High-toughness, extensile and self-healing PDMS elastomers constructed by decuple hydrogen bonding

Elastomers are widely used in traditional industries and new intelligent fields. However, they are inevitably damaged by electricity, heat, force, etc. during the working process. With the continuous improvement of reliability and environmental protection requirements in human production and living, it is vital to develop elastomer materials with good mechanical properties that are not easily damaged and can self-heal after being damaged. Nevertheless, there are often contradictions between mechanical properties and self-healing as well as toughness, strength, and ductility. Herein, a strong and dynamic decuple hydrogen bonding based on carbon hydrazide (CHZ) is reported, accompanied with soft polydimethylsiloxane (PDMS) chains to prepare self-healing (efficiency 98.7%), recyclable, and robust elastomers (CHZ-PDMS). The strategy of decuple hydrogen bonding will significantly impact the study of the mechanical properties of elastomers. High stretchability (1731%) and a high toughness of 23.31 MJ m-3 are achieved due to the phase-separated structure and energy dissipation. The recyclability of CHZ-PDMS further supports the concept of environmental protection. The application of CHZ-PDMS as a flexible strain sensor exhibited high sensitivity.

Self-Assembled Supramolecular Micelles Based on Multiple Hydrogen Bonding Motifs for the Encapsulation and Release of Fullerene

Living creatures involve several defense mechanisms, such as protecting enzymes to protect organs and cells from the invasion of free radicals. Developing antioxidant molecules and delivery systems to working with enzymes is vital. In this study, a supramolecular polymer PNI-U-DPy was used to encapsulate C₆₀, a well-known antioxidant that is hard to dissolve or disperse in the aqueous media. PNI-U-DPy exhibits characteristics similar to PNIPAM but could form micelles even when the environment temperature is lower than its LCST. The U-DPy moieties could utilize their strong complementary hydrogen bonding-interaction to create a physically crosslinked network within PNIPAM micelles, thus adjusting its LCST to a value near the physiological temperature. Morphological studies suggested that C₆₀ could be effectively loaded into PNI-U-DPy micelles with a high loading capacity (29.12%), and the resulting complex PNI-C₆₀ is stable and remains temperature responsive. A series of measurements under variable temperatures was carried out and showed that a controlled release process proceeded. Furthermore, PNI-C₆₀ exhibits hydroxyl radicals scavenging abilities at a low dosage and could even be adjusted by temperature. It can be admitted that the micelle system can be a valuable alternative for radical scavengers and may be delivered to the desired position with good dispersibility and thermo-responsivity. It is beneficial to the search progress of scientists for drug delivery systems for chemotherapeutic treatments and biomedical applications.

Self-Assembled Supramolecular Micelles with pH-Responsive Properties for More Effective Cancer Chemotherapy

pH-Responsive hydrogen-bonded supramolecular micelles, composed of a water-soluble poly(ethylene glycol) polymer with two terminal sextuple hydrogen bonding groups, can spontaneously organize in aqueous media to give well-defined, uniformly sized spherical micelles. The supramolecular micelles exhibit a number of unique physical characteristics, such as interesting amphiphilic behavior, desirable micellar size and nanospherical morphology, excellent biocompatibility, tailorable drug-loading capacities, and high structural stability in media containing serum or red blood cells. In addition, the drug release kinetics of drug-loaded micelles can be easily manipulated to achieve the desired release profile by regulating the environmental pH, thus these micelles are highly attractive candidates as an intelligent drug carrier system for cancer therapy. Cytotoxicity assays showed that the drug-loaded micelles induced pH-dependent intracellular drug release and exerted strong antiproliferative and cytotoxic activities toward cancer cells. Importantly, cellular uptake and flow cytometric analyses confirmed that a mildly acidic intracellular environment significantly increased cellular internalization of the drug-loaded micelles and subsequent drug release in the cytoplasm and nucleus of cancer cells, resulting in more effective induction of apoptotic cell death. Thus, this system may provide an efficient route toward achieving the fundamental properties and practical realization of pH-sensitive drug-delivery systems for chemotherapy.

Supramolecular Polymer Network-Mediated Structural Phase Transitions within Polymeric Micelles in Aliphatic Alcohols

Self-complementary supramolecular polymers (SCSPs), an efficient combination of sextuple hydrogen-bonded dimer moieties and a temperature-responsive polymer, can promote the construction of stable supramolecular polymer networks (SPNs) that enable the formation of well-defined nanospherical micelles in aliphatic alcohols. These micelles undergo tailorable, thermoresponsive phase transitions at the upper critical solution temperature (UCST) and have a desirable spherical morphology and size ranges, thus, are potential candidates for applications in interfacial engineering and biomedical fields. Moreover, concentration-dependent UCST measurements and variable-temperature experiments indicated that the hydrogen-bonded complexes are strong enough to form stable intermolecularly entangled SPNs within the micelles, even above the UCST or at low concentrations in solution, which enables the micelles to undergo reversible temperature-dependent conformational changes between insoluble and soluble globules without significant changes in particle size or size distribution. Thus, this newly discovered system offers a new approach toward the development of next-generation temperature-responsive SCSPs with the desired structural stability that undergoes UCST transitions.

Readily functionalized AAA-DDD triply hydrogen-bonded motifs

Herein we present a new, readily functionalized AAA-DDD hydrogen bond array. A novel AAA monomeric unit (3a-b) was obtained from a two-step synthetic procedure starting with 2-aminonicotinaldehyde via microwave radiation (overall yield of 52-66%). 1H NMR and fluorescence spectroscopy confirmed the complexation event with a calculated association constant of 1.57 × 107 M-1. Likewise, the usefulness of this triple hydrogen bond motif in supramolecular polymerization was demonstrated through viscosity measurements in a crosslinked supramolecular alternating copolymer.

Self-assembled supramolecular polymers with tailorable properties that enhance cell attachment and proliferation

Self-assembled supramolecular scaffolds, a combination of noncovalent interactions within a biocompatible polymer substrate, can be used for efficient construction of highly-controlled self-organizing hierarchical structures; these newly-developed biomaterials exhibit excellent mechanical properties, tunable surface hydrophilicity, low cytotoxicity and high biodegradability, making them highly attractive for tissue engineering and regenerative medicine applications. Herein, we demonstrate a novel supramolecular poly(ε-caprolactone) (PCL) containing self-complementary sextuple hydrogen-bonded uracil-diamidopyridine (U-DPy) moieties, which undergoes spontaneous self-assembly to form supramolecular polymer networks. Inclusion of various U-DPy contents enhanced the mechanical strength and viscosities of the resulting materials by up to two orders of magnitude compared to control PCL. Surface wettability and morphological studies confirmed physically-crosslinked films can be readily tailored to provide the desired surface properties. Cell viability assays indicated the excellent in vitro biocompatibility of U-DPy-functionalized substrates and indicate the potential of these materials for various biomedical applications. More importantly, mouse fibroblast NIH/3T3 cells cultured on these substrates displayed a more elongated cell morphology and had substantially higher cell densities than cells seeded on control PCL substrate, which indicates that introduction of U-DPy moieties into polymer matrixes could be used to create tissue culture surfaces that enhance cell attachment and proliferation. This new system is suggested as a potential route towards the practical realization of next-generation tissue-engineering scaffolds.

STATEMENT OF SIGNIFICANCE

In this study, we report a significant breakthrough in development of self-assembled supramolecular polymers to form well-defined scaffolds through self-complementary hydrogen-bonding interactions. These newly developed materials exhibited extremely good mechanical properties, fine-tunable hydrophilic characteristics and excellent biocompatibility due to hydrogen-bond-induced physical cross-linking. Importantly, cell adhesion and proliferation assays indicated that these substrates efficiently promoted the growth of mouse embryonic fibroblasts NIH/3T3 cells in vitro. Thus, this finding provides a simple and effective route for the development of next-generation tissue-engineering scaffolds that have improved mechanical properties, increased surface hydrophilicity and can enhance the growth and biological activity of adherent cells.

Dynamic supramolecular self-assembly: hydrogen bonding-induced contraction and extension of functional polymers

A ureido-cytosine-functionalized supramolecular polymer can be manipulated to control nano-scale microstructures and its ability to form long-range order during self-assembly.

Lamellar mesoscopic organization of supramolecular polymers: a necessary pre-ordering secondary structure

Thy-functionalized PPGs organize in lamellae due to the alignment of amide links in a β-sheet-like secondary structure analogous to proteins.

Highly efficient drug delivery systems based on functional supramolecular polymers: In vitro evaluation

The novel concept of modifying and enhancing the properties of existing functional micelles through self-complementary interactions has significant potential. In this study, a practical approach to living polymerization of functionalized thermoresponsive monomers enabled the incorporation of self-constituted multiple hydrogen bonded groups into micelles that have potential as supramolecular drug-delivery systems. Phase transitions and morphological studies in aqueous solution showed that the microstructure can be controlled to achieve well-defined vesicle-like micelles with respect to the strength of the hydrogen bond segment. Thus, the resulting micelles have a very low critical micellization concentration and very high loading capacity (16.1%), making the loading process extremely stable and efficient. Incorporation of the anticancer drug doxorubicin (DOX) affected the micellization process in aqueous solution and enabled fine-tuning of drug loading and precise control of drug release rate with excellent sensitivity. Release studies in vitro showed that DOX-loaded micelles exerted dose-dependent cytotoxicity against human liver carcinoma (HepG2) cells at the physiological temperature of 37°C. In addition, DOX-loaded micelles were efficiently endocytosed by the cancer cells, which may enable the micelles to serve as suitable vehicles for effective delivery of anticancer drugs to primary tumors and metastatic disease. This newly developed material may provide a potential route towards next-generation drug delivery vehicles.

STATEMENT OF SIGNIFICANCE

A breakthrough innovation in water-based thermo-responsive polymers has enabled significant progress in developing smart stimuli-responsive nanocarriers by generating novel "supramolecular polymeric micelles" via self-complementary hydrogen-bonding interactions. These newly developed micelles exhibit extremely high micellar stability and drug loading capacity (up to 16%), excellent thermo-responsive behavior and precise control of drug release rate due to hydrogen-bond-induced physical cross-linking. In addition, doxorubicin-loaded micelles were efficiently endocytosed by the cancer cells, which allows them to serve as suitable vehicles for effective delivery of anticancer drugs to primary tumors and metastatic disease. Thus, this work provides a potential route for the development of next generation multifunctional nanocarriers that have improved safety and to increase the therapeutic efficacy of anticancer therapy.

Supramolecular Assembly Mediates the Formation of Single-Chain Polymeric Nanoparticles

A breakthrough innovation in water-based polymeric nanoparticles has enabled significant progress in mimicking the folding of natural proteins by generating novel "single-chain polymeric nanoparticles" (SCPNs) via supramolecular interactions. In this study, a practical approach to the living polymerization of functionalized oligo(ethylene glycol) methacrylate monomers allows the incorporation of self-constituted multiple hydrogen-bonded groups into physically cross-linked polymer networks, which enables the formation of highly functionalized SCPNs in an aqueous environment. The newly developed materials are particularly attractive from a practical point of view since they have a very low critical micellization concentration and uniform particle diameters of ca. 25 nm, making them extremely stable under dilute conditions. Concentration-dependent experiments showed that SCPNs formed at polymer concentrations up to 40 mg/mL with no significant change in morphology observed. Moreover, the formed SCPNs had a very high stability in an aqueous solution containing surfactant, suggesting potential for a wide variety of applications as a promising candidate nanocarrier for bioimaging, controlled release, and drug delivery systems.

Large-scale production of ureido-cytosine based supramolecular polymers with well-controlled hierarchical nanostructures

A novel UrCy–PPG was developed for the synthesis of high-quality supramolecular polymers in large-scale production utilizing only commercially-available chemicals.