Aggregation-Induced Emission Luminogen Assisted Self-Assembly and Morphology Transition of Amphiphilic Glycopolypeptide with Bioimaging Application

Morphologically Tunable Rectangular Platelets Self-Assembled from Diblock Molecular Brushes Containing Azopyridine Pendants

Two-dimensional (2D) platelet structures are of growing importance as building blocks for the preparation of optical and electrical devices. However, the creation of morphologically tunable rectangular platelets through polymer self-assembly still remains a challenge. Herein, we describe a rational strategy for the fabrication of 2D rectangular platelets by stacking azopyridine-containing diblock molecular brushes in two dimensions in a selective solvent. Amphiphilic PEG-co-(PtBA-g-PAzoPy) DMBs with poly(ethylene glycol) (PEG) block, poly(t-butyl acrylate) (PtBA) backbone, and poly(6-(4-(4-pyridyazo)phenoxy)-hexyl methacrylate) (PAzoPy) brush were synthesized by sequential reversible addition-fragmentation chain transfer polymerization and atom transfer radical polymerization. Various rectangular platelets were obtained via the solution self-assembly of PEG-co-(PtBA-g-PAzoPy) through a heating-cooling-aging process in which the morphology and size of platelets could be controlled by adjusting the composition of DMBs as well as the solvent polarity. In addition, we investigated the metal chelation ability and H-bonding-assisted co-assembly capability of PEG-co-(PtBA-g-PAzoPy). The results displayed that 2D hybrids and flower-like platelets were formed, respectively. Our study presents an efficient method to fabricate rectangular platelets with tunable morphologies.

Nanostructured multifunctional stimuli-responsive glycopolypeptide-based copolymers for biomedical applications

Inspired by natural resources, such as peptides and carbohydrates, glycopolypeptide biopolymer has recently emerged as a new form of biopolymer being recruited in various biomedical applications. Glycopolypeptides with well-defined secondary structures and pendant glycosides on the polypeptide backbone have sparked lots of research interest and they have an innate ability to self-assemble in diverse structures. The nanostructures of glycopolypeptides have also opened up new perspectives in biomedical applications due to their stable three-dimensional structures, high drug loading efficiency, excellent biocompatibility, and biodegradability. Although the development of glycopolypeptide-based nanocarriers is well-studied, their clinical translation is still limited. The present review highlights the preparation and characterization strategies related to glycopolypeptides-based copolymers, followed by a comprehensive discussion on their biomedical applications with a specific focus on drug delivery by various stimuli-responsive (e.g., pH, redox, conduction, and sugar) nanostructures, as well as their beneficial usage in diagnosis and regenerative medicine.

Self-Assembly of an Amphiphilic Bile Acid Dimer: A Combined Experimental and Theoretical Study of Its Medium-Responsive Fluorescence

This work describes the synthesis and aggregation behavior of a dimeric bile acid derivative in which two steroid cores are bridged by a p-di(phenylethynyl)phenylene fluorophore. The studied compound contains three key characteristics: (a) restricted conformational equilibrium in solution, (b) efficient fluorescence conferred by the bridge, and (c) medium responsiveness encoded in the steroid fragments. The incorporation of the three components afforded a compound that generates nano- and micrometric spherical particles with aggregation-responsive fluorescence emission. The observed self-assembly process of the featured molecule was induced by the gradual addition of water to the tetrahydrofuran (THF) solution. This aggregation led to significant changes in fluorescence that went from two bands at λ_em values of 370 and 390 nm in pure THF to a new spectrum with two maxima at λ_em values of 395 and 418 nm at high water contents, without a decrease in emission. The observed changes can be ascribed to weakly coupled aggregation, a hypothesis supported by multiscale molecular modeling, which sheds light on the mechanism of the self-assembly of this unconventional amphiphile.

Tunable AggregationInduced Emission Fluorophore with the Assistance of the SelfAssembly of Block Copolymers by Controlling the Morphology and Secondary Conformation for Bioimaging

Aggregation-induced emission (AIE) luminogens with highly tunable properties show great potential for many applications. In this study, we synthesized a new family of AIE-type poly(ethylene glycol)-block-poly(9-anthrylmethyl lysine) (PEG-b-PLys-An) diblock copolymers by taking advantage of amphiphilic self-assembly and rigid helical backbones. These copolymers can self-assemble into various assemblies through nanoprecipitation methods. The micelles using N,N-dimethylformamide (DMF) as a cosolvent present brighter fluorescence than the vesicles prepared from tetrahydrofuran (THF). We demonstrate that the decreased solubility of copolymers in DMF results in the formation of more compact micelles with more excimer formation during the self-assembly process, while better solvent THF favors the formation of vesicles with stretched core chains. In addition, the secondary conformation of the polypeptide block shows pronounced effects on the fluorescence property. We further show the internalization of the assemblies using two types of cells by cellular uptake experiments. By the delicate design of the block copolymer, we successfully prepare the morphology- and conformation-dependent AIE materials for potential biomedical applications.

Hierarchy of Complex Glycomacromolecules: From Controlled Topologies to Biomedical Applications

Carbohydrates bearing a distinct complexity use a special code (Glycocode) to communicate with carbohydrate-binding proteins at a high precision to manipulate biological activities in complex biological environments. The level of complexity in carbohydrate-containing macromolecules controls the amount and specificity of information that can be stored in biomacromolecules. Therefore, a better understanding of the glycocode is crucial to open new areas of biomedical applications by controlling or manipulating the interaction between immune cells and pathogens in terms of trafficking and signaling, which would become a powerful tool to prevent infectious diseases. Even though a certain level of progress has been achieved over the past decade, synthetic glycomacromolecules are still lagging far behind naturally existing glycans in terms of complexity and precision because of insufficient and inefficient synthetic techniques. Currently, specific targeting at a cellular level using synthetic glycomacromolecules is still challenging. It is obvious that multidisciplinary collaborations are essential between different specialized disciplines to enhance the carbohydrate receptor-targeting paradigm for new biomedical applications. In this Perspective, recent developments in the synthesis of sophisticated glycomacromolecules are highlighted, and their biological and biomedical applications are also discussed in detail.

Fluorescent homopolypeptide toroids

Toroids are important ring-like nanostructures in living systems; intrinsically luminogenic toroids are promising in bioimaging but it is challenging to synthesize such nanoparticles. Herein, we report a fluorescent toroid that...

Branched Aggregates with Tunable Morphology via Hierarchical Self-Assembly of Azobenzene-Derived Molecular Double Brushes

Hierarchical self-assembly is one of the most effective approaches to fabricate nature-inspired materials with subtle nanostructures. We report a distinct hierarchical self-assembly process of molecular double brushes (MDBs) with each graft site carrying a poly(azobenzene-acrylate) (PAzo) chain and a poly(ethylene oxide) (PEO) chain. Asymmetric tapered worm (ATW) nanostructures with chain-end reactivity assembling from the azobenzene-derived MDBs serve as primary subunits to prepare branched supermicelles by increasing water content (C_w ) in THF/water. Various natural Antedon-shaped multiarm worm-like aggregates (MWAs) can be created via the particle-particle connection of ATWs. Intriguingly, the azobenzene moieties undergo trans-cis isomerization upon UV irradiation and further promote a morphology evolution of MWAs. Multiscale supermicelles comprised of starfish shapes with differing central body and arm morphologies (e.g., compare to the biological specimens Luidia ciliaris and Crossaster papposus) were prepared by manipulating irradiation time.

Nanomaterials with Supramolecular Assembly Based on AIE Luminogens for Theranostic Applications

One of the major pursuits of biomedical science is to develop advanced strategies for theranostics, which is expected to be an effective approach for achieving the transition from conventional medicine to precision medicine. Supramolecular assembly can serve as a powerful tool in the development of nanotheranostics with accurate imaging of tumors and real-time monitoring of the therapeutic process upon the incorporation of aggregation-induced emission (AIE) ability. AIE luminogens (AIEgens) will not only enable fluorescence imaging but will also aid in improving the efficacy of therapies. Furthermore, the fluorescent signals and therapeutic performance of these nanomaterials can be manipulated precisely owing to the reversible and stimuli-responsive characteristics of the supramolecular systems. Inspired by rapid advances in this field, recent research conducted on nanotheranostics with the AIE effect based on supramolecular assembly is summarized. Here, three representative strategies for supramolecular nanomaterials are presented as follows: a) supramolecular self-assembly of AIEgens, b) the loading of AIEgens within nanocarriers with supramolecular assembly, and c) supramolecular macrocycle-guided assembly via host-guest interactions. Meanwhile, the diverse applications of such nanomaterials in diagnostics and therapeutics have also been discussed in detail. Finally, the challenges of this field are listed in this review.

Self-Assembly and Photoinduced Spindle-Toroid Morphology Transition of Macromolecular Double-Brushes with Azobenzene Pendants

Asymmetric macromolecular double-brushes (MDBs) are composed of two different side chains grafted on a linear backbone, possessing distinct assembly behaviors in comparison with conventional amphiphiles, owing to the Janus architecture and combined effects of backbone and hetero double-brushes. Additionally, the introduction of unique functionalities and responsiveness into the self-assembly system of MDBs endows extra opportunities to pursue morphologic diversity and intriguing properties. Herein, we report the synthesis of Janus-like MDBs of polyacrylate-g-poly(6-(4-butyl-4'-oxyazobenzene) hexyl acrylate)/poly(ethylene oxide) (PA-g-PAzo/PEO), in which hydrophilic PEO and hydrophobic PAzo brushes were grafted using the combination of concurrent ATRP and click reaction. Due to the special Janus topology and inter/intramolecular association of pendant azobenzene groups, amphiphilic PA-g-PAzo/PEO self-assembled into multimolecular rod and spindle-like aggregates. It is interesting that a transition of spindle-toroid-spindle was observed upon the alternative irradiation between UV and visible light, which is ascribed to the trans-to-cis isomerization of azobenzene molecular brushes. To our best knowledge, this is the first time that azobenzene-containing MDBs enable the fabrication of distinctive self-assembled morphologies and photoinduced toroid formation. The controlled synthesis of MDBs with unique functionalities and subsequent development of their structure-property relationships would shed light on the design and optimization of bottlebrush-based nanomaterials.

AIE-active micelles formed by self-assembly of an amphiphilic platinum complex possessing isoxazole moieties

We report a luminescent micelle that is prepared through the self-assembly of an amphiphilic, neutral Pt(ii) complex with isoxazole moieties in THF/water on account of its aggregation-induced emission (AIE) property.