An AB2 -Type Hyperbranched Supramolecular Polymer Based on Calix[4]pyrrole Anion Recognition: Construction, Stimuli-Responsiveness, and Morphology Tuning

An AB₂ -type monomer comprised of a calix[4]pyrrole skeleton and alternating bis-carboxylate units is reported and used for the construction of a novel supramolecular hyperbranched polymer based on anion recognition ability of calix[4]pyrrole. ¹ H-, DOSY-NMR spectroscopy, viscosity measurements, and dynamic light scattering techniques are used for the characterization of the supramolecular hyperbranched polymer exhibiting thermo-, pH-, and chemical responsiveness, as well as concentration dependent morphology tune as inferred from electron microscopy analyses. The present study enriches the field of supramolecular polymers with a new construction motif, building block, and provides a simple approach for the fabrication of smart polymer material with multi-responsiveness and -morphologies. This article is protected by copyright. All rights reserved.

Polymeric Delivery of Therapeutic Nucleic Acids

The advent of genome editing has transformed the therapeutic landscape for several debilitating diseases, and the clinical outlook for gene therapeutics has never been more promising. The therapeutic potential of nucleic acids has been limited by a reliance on engineered viral vectors for delivery. Chemically defined polymers can remediate technological, regulatory, and clinical challenges associated with viral modes of gene delivery. Because of their scalability, versatility, and exquisite tunability, polymers are ideal biomaterial platforms for delivering nucleic acid payloads efficiently while minimizing immune response and cellular toxicity. While polymeric gene delivery has progressed significantly in the past four decades, clinical translation of polymeric vehicles faces several formidable challenges. The aim of our Account is to illustrate diverse concepts in designing polymeric vectors towards meeting therapeutic goals of in vivo and ex vivo gene therapy. Here, we highlight several classes of polymers employed in gene delivery and summarize the recent work on understanding the contributions of chemical and architectural design parameters. We touch upon characterization methods used to visualize and understand events transpiring at the interfaces between polymer, nucleic acids, and the physiological environment. We conclude that interdisciplinary approaches and methodologies motivated by fundamental questions are key to designing high-performing polymeric vehicles for gene therapy.

Morphological transition of amphiphilic block copolymer/PEGylated phospholipid complexes induced by the dynamic subtle balance interactions in the self-assembled aggregates

Recently, there has been an increasing interest in the control of morphological transition of block copolymer aggregates. Here, we report how to control the morphological transition of methoxy polyethylene glycol–poly(d,l-lactic acid) (PDLLA–MPEG) by adding 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)] (DSPE–PEG). In the aggregates formed by dialyzing DSPE–PEG/PDLLA–MPEG mixed solutions against water, the two hydrophobic fatty acid tails of DSPE–PEG will preferentially anchor to the hydrophobic segment end of PDLLA–MPEG by interdigitating between these two tails and PDLLA segments. Consequently, DSPE–PEG and PDLLA–MPEG will form “ABA” temporary supra-amphiphiles in which A represents a poly(ethylene glycol) (PEG) chain segment and B is a mixed hydrophobic segment composed of PDLLA and DSPE segments; the repulsive force derived from the PEG segments of DSPE–PEG can affect the stability of “ABA” temporary supra-amphiphiles. Our results show that the dynamic subtle balance between the number of “ABA” temporary supra-amphiphiles formed and the strength of repulsive force between the PEG segments of DSPE–PEG drives the morphological structure of DSPE–PEG/PDLLA–MPEG aggregates to change from micelles to vesicles, then to semi-vesicles and finally to mixed micelles, with increasing DSPE–PEG additions.

Morphology-tunable and pH-responsive supramolecular self-assemblies based on AB2-type host-guest-conjugated amphiphilic molecules for controlled drug delivery

Although stimuli-responsive supramolecular self-assemblies have been constructed, the controlled drug delivery induced by morphology transitions of these supramolecular self-assemblies on the basis of host-guest-conjugated monomers (HGCMs) are few reported. In this paper, the self-assembly behaviors of AB2-type HGCMs, e.g., β-cyclodextrin-benzimidazole2 (β-CD-BM2), were investigated at neutral and acidic pH conditions, respectively. Specifically, β-CD-BM2 first self-assembled into fan-shaped supramolecular self-assemblies with a hydrodynamic diameter of 163 nm at neutral pH, whereas they were further dissociated into spherical supramolecular self-assemblies with a size of 52 nm under acidic conditions. This morphology transition process was utilized to conduct a two-stage DOX delivery under neutral and acidic pH. Basic cell experiments demonstrated that the drug-loaded β-CD-BM2-based supramolecular self-assemblies with varied morphology could inhibit cancer cell proliferation, indicating their potential application in the field of drug delivery.

Construction of β-cyclodextrin-based supramolecular hyperbranched polymers self-assemblies using AB2-type macromonomer and their application in the drug delivery field

Despite some efforts have been made in the research of supramolecular hyperbranched polymers (SHPs) self-assemblies, the study which has not been consideration to date is the influence of incoming stimuli-responsive polymer chain on their self-assembly property undergo outer stimuli. The introduction of stimuli-responsive segments which could maintain their hydrophilic property are expected to affect the self-assembly behaviour of SHPs and expand their further biomedical application. In this paper, AB₂-type macromolecular monomer, LA-(CD-PDMA)₂, which consisted one lithocholic acid (LA) and two β-cyclodextrin terminated poly(2-(dimethylamino)ethyl methacrylate) segments (CD-PDMA) was synthesized. LA-(CD-PDMA)₂ based SHP were obtained based on the host-guest inclusion interactions of CD/LA moietes and with PDMA as pH-responsive hydrophilic chains. As a control to study the influence of incoming PDMA chains, both LA-(CD-PDMA)₂ based SHPs-1 and LA-CD₂ based SHPs-2 self-assemblies were comparatively investiged through 2D ¹H NMR ROESY, transmission electron microscopy (TEM) and dynamic light scattering (DLS). The results suggested that except for the higher drug loading efficiency LA-(CD-PDMA)₂ based SHPs-1 pocessing, the release rates of SHPs-1 increased notably at pH 5.0 than that of pH 7.4 due to the repulsion and stretch of protonated PDMA chains while the release rates of SHPs-2 showed no obvious difference. Finally, basic cell experiments demonstrated that the SHPs based self-assemblies can be internalized into cancer cells, indicating their potential application in the drug delivery field.

Functional materials generated by allying cyclodextrin-based supramolecular chemistry with living polymerization

Cyclodextrin molecules are cyclic oligosaccharides that display a unique structure including an inner side and two faces on their outer sides.

Interfacial rheological behaviors of inclusion complexes of cyclodextrin and alkanes

The transformation of cyclodextrins (CDs) and alkanes from separated monomers to inclusion complexes at the interface is illustrated by analyzing the evolution of interfacial tension along with the variation of interfacial area for an oscillating drop. Amphiphilic intermediates are formed by threading one CD molecule on one alkane molecule at the oil/aqueous interface. After that, the amphiphilic intermediates transform into non-amphiphilic supramolecules which further assemble through hydrogen bonding at the oil/aqueous interface to generate a rigid network. With the accumulation of supramolecules at the interface, microcrystals are formed at the interface. The supramolecules of dodecane@2α-CD grow into microrods which form an unconsolidated shell and gradually cover the drop. However, the microcrystals of dodecane@2β-CD are significantly smaller which fabricate into skin-like films at the interface. The amphiphilic intermediates during the transformation increase the feasibility of self-emulsification and the skin-like films enhance the stability of the emulsion. With these unique properties, CDs can be promising for application in hydrophobic drug delivery, food industry and enhanced oil recovery.

Supramolecular hyperbranched polymers

This feature article presents a systematic summary of the synthesis strategies including direct and indirect approaches for obtaining supramolecular hyperbranched polymers (SHPs).

Reversible morphology transitions of supramolecular polymer self-assemblies for switch-controlled drug release

A novel method for switch-controlled drug release was developed through the reversible morphology transitions of supramolecular branched copolymer self-assemblies. The reversible transitions from vesicles to nanoparticles were successfully achieved by alternating UV and visible light irradiation to obtain morphology-controlled drug release in a switch mode.

Supramolecular polymerization induced self-assembly into micelle and vesicle via acid–base controlled formation of fluorescence responsive supramolecular hyperbranched polymers

Micellar and vesicular aggregates were achieved in situ by supramolecular polymerization of π-conjugated AB2 monomers with dibenzo-24-crown-8 and dibenzylammonium groups.

Macroscopic switches constructed through host–guest chemistry

In this feature article, we discuss recent developments in macroscopic contact angle switches formed by different macrocyclic hosts and highlight the properties of these new functional surfaces and their potential applications.

PGMA-based supramolecular hyperbranched polycations for gene delivery

PGMA-based supramolecular hyperbranched polycations were synthesized for effective gene delivery.

Photo-controlled host–guest interaction as a new strategy to improve the preparation of “breathing” hollow polymer nanospheres for controlled drug delivery

Photo-controlled host–guest interaction is used to improve the core removal method for preparing “breathing” hollow nanospheres as drug delivery.