Self-Assembly Behavior and Biocompatible Cross-Linking of Double Hydrophilic Linear-Brush Block Copolymers

Size- and Shape-controlled Biodegradable Polymer Brushes Based on l-Amino Acid for Intracellular Drug Delivery and Deep-Tissue Penetration

We report size- and shape-controlled polymer brushes based on l-amino acid bioresource and study the role of polymer topology on the enzymatic biodegradation and deep-tissue penetration under in vitro and in vivo. For this purpose, l-tyrosine-based propargyl-functionalized monomer is tailor-made and polymerized via solvent-free melt polycondensation strategy to yield hydrophobic and clickable biodegradable poly(ester-urethane)s. Postpolymerization click chemistry strategy is applied to make well-defined amphiphilic one-dimensional rodlike and three-dimensional spherical polymer brushes by merely varying the lengths of PEG-azides in the reaction. These core-shell polymer brushes are found to be nontoxic and nonhemolytic and capable of loading clinical anticancer drug doxorubicin and deep-tissue penetrable near-infrared biomarker IR-780. In vitro enzymatic drug-release kinetics and lysotracker-assisted real-time live-cell confocal bioimaging revealed that the rodlike polymer brush is superior than its spherical counterparts for faster cellular uptake and enzymatic biodegradation at the endolysosomal compartments to release DOX at the nucleus. Further, in vivo live-animal bioimaging by IVIS technique established that the IR-780-loaded rodlike polymer brush exhibited efficient deep-tissue penetration ability and emphasized the importance of polymer brush topology control for biological activity. Polymer brushes exhibit good stability in the blood plasma for more than 72 h, they predominately accumulate in the digestive organs like liver and kidney, and they are less toxic to heart and brain tissues. IVIS imaging of cryotome tissue slices of organs confirmed the deep-penetrating ability of the polymer brushes. The present investigation opens opportunity for bioderived and biodegradable polymer brushes as next-generation smart drug-delivery scaffolds.

Reduction-responsive double hydrophilic block copolymer nano-capsule synthesized via RCMP-PISA

Double hydrophilic block copolymer vesicles synthesized via RCMP-PISA are degradable under a reductive conditions.

Polysaccharide nanoparticles: from fabrication to applications

The present review highlights the developments in polysaccharide nanoparticles with a particular focus on applications in biomedicine, cosmetics and food.

Aggregation of a double hydrophilic block glycopolymer: the effect of block polymer ratio

Double hydrophilic block glycopolymers (DHBGs) composed of glycopolymers and polyethylene glycol (PEG) aggregate in aqueous solution. However, there are no guidelines to direct and design DHBG aggregation. Herein, we investigated the effect of the ratio of glycopolymer length to PEG length on the structure, and report that structure size could be influenced by the block polymer ratio. Nine kinds of DHBG with different glycopolymers and PEG lengths were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. The aggregation capability of DHBG was investigated by transmission electron microscopy (TEM) and dynamic light scattering (DLS). In all cases, the DHBGs formed the spherical structures, even when the PEG and glycopolymer lengths were quite different. The size of the structure was controlled by the ratio of the PEG length to the glycopolymer length. The aggregation of the DHBGs was induced by hydrogen bonding between the sugar moieties. The aggregation of the DHBG was affected by temperature and concentration.

PEGylated gold nanoparticles promoted rapid macromolecular chain-end transformation and formation of injectable hydrogels

Highly stable PEGylated Au NPs with low grafting density exhibit significant effect towards azide–alkyne click cycloaddition and Michael addition reactions leading to rapid formation of injectable hydrogels and biologically relevant macromolecules.

Tannic Acid-Mediated Aggregate Stabilization of Poly(N-vinylpyrrolidone)-b-poly(oligo (ethylene glycol) methyl ether methacrylate) Double Hydrophilic Block Copolymers

The self-assembly of block copolymers in aqueous solution is an important field in modern polymer science that has been extended to double hydrophilic block copolymers (DHBC) in recent years. In here, a significant improvement of the self-assembly process of DHBC in aqueous solution by utilizing a linear-brush macromolecular architecture is presented. The improved self-assembly behavior of poly(N-vinylpyrrolidone)-b-poly(oligo(ethylene glycol) methyl ether methacrylate) (PVP-b-P(OEGMA)) and its concentration dependency is investigated via dynamic light scattering (DLS) (apparent hydrodynamic radii ≈ 100-120 nm). Moreover, the DHBC assemblies can be non-covalently crosslinked with tannic acid via hydrogen bonding, which leads to the formation of small aggregates as well (apparent hydrodynamic radius ≈ 15 nm). Non-covalent crosslinking improves the self-assembly and stabilizes the aggregates upon dilution, reducing the concentration dependency of aggregate self-assembly. Additionally, the non-covalent aggregates can be disassembled in basic media. The presence of aggregates was studied via cryogenic scanning electron microscopy (cryo-SEM) and DLS before and after non-covalent crosslinking. Furthermore, analytical ultracentrifugation of the formed aggregate structures was performed, clearly showing the existence of polymer assemblies, particularly after non-covalent crosslinking. In summary, we report on the completely hydrophilic self-assembled structures in solution formed from fully biocompatible building entities in water.

Temperature-Responsive Behavior of Double Hydrophilic Carboxy-Sulfobetaine Block Copolymers and Their Self-Assemblies in Water

The block copolymer poly(2-((2-(methacryloyloxy)ethyl)dimethylammonio)acetate)- b-poly(3-( N-(2-metharyloylethyl)- N, N-dimethylammonio)propanesulfonate) (PGLBT- b-PSPE) was synthesized by reversible addition-fragmentation chain transfer (RAFT) technique under precise control. The PGLBT- b-PSPE block copolymers showed upper critical solution temperature (UCST) behavior originating from PSPE moieties. Unlike PSPE homopolymers, the transmittance change with temperature was gradual, and unexpected retardation or slight changes in a reverse direction were found at the intermediate stage. Light scattering and ¹H NMR studies proved that the block copolymers formed spherical micelles that were composed of a PSPE core and PGLBT shell around room temperature and lower temperatures, and slowly disassociated with temperature increase. During the transition, fast (small particle) and slow (large particle) diffusive modes were detected by dynamic light scattering (DLS), which implied that the unimers were escaping from the self-assembled structure and swollen micelles, respectively. At sufficiently high temperatures where the solutions became almost transparent, the slow mode eventually disappeared, and only the fast mode remained. In addition, once the polymeric particles are formed, the size did not vary much with additional cooling. The transition point and the pattern of transmittance alteration were dependent on the degree of polymerization and the [PGLBT]:[PSPE] ratios; more PGLBT made the block copolymer less responsive to temperature and led the cloud point to lower degrees. However, random copolymers PGLBT- r-PSPE did not show any temperature-responsivity, and even small amount of GLBTs (10%) distributed in a PSPE chain significantly suppressed the transition.

Poly(ethylene glycol) brush-b-poly(N-vinylpyrrolidone)-based double hydrophilic block copolymer particles crosslinked via crystalline α-cyclodextrin domains

Self-assembly of block copolymers is a significant area of polymer science. The self-assembly of completely water-soluble block copolymers is of particular interest, albeit a challenging task. In the present work the self-assembly of a linear-brush architecture block copolymer, namely poly(N-vinylpyrrolidone)-b-poly(oligoethylene glycol methacrylate) (PVP-b-POEGMA), in water is studied. Moreover, the assembled structures are crosslinked via α-CD host/guest complexation in a supramolecular way. The crosslinking shifts the equilibrium toward aggregate formation without switching off the dynamic equilibrium of double hydrophilic block copolymer (DHBC). As a consequence, the self-assembly efficiency is improved without extinguishing the unique DHBC self-assembly behavior. In addition, decrosslinking could be induced without a change in concentration by adding a competing complexation agent for α-CD. The self-assembly behavior was followed by DLS measurement, while the presence of the particles could be observed via cryo-TEM before and after crosslinking.

Self-assembly of the double hydrophilic block copolymer poly(N-vinylpyrrolidone)-b-poly(oligoethylene glycol methacrylate) and supramolecular crosslinking via α-cyclodextrin in water is presented.

Galactose-Functionalized Double-Hydrophilic Block Glycopolymers and Their Thermoresponsive Self-Assembly Dynamics

Glycopolymers with large galactose units are attractive in biological processes because of their ability to selectively recognize lectin proteins. Recently, thermoresponsive double-hydrophilic block glycopolymers (TDHBGs) have been designed, which allow sugar residues to expose or hide via the lower critical solution temperature (LCST)-type phase transition. In this work, we first synthesize a new type of TDHBGs, composed of a thermoresponsive poly(di(ethylene glycol)methyl ether methacrylate) block and a galactose-functionalized, poly(6- O-vinyladipoyl-d-galactose) (POVNG) block. The LCST can be tuned by varying the size of the POVNG block. Then, we have systematically investigated their thermoresponsive self-assembly behavior, using static and dynamic light scattering techniques, combined with transmission electron microscopy (TEM) imaging. It is found that the TDHBGs possess both micellization and LCST-type transition, and there exist strong interactions between them, depending on the concentration and structure of the TDHBGs. It is particularly interesting that for the same type of TDHBGs under different conditions, such interactions result in rich morphologies of the formed micelles (or nanoparticles) such as spheres, hollow spheres, prolate ellipsoids, crystal-like, and so on, thus potentially enriching their biological applications by noting that they are hepatoma-targeting glycopolymers.

Self-Assembly of a Double Hydrophilic Block Glycopolymer and the Investigation of Its Mechanism

We report the self-assembly of a double hydrophilic block glycopolymer (DHBG) via hydrogen bonding and coordinate bonding. This DHBG, composed of poly(ethylene)glycol (PEG) and glycopolymer, self-assembled into a well-defined structure. The DHBG was prepared through the controlled radical polymerization of trimethylsilyl-protected propargyl methacrylate using a PEG-based reversible addition-fragmentation chain transfer reagent, followed by sugar conjugation using click chemistry. The DHBG self-assembly capability was investigated by transmission electron microscopy and dynamic light scattering. Interestingly, the DHBG self-assembled into a spherical structure in aqueous solution. Hydrogen bonding and coordinate bonding with Ca²⁺ were identified as the driving forces for self-assembly.

Cisplatin-Encapsulated Polymeric Nanoparticles with Molecular Geometry-Regulated Colloidal Properties and Controlled Drug Release

Encapsulation of chemotherapeutic agents inside a nanoscale delivery platform can provide an attractive therapeutic strategy with many pharmaceutical benefits, such as increased plasma solubility, prolonged in vivo circulation, and reduced acute toxicity. Given that the biological activities of polymeric nanoparticles are highly dependent on their colloidal structures, the molecular geometry-regulated programming of self-assembled nanoscale architecture is of great interest for chemical design of an ideal delivery platform. In this report, we demonstrate that the molecular geometry of block-copolymer excipients can govern the level of drug-loading capacity and core hydrophobicity of polymeric nanoparticles, which can eventually control the pH-sensitive drug-release property. Atom-transfer radical polymerization was employed as a controlled synthetic method for the copolymer excipients, which contain the metal-chelating poly(acrylic acid) block linked to either a small mPEG-grafted poly(methacrylate) to generate a bulky brush-like chains or a simple linear mPEG segment. During the coordination of cis-diammineplatinum(II) as an active pharmacophore of cisplatin, aqueous-phase size-exclusion chromatography analyses exhibited highly different self-association kinetic regimes prompted by versatile molecular geometry of copolymer excipients, which further allows us to explore the molecular geometry-colloidal property relationship.

Thermoadaptive Supramolecular α-Cyclodextrin Crystallization-Based Hydrogels via Double Hydrophilic Block Copolymer Templating

Supramolecular hydrogels play a prominent role in contemporary research of hydrophilic polymers. Especially, hydrogels based on α-cyclodextrin/poly(ethylene glycol) (α-CD/PEG) complexation and crystal formation are studied frequently. Here, the effect of double hydrophilic block copolymers (DHBCs) on α-CD/PEG hydrogel properties is investigated. Therefore, a novel DHBC, namely poly(N-vinylpyrrolidone)-b-poly(oligo ethylene glycol methacrylate) (PVP-b-POEGMA), was synthesized via a combination of reversible deactivation radical polymerization and modular conjugation methods. In the next step, hydrogel formation was studied after α-CD addition. Interestingly, DHBC-based hydrogels showed a significant response to thermal history. Heating of the gels to different temperatures led to different mechanical properties after cooling to ambient temperature, i.e., gels with mechanical properties similar to the initial gels or weak flowing gels were obtained. Thus, the hydrogels showed thermoadaptive behavior, which might be an interesting property for future applications in sensing.