Cooperative macromolecular self-assembly toward polymeric assemblies with multiple and bioactive functions

Seeded RAFT Polymerization-Induced Self-assembly: Recent Advances and Future Opportunities

Over the past decade, polymerization-induced self-assembly (PISA) has fully proved its versatility for scale-up production of block copolymer nanoparticles with tunable sizes and morphologies; yet, there are still some limitations. Recently, seeded PISA approaches combing PISA with heterogeneous seeded polymerizations have been greatly explored and are expected to overcome the limitations of traditional PISA. In this review, recent advances in seeded PISA that have expanded new horizons for PISA are highlighted including i) general considerations for seeded PISA (e.g., kinetics, the preparation of seeds, the selection of monomers), ii) morphological evolution induced by seeded PISA (e.g., from corona-shell-core nanoparticles to vesicles, vesicles-to-toroid, disassembly of vesicles into nanospheres), and iii) various well-defined nanoparticles with hierarchical and sophisticated morphologies (e.g., multicompartment micelles, porous vesicles, framboidal vesicles, AXn -type colloidal molecules). Finally, new insights into seeded PISA and future perspectives are proposed.

Self-Assembled Polymeric Materials: Design, Morphology, and Functional-Oriented Applications

This Review focuses on the current research advances of the synthesis of various amphiphilic block copolymers (ABCs), such as conventional ABCs and newly-presented polyprodrug amphiphiles (PPAs), and the development of corresponding self-assemblies in selective solvents driven by the intermolecular interactions, like noncovalent hydrophobic interactions, π-π interactions, and hydrogen bonds, between ABCs or preformed small polymeric nanoparticles. The design of these assemblies is systematically introduced, and the diverse examples concerning the unique assembly structures along with the fast development of their exclusive properties and various applications in different fields were discussed. Possible perspectives on the existential challenges and glorious future were elucidated finally. We hope this review will provide a convenient way for readers to motivate more evolutional innovative concepts and methods to design next generation of novel polymeric nanoassemblies, and fill the gap between material design and practical applications. This article is protected by copyright. All rights reserved.

Polymeric nanostructures based on azobenzene and their biomedical applications: synthesis, self-assembly and stimuli-responsiveness

Amphiphilic polymers can self-assemble to form nanoparticles with different structures under suitable conditions. Polymer nanoparticles functionalized with aromatic azo groups are endowed with photo-responsive properties. In recent years, a variety of photoresponsive polymers and nanoparticles have been developed based on azobenzene, using different molecular design strategies and synthetic routes. This article reviews the progress of this rapidly developing research field, focusing on the structure, synthesis, assembly and response of photo-responsive polymer assemblies. According to the molecular structure, photo-responsive polymers can be divided into linear polymers containing azobenzene in a side chain, linear polymers containing azobenzene in the main chain, linear polymers containing azobenzene in an end group, branched polymers containing azobenzene and supramolecular polymers containing azobenzene. These systems have broad biomedical application prospects in the field of drug delivery and imaging applications.

Self-assembly of amino acids toward functional biomaterials

Biomolecules, such as proteins and peptides, can be self-assembled. They are widely distributed, easy to obtain, and biocompatible. However, the self-assembly of proteins and peptides has disadvantages, such as difficulty in obtaining high quantities of materials, high cost, polydispersity, and purification limitations. The difficulties in using proteins and peptides as functional materials make it more complicate to arrange assembled nanostructures at both microscopic and macroscopic scales. Amino acids, as the smallest constituent of proteins and the smallest constituent in the bottom-up approach, are the smallest building blocks that can be self-assembled. The self-assembly of single amino acids has the advantages of low synthesis cost, simple modeling, excellent biocompatibility and biodegradability in vivo. In addition, amino acids can be assembled with other components to meet multiple scientific needs. However, using these simple building blocks to design attractive materials remains a challenge due to the simplicity of the amino acids. Most of the review articles about self-assembly focus on large molecules, such as peptides and proteins. The preparation of complicated materials by self-assembly of amino acids has not yet been evaluated. Therefore, it is of great significance to systematically summarize the literature of amino acid self-assembly. This article reviews the recent advances in amino acid self-assembly regarding amino acid self-assembly, functional amino acid self-assembly, amino acid coordination self-assembly, and amino acid regulatory functional molecule self-assembly.

Self-assembling peptides as vectors for local drug delivery and tissue engineering applications

Molecular self-assembly has forged a new era in the development of advanced biomaterials for local drug delivery and tissue engineering applications. Given their innate biocompatibility and biodegradability, self-assembling peptides (SAPs) have come in the spotlight of such applications. Short and water-soluble SAP biomaterials associated with enhanced pharmacokinetic (PK) and pharmacodynamic (PD) responses after the topical administration of the therapeutic systems, or improved regenerative potential in tissue engineering applications will be the focus of the current review. SAPs are capable of generating supramolecular structures using a boundless array of building blocks, while peptide engineering is an approach commonly pursued to encompass the desired traits to the end composite biomaterials. These two elements combined, expand the spectrum of SAPs multi-functionality, constituting them potent biomaterials for use in various biomedical applications.

Gemcitabine-retinoid prodrug loaded nanoparticles display in vitro antitumor efficacy towards drug-resilient human PANC-1 pancreatic cancer cells

The treatment of pancreatic cancer with gemcitabine is hampered by its rapid metabolism in vivo, the dense stroma around the tumor site which prevents the drug from reaching the cancerous cells and drug resistance. To address these challenges, this study describes the preparation of a retinoid prodrug of gemcitabine, GemRA (gemcitabine conjugated to retinoic acid), and its formulation into a nanoparticulate system applicable for pancreatic cancer treatment. Retinoic acid targets stellate cells which are part of the stroma and can thus augment the delivery of gemcitabine. GemRA dissolved in dimethylsulfoxide presented efficacy towards PANC-1 (human) and mT4 (mouse) pancreatic cancer cell lines but its poor solubility in aqueous solution affects its applicability. Thus, the preparation of the nanoparticles was initially attempted through self-assembly of GemRA, which resulted in the formation of unstable aggregates that precipitated during preparation. As a result, encapsulation of the drug into micelles of polyethylene glycol-retinoic acid (PGRA) amphiphilic conjugates was accomplished and resulted in successful incorporation of GemRA into nanoparticles of ca. 33 nm by dynamic light scattering and 25 nm by transmission electron microscopy. The nanoparticles had good stability in aqueous media and protected gemcitabine from the enzymatic action of cytidine deaminase, which converts gemcitabine to its inactive metabolite upon circulation. Cellular uptake of the nanoparticles by PANC-1 cells was confirmed by fluorescence spectroscopy and flow cytometry. Treatment of PANC-1 cells in vitro with the prodrug-loaded nanoparticles resulted in a significant reduction in cell viability (IC50 ca. 5 μM) compared to treatment with gemcitabine (IC50 > 1000 μM). The ability of the GemRA-loaded nanoparticles to induce cellular apoptosis of treated PANC-1 cells was ascertained via a TUNEL assay suggesting these nanoparticles are effective in pancreatic cancer treatment.

Systematic and Quantitative Structure-Property Relationships of Polymeric Medical Nanomaterials: From Systematic Synthesis and Characterization to Computer Modeling and Nano-Bio Interaction and Toxicity

Nanomaterials allow designing targeted therapies, facilitate molecular diagnostics, and are therefore enabling platforms for personalized medicine. A systematic science and a predictive understanding of molecular/supramolecular structure relationships and nanoparticle structure/biological property relationships are needed for rational design and clinical progress but are hampered by the anecdotal nature, nonsystematic and nonrepresentative nanomaterial assortment, and oligo-disciplinary approach of many publications. Here, we find that a systematic and comprehensive multidisciplinary approach to production and exploration of molecular-structure/nanostructure relationship and nano-bio structure/function relationship of medical nanomaterials can be achieved by combining systematic chemical synthesis, thorough physicochemical analysis, computer modeling, and biological experiments, as shown in a nanomaterial family of amphiphilic, micelle-forming oxazoline/siloxane block copolymers suited for the clinical application. This comprehensive interdisciplinary approach leads to improved understanding of nanomaterial structures, allows good insights into binding modes for the nanomaterial protein corona, induces the design of minimal cell-binding materials, and yields rational strategies to avoid toxicity. Thus, this work contributes to a systematic and scientific basis for rational design of medical nanomaterials.

pH-Responsive Polyketone/5,10,15,20-Tetrakis-(Sulfonatophenyl)Porphyrin Supramolecular Submicron Colloidal Structures

In this work, we prepared color-changing colloids by using the electrostatic self-assembly approach. The supramolecular structures are composed of a pH-responsive polymeric surfactant and the water-soluble porphyrin 5,10,15,20-tetrakis-(sulfonatophenyl)porphyrin (TPPS). The pH-responsive surfactant polymer was achieved by the chemical modification of an alternating aliphatic polyketone (PK) via the Paal–Knorr reaction with N-(2-hydroxyethyl)ethylenediamine (HEDA). The resulting polymer/dye supramolecular systems form colloids at the submicron level displaying negative zeta potential at neutral and basic pH, and, at acidic pH, flocculation is observed. Remarkably, the colloids showed a gradual color change from green to pinky-red due to the protonation/deprotonation process of TPPS from pH 2 to pH 12, revealing different aggregation behavior.

Ultrasound-Activated Cascade Effect for Synergistic Orthotopic Pancreatic Cancer Therapy

In some malignant tumor, especially for pancreatic tumor, poor solid-tumor penetration of nanotherapeutics impedes their treatment efficacy. Herein, we develop a polymer-peptide conjugate with the deep tissue penetration ability, which undergoes a cascade process under ultrasound (US), including (1) the singlet oxygen ¹O₂ is generated by P18, (2) the thioketal bond is cleaved by the ¹O₂, (3) the departure of PEG chains leads to the in situ self-assembly, and (4) the resultant self-assembled PK nanoparticles show considerable cellular internalization. Owing to the synergistic effect of US on increasing the membrane permeability, the endocytosis and lysosome escape of PK nanoparticles are further enhanced effectively, resulting in the improved therapeutic efficacy. Thanks to the high tissue-penetrating depth and spatial precision of US, PTPK presents enhanced tumor inhibition in an orthotopic pancreatic tumor model. Therefore, the US-activated cascade effect offers a novel perspective for precision medicine and disease theranostics.

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PPCs in single molecule state present remarkable solid-tumor penetrability

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US induced in situ self-assembly of PPCs is verified

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Assembled nanoparticles and US synergistically contribute to the cellular internalization

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US-activated cascade effect leads to effective inhibition of pancreatic tumor growth

Selective Self-Assembly of 5-Fluorouracil through Nonlinear Solvent Response Modulates Membrane Dynamics

Controllable self-assembly and understanding of the interaction between single metabolite fibrils and live-cell membranes have paramount importance in providing minimal treatment in several neurodegenerative disorders. Here, utilizing the nonlinear nature and peculiar hydrogen bonding behavior of the dimethyl sulfoxide (DMSO)-water mixture, the selective self-assembly of a single metabolite 5-fluorouracil (5-FU) is achieved. A direct correlation between water availability and selective self-assembly of 5-FU is ratified from the excited-state dynamics. The specific fibrillar structures of 5-FU exhibit a great potential to modulate live cell membrane fluidity and model membrane lipid distribution. After 5-FU fibril addition, a disorder of H-bonded water molecules arises several layers beyond the first hydration shell of the polar headgroups, which essentially modifies interfacial water structure and dynamics. Overall, our results shed light on the role of solvent to govern specific self-assembly and also lay the foundation accounting for the earlier stage of several diseases and multidrug resistance.

Hierarchical self-assembly of a PS-b-P4VP/PS-b-PNIPAM mixture into multicompartment micelles and their response to two-dimensional confinement

Finely tuned synergistic effects among different blocks could realize intriguing hierarchical self-assembly of block copolymers and such hierarchical self-assembly could be manipulated by cylindrical confinement to tune the structures of assemblies.

Mimicking Molecular Chaperones to Regulate Protein Folding

Folding and unfolding are essential ways for a protein to regulate its biological activity. The misfolding of proteins usually reduces or completely compromises their biological functions, which eventually causes a wide range of diseases including neurodegeneration diseases, type II diabetes, and cancers. Therefore, materials that can regulate protein folding and maintain proteostasis are of significant biological and medical importance. In living organisms, molecular chaperones are a family of proteins that maintain proteostasis by interacting with, stabilizing, and repairing various non-native proteins. In the past few decades, efforts have been made to create artificial systems to mimic the structure and biological functions of nature chaperonins. Herein, recent progress in the design and construction of materials that mimic different kinds of natural molecular chaperones is summarized. The fabrication methods, construction rules, and working mechanisms of these artificial chaperone systems are described. The application of these materials in enhancing the thermal stability of proteins, assisting de novo folding of proteins, and preventing formation of toxic protein aggregates is also highlighted and explored. Finally, the challenges and potential in the field of chaperone-mimetic materials are discussed.

Adaptive Polymeric Assemblies for Applications in Biomimicry and Nanomedicine

Dynamic and adaptive self-assembly systems are able to sense an external or internal (energy or matter) input and respond via chemical or physical property changes. Nanomaterials that show such transient behavior have received increasing interest in the field of nanomedicine due to improved spatiotemporal control of the nanocarrier function. In this regard, much can be learned from the field of systems chemistry and bottom-up synthetic biology, in which complex and intelligent networks of nanomaterials are designed that show transient behavior and function to advance our understanding of the complexity of living systems. In this Perspective, we highlight the recent advancements in adaptive nanomaterials used for nanomedicine and trends in transient responsive self-assembly systems to envisage how these fields can be integrated for the formation of next-generation adaptive stimuli-responsive nanocarriers in nanomedicine.

Associative properties of poly(ethylene glycol)-poly(vinyl acetate) comb-like graft copolymers in water

The self-assembly of amphiphilic graft copolymers is generally reported for polymer melts or polymers deposited onto surfaces, while a small number of cases deal with binary mixtures with water. We report on the associative properties of poly(ethylene glycol)-graft-poly(vinyl acetate) (PEG-g-PVAc) comb-like copolymers in water, demonstrating the existence of a percolative behaviour when increasing the PEG-g-PVAc content. Rheology, light- and small-angle X-ray scattering experiments, together with dissipative particle dynamics simulations, reveal a progressive transition from spherical polymer single-chain nanoparticles (SCNPs) towards hierarchically complex structures as the weight fraction of the polymer in water increases. The ability of PEG-g-PVAc to attain different nano- and microstructures is of great importance in numerous applications such as in the fields of cosmetics, detergency and drug delivery.

Addressable Peptide Self-Assembly on the Cancer Cell Membrane for Sensitizing Chemotherapy of Renal Cell Carcinoma

Chemotherapy has been validated unavailable for treatment of renal cell carcinoma (RCC) in clinic due to its intrinsic drug resistance. Sensitization of chemo-drug response plays a crucial role in RCC treatment and increase of patient survival. Herein, a recognition-reaction-aggregation (RRA) cascaded strategy is utilized to in situ construct peptide-based superstructures on the renal cancer cell membrane, enabling specifically perturbing the permeability of cell membranes and enhancing chemo-drug sensitivity in vitro and in vivo. First, P1-DBCO can specifically recognize renal cancer cells by targeting carbonic anhydrase IX. Subsequently, P2-N₃ is introduced and efficiently reacts with P1-DBCO to form a peptide P3, which exhibits enhanced hydrophobicity and simultaneously aggregates into a superstructure. Interestingly, the superstructure retains on the cell membrane and perturbs its integrity/permeability, allowing more doxorubicin (DOX) uptaken by renal cancer cells. Owing to this increased influx, the IC₅₀ is significantly reduced by nearly 3.5-fold compared with that treated with free DOX. Finally, RRA strategy significantly inhibits the tumor growth of xenografted mice with a 3.2-fold enhanced inhibition rate compared with that treated with free DOX. In summary, this newly developed RRA strategy will open a new avenue for chemically engineering cell membranes with diverse biomedical applications.

Fabrication of Hybrid Polymeric Micelles Containing AuNPs and Metalloporphyrin in the Core

Multi-structure assemblies consisting of gold nanoparticles and porphyrin were fabricated by using diblock copolymer, poly(ethylene glycol)-block-poly(4-vinylpyridine) (PEG-b-P4VP). The copolymer of PEG-b-P4VP was used in the formation of core-shell micelles in water, in which the P4VP block serves as the core, while the PEG block forms the shell. In the micellar core, gold nanoparticle and metalloporphyrin were dispersed through the axial coordination. Structural and morphological characterizations of the complex micelle were carried out by transmission electron microscopy, laser light scatting, and UV-visible spectroscopy. Metalloporphyrin in the complex micelle exhibited excellent photostability by reducing the generation of the singlet oxygen. This strategy may provide a novel approach to design photocatalysts that have target applications in photocatalysis and solar cells.

Composite Nanotube Ring Structures Formed by Two-Step Self-Assembly for Drug Loading/Release

Nanotube rings are barely reported novel structures formed by the self-assembly of soft matter, as compared with nanotube structures and ring structures. The two-step self-assembly of amphiphilic copolymer AB and solvophobic copolymer CDC was studied. We found that nanotube rings can be formed from a certain mass ratio of copolymer CDC to copolymer AB and block D of certain rigidity. More interestingly, we discovered a new strategy for drug loading and release, which is different from the usual strategies reported in the literature. The present study provides a new rationale for the self-assembly of copolymers.

Poly(β-Amino Esters): Synthesis, Formulations, and Their Biomedical Applications

Poly(β-amino ester) (abbreviated as PBAE or PAE) refers to a polymer synthesized from an acrylate and an amine by Michael addition and has properties inherent to tertiary amines and esters, such as pH responsiveness and biodegradability. The versatility of building blocks provides a library of polymers with miscellaneous physicochemical and mechanical properties. When used alone or together with other materials, PBAEs can be fabricated into different formulations in order to fulfill various requirements in drug delivery (for instance, gene, anticancer drugs, and antimicrobials delivery) and natural complex mimicry (nanochaperones). This progress report discusses the recent developments in design, synthesis, formulations, and applications of PBAEs in biomedical fields and provides a perspective view for the future of the PBAEs.

Foe to Friend: Supramolecular Nanomedicines Consisting of Natural Polyphenols and Bortezomib

Bortezomib (BTZ) is a first-in-class boronate proteasome inhibitor used for cancer therapy, but its therapeutic efficacy is usually inhibited by dietary polyphenols due to boronate-catechol complexation. Benefiting from such dynamic covalent chemistry, herein we describe a novel class of supramolecular nanomedicines by rationally converting natural polyphenols from foe to friend through polyphenol-mediated BTZ assembly strategy. The simple conjugation of BTZ to catechol-containing natural polyphenols via boronate ester bond allows the facile formation of dynamic drug amphiphiles, with pH-dependent assembly/disassembly behaviors under different physiological conditions. Ferric ion was also incorporated into the supramolecular system via metal-phenolic coordination interaction to both introduce bioimaging function and facilitate stability of the supramolecular nanomedicines. Our investigation revealed that the supramolecular nanomedicine consisting of natural polyphenol, BTZ and ferric ion dramatically induced apoptosis on cancer cells and suppressed tumor growth in both subcutaneous and bone tumor models with limited adverse effects. Such natural polyphenol-mediated small drug assembly strategy enables the robust fabrication of supramolecular nanomedicines for efficient delivery and controlled release of BTZ in targeted tumor sites, which could be further employed in other types of boronic acid-containing supramolecular therapeutics toward a wide range of diseases.

Nanocarriers with conjugated antimicrobials to eradicate pathogenic biofilms evaluated in murine in vivo and human ex vivo infection models

Conventional antimicrobials are becoming increasingly ineffective for treating bacterial infection due to the emergence of multi-drug resistant (MDR) pathogens. In addition, the biofilm-mode-of-growth of infecting bacteria impedes antimicrobial penetration in biofilms. Here, we report on poly(ethylene)glycol-poly(β-amino esters) (PEG-PAE) micelles with conjugated antimicrobials, that can uniquely penetrate biofilms, target themselves to bacterial cell surfaces once inside the low-pH environment of a biofilm and release conjugated antimicrobials through degradation of their ester-linkage with PAE by bacterial lipases. In vitro, PEG-PAE micelles with conjugated Triclosan (PEG-PAE-Triclosan) yielded no inadvertent leakage of their antimicrobial cargo and better killing of MDR Staphylococcus aureus, Escherichia coli and oral streptococcal biofilms than Triclosan in solution. In mice, PEG-PAE-Triclosan micelles with conjugated Triclosan yielded better eradication efficacy towards a MDR S. aureus-infection compared with Triclosan in solution and Triclosan-loaded micelles at equal Triclosan-equivalent concentrations. Ex vivo exposure of multi-species oral biofilms collected from orthodontic patients to PEG-PAE-Triclosan micelles, demonstrated effective bacterial killing at 30-40 fold lower Triclosan-equivalent concentrations than achieved by Triclosan in solution. Importantly, Streptococcus mutans, the main causative organism of dental caries, was preferentially killed by PEG-PAE-Triclosan micelles. Thus PEG-PAE-Triclosan micelles present a promising addendum to the decreasing armamentarium available to combat infection in diverse sites of the body. STATEMENT OF SIGNIFICANCE: pH-adaptive polymeric micelles with conjugated antimicrobials can efficiently eradicate infectious biofilms from diverse body sites in mice and men. An antimicrobial was conjugated through an ester-linkage to a poly(ethylene glycol) (PEG)/poly(β-amino ester) block copolymer to create micellar nanocarriers. Stable micelle structures were formed by the hydrophobic poly(β-amino ester) inner core and a hydrophilic PEG outer shell. Thus formed PEG-PAE-Triclosan micelles do not lose their antimicrobial cargo underway to an infection site through the blood circulation, but penetrate and accumulate in biofilms to release antimicrobials once inside a biofilm through degradation of its ester-linkage by bacterial lipases, to kill biofilm-embedded bacteria at lower antimicrobial concentrations than when applied in solution. PEG-PAE-Triclosan micelles effectively eradicate biofilms of multi-drug-resistant pathogens and oral bacteria, most notably highly cariogenic Streptococcus mutans, in mice and men respectively, and possess excellent clinical translation possibilities.

Cooperation of Amphiphilicity and Smectic Order in Regulating the Self-Assembly of Cholesterol-Functionalized Brush-Like Block Copolymers

Nanoparticle morphology significantly affects the application of nanometer-scale materials. Understanding nanoparticle formation mechanisms and directing morphological control in nanoparticle self-assembly processes have received wide attention. Herein, a series of brush-like amphiphilic liquid crystalline block copolymers, PChEMA _m- b-POEGMA _n, containing cholesteryl mesogens with different hydrophobic/hydrophilic block ratios were designed and synthesized. The self-assembly behaviors of the resulting PChEMA _m- b-POEGMA _n block copolymers in different solvents (tetrahydrofuran/H₂O, 1,4-dioxane/H₂O, and N, N-dimethylformamide) were investigated in detail. Desirable micellar aggregates with well-organized architectures, including short cylindrical micelles, nanofibers, fringed platelets, and ellipsoidal vesicles with smectic micellar cores, were observed in 1,4-dioxane/H₂O with an increasing hydrophobic block ratio. Although both amphiphilicity and smectic order governed the self-assembly, these two factors were differently balanced in the different solvents. This unique supramolecular system provides a new strategy for the design of advanced functional nanomaterials with tunable morphologies.

Surface-adaptive zwitterionic nanoparticles for prolonged blood circulation time and enhanced cellular uptake in tumor cells

Recently, zwitterionic materials have been developed as alternatives to PEG for prolonging the circulation time of nanoparticles without triggering immune responses. However, zwitterionic coatings also hindered the interactions between nanoparticles and tumor cells, leading to less efficient uptake of nanoparticles by cancer cells. Such effect significantly limited the applications of zwitterionic materials for the purposes of drug delivery and the development to novel therapeutic agents. To overcome these issues, surface-adaptive mixed-shell micelles (MSMs) with poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC)/poly(β-amino ester) (PAE) heterogeneous surfaces were constructed. Owing to the synergistic effect of zwitterionic coatings and micro-phase-separated surfaces, PMPC mixed-shell micelles exhibited the improved blood circulation time compared to single-PEG-shell micelles (PEGSMs) and single-PMPC-shell micelles (PMPCSMs). Moreover, such MSMs can convert their surface to positively charged ones in response to the acidic tumor microenvironment, leading to a significant enhancement in cellular uptake of MSMs by tumor cells. This strategy demonstrated a general approach to enhance the cellular uptake of zwitterionic nanoparticles without compromising their long circulating capability, providing a practical method for improving the tumor-targeting efficiency of particulate drug delivery systems.

STATEMENT OF SIGNIFICANCE

Herein we demonstrate a general strategy to integrate non-fouling zwitterionic surface on the nanoparticles without compromising their capability of tumor accumulation, by constructing a surface-adaptive mixed-shell micelles (MSMs) with poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC)/poly(β-amino ester) (PAE) heterogeneous surfaces. At the blood pH (7.4), PAE chains collapsed to the inner of the shell due to the deprotonation, and the forming micro-phase separation structure was synergistic with zwitterionic surface to prolong the circulation time of MSMs in the blood. While at the tumor sites, PAE was protonated, and the positively charged surface of MSMs enhanced cellular uptake. This self-assembly-based strategy is compatible to other zwitterionic materials, endowing a great flexibility for the construction of responsive drug delivery systems particularly to the novel chemotherapeutic agents.

pH-Induced evolution of surface patterns in micelles assembled from dirhamnolipids: dissipative particle dynamics simulation

Dissipative particle dynamics (DPD) simulation is used to study the effect of pH on the morphological transition in micelles assembled from dirhamnolipids (diRLs), and analyze the pH-driven mechanism and influence factors of micellar surface patterns.

Polymerization-induced self-assembly of large-scale iohexol nanoparticles as contrast agents for X-ray computed tomography imaging

Fundamental research for CT imaging, in which iohexol nanoparticles (INPs) were synthesised using a one-pot strategy via polymerization-induced self-assembly (PISA).

Compact Vesicles Self-Assembled from Binary Graft Copolymers with High Hydrophilic Fraction for Potential Drug/Protein Delivery

Hollow vesicles self-assembled from amphiphilic copolymers are of great interest in biomedicine field as drug and protein carriers. Efficient preparation of polymeric vesicles with high stability in vivo is highly desirable. Herein, a novel cooperative self-assembly of two graft copolymers (GCPs) with reversed hydrophilic-hydrophobic segments is investigated to achieve morphology control for biomedical application. Interestingly, nanosized vesicles are obtained for the binary system with relatively high hydrophilic fraction (f_hydrophilic, ∼60%), contrary to what is found in its single-component counterpart. The cooperative self-assembly endowed the hybrid vesicles with excellent resistance to protein adsorption, prolonged blood circulation time, as well as low leakage of hydrophilic drugs/proteins. Furthermore, the biological activity of the protein is well preserved inside the cooperative vesicles, making it a promising candidate as the protein carrier.

Intracellular construction of topology-controlled polypeptide nanostructures with diverse biological functions

Topological structures of bio-architectonics and bio-interfaces play major roles in maintaining the normal functions of organs, tissues, extracellular matrix, and cells. In-depth understanding of natural self-assembly mechanisms and mimicking functional structures provide us opportunities to artificially control the natural assemblies and their biofunctions. Here, we report an intracellular enzyme-catalyzed polymerization approach for efficient synthesis of polypeptides and in situ construction of topology-controlled nanostructures. We reveal that the phase behavior and topological structure of polypeptides are encoded in monomeric peptide sequences. Next, we elucidate the relationship between polymerization dynamics and their temperature-dependent topological transition in biological conditions. Importantly, the linearly grown elastin-like polypeptides are biocompatible and aggregate into nanoparticles that exhibit significant molecular accumulation and retention effects. However, 3D gel-like structures with thermo-induced multi-directional traction interfere with cellular fates. These findings allow us to exploit new nanomaterials in living subjects for biomedical applications.

Unveiling the Self-Assembling Behavior of 5-Fluorouracil and its N,N'-Dimethyl Derivative: A Spectroscopic and Microscopic Approach

Under physiological conditions, 5-fluorouracil (5-FU), an anticancer drug, self-assembles into fibrils by strong hydrogen-bonding network, whereas its N,N'-dimethyl derivative, 5-fluoro-1,3-dimethyluracil (5-FDMU), does not make fibrils due to lack of strong hydrogen-bonding motif. In vitro, 5-FU self-assembly is sensitive to physicochemical conditions like the pH and ionic strength of the solution, which tune the strength of the noncovalent driving forces. Here we report a surprising finding that the buffer, which is necessary to control the pH and is typically considered to be inert, also significantly influences 5-FU self-assembly, which indicates an important role of counterions in the fibril formation. We have also monitored concentration- and time-dependent fibrillar growth of 5-FU. Again, fibril growth process is probed under dynamic conditions using microfluidic platform. The self-assembly of 5-FU compared with its N,N'-dimethyl derivative shows lower cytotoxicity to the cultured human erythroleukemic cells (K562 cells), which plausibly states the reason behind the greater effectiveness of 5-FU derivative drugs than 5-FU itself.

Thermoresponsive cyclodextrins with benzenesulfonamide showing tunable inhibition for carbonic anhydrase

Monodisperse thermoresponsive cyclodextrins appended with benzenesulfonamides were demonstrated to reversibly regulate the enzymatic activity of carbonic anhydrase, which was found to be dependent on both scaffold effect and thermoresponsiveness.

Formulating Polyethylene Glycol as Supramolecular Emulsifiers for One-Step Double Emulsions

One-step double emulsions via only one-step emulsification are leading to an attractive branch of emulsion research studies owing to the ease of preparation and reduced surfactant numbers. In addition to controlling the oil/water ratio, exploiting emulsifiers with desirable amphiphilicity that can stabilize both the inner and outer water/oil interfaces is crucial to the formation of one-step double emulsions. In particular, new emulsifiers with saving laborious efforts are highly preferred in consideration of low cost and practical applications. In this work, a commonly used homopolymer, polyethylene glycol (PEG), was attempted as emulsifiers to prepare emulsions via one-step emulsification. PEG is generally considered as a hydrophilic polymer and always anchored with a hydrophobic polymer to make the copolymer amphiphilic. In the water-chloroform binary system, PEG itself exhibits amphiphilic performance and tailors the formation of single emulsions or double W/O/W emulsions on the dependence of the oil/water ratio and the PEG concentration. A possible mechanism as explained by dissipative particle dynamics simulation was proposed to demonstrate the amphiphilic feature and emulsification capability of PEG. The amphiphilicity of PEG was further tuned by interacting with iodine as a result of the formation of a supramolecular complex, which, in turn, led to the conversion from single emulsions to O/W/O double emulsions. It is believed that this line of research provides inspiration for the preparation of controllable emulsions through supramolecular routes.

Functional Built-In Template Directed Siliceous Fluorescent Supramolecular Vesicles as Diagnostics

Functional template directed synthesis of hybrid siliceous fluorescent vesicle (HSFV) is fabricated by using fluorescent vesicle as a built-in template. The template vesicle is the ionic self-assembly of an aggregation-induced emission (AIE) fluorogen. Upon depositing folic acid modified silica shell on its surface, the obtained HSFVs display low cytotoxicity, significant fluorescence, and targeted drug delivery toward cancer cells. Furthermore, the wall-thickness of the HSFVs can be controlled via altered concentration of silica source. This is the first report of HSFV employing the template vesicle as a built-in fluorescent agent, which represents a good example of rational design for an effective diagnostics, and may open up a new avenue for precision medicine.

Bioreducible, hydrolytically degradable and targeting polymers for gene delivery

Recently, synthetic gene carriers have been intensively developed owing to their promising application in gene therapy and considered as a suitable alternative to viral vectors because of several benefits. But cationic polymers still face some problems like low transfection efficiency, cytotoxicity, and poor cell recognition and internalization. The emerging engineered and smart polymers can respond to some changes in the biological environment like pH change, ionic strength change and redox potential, which is beneficial for cellular uptake. Redox-sensitive disulfide based and hydrolytically degradable cationic polymers serve as gene carriers with excellent transfection efficiency and good biocompatibility owing to degradation in the cytoplasm. Additionally, biodegradable polymeric micelles with cell-targeting function are recently emerging gene carriers, especially for the transfection of endothelial cells. In this review, some strategies for gene carriers based on these bioreducible and hydrolytically degradable polymers will be illustrated.

Spatiotemporal Control of Supramolecular Self-Assembly and Function

The enzyme-triggered self-assembly of peptides has flourished in controlling the self-assembly kinetics and producing nanostructures that are typically inaccessible by conventional self-assembly pathways. However, the diffusion and nanoscale chemical gradient of self-assembling peptides generated by the enzyme also significantly affect the outcome of self-assembly, which has not been reported yet. In this work, we demonstrated for the first time a spatiotemporal control of enzyme-triggered peptide self-assembly. By simply adjusting the temperature, we could change both the catalytic activity of the enzyme of phosphatase and their aggregation states. The strategy kinetically controls the production rate of self-assembling peptides and spatially controls their distribution in the system, leading to the formation of nanoparticles at 37 °C and nanofibers at 4 °C. The nanofibers showed ∼10 times higher cellular uptake by 3T3 cells than the nanoparticles, thanks to their higher stability and more ordered structures. Using such spatiotemporal control, we could prepare optimized nanoprobes with low background fluorescence, rapid and high cellular uptake, and high sensitivity. We postulate that this strategy would be very useful in general for preparing self-assembled nanomaterials with controllable morphology and function.

Dual Enzymatic Reaction-Assisted Gemcitabine Delivery Systems for Programmed Pancreatic Cancer Therapy

Dual enzymatic reactions were introduced to fabricate programmed gemcitabine (GEM) nanovectors for targeted pancreatic cancer therapy. Dual-enzyme-sensitive GEM nanovectors were prepared by conjugation of matrix metalloproteinase-9 (MMP-9) detachable poly(ethylene glycol) (PEG), cathepsin B-cleavable GEM, and targeting ligand CycloRGD to CdSe/ZnS quantum dots (QDs). The GEM nanovectors decorated with a PEG corona could avoid nonspecific interactions and exhibit prolonged blood circulation time. After GEM nanovectors were accumulated in tumor tissue by the enhanced permeability and retention (EPR) effect, the PEG corona can be removed by overexpressed MMP-9 in tumor tissue and RGD would be exposed, which was capable of facilitating cellular internalization. Once internalized into pancreatic cancer cells, the elevated lysosomal cathepsin B could further promote the release of GEM. By employing dual enzymatic reactions, the GEM nanovectors could achieve prolonged circulation time while maintaining enhanced cellular internalization and effective drug release. The proposed mechanism of the dual enzymatic reaction-assisted GEM delivery system was fully investigated both in vitro and in vivo. Meanwhile, compared to free GEM, the deamination of GEM nanovectors into inactive 2',2'-difluorodeoxyuridine (dFdU) could be greatly suppressed, while the concentration of the activated form of GEM (gemcitabine triphosphate, dFdCTP) was significantly increased in tumor tissue, thus exhibiting superior tumor inhibition activity with minimal side effects.

Zinc porphyrin/fullerene/block copolymer micelle for enhanced electron transfer ability and stability

The complex micelle is constructed through an electrostatic self-assembly strategy as an efficient donor–acceptor system in water with electron transfer ability.

The synergistic effect between KLVFF and self-assembly chaperones on both disaggregation of beta-amyloid fibrils and reducing consequent toxicity

A new synergistic system combining KLVFF peptide and self-assembly chaperone can synchronize disaggregating amyloid fibrils and reducing consequent toxicity.

Photoresponsive amphiphilic block macrocycles bearing azobenzene side chains

The cyclic architecture has an impact on the photoisomerization and packing behavior of micellar aggregates of amphiphilic block copolymers bearing pendant azobenzene and carboxyl groups as compared to their linear counterparts.