Self-Sorting of Amphiphilic Copolymers for Self-Assembled Materials in Water: Polymers Can Recognize Themselves

Enhancing stem cell therapy efficacy with functional lignin modified cerium-iron nanozyme through magnetic resonance imaging tracking and apoptosis protection in inflammatory environment

Stem cell transplantation provides a promising approach for addressing inflammation and functional disorders. Nonetheless, the viability of these transplanted cells diminishes significantly within pathological environments, limiting their therapeutic potential. Moreover, the non-invasive tracking of these cells in vivo remains a considerable challenge, hampering the assessment of their therapeutic efficacy. Transition-metal oxide nanocrystals, known for their unique "enzyme-like" catalytic property and imaging capability, provide a new avenue for clinical application. In this study, the lignin as a biocompatible macromolecule was modified with poly (ethylene glycol) through chain-transfer polymerization, and then it was utilized to incorporate superparamagnetic iron oxide and cerium oxide nanocrystals creating a functional nanozyme. The iron oxide nanocrystals self-assembled into the hydrophobic core of nano system, while the in-situ mineralization of cerium oxide particles was carried out with the assistance of peripheral phenolic hydroxyl groups. The product, cerium‑iron core-shell nanozyme, enabled effective stem cells labeling through endocytosis and exhibited catalase and superoxide dismutase activities within the cells. As a result, it could scavenge highly destructive hydroxyl radicals and peroxyl radicals, shielding stem cells from apoptosis in inflammatory environment and maintaining their differentiation ability. Additionally, when these functionalized stem cells were administered to mice with acute inflammation, not only did they alleviate disease symptoms, but they also allowed for the visualization using T2-weighted magnetic resonance imaging. This innovative therapeutic approach provides a new strategy for combatting diseases.

Dynamic Interfaces in Self-Healable Polymers

It is well-established that interfaces play critical roles in biological and synthetic processes. Aside from significant practical applications, the most accessible and measurable quantity is interfacial tension, which represents a measure of the energy required to create or rejoin two surfaces. Owing to the fact that interfacial processes are critical in polymeric materials, this review outlines recent advances in dynamic interfacial processes involving physics and chemistry targeting self-healing. Entropic interfacial energies stored during damage participate in the recovery, and self-healing depends upon copolymer composition and monomer sequence, monomer molar ratios, molecular weight, and polymer dispersity. These properties ultimately impact chain flexibility, shape-memory recovery, and interfacial interactions. Self-healing is a localized process with global implications on mechanical and other properties. Selected examples driven by interfacial flow and shape memory effects are discussed in the context of covalent and supramolecular rebonding targeting self-healable materials development.

Block Sequence Effects on the Self-Assembly Behaviors of Polypeptide-Based Penta-Block Copolymer Hydrogels

Peptide-based hydrogels have great potential for applications in tissue engineering, drug delivery, and so on. We systematically synthesize, characterize, and investigate the self-assembly behaviors of a series of polypeptide-based penta-block copolymers by varying block sequences and lengths. The copolymers contain hydrophobic blocks of poly(γ-benzyl-l-glutamate) (PBG, Bx) and two kinds of hydrophilic blocks, poly(l-lysine) (PLL, Ky) and poly(ethylene glycol) (PEG, EG34), where x and y are the number of repeating units of each block, where PBG and PLL blocks have unique functions for nerve regeneration and cell adhesion. It shows that a sufficient length of the middle hydrophilic segment capped with hydrophobic end PBG blocks is required. They first self-assemble into flower-like micelles and sequentially form transparent hydrogels (as low as 2.3 wt %) with increased polymer concentration. The hydrogels contain a microscale porous structure, a desired property for tissue engineering to facilitate the access of nutrient flow for cell growth and drug delivery systems with high efficiency of drug storage. We hypothesize that the structure of Bx-Ky-EG34-Ky-Bx agglomerates is beyond micron size (transparent), while that of Ky-Bx-EG34-Bx-Ky is on the submicron scale (opaque). We establish a working strategy to synthesize a polypeptide-based block copolymer with a wide window of sol-gel transition. The study offers insight into rational polypeptide hydrogel design with specific morphology, exploring the novel materials as potential candidates for neural tissue engineering.

Dual pH- and Thermo-Sensitive Poly(N-isopropylacrylamide-co-allylamine) Nanogels for Curcumin Delivery: Swelling-Deswelling Behavior and Phase Transition Mechanism

Curcumin (Cur) is a beneficial ingredient with numerous bioactivities. However, due to its low solubility and poor bioavailability, its therapeutic application is limited. In this work, we prepared poly-N-isopropylacrylamide p(NIPAm) and polyallylamine p(Am)-based nanogel (p(NIPAm-co-Am)) NG for a dual pH- and temperature-sensitive copolymer system for drug delivery application. In this copolymer system, the p(NIPAm) segment was incorporated to introduce thermoresponsive behavior and the p(Am) segment was incorporated to introduce drug binding sites (amine groups) in the resulting (p(NIPAm-co-Am)) NG system. Various instrumental characterizations including ¹H nuclear magnetic resonance (¹H NMR) spectroscopy, Fourier transform infrared (FT-IR) analysis, scanning electron microscopy (SEM), zeta potential, and particle size analysis were performed to confirm the copolymer synthesis. Curcumin (Cur), an anticancer bioactive substance, was employed to assess the in vitro drug loading and release performance of the resulting copolymer nanogels system at varied pH levels (pH 7.2, 6.5, and 4.0) and temperatures (25 °C, 37 °C, and 42 °C). The cytocompatibility of the p(NIPAm-co-Am) NG sample was also tested on MDA-MB-231 cells at various sample concentrations. All the study results indicate that the p(NIPAm-co-Am) NG produced might be effective for drug loading and release under pH and temperature dual-stimuli conditions. As a result, the p(NIPAm-co-Am) NG system has the potential to be beneficial in the use of drug delivery applications in cancer therapy.

En Route to Stabilized Compact Conformations of Single-Chain Polymeric Nanoparticles in Complex Media

Precise control over the folding pathways of polypeptides using a combination of noncovalent and covalent interactions has evolved into a wide range of functional proteins with a perfectly defined 3D conformation. Inspired hereby, we develop a series of amphiphilic copolymers designed to form compact, stable, and structured single-chain polymeric nanoparticles (SCPNs) of defined size, even in competitive conditions. The SCPNs are formed through a combination of noncovalent interactions (hydrophobic and hydrogen-bonding interactions) and covalent intramolecular cross-linking using a light-induced [2 + 2] cycloaddition. By comparing different self-assembly pathways of the nanoparticles, we show that, like for proteins in nature, the order of events matters. When covalent cross-links are formed prior to the folding via hydrophobic and supramolecular interactions, larger particles with less structured interiors are formed. In contrast, when the copolymers first fold via hydrophobic and hydrogen-bonding interactions into compact conformations, followed by covalent cross-links, good control over the size of the SCPNs and microstructure of the hydrophobic interior is achieved. Such a structured SCPN can stabilize the solvatochromic dye benzene-1,3,5-tricarboxamide-Nile Red via molecular recognition for short periods of time in complex media, while showing slow exchange dynamics with the surrounding complex media at longer time scales. The SCPNs show good biocompatibility with cells and can carry cargo into the lysosomal compartments of the cells. Our study highlights the importance of control over the folding pathway in the design of stable SCPNs, which is an important step forward in their application as noncovalent drug or catalyst carriers in biological settings.

New Water-Soluble Magnetic Field-Induced Drug Delivery System Obtained Via Preferential Molecular Marriage over Narcissistic Self-Sorting

Nanomaterials that respond to stimuli are of considerable interest for drug delivery applications. Drug delivery has been a leading challenge when it comes to the externally triggered controlled release of hydrophobic drugs. The present paper describes a unique arrangement of polymers in a competitive environment derived from the dynamic self-sorting behavior of the hydrophobic chains of amphiphilic mPEG-PLLA and poly-l-lactic acid (PLLA)-coated iron oxide nanoparticles IONP@PLLA to achieve a core-shell structure in which the hydrophobic PLLA part acts as a dense core and poly(ethylene glycol) (PEG) as an uncrowded shell. By using irreversible covalent interactions created by hydrophobic polymer-functionalized IONPs, it was possible to selectively form socially self-sorted nanocarriers (SS-NCs) with a higher hydrophobic core than the hydrophilic shell over narcissistic self-sorted nanocarriers (NS-NCs), that is, homo-micelles of amphiphilic polymers. The higher hydrophobic core of SS-NCs is indeed helpful in achieving higher drug [doxorubicin (DOX)] loading and encapsulation efficiencies of around 17 and 90%, respectively, over 10.3 and 65.6% for NS-NCs. Furthermore, due to the presence of IONPs and the densely packed hydrophobic compartments, the controlled release of DOX was facilitated by direct magnetism and temperature stimulation when an alternating magnetic field (AMF) was applied. An appreciably higher rate of drug release (∼50%) than that without AMF (∼18%) was achieved under ambient conditions in 24 h. The present study, therefore, proposes a new drug delivery system that exceeds homo-micelles and adds an extra feature of manipulating drug release through magnetism and temperature, that is, hyperthermia.

Single-component nanodiscs via the thermal folding of amphiphilic graft copolymers with the adjusted flexibility of the main chain

Nanodiscs have attracted considerable attention as structural scaffolds for membrane-protein research and as biomaterials in e.g. drug-delivery systems. However, conventional disc-fabrication methods are usually laborious, and disc fabrication via the self-assembly of amphiphiles is difficult. Herein, we report the formation of polymer nanodiscs based on the self-assembly of amphiphilic graft copolymers by adjusting the persistence length of the main chain. Amphiphilic graft copolymers with a series of different main-chain persistence lengths were prepared and these formed, depending on the persistence length, either rods, discs, or vesicles. Notably, polymer nanodiscs were formed upon heating a chilled polymer solution without the need for any additives, and the thus obtained nanodiscs were used to solubilize a membrane protein during cell-free protein synthesis. Given the simplicity of this disc-fabrication method and the ability of these discs to solubilize membrane proteins, this study considerably expands the fundamental and practical scope of graft-copolymer nanodiscs and demonstrates their utility as tools for studying the structure and function of membrane proteins.

Self-sorting assembly of artificial building blocks

Self-assembly to build high-level structures, which is ubiquitous in living systems, has captured the imagination of scientists, striving to emulate the intricacy, homogeneity and versatility of the naturally occurring systems, and to pursue a similar level of organization in artificial building blocks. In particular, self-sorting assembly in multicomponent systems, based on the spontaneous recognition and consequent spatial aggregation of the same or interactive building units, is able to realize very complicated assembly behaviours, and usually results in multiple well-ordered products or hierarchical structures in a one-step manner. This highly efficient assembly strategy has attracted tremendous research attention in recent years, and numerous examples have been reported in artificial systems, particularly with supramolecular and polymeric building blocks. In the current review, we summarize the progress in recent years, and classify them into five main categories, based on their working mechanisms or principles. With the review of these strategies, we hope to provide not only some deep insights into this field, but also and more importantly, useful thoughts in the design and fabrication of self-sorting systems in the future.

Helicity-driven chiral self-sorting supramolecular polymerization with Ag+: right- and left-helical aggregates

The study of chiral self-sorting is extremely important for understanding biological systems and for developing applications for the biomedical field. In this study, we attempted an unprecedented chiral self-sorting supramolecular...

Construction of multifunctional carboxymethyl cellulose nanohydrogel carriers based on near-infrared DNA-templated quantum dots for tumor theranostics

Multifunctional therapeutic platforms with targeted delivery, fast diagnosis, and efficient therapy could effectively reduce side effects and improve treatment in the clinical therapy of tumors. Near-infrared DNA-templated CdTeSe quantum dots (DNA-CdTeSe QDs) were developed as building blocks to construct a multifunctional carboxymethyl cellulose (CMC)-based nanohydrogel as a nanocarrier to address the challenges of serious side effects and precise treatment in cancer theranostics, including active tumor targeting, fluorescence tracking, controlled drug release, chemotherapy and gene regulation. Single-stranded DNA containing the complementarity sequence of miRNA and cystine, as co-crosslinkers, initiated hybridization between the DNA-CdTeSe QD-modified CMC chain with the anti-nucleolin aptamer DNA (AS1411)-modified CMC chain to form the hydrogels. DOX, as a model drug, was successfully incorporated into the hydrogels. The synthesized multifunctional hydrogel nanocarriers with an average diameter of 150 nm could be taken up through targeting and achieved the controlled release of DOX by triggering both glutathione (GSH) and miRNA in the tumor microenvironment. The CdTeSe QDs trapped in nanohydrogels acted as fluorophores for bioimaging in the diagnosis and treatment process. The proposed multifunctional delivery system provided a potential platform for tumor imaging and precise therapy.

Multifunctional carboxymethyl cellulose nanohydrogel carriers for tumor theranostics.

Phase Transitions in Poly(vinylidene fluoride)/Polymethylene-Based Diblock Copolymers and Blends

The crystallization and morphology of two linear diblock copolymers based on polymethylene (PM) and poly(vinylidene fluoride) (PVDF) with compositions PM23-b-PVDF77 and PM38-b-PVDF62 (where the subscripts indicate the relative compositions in wt%) were compared with blends of neat components with identical compositions. The samples were studied by SAXS (Small Angle X-ray Scattering), WAXS (Wide Angle X-ray Scattering), PLOM (Polarized Light Optical Microscopy), TEM (Transmission Electron Microscopy), DSC (Differential Scanning Calorimetry), BDS (broadband dielectric spectroscopy), and FTIR (Fourier Transform Infrared Spectroscopy). The results showed that the blends are immiscible, while the diblock copolymers are miscible in the melt state (or very weakly segregated). The PVDF component crystallization was studied in detail. It was found that the polymorphic structure of PVDF was a strong function of its environment. The number of polymorphs and their amount depended on whether it was on its own as a homopolymer, as a block component in the diblock copolymers or as an immiscible phase in the blends. The cooling rate in non-isothermal crystallization or the crystallization temperature in isothermal tests also induced different polymorphic compositions in the PVDF crystals. As a result, we were able to produce samples with exclusive ferroelectric phases at specific preparation conditions, while others with mixtures of paraelectric and ferroelectric phases.

Thermoresponsive Polysaccharide Graft Polymer Vesicles with Tunable Size and Structural Memory

Controlling polymer vesicle size is difficult and a major obstacle for their potential use in biomedical applications, such as drug-delivery carriers and nanoreactors. Herein, we report size-tunable polymer vesicles based on self-assembly of a thermoresponsive amphiphilic graft copolymer. Unilamellar polymer vesicles form upon heating chilled polymer solutions, and vesicle size can be tuned in the range of 40-70 nm by adjusting the initial polymer concentration. Notably, the polymer can reversibly switch between a monomer state and a vesicle state in accordance with a cooling/heating cycle, which changes neither the size nor the size distribution of the vesicles. This lack of change suggests that the polymer memorizes a particular vesicle conformation. Given our vesicles' size tunability and structural memory, our research considerably expands the fundamental and practical scope of thermoresponsive amphiphilic graft copolymers and renders amphiphilic graft copolymers useful tools for synthesizing functional self-assembled materials.

Solvent effects leading to a variety of different 2D structures in the self-assembly of a crystalline-coil block copolymer with an amphiphilic corona-forming block

We describe a polyferrocenyldimethylsilane (PFS) block copolymer (BCP), PFS27-b-P(TDMA65-ran-OEGMA69) (the subscripts refer to the mean degrees of polymerization), in which the corona-forming block is a random brush copolymer of hydrophobic tetradecyl methacrylate (TDMA) and hydrophilic oligo(ethylene glycol) methyl ether methacrylate (OEGMA). Thus, the corona is amphiphilic. This BCP generates a remarkable series of different structures when subjected to crystallization-driven self-assembly (CDSA) in solvents of different polarity. Long ribbon-like micelles formed in isopropanol, and their lengths could be controlled using both self-seeding and seeded growth protocols. In hexanol, the BCP formed more complex structures. These objects consisted of oval platelets connected to long fiber-like micelles that were uniform in width but polydisperse in length. In octane, relatively uniform rectangular platelets formed. Finally, a distinct morphology formed in a mixture of octane/hexanol, namely uniform oval structures, whose height corresponded to the fully extended PFS block. Both long and short axes of these ovals increased with the initial annealing temperature and with the BCP concentration. The self-seeding protocol also afforded uniform two-dimensional structures. Seeded growth experiments, in which a solution of the BCP in THF was added to a colloidal solution of the oval micelles led to a linear increase in area while maintaining the aspect ratio of the ovals. These experiments demonstrate the powerful effect of the amphiphilic corona chains on the CDSA of a core crystalline BCP in solvents of different hydrophilicity.

Selective Coupling and Polymerization of Folded Polymer Micelles to Nanodomain Self-Assemblies

Herein, we developed selective coupling and polymerization systems of folded polymer micelles via physical interaction in water. The polymer micelles serve as nanodomains to provide double core micelles, alternating necklace micelles, and micelle-connected hydrogels. For this, cation- or anion-tail unimer micelles and amine- or carboxy-tail unimer micelles were designed; the unimer micelles consist of folded amphiphilic random copolymers carrying hydrophilic poly(ethylene glycol) and hydrophobic or hydrogen-bonding pendants. Mixing a cation-tail micelle and an anion-tail micelle, and even the combination of a double cation-tail micelle and a double anion-tail micelle, selectively provided double-core micelles in water without forming large aggregates. Double core micelles afforded structural transformation into linear or cyclic polymers and dynamic exchange of the micelle domains. In contrast, mixing amine-tail micelles and carboxy-tail micelles gave an alternating necklace micelle or a hydrogel. The controlled connection of polymer micelles was achieved by designing suitable physical interaction. This technique opened new ways to create various nanodomain self-assemblies with controlled higher-order structure.

Two-dimensional infrared spectral explorations into bilayer and monolayer self-assemblies of amphiphilic polypeptides

Poly(2-(3-((2-hydroxyethyl)amino)-3-oxopropyl)ethyleneamido) (PHAOE) is an amphiphilic polypeptide. The self-assembly is significant, but the ultrafast dynamic analyses of the peptide self-assembly are exiguous and worth further exploring. In this investigation, the temporal dynamic characteristics of the aggregates and unaggregated PHAOEs are mined by the two-dimensional infrared (2D IR) spectroscopy. The homogeneous and inhomogeneous diffusion processes of the carbonyl stretching modes of the unaggregated PHAOEs are slower than those of the self-assemblies. The inhomogeneous spectral diffusion proportion of the biopolymer PHAOE in methanol is greater than that in dimethyl sulfoxide (DMSO). The solvation shells surround the aggregates and unaggregated PHAOEs in the protic solvent methanol, but there are not any solvation shells around the aggregates or unaggregated PHAOEs in the dipolar solvent DMSO. The massive hydrogen-bonded monolayer self-assembly has merely an aggregate of PHAOEs and no solvation shell in DMSO. But the hydrogen-bonded bilayer self-assembly has a self-assembled methanol shell and an interior aggregate of PHAOEs in methanol. The self-assemblies of PHAOEs motivate the methanols to self-assemble. The large delocalized amide structure results in the fast spectral diffusion of the carbonyl stretching mode.Communicated by Ramaswamy H. Sarma.

N-Centered Chiral Self-Sorting and Supramolecular Helix of Tröger's Base-Based Dimeric Macrocycles in Crystalline State

Three stereoisomers of Tröger's Base-based dimeric macrocycles Trögerophane 1 (T1) including one pair of enantiomers (rac-T1) and one meso isomer (R_2NS_2N-T1) were obtained and fully characterized by X-ray analysis. In the crystalline stacking state R_2NS_2N-T1 showed heterochiral self-sorting behavior along a axis with cofacial π-π stacking interactions, while rac-T1 showed heterochiral self-sorting behavior along c axis with slipped π-π stacking interactions, respectively. Meanwhile both of them showed homochiral self-sorting behavior along b axis as well as one pair of supramolecular helixes were formed in both cases. All the self-sorting behaviors are controlled by two chiral Tröger's Base units from neighboring molecules. To the best of our knowledge, such chiral self-sorting and supramolecular helixes of N-centered chiral superstructures is a rare example. In addition, R_2NS_2N-T1 and rac-T1 demonstrated different adsorption capacities toward the vapor of dichloromethane and acetone, respectively.

Self-assembly of amphiphilic block pendant polymers as microphase separation materials and folded flower micelles

Herein, we created amphiphilic polymers bearing hydrophilic/hydrophobic block pendants as a new class of self-assembled materials for microphase separation in the solid state and folded flower micelles in water.