, but upon increasing the number of layers of printed material by repeated printing over each droplet, the dry deposit approaches closer to a disc shape. It is also possible to print parallel tracks by reducing the droplet separation in the array until neighbouring droplets overlap before they dry. The droplets coalesce to form a strip of width roughly equal to the diameter of the droplets. Evaporation-driven capillary flow sends the nanowires to the edges of the strip and when dry they form parallel tracks of CdS/λ-DNA nanowire bundles. Both droplets and tracks were printed onto Pt-on-glass interdigitated microelectrodes (10 μm width, 10 μm gap). The current-voltage characteristics of these two-terminal devices were approximately ohmic, but with some hysteresis. The conductance increased with temperature as a simple activated process with activation energies of 0.57 ± 0.02 eV (tracks) and 0.39 ± 0.02 eV (droplets). The impedance spectra of the printed films were consistent with hopping between CdS grains.

A Nonconventional Approach to Patterned Nanoarrays of DNA Strands for Template-Assisted Assembly of Polyfluorene Nanowires

DNA molecules have been widely recognized as promising building blocks for constructing functional nanostructures with two main features, that is, self-assembly and rich chemical functionality. The intrinsic feature size of DNA makes it attractive for creating versatile nanostructures. Moreover, the ease of access to tune the surface of DNA by chemical functionalization offers numerous opportunities for many applications. Herein, a simple yet robust strategy is developed to yield the self-assembly of DNA by exploiting controlled evaporative assembly of DNA solution in a unique confined geometry. Intriguingly, depending on the concentration of DNA solution, highly aligned nanostructured fibrillar-like arrays and well-positioned concentric ring-like superstructures composed of DNAs are formed. Subsequently, the ring-like negatively charged DNA superstructures are employed as template to produce conductive organic nanowires on a silicon substrate by complexing with a positively charged conjugated polyelectrolyte poly[9,9-bis(6'-N,N,N-trimethylammoniumhexyl)fluorene dibromide] (PF2) through the strong electrostatic interaction. Finally, a monolithic integration of aligned arrays of DNA-templated PF2 nanowires to yield two DNA/PF2-based devices is demonstrated. It is envisioned that this strategy can be readily extended to pattern other biomolecules and may render a broad range of potential applications from the nucleotide sequence and hybridization as recognition events to transducing elements in chemical sensors.

Long conducting polymer nanonecklaces with a 'beads-on-a-string' morphology: DNA nanotube-template synthesis and electrical properties

Complex and functional nanostructures are always desired. Herein, we present the synthesis of novel long conducting polymer nanonecklaces with a 'beads-on-a-string' morphology by the DNA nanotube-template approach and in situ oxidative polymerization of the 3-methylthiophene monomer with FeCl3 as the oxidant/catalyst. The length of the nanonecklaces is up to 60 μm, and the polymer beads of around 20-25 nm in diameter are closely packed along the axis of the DNA nanotube template with a density of ca. 45 particles per μm. The formation of porous DNA nanotubes impregnated with FeCl3 was also demonstrated as intermediate nanostructures. The mechanisms for the formation of both the porous DNA nanotubes and the conducting polymer nanonecklaces are discussed in detail. The as-synthesized polymer/DNA nanonecklaces exhibit good electrical properties.

Preparation and electrical properties of a copper-conductive polymer hybrid nanostructure

Conductive copper–polymer hybrid nanowires prepared by templating on DNA.

From nucleobase to DNA templates for precision supramolecular assemblies and synthetic polymers

In this minireview, we report on the recent advances of utilization of nucleobases and DNA as templates to achieve well-defined supramolecular polymers, synthetic polymers, and sequence-controlled polymers.

Chiral supramolecular organization and cooperativity in DNA-templated assemblies of ZnII–chromophore complexes

Templated cooperative binding induced assembly of chromophores is achieved via interactions between Zn-complexes and the DNA phosphodiester backbone.