Dendritic Architectures Research Articles

Visible Light [2 + 2] Cycloadditions of Thermoresponsive Dendronized Styryltriazines To Exhibit Tunable Microconfinement.

Visible light-triggered photochemical reactions in aqueous media are highly valuable to tailor molecular structures and properties in an ecofriendly manner. Here we report visible light-induced catalyst-free [2 + 2] cycloadditions of thermoresponsive dendronized styryltriazines, which show tunable microconfinement to guest dyes in aqueous media. These dendronized styryltriazines are constituted of conjugated mono- or tristyryltriazines, which carry hydrophilic dendritic oligoethylene glycol (OEG) pendants. They underwent efficient [2 + 2] cycloadditions to form dendronized cyclobutane dimers or oligomers in water through irradiation with visible light of 400 nm, and their cycloaddition behavior was dominated by dendritic architectures and solvent conditions. Dendronization with dendritic OEGs also afforded them characteristic thermoresponsive properties with tunable phase transition temperatures in the range 36-65 °C, which can be further modulated through photocycloaddition of styryltriazine chromophores. Importantly, dendronized styryltriazines can form tunable microenvironments in aqueous media, which encapsulate hydrophobic solvatochromic Nile red to exhibit variable photophysical properties. The encapsulated guest dye can be simultaneously released through noninvasive visible light-induced [2 + 2] cycloaddition reactions.

Targeted Modulation of Redox and Immune Homeostasis in Acute Lung Injury Using a Thioether-Functionalized Dendrimer.

Acute lung injury (ALI) is the pathophysiological precursor of acute respiratory distress syndrome. It is characterized by increased oxidative stress and exaggerated inflammatory response that disrupts redox reactions and immune homeostasis in the lungs, thereby posing significant clinical challenges. In this study, an internally functionalized thioether-enriched dendrimer Sr-G4-PEG is developed, to scavenge both proinflammatory cytokines and reactive oxygen species (ROS) and restore homeostasis during ALI treatment. The dendrimers are synthesized using an efficient and orthogonal thiol-ene "click" chemistry approach that involves incorporating thioether moieties within the dendritic architectures to neutralize the ROS. The ROS scavenging of Sr-G4-PEG manifests in its capacity to sequester proinflammatory cytokines. The synergistic effects of scavenging ROS and sequestering inflammatory cytokines by Sr-G4-PEG contribute to redox remodeling and immune homeostasis, along with the modulation of the NLRP3-pyroptosis pathway. Treatment with Sr-G4-PEG enhances the therapeutic efficacy of ALIs by alleviating alveolar bleeding, reducing inflammatory cell infiltration, and suppressing the release of inflammatory cytokines. These results suggest that Sr-G4-PEG is a potent nanotechnological candidate for remodeling redox and immune homeostasis in the treatment of ALIs, demonstrating the great potential of dendrimer-based nanomedicine for the treatment of respiratory pathologies.

A Dendritic Architecture‐Based Deep Learning for Tumor Detection

Brain tumor detection typically involves classifying various tumor types. Traditional classifiers, based on the McCulloch‐Pitts model, have faced criticism due to their oversimplified structure and limited capabilities in detecting brain tumor images with complex features. In this study, we propose a multiclassification model inspired by dendritic architectures in neurons, which leverages synaptic and dendritic nonlinear information processing capabilities. Experimental results using brain tumor detection datasets demonstrate that our proposed model outperforms other state‐of‐the‐art models across all evaluation metrics. © 2024 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

Metal-Organic Frameworks Constructed from Branched Oligomers.

Metal-organic frameworks (MOFs) prepared from oligomeric or polymeric organic ligands have been studied and are termed oligoMOFs and polyMOFs, respectively. Herein, several oligoMOFs are described that have been prepared from branched oligomers with dendritic or star-like architectures. Branched oligomeric ligands with four (4(H2bdc)-b) or eight (8(H2bdc)-b) 1,4-benzene dicarboxylic acid (H2bdc) groups were prepared and used to synthesize isoreticular-type Zn(II)-based MOFs (IRMOF). A branched tetramer (4(H2bdc)-b) produced an oligoIRMOF-1 with improved ambient stability compared with IRMOF-1 or previously described oligoMOFs. To understand the effect of the ligand architecture, oligoIRMOFs were also prepared from a linear tetramer (4(H2bdc)-l). For a branched octamer (8(H2bdc)-b), it was found that the addition of an organic base was required to produce crystalline oligoIRMOFs. Multivariate MOFs (MTV-MOFs) could also be readily prepared with a combination of an octamer (8(H2bdc)-b) and H2bdc.

Click synthesis of dendronized malonates for the preparation of amphiphilic dendro[60]fullerenes.

Fullerene C60 and its malonate derivatives, produced via the Bingel-Hirsch reaction, have displayed promising properties against various diseases. These molecules have great therapeutic potential, but their broad use has been limited due to poor aqueous solubility and toxicity caused by accumulation. In this study, we synthesized new malonates and malonamides attached to first- and second-generation polyester dendrons using click chemistry (CuAAC). These dendrons were then linked at C60 through the Bingel-Hirsch reaction, resulting in an amphiphilic system that retains the hydrophobic nature of C60. The dendronized malonate derivatives showed good reaction yields for the Bingel-Hirsch mono-adducts and were easier to work with than the corresponding malonamides. However, the malonamide derivatives, which were obtained through a multistep reaction sequence, showed moderate yields in the Bingel-Hirsch reaction. Surprisingly, removing acetonide protecting groups from dendritic architectures was more challenging than anticipated, likely due to product decomposition. Only the corresponding free malonate derivatives 25 and 26 were obtained, but in a low yield due to decomposition under the reaction conditions. Meanwhile, it was not possible to obtain the corresponding malonamide derivatives 27 and 28. Currently, efforts are being made to improve the production of the desired molecules and to design new synthesis routes that allow direct access to the desired poly-hydroxylated derivatives. These derivatives will be evaluated as multitarget ligands against Alzheimer's disease, through their use as inhibitors of amyloid β-peptide aggregation, acetylcholinesterase modulators, and antioxidants.

Unveiling the morphological influence of nitrogen-doped carbonized wood anchored 3D transition metal oxide microarchitectures on catalytic activity: A trifunctional electrocatalyst for sensing and energy conversion

The rational construction and advancement of binder-free, self-standing, and cost-effective electrodes endowed with highly active trifunctional electrocatalysts represent a pivotal nexus between the research domains of energy and healthcare applications. However, the lack of proficient non-precious-metal trifunctional electrocatalysts bridging the aforementioned research domains remains a pinnacle barrier. Herein, we proposed distinct fabrication protocols to construct morphologically diverse three-dimensional (3D) CuO microarchitectures directly docked over the naturally inherited carbon channels of nitrogen-doped carbonized wood (NCW) (CuO@NCW) obtained by the carbonization of waste wood monoliths and explored the efficacy of different catalytic designs towards the trifunctional performances on non-enzymatic glucose sensing and glucose oxidation-assisted water splitting. Among the diverse binder-free engineered electrodes, CuO@NCW obtained via the facile electrodeposition (E) route (dubbed as CuO-E@NCW) demonstrated proficient electrocatalytic trifunctionality benefitting from the allied merits of the robustly anchored 3D porous dendritic architectures equipped with ample porosity and momentous interconnectivity. The as-fabricated CuO-E@NCW electrode as a glucose sensor displays two broad linear ranges between 0.01 and 0.5 mM and 0.5–4.0 mM with corresponding elevated sensitivities of 24.6 and 7.2 mA mM−1 cm−2, with a lower limit of detection of 0.0013 mM (S/N = 3). Besides, this best-performing electrode delivers a high current density of 50 mA cm−2 with a low cell voltage of 1.39 V in the glucose electrolysis system, which is 170 mV lower compared with stereotypical alkaline water splitting.

Dendrimers: Exploring Their Wide Structural Variety and Applications.

Dendrimers constitute a distinctive category of synthetic materials that bear resemblance to proteins in various aspects, such as discrete structural organization, globular morphology, and nanoscale dimensions. Remarkably, these attributes coexist with the capacity for facile large-scale production. Due to these advantages, the realm of dendrimers has undergone substantial advancement since their inception in the 1980s. Numerous reviews have been dedicated to elucidating this subject comprehensively, delving into the properties and applications of quintessential dendrimer varieties like PAMAM, PPI, and others. Nevertheless, the contemporary landscape of dendrimers transcends these early paradigms, witnessing the emergence of a diverse array of novel dendritic architectures in recent years. In this review, we aim to present a comprehensive panorama of the expansive domain of dendrimers. As such, our focus lies in discussing the key attributes and applications of the predominant types of dendrimers existing today. We will commence with the conventional variants and progressively delve into the more pioneering ones, including Janus, supramolecular, shape-persistent, and rotaxane dendrimers.

Tuning the fraction free volume of hyperbranched 6FDA/TAPA polyimide membrane via DAM for enhanced gas separation performance

AbstractAn effective strategy to optimize the gas separation performance of hyperbranched polyimide (hyper‐PI) membranes by tuning their average cavity sizes is reported. Triphenylamine (TAPA) and 4,4′‐(Hexafluoroisopropylidene) diphthalic anhydride (6FDA) were used to prepare the hyper‐PI membrane, and the transformation in free fraction volume (FFV) was realized by the addition of an extra B2‐type monomer, 2,4,6‐Trimethylbenzene‐1,3‐diamine (DAM). In hyperbranched networks, DAM, in conjunction with 6FDA, generates longer linear parts and reduces the density of dendritic architectures formed by TAPA. The conformational freedom of hyperbranched TAPA‐6FDA is restricted, and chain packing is hindered. The ratio of DAM:TAPA predominantly influences both the average cavity sizes and the FFVs of the membranes, leading to the variation in gas permeabilities. DAM5:TAPA1‐6FDA shows the best performance in both O2/N2 and CO2/N2 separations.

Prenatal Di-methoxyethyl phthalate exposure impairs cortical neurogenesis and synaptic activity in the mice.

Di-methoxyethyl phthalate (DMEP) is a well-known environmentally prevalent endocrine disruptor and may be associated with neurodevelopmental disorders including attention deficit/hyperactivity disorder and intellectual disability. However, the regulatory mechanisms leading to these neurodevelopmental disorders are still poorly understood. Here, we demonstrate that prenatal DMEP exposure causes abnormal brain morphology and function in the mice. DMEP (50 mg/kg) was chronically administered to pregnant mice orally once a day starting on embryonic day 0 (E0) to breast-feeding cessation for the fetus. We found that prenatal DMEP exposure significantly reduced the number of neurons in the parietal cortex by impairing neurogenesis and gliogenesis during the developing cortex. Moreover, we found that prenatal DMEP exposure impaired dendritic spine architectures and synaptic activity in the parietal cortex. Finally, prenatal DMEP exposure in mice induces hyperactivity and reduces anxiety behaviors. Altogether, our study demonstrates that prenatal DMEP exposure leads to abnormal behaviors via impairment of neurogenesis and synaptic activity.

Understanding the microstructure and mechanical performance of heat-treated Inconel 625/TiC composite produced by laser powder bed fusion

This work aims to develop and characterize Inconel 625 (IN625) reinforced with 1 wt% of sub-micrometric TiC particles processed by the Laser Powder Bed Fusion (LPBF) process. The effect of TiC particles on the IN625 alloy was investigated in the as-built and two heat-treated conditions. A volumetric energy density of 99 J/mm3 could produce bulk IN625 and IN625/TiC samples with residual porosity less than 0.15%. The as-built IN625 and IN625/TiC showed columnar grains along the building direction and sub-micrometric dendritic architectures. The as-built IN625/TiC presented higher hardness, tensile strength, and similar elongation at failure with respect to the as-built IN625 alloy. These mechanical properties are mainly attributed to the reinforcement effect of the TiC particles predominantly located along the grain boundaries, melt pool contours, and interdendritic areas. After heat treatments at 980 °C and 1150 °C, the IN625 alloy and IN625/TiC composite presented different microstructure stability and mechanical properties evolution, revealing greater hardness and tensile strength for the composite. In particular, when heat-treated, the IN625 was subjected to a remarkable dendritic dissolution at 980 °C and recrystallization at 1150 °C. Conversely, the IN625/TiC revealed a limited dendritic dissolution at 980 °C and the inhibition of recrystallization at 1150 °C. Overall, the pinning effect of the TiC particles was effective in providing less microstructure and mechanical properties variations under heat treatments. The current work describes the effect of adding TiC particles on the microstructure stabilization and mechanical properties evolution of additively processed LPBFed IN625 alloy in as-built and heat-treated conditions.

Dynamic Control over Hierarchically Dendritic Architectures of Simple Heterogenous Monomers by Living Supramolecular Assembly.

The successful preparation of supramolecular block copolymers (SBCPs) by living supramolecular assembly technology requires two kinetic systems in which both the seed (nucleus) and heterogenous monomer providers are in non-equilibrium. However, employing simple monomers to construct the SBCPs via this technology is almost impossible because the low spontaneous nucleation barrier of simple molecules prevents the formation of kinetic states. Here, with the help of confinement from layered double hydroxide (LDH), various simple monomers successfully form living supramolecular co-assemblies (LSCA). LDH overcomes a considerable energy barrier to obtain living seeds to support the growth of the inactivated second monomer. The ordered LDH topology is sequentially mapped to the seed, second monomer, and binding sites. Thus, the multidirectional binding sites are endowed with the ability to branch, making the branch length of dendritic LSCA reach its maximum value of 3.5 cm so far. The strategy of universality will guide exploration into the development of multi-function and multi-topology advanced supramolecular co-assemblies.

Investigating the Cusp Between Dendritic and Supermolecular Architectures in Self‐Organizing Liquid Crystals

AbstractLiquid Crystals are thought of as being complex fluids, underpinned by self‐assembly and self‐organisation within partially ordered fluids, and which sit between solid and liquid states of matter. The realm of the field stretches from low molar mass to polymeric materials, from organic to inorganic substances, and from being functional materials to biological organelles. In this article, we explore the cusp of the change over from nano‐ to macro‐sciences through the formation of ‘supermolecular’ systems, and we debate if such materials are in fact oligomers or materials having giant molecules possessing discrete chemical constitutions? We performed this investigation by synthesising mesogenic materials based upon difluoroterphenyls, terminally substituted with a chiral motif based on (S)‐2‐octanol, and which could be appended onto a variety of siloxane scaffolds. We studied the structures and properties of six mesomorphic materials in which we systematically increased the number of mesogenic units attached to the scaffold.

Thermoresponsive Dendronized Microgels through In Situ Cross-Linking Polymerization to Exhibit Enhanced Confinement for Solvatochromic Dyes

Polymeric microgels form a class of promising materials for various applications based on their highly tunable swelling and cooperative interactions between the cross-linked polymer chains. Here, we report on a convenient route for the fabrication of polymeric microgels through in situ cross-linking polymerization of thermally collapsed macromonomers carrying 3-fold dendritic oligoethylene glycol (OEG) pendants, affording thermoresponsive dendronized microgels with intriguing microconfinement. This methodology has been proven to be versatile and can be used to prepare intelligent microgels through homopolymerization of thermoresponsive dendronized macromonomers, or via copolymerization with either hydrophobic or hydrophilic, and dendronized or nondendronized comonomers. The thermoresponsive microgels of uniform sizes undergo shrinking or swelling by changing the temperature above or below their phase transition temperatures and thus exhibit tunable microconfinement to encapsulated solvatochromic dye molecules. This outstanding capacity for confinement by the microgels is compared to linear copolymers with or without dendritic architectures and is proposed to originate from both dendritic crowding effects and cooperative interactions between polymer chains within the network. This remarkable feature of microconfinement opens a new era for microgels to reversibly encapsulate and protect guest molecules and provides a platform to manipulate the functions of the encapsulated guests through external stimuli.

Synthesis of Dendrimer Conjugates with Naproxen and their Anticancer Activity

Abstract: Here we report the easy synthesis of dendrimer conjugates with four and eight naproxen moieties at the periphery. The synthesis involved two steps protection-deprotection sequence joined with triethylene glycol. A comparison was made between the cytotoxicity of dendron-naproxen conjugates and that of G1.0 G2.0 dendrimer-naproxen conjugates. Cytotoxicity studies showed that dendron conjugates were toxic towards all cancer cell lines studied, and their toxicity was significantly lower than that of dendrimer conjugates. However, dendrimer conjugates showed higher cytotoxicity and selectivity against K-562 and SKLU- 1 than dendron conjugates.

Polymeric architecture as a tool for controlling the reactivity of palladium(II) loaded nanoreactors.

Self-assembled systems, like polymeric micelles, have become great facilitators for conducting organic reactions in aqueous media due to their broad potential applications in green chemistry and biomedical applications. Massive strides have been taken to improve the reaction scope of such systems, enabling them to perform bioorthogonal reactions for prodrug therapy. Considering these significant advancements, we sought to study the relationships between the architecture of the amphiphiles and the reactivity of their PdII loaded micellar nanoreactors in conducting depropargylation reactions. Towards this goal, we designed and synthesized a series of isomeric polyethylene glycol (PEG)-dendron amphiphiles with different dendritic architectures but with an identical degree of hydrophobicity and hydrophilic to lipophilic balance (HLB). We observed that the dendritic architecture, which serves as the main binding site for the PdII ions, has greater influence on the reactivity than the hydrophobicity of the dendron. These trends remained constant for two different propargyl caged substrates, validating the obtained results. Density functional theory (DFT) calculations of simplified models of the dendritic blocks revealed the different binding modes of the various dendritic architectures to PdII ions, which could explain the observed differences in the reactivity of the nanoreactors with different dendritic architectures. Our results demonstrate how tuning the internal architecture of the amphiphiles by changing the orientation of the chelating moieties can be used as a tool for controlling the reactivity of PdII loaded nanoreactors.

Cathodoluminescence Spectroscopy of Complex Dendritic Au Architectures for Application in Plasmon‐Mediated Photocatalysis and as SERS Substrates

AbstractComplex 3D metallic nanostructures with large surface areas and broadband absorption are attractive candidates for efficient photocatalysis and spectroscopy. Here, hierarchical Au dendrites are self‐assembled over centimeter‐scales by electrodeposition and the plasmon modes are locally mapped using cathodoluminescence spectroscopy. A correlation between the spatial and spectral distribution of the plasmonic “hot‐spots” and the morphology of these structures are demonstrated. Electrodynamic simulations show that the spectra of the plasmon modes are determined by the local geometry of sharp features. Their performance as both surface‐enhanced Raman scattering (SERS) substrates and as photocatalysts for the N‐demethylation reaction of methylene blue is investigated. High hot‐spot densities result in larger SERS enhancement, while the sample with the lowest hot‐spot density has a reaction yield 136% larger than the sample with the highest density. These findings indicate that maximizing the hot‐spot density is not sufficient to optimize plasmonic substrates for all applications. The spectral and spatial distribution of the plasmon resonances will modify the hot electron generation efficiency and need to be considered for plasmon‐enhanced photocatalysis. This work extends the understanding of light–matter interactions in complex 3D structures and provides direction for the rational design of plasmonic architectures for different applications.

Sequence-controlled heterolayered lanthanide-complex dendritic architectures constructed from modular Ln-DOTA derivatives

Heterometallic lanthanide complexes, especially with specific metal arrays, are attracting special attention due to their unusual physical properties, which have found many applications in various fields, including high-performance molecular optical/magnetic devices and multifunctional probes for bioassays and bioimaging. However, due to the similar chemical properties of lanthanide ions, their construction is still challenging. Here, we report a new modular approach for the facile and efficient preparation of sequence-specific heterometallic lanthanide-complex-based dendritic architectures, which are termed as sequence-controlled heterolayered lanthanide-ligand structures (SHELLs). As a demonstration, a series of SHELLs containing desired lanthanide chelates with designed sequences are quickly synthesized by iterative covalent linking and extensively characterized with various instruments. The special optical and/or magnetic features of these dendritic structures implicate their promising potential as multifunctional agents. Our study underlines the bright prospective of SHELLs and the substantial significance of this modular strategy for the development of well-ordered giant heterometallic architectures. • Our modular approach permits quick assembly of heterometallic lanthanide complexes • Multicolor luminescence within one single molecule is achieved with SHELLs • Multifunctional SHELLs are prepared through modular assembly of functional units In spite of their challenging construction, heterometallic lanthanide complexes have found many applications in various fields. Yang et al. report a modular approach for facile and efficient preparation of sequence-controlled heterolayered lanthanide-ligand structures (SHELLs), offering quick access to well-ordered multifunctional heterometallic lanthanide-complex-based dendritic architectures.

Click Reaction in the Synthesis of Dendrimer Drug-delivery Systems.

Drug delivery systems are designed for the targeted delivery and controlled release of medicinal agents. Among the materials employed as drug delivery systems, dendrimers have gained increasing interest in recent years because of their properties and structural characteristics. The use of dendrimer-nanocarrier formulations enhances the safety and bioavailability, increases the solubility in water, improves stability and pharmacokinetic profile, and enables efficient delivery of the target drug to a specific site. However, the synthesis of dendritic architectures through convergent or divergent methods has drawbacks and limitations that disrupt aspects related to design and construction, and consequently, slow down the transfer from academia to industry. In that sense, the implementation of click chemistry has received increasing attention in the last years, as it offers new efficient approaches to obtain dendritic species in good yields and higher monodispersity. This review focuses on recent strategies for building dendrimer drug delivery systems using click reactions from 2015 to early 2021. The dendritic structures showed in this review are based on β -cyclodextrins (β-CD), poly(amidoamine) (PAMAM), dendritic poly (lysine) (PLLD), dimethylolpropionic acid (bis-MPA), phosphoramidate (PAD), and poly(propargyl alcohol-4-mercaptobutyric (PPMA).

Au Cluster-Cored Dendrimers Fabricated by Direct Synthesis and Post-functionalization Routes.

The use of dendrimers and dendrons as stabilizing agents for metal nanoparticles and nanoclusters has captured interest in both the biomedicine and catalysis fields. Herein, we describe the synthesis of Au cluster-cored dendrimers by either direct synthesis or multi-step functionalization pathways. Direct synthesis of Au cluster-cored dendrimers was performed by the Brust-Schiffrin method using cystamine core poly(amidoamine) (PAMAM) dendrons as capping agents. Alternatively, a divergent approach to make nanoclusters with dendritic branching groups by functionalizing glycine-cystamine Au clusters was also carried out. This synthesis involved sequential Michael addition reactions of methyl acrylate followed by a subsequent amide coupling reaction with ethylenediamine on amine-terminated Au nanoclusters to form dendritic architectures around the Au core. The chemical structure of the ligands was confirmed by proton nuclear magnetic resonance after each functionalization reaction, and the cluster size was characterized by transmission electron microscopy. Au cluster-cored dendrimers with amine or ester terminal groups on the surface were produced. The resulting amine- and ester-terminated Au cluster-cored dendrimers synthesized by the divergent method are stable in solution and in the presence of excess reducing agent. In contrast, amine-terminated Au cluster-cored dendrimers synthesized by direct synthesis undergo aggregation in solution over time as a result of the high reactivity of the surface, while ester-terminated Au cluster-cored dendrimers formed by direct synthesis have much larger core sizes than seen using the divergent approach. Finally, the catalytic activities of these clusters for 4-nitrophenol reductions have been investigated. Cluster-cored dendrimers formed by direct synthesis had larger core sizes and higher catalytic activities than those formed by the divergent approach, which is likely due to the poor passivation of the Au surface for the directly synthesized clusters. Furthermore, Au cluster-cored dendrimers with less sterically bulky dendrons showed higher catalytic activities.

Accelerating Pd Electrocatalysis for CO2-to-Formate Conversion across a Wide Potential Window by Optimized Incorporation of Cu.

Electrochemical reduction of carbon dioxide (CO2) to formate is a viable way to reduce CO2 emissions and realize a carbon-neutral energy cycle. Although Pd can convert CO2 to formate with a high Faradaic efficiency at minimal overpotentials, it suffers from a limited and narrow potential window. Alloying is an important strategy for the catalyst design and tuning the electronic structures. Here, we report a series of PdCu bimetallic alloy catalysts with tunable compositions based on dendritic architectures. Optimal introduction of Cu atoms into the Pd matrix facilitates formate production and suppresses CO generation. In 0.1 M KHCO3 aqueous solution, our best candidate, Pd82Cu18 catalyst, delivered a high formate Faradaic efficiency of 96.0% at -0.3 V versus RHE. More interestingly, the high selectivity (>90%) toward formate maintained an enlarged electrochemical potential window of 600 mV. The ensemble effect with electronic coupling between Pd and Cu upon alloying and its induced moderate surface O-containing configuration were found to enhance the formate formation and suppress CO poisoning during CO2 reduction.