Self-assembly Of Units Research Articles

A enzyme-free fluorescence quenching sensor for amplified detection of kanamycin in milk based on competitive triggering strategies.

In this work, we constructed a FAM fluorescence quenching biosensor based on an aptamer competition recognition and enzyme-free amplification strategy. We design a competing unit consisting of an aptamer chain and a complementary chain, and a catalytic hairpin self-assembly (CHA) unit consisting of two hairpins in which the complementary chain can trigger the catalytic hairpin self-assembly. In the initial state, the aptamer chain is combined with the complementary chain, the catalytic hairpin self-assembly unit is inhibited, the FAM fluorescence group was far away from the BHQ1 quenching group, and the fluorescence is turn-on. In the presence of kanamycin, the aptamer chain recognizes kanamycin and doesn't form double chains, resulting in the free complementary chain triggering hairpin 1 (H1), and then H1 triggering hairpin 2 (H2), FAM fluorophore is close to the BHQ1 quenching group, and the fluorescence is off-on. When H1 and H2 form a cyclic reaction, enzyme-free amplification is achieved and there is significant output of the fluorescence signal. Therefore, the biosensor has good performance in detecting kanamycin, the detection line is 54 nM, the linear range is 54 nM-0.9 μM, and it can achieve highly selective detection of kanamycin. Kanamycin residue may cause serious harm to human health. The high sensitivity detection of kanamycin is urgent, so this project has a great application potential for food detection.

Exploring anticancer and antibacterial activities of two self-assembling units: Band gap calculations, DFT studies, and polymorphism of a carbohydrazone ligand

The synthesis and physicochemical characterization of a novel self-assembling unit 1,3-bis(4-hydroxyphenylmethylideneamino)guanidine hydrochloride (H5L1) and polymorphic crystal structures of an analogous proligand 1,5-bis(4-hydroxybenzaldehyde) carbohydrazone (H4L2. DMF & H4L2. H2O) are reported. The crystal systems of H4L2. DMF and H4L2. H2O are monoclinic with C2/c and P21/c space groups. The intermolecular contacts are calculated by Hirshfeld surface analyses, which reveal that H···H interactions have a maximum contribution in the total Hirshfeld surfaces in both the crystal structures. The study also signifies that hydrogen bonding interactions are dominant in the crystal lattice of H4L2. H2O, while the C–H∙∙∙π interactions are also significant in H4L2. DMF lattice. Density functional theory is used for optimizing geometry and calculating quantum chemical parameters. Theoretical frontier molecular energy gaps in the gas phase for H5L1 and H4L2 are found to be 3.49 and 4.09 eV respectively. The solid-state band gaps of H5L1 and H4L2 are determined experimentally using the Kubelka-Munk model and are found to be 2.72 and 2.43 eV respectively, which is indicative of strong intermolecular association in the solid lattice of H4L2. ADME properties are estimated to predict the drug-likeness of the compounds. In vitro antibacterial activity study reveals that the diaminoguanidine based proligand is a more efficient inhibitor against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacterial species. Also, in vitro study of the compounds against human breast cancer MCF-7 cells shows that with the increase in the concentrations of the compounds the percentage of cell viability decreases, which indicates the anticancer potentials of both compounds. The IC50 values of H5L1 and H4L2 against MCF-7 cell lines (205.62 and 247.31 µg/mL) are also found to be better compared to the same (274.59 and 375.45 µg/mL) against the non-cancerous Mouse Fibroblast (L929) cell lines.

High-Performance Dopamine-Based Supramolecular Bio-Adhesives.

The need for wound closure or surgical procedures has been commonly met by the application of sutures. Unfortunately, these are often invasive or subject to contamination. Alternative solutions are offered by surgical adhesives that can be applied and set without major disruption; a new class of supramolecular-based adhesives provides potential solutions to some of these challenges. In this study, a series of polymers utilizing dopamine as a self-assembling unit are synthesized. It is found that these motifs act as extremely effective adhesives, with control over the mechanical strength of the adhesion and materials' tensile properties enabled by changing monomer feed ratios and levels of cross-linking. These materials significantly outperform commercially available bio-adhesives, showing yield strengths after adhesion at least two times higher than that of BioGlue and Tisseel, as well as the ability to re-adhere with significant recovery of adhesion strength. Promisingly, the materials are shown to be non-cytotoxic, with cell viability > 90%, and able to perform in aqueous environments without significant loss in strength. Finally, the removal of the materials, is possible using benign organic solvents such as ethanol. These properties all demonstrate the effectiveness of the materials as potential bio-adhesives, with potential advantages for use in surgery.

Increasing Dimensionality in Self-Assembly: Toward Two-Dimensional Supramolecular Polymers.

Different approaches to achieve 2D supramolecular polymers, as an alternative to the covalent bottom-up approaches reported for the preparation of 2D materials, are reviewed. The significance of the operation of weak non-covalent forces to induce a lateral growth of a number of self-assembling units is collected. The examples of both thermodynamically and kinetically controlled formation of 2D supramolecular polymers showed in this review demonstrate the utility of this strategy to achieve new 2D materials with biased morphologies (nanosheets, scrolls, porous surfaces) and showing elegant applications like chiral recognition, enantioselective uptake or asymmetric organic transformations. Furthermore, elaborated techniques like seeded or living supramolecular polymerizations have been demonstrated to give rise to complex 2D nanostructures.

Shape-Assisted Self-Assembly of Hexa-Substituted Carpyridines into 1D Supramolecular Polymers.

The extent of the influence that molecular curvature plays on the self-assembly of supramolecular polymers remains an open question in the field. We began addressing this fundamental question with the introduction of "carpyridines", which are saddle-shaped monomers that can associate with one another through π-π interactions and in which the rotational and translational movements are restricted. The topography displayed by the monomers led, previously, to the assembly of highly ordered 2D materials even in the absence of strong directional interactions such as hydrogen bonding. Here, we introduce a simple strategy to gain control over the dimensionality of the formed structures yielding classical unidimensional polymers. These have been characterized using well-established protocols allowing us to determine and confirm the self-assembly mechanism of both fibers and sheets. The calculated interaction energies are significantly higher than expected for flexible self-assembling units lacking classical "strong" non-covalent interactions. The versatility of this supramolecular unit to assemble into either supramolecular fibers or 2D sheets with strong association energies highlights remarkably well the potential and importance of molecular shape for the design of supramolecular materials and the applications thereof.

A label-free colorimetric 3D paper-based device for ochratoxin A detection using G-quadruplex/hemin DNAzyme with a smartphone readout

The colorimetric sensor usually depends on enzyme-mediated signal amplification to achieve trace analysis of ochratoxin A (OTA) residues in food samples. However, the enzyme labeling and manual addition of reagents steps increased assay time and operation complexity, restricting their application in point-of-care testing (POCT). Herein, we report a label-free colorimetric device integrating a 3D paper-based analytical device and a smartphone as handheld readout for rapid and sensitive detection of OTA. Using vertical-flow design, the paper-based analytical device enables the specific recognition of target and self-assembly of G-quadruplex (G4)/hemin DNAzyme to be performed, then employs DNAzyme for transducing the OTA binding event signal into a colorimetric signal. The design of independent functional units, including biorecognition unit, self-assembly unit and colorimetric units, which can address crowding and disorder of biosensing interfaces and improve the recognition efficiency of aptamer (apta). In addition, we eliminated signal losses and nonuniform coloring by introducing carboxymethyl chitosan (CMCS) to obtain perfectly focused signals on colorimetric unit. On the basis of parameter optimization, the device exhibited a detection range of 0.1–500 ng/mL and a detection limit of 41.9 pg/mL for OTA. Importantly, good results were obtained in spiked real samples, indicating applicability and reliability of developed device.

Unsupervised Data-Driven Reconstruction of Molecular Motifs in Simple to Complex Dynamic Micelles.

The reshuffling mobility of molecular building blocks in self-assembled micelles is a key determinant of many their interesting properties, from emerging morphologies and surface compartmentalization, to dynamic reconfigurability and stimuli-responsiveness. However, the microscopic details of such complex structural dynamics are typically nontrivial to elucidate, especially in multicomponent assemblies. Here we show a machine-learning approach that allows us to reconstruct the structural and dynamic complexity of mono- and bicomponent surfactant micelles from high-dimensional data extracted from equilibrium molecular dynamics simulations. Unsupervised clustering of smooth overlap of atomic position (SOAP) data enables us to identify, in a set of multicomponent surfactant micelles, the dominant local molecular environments that emerge within them and to retrace their dynamics, in terms of exchange probabilities and transition pathways of the constituent building blocks. Tested on a variety of micelles differing in size and in the chemical nature of the constitutive self-assembling units, this approach effectively recognizes the molecular motifs populating them in an exquisitely agnostic and unsupervised way, and allows correlating them to their composition in terms of constitutive surfactant species.

Self-Healing, Robust, Liquid-Repellent Coatings Exploiting the Donor-Acceptor Self-Assembly.

Liquid-repellent coatings with rapid self-healing and strong substrate adhesion have tremendous potential for industrial applications, but their formulation is challenging. We exploit synergistic chemistry between donor-acceptor self-assembly units of polyurethane and hydrophobic metal-organic framework (MOF) nanoparticles to overcome this challenge. The nanocomposite features a nanohierarchical morphology with excellent liquid repellence. Using polyurethane as a base polymer, the incorporated donor-acceptor self-assembly enables high strength, excellent self-healing property, and strong adhesion strength on multiple substrates. The interaction mechanism of donor-acceptor self-assembly was revealed via density functional theory and infrared spectroscopy. The superhydrophobicity of polyurethane was achieved by introducing alkyl-functionalized MOF nanoparticles and post-application silanization. The combination of the self-healing polymer and nanohierarchical MOF nanoparticles results in self-cleaning capability, resistance to tape peel and high-speed liquid jet impacts, recoverable liquid repellence over a self-healed notch, and low ice adhesion up to 50 icing/deicing cycles. By exploiting the porosity of MOF nanoparticles in our nanocomposites, fluorine-free, slippery liquid-infused porous surfaces with stable, low ice adhesion strengths were also achieved by infusing silicone oil into the coatings.

Mechanoluminescent Device: In Situ Renewable Carbazole Derivatives Sandwiched by Self-Healing Disulfide-Containing Polyurethane for Mechanical Signals Detection

Mechanoluminescent (ML) materials can emit visible light by utilizing mechanical energy, which shows unique advantages in visual mechanical sensing, displays, and biomechanical monitoring due to the correlation between force stimulation and luminescence intensity. Most organic ML materials exhibit luminescence intensity attenuation, disappearing completely with force stimulation and failing to recover. Here, organic luminogens (Cz-alkyl6) can be synthesized by introducing a soft alkyl chain into the carbazole, which exhibits ML emission with self-assembly units. Furthermore, organic luminogens can be generated repeatedly by simply recrystallizing the fracture crystal in situ after a short thermal treatment (70 °C) within 14 s. More importantly, the quantitative correlation between force pressure and ML intensity has been established by a sandwich-type ML device based on a novel carbazole derivative (Cz-alkyl6). The ML device presents a capacity for detecting mechanical signals up to 13 N according to its ML intensity (≤275 a.u.), exhibiting potential application value in engineering damage detection, anticounterfeiting, and advanced visual mechanical sensing.

Chiral supramolecular polymers.

As an active branch within the field of supramolecular polymers, chiral supramolecular polymers (SPs) are an excellent benchmark to generate helical structures that can clarify the origin of homochirality in Nature or help determine new exciting functionalities of organic materials. Herein, we highlight the most utilized strategies to build up chiral SPs by using chiral monomeric units or external stimuli. Selected examples of transfer of asymmetry, in which the point or axial chirality contained by the monomeric units is efficiently transferred to the supramolecular scaffold yielding enantioenriched helical structures, will be presented. The importance of the thermodynamics and kinetics associated with those processes is stressed, especially the influence that parameters such as the helix reversal and mismatch penalties exert on the achievement of amplification of asymmetry in co-assembled systems will also be considered. Remarkable examples of breaking symmetry, in which chiral supramolecular polymers can be attained from achiral self-assembling units by applying external stimuli like stirring, solvent or light, are highlighted. Finally, the specific and promising applications of chiral supramolecular polymers are presented with recent relevant examples.

Application of functional peptides in the electrochemical and optical biosensing of cancer biomarkers.

Early screening and diagnosis are the most effective ways to prevent the occurrence and progression of cancers, thus many biosensing strategies have been developed to achieve economic, rapid, and effective detection of various cancer biomarkers. Recently, functional peptides have been gaining increasing attention in cancer-related biosensing due to their advantageous features of a simple structure, ease of synthesis and modification, high stability, and good biorecognition, self-assembly and antifouling capabilities. Functional peptides can not only act as recognition ligands or enzyme substrates for the selective identification of different cancer biomarkers but also function as interfacial materials or self-assembly units to improve the biosensing performances. In this review, we summarize the recent advances in functional peptide-based biosensing of cancer biomarkers according to the used techniques and the roles of peptides. Particular attention is focused on the use of electrochemical and optical techniques, both of which are the most commonly used techniques in the field of biosensing. The challenges and promising prospects of functional peptide-based biosensors in clinical diagnosis are also discussed.

An Overview of the Supramolecular Systems for Gene and Drug Delivery in Tissue Regeneration.

Tissue regeneration is a prominent area of research, developing biomaterials aimed to be tunable, mechanistic scaffolds that mimic the physiological environment of the tissue. These biomaterials are projected to effectively possess similar chemical and biological properties, while at the same time are required to be safely and quickly degradable in the body once the desired restoration is achieved. Supramolecular systems composed of reversible, non-covalently connected, self-assembly units that respond to biological stimuli and signal cells have efficiently been developed as preferred biomaterials. Their biocompatibility and the ability to engineer the functionality have led to promising results in regenerative therapy. This review was intended to illuminate those who wish to envisage the niche translational research in regenerative therapy by summarizing the various explored types, chemistry, mechanisms, stimuli receptivity, and other advancements of supramolecular systems.

Construction of size-transformable supramolecular nano-platform against drug-resistant colorectal cancer caused by Fusobacterium nucleatum

The presence of Fusobacterium nucleatum (F. nucleatum) in the community of colorectal cancer (CRC) accounts for its chemotherapy resistance. To resolve this drawback, we prepared multifaceted supramolecular nanomedicine by conjugating lauric acid (LA) and platinum (IV) oxaliplatin prodrug to hyperbranched polyglycidyl ether (PG), followed by addition of cucurbit[7]uril (CB[7]) to elicit supramolecular assembly. In principle, LA is used to eliminate the F. nucleatum, thereby enhancing chemotherapeutic efficacy of oxaliplatin. CB[7] facilitates host–guest complexation with oxaliplatin, allowing its activation specifically in the spermine-overexpressed CRC tumors. Moreover, CB[7] conduces to supramolecular assembly between the self-assembly units of PG-Pt-LA nanoparticles, representing a novel size-transformable supramolecular nanomedicine (PG-Pt-LA/CB[7]), which can address the dilemma of long circulation and deep penetration existed in nanomedicine. In F. nucleatum co-localized HT29 mouse model and CT26luc mouse model, PG-Pt-LA/CB[7] is validated to be a targeted, safe and effective nanomedicine that can substantially promote the chemotherapeutic efficacy in the treatment of drug-resistant CRC.

Toward Chemotactic Supramolecular Nanoparticles: From Autonomous Surface Motion Following Specific Chemical Gradients to Multivalency-Controlled Disassembly.

Nature designs chemotactic supramolecular structures that can selectively bind specific groups present on surfaces, autonomously scan them moving along density gradients, and react once a critical concentration is encountered. Since such properties are key in many biological functions, these also offer inspirations for designing artificial systems capable of similar bioinspired autonomous behaviors. One approach is to use soft molecular units that self-assemble in an aqueous solution generating nanoparticles (NPs) that display specific chemical groups on their surface, enabling multivalent interactions with complementarily functionalized surfaces. However, a first challenge is to explore the behavior of these assemblies at sufficiently high-resolution to gain insights on the molecular factors controlling their behaviors. Here, by coupling coarse-grained molecular models and advanced simulation approaches, we show that it is possible to study the (autonomous or driven) motion of self-assembled NPs on a receptor-grafted surface at submolecular resolution. As an example, we focus on self-assembled NPs composed of facially amphiphilic oligomers. We observe how tuning the multivalent interactions between the NP and the surface allows to control of the NP binding, its diffusion along chemical surface gradients, and ultimately, the NP reactivity at determined surface group densities. In silico experiments provide physical–chemical insights on key molecular features in the self-assembling units which determine the dynamic behavior and fate of the NPs on the surface: from adhesion, to diffusion, and disassembly. This offers a privileged point of view into the chemotactic properties of supramolecular assemblies, improving our knowledge on how to design new types of materials with bioinspired autonomous behaviors.

Conjugated microporous poly(aniline)s for removal of low-concentration formaldehyde

Removal of indoor formaldehyde is important but challenging due to the very low concentration. Here, we showed the applicability of a new class of conjugated microporous poly(aniline)s (CMPAs) in this formaldehyde capture. The unique properties of rich ultramicroporosity and benzenoid amine (–NH–) groups made the resulting CMPAs ideal platforms for the efficient low-concentration formaldehyde adsorption, through the interaction between benzenoid amine groups and formaldehyde via Mannich reaction and H-bond in the ultramicropore. They therefore exhibited ultrafast adsorption, receiving > 80% removal efficiency for ca 0.7 ppm formaldehyde within 60 min, and benchmarking storage capacity, achieving ca. 2679.68 mg·g−1 for CMPA-2. Our CMPAs also worked well in a self-assembled air clean unit, keeping kinetically reducing average 98% of formaldehyde after treatment of 4000 BV polluted air (with ca. 25 ppm formaldehyde) without break-through. Outcomes highlighted the potential of CMPAs for the clean-up of airborne formaldehyde for human health protection in next generation.

Distance Matters: Biasing Mechanism, Transfer of Asymmetry, and Stereomutation in N-Annulated Perylene Bisimide Supramolecular Polymers.

The synthesis of two series of N-annulated perylene bisimides (PBIs), compounds 1 and 2, is reported, and their self-assembling features are thoroughly investigated by a complete set of spectroscopic measurements and theoretical calculations. The study corroborates the enormous influence that the distance between the PBI core and the peripheral groups exerts on the chiroptical properties and the supramolecular polymerization mechanism. Compounds 1, with the peripheral groups separated from the central PBI core by two methylenes and an ester group, form J-type supramolecular polymers in a cooperative manner but exhibit negligible chiroptical properties. The lack of clear helicity, due to the staircase arrangement of the self-assembling units in the aggregate, justifies these features. In contrast, attaching the peripheral groups directly to the N-annulated PBI core drastically changes the self-assembling properties of compounds 2, which form H-type aggregates following an isodesmic mechanism. These H-type aggregates show a strong aggregation-caused quenching (ACQ) effect that leads to nonemissive aggregates. Chiral (S)-2 and (R)-2 experience an efficient transfer of asymmetry to afford P- and M-type aggregates, respectively, although no amplification of asymmetry is achieved in majority rules or “sergeants-and-soldiers” experiments. A solvent-controlled stereomutation is observed for chiral (S)-2 and (R)-2, which form helical supramolecular polymers of different handedness depending on the solvent (methylcyclohexane or toluene). The stereomutation is accounted for by considering the two possible conformations of the terminal phenyl groups, eclipsed or staggered, which lead to linear or helical self-assemblies, respectively, with different relative stabilities depending on the solvent.

Photoinduced Architectural Transformation of Noncovalent Fluorescent Photochromic Organic Nanoparticles as Evidenced by Amplified Fluorescence Photoswitching

Dual nanoparticles endowed with emission photoswitching ability are produced by the flash coprecipitation of fluorophores and photochromes in water in order to investigate the mutual interplay between the self-assembled photoactive units as a function of their respective ratio. Photophysical studies show that high fluorophore/photochrome ratios favor very fast on/off fluorescence photoswitching, while the opposite is true for recovering emission thanks to the strong antenna effects permitted by the spatially confined entities in nanoparticles. Attempts to regenerate the initial state upon visible irradiation reveal unexpected structural transformations, which result from the noncovalent dye self-assemblies. Morphological investigations support phototriggered photochrome clustering within and around the fluorescent core of the dual nanoparticles after a UV–vis cycle or irradiation, causing partitioning of the photoactive units. The photoinduced morphological changes provide attractive prospects in the fabrication of smart drug delivery systems where active material release by external stimuli represents a very dynamic research area.

Halogenation Regulates Supramolecular Chirality at Hierarchical Levels of Self-Assembled N-Terminal Aromatic Amino Acids.

Halogenation brings about dramatic variations to the performance of self-assembled organic species, such as luminescence and crystallinity, but it has seldom been utilized for chirality control. Here we show the halogenation effect of self-assembling organic building units on supramolecular chirality and chiroptical responses. N-terminal aromatic amino acids with different substituted halogen atoms at p-phenylalanine residues self-assembled into one-dimensional fibrous structures. Halogenation induced the emergence of macroscopic chirality regardless of halogen properties like electronegativity, generating exclusive homochiral helical structures. Solid-state X-ray structures and time-dependent density functional theory were utilized for calculated electronic circular dichroism spectra, which evidenced the diverse driving forces to enable chiral molecular arrangements, including H-bonds and halogen bonds. Red-shifted luminescence was observed in brominated building units, giving rise to active circularly polarized luminescence. This work elucidates the multiple roles of halogen in chiral self-assembly systems, which provides insight into the rational control over supramolecular chirality and their chiroptical applications.

Fe–N–C single-atom catalysts with an axial structure prepared by a new design and synthesis method for ORR

FePc powder sublimates losing H atoms to form unstable fragments at 450 °C which self-assemble to form units with a double-layer structure. The self-assembly units are driven by argon gas at 70 °C to where the substrate is located and crystallize to form Fe-N5/C@G catalyst.

Room temperature and non-halogenated solvent processed terpolymers for high-efficient polymer solar cells

Most of polymer solar cells (PSCs) are currently processed using halogenated solvents and require high temperature manufacturing. However, the realization of non-halogenated environmental-friendly solvents processing and room temperature treatment are the basis for future commercialization of batteries. In this work, two terpolymers PffBT4T-4T2FC-9/1 and PffBT4T-4T2FC-4/1 were synthesized by introducing a self-assembly third unit, bis(2-hexyldecyl)5,5‴-dibromo-3″,4′-difluoro-[2,2’:5′,2’’:5″,2‴-quaterthiophene]-3,3‴-dicarboxylate (4T2FC) into the poly [(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-alt-(3,3‴-di (2-octyldodecyl)-2,2’; 5′,2’’; 5″,2‴-quaterthiophen-5,5‴-diyl)] (PffBT4T-2OD) polymer matrix via random copolymerization. The obtained terpolymers have relatively weaker self-aggregation properties and enable the spin-coating process at room temperature compared with the pristine copolymer PffBT4T-2OD. More importantly, the ester group of the 4T2FC unit can improve the solubility of the conjugated polymers in halogen-free solvent. Ultimately, a superior power conversion efficiency (PCE) of 9.11% was obtained from the optoelectronic device based on PffBT4T-4T2FC-9/1, which is one of the highest values of PSCs based on fullerene system treated with non-halogenated solvents at room temperature. These results demonstrate that these new terpolymers with ester group are promising candidates for high performance environmental-friendly solvent processed solar cells.