One-pot syntheses of dual-responsive core cross-linked polymeric micelles and covalently entrapped drug by click chemistry

Structural Determinants of Stimuli-Responsiveness in Amphiphilic Macromolecular Nano-assemblies

Stimuli-responsive nano-assemblies from amphiphilic macromolecules could undergo controlled structural transformations and generate diverse macroscopic phenomenon under stimuli. Due to the controllable responsiveness, they have been applied for broad material and biomedical applications, such as biologics delivery, sensing, imaging, and catalysis. Understanding the mechanisms of the assembly-disassembly processes and structural determinants behind the responsive properties is fundamentally important for designing the next generation of nano-assemblies with programmable responsiveness. In this review, we focus on structural determinants of assemblies from amphiphilic macromolecules and their macromolecular level alterations under stimuli, such as the disruption of hydrophilic-lipophilic balance (HLB), depolymerization, decrosslinking, and changes of molecular packing in assemblies, which eventually lead to a series of macroscopic phenomenon for practical purposes. Applications of stimuli-responsive nano-assemblies in delivery, sensing and imaging were also summarized based on their structural features. We expect this review could provide readers an overview of the structural considerations in the design and applications of nanoassemblies and incentivize more explorations in stimuli-responsive soft matters.

Peptide-guided delivery improves the therapeutic efficacy and safety of glucocorticoid drugs for treating acute lung injury

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are life-threatening conditions with excessive inflammation in the lung. Glucocorticoids had been widely used for ALI/ARDS, but their clinical benefit remains unclear. Here, we tackled the problem by conjugating prednisolone (PSL) with a targeting peptide termed CRV. Systemically administered CRV selectively homes to the inflamed lung of a murine ALI model, but not healthy organs or the lung of healthy mice. The expression of the CRV receptor, retinoid X receptor β, was elevated in the lung of ALI mice and patients with interstitial lung diseases, which may be the basis of CRV targeting. We then covalently conjugated PSL and CRV with a reactive oxygen species (ROS)-responsive linker in the middle. While being intact in blood, the ROS linker was cleaved intracellularly to release PSL for action. In vitro, CRV-PSL showed an anti-inflammatory effect similar to that of PSL. In vivo, CRV conjugation increased the amount of PSL in the inflamed lung but reduced its accumulation in healthy organs. Accordingly, CRV-PSL significantly reduced lung injury and immune-related side effects elsewhere. Taken together, our peptide-based strategy for targeted delivery of glucocorticoids for ALI may have great potential for clinical translation.

Recent developments in selenium-containing polymeric micelles: prospective stimuli, drug-release behaviors, and intrinsic anticancer activity

Selenium is capable of forming a dynamic covalent bond with itself and other elements and can undergo metathesis and regeneration reactions under optimum conditions. Its dynamic nature endows selenium-containing polymers with striking sensitivity towards some environmental alterations. In the past decade, several selenium-containing polymers were synthesized and used for the preparation of oxidation-, reduction-, and radiation-responsive nanocarriers. Recently, thioredoxin reductase, sonication, and osmotic pressure triggered the cleavage of Se-Se bonds and swelling or disassembly of nanostructures. Moreover, some selenium-containing nanocarriers form oxidation products such as seleninic acids and acrylates with inherent anticancer activities. Thus, selenium-containing polymers hold promise for the fabrication of ultrasensitive and multifunctional nanocarriers of radiotherapeutic, chemotherapeutic, and immunotherapeutic significance. Herein, we discuss the most recent developments in selenium-containing polymeric micelles in light of their architecture, multiple stimuli-responsive properties, emerging immunomodulatory activities, and future perspectives in the delivery and controlled release of anticancer agents.

Synthesis of Block Copolymer Brush by RAFT and Click Chemistry and Its Self-Assembly as a Thin Film

A well-defined block copolymer brush poly(glycidyl methacrylate)-graft-(poly(methyl methacrylate)-block- poly(oligo(ethylene glycol) methyl ether methacrylate)) (PGMA-g-(PMMA-b-POEGMA)) is synthesized via grafting from an approach based on a combination of click chemistry and reversible addition-fragmentation chain transfer (RAFT) polymerization. The resulting block copolymer brushes were characterized by ¹H-NMR and size exclusion chromatography (SEC). The self-assembly of the block copolymer brush was then investigated under selective solvent conditions in three systems: THF/water, THF/CH₃OH, and DMSO/CHCl₃. PGMA-g-(PMMA-b-POEGMA) was found to self-assemble into spherical micelle structures as analyzed by transmission electron microscopy (TEM) and dynamic light scattering (DLS). The average size of the particles was much smaller in THF/CH₃OH and DMSO/CHCl₃ as compared with the THF/water system. Thin film of block copolymer brushes with tunable surface properties was then prepared by the spin-coating technique. The thickness of the thin film was confirmed by scanning electron microscopy (SEM). Atom force microscopy (AFM) analysis revealed a spherical morphology when the block copolymer brush was treated with poor solvents for the backbone and hydrophobic side chains. The contact angle measurements were used to confirm the surface rearrangements of the block copolymer brushes.

pH-triggered intracellular release of doxorubicin by a poly(glycidyl methacrylate)-based double-shell magnetic nanocarrier

Two core-double-shell pH-sensitive nanocarriers were fabricated using Fe₃O₄ as magnetic core, poly(glycidyl methacrylate-PEG) and salep dialdehyde as the first and the second shell, and doxorubicin as the hydrophobic anticancer drug. Two nanocarriers were different in the drug loading steps. The interaction between the first and the second shell assumed to be pH-sensitive via acetal cross linkages. The structure of nanocarriers, organic shell loading, magnetic responsibility, morphology, size, dispersibility, and drug loading content were investigated by IR, NMR, TG, VSM, XRD, DLS, HRTEM and UV-Vis analyses. The long-term drug release profiles of both nanocarriers showed that the drug loading before cross-linking between the first and second shell led to a more pH-sensitive nanocarrier exhibiting higher control on DOX release. Cellular toxicity assay (MTT) showed that DOX-free nanocarrier is biocompatible having cell viability greater than 80% for HEK-293 and MCF-7 cell lines. Besides, high cytotoxic effect observed for drug-loaded nanocarrier on MCF-7 cancer cells. Cellular uptake analysis showed that the nanocarrier is able to transport DOX into the cytoplasm and perinuclear regions of MCF-7 cells. In vitro hemolysis and coagulation assays demonstrated high blood compatibility of nanocarrier. The results also suggested that low concentration of nanocarrier have a great potential as a contrast agent in magnetic resonance imaging (MRI).

Fabrication of Core Crosslinked Polymeric Micelles as Nanocarriers for Doxorubicin Delivery: Self-Assembly, In Situ Diselenide Metathesis and Redox-Responsive Drug Release

Polymeric micelles (PMs) have been used to improve the poor aqueous solubility, slow absorption and non-selective biodistribution of chemotherapeutic agents (CAs), albeit, they suffer from disassembly and premature release of payloads in the bloodstream. To alleviate the thermodynamic instability of PMs, different core crosslinking approaches were employed. Herein, we synthesized the poly(ethylene oxide)-b-poly((2-aminoethyl)diselanyl)ethyl l-aspartamide)-b-polycaprolactone (mPEG-P(LA-DSeDEA)-PCL) copolymer which self-assembled into monodispersed nanoscale, 156.57 ± 4.42 nm, core crosslinked micelles (CCMs) through visible light-induced diselenide metathesis reaction between the pendant selenocystamine moieties. The CCMs demonstrated desirable doxorubicin (DOX)-loading content (7.31%) and encapsulation efficiency (42.73%). Both blank and DOX-loaded CCMs (DOX@CCMs) established appreciable colloidal stability in the presence of bovine serum albumin (BSA). The DOX@CCMs showed redox-responsive drug releasing behavior when treated with 5 and 10 mM reduced glutathione (GSH) and 0.1% H2O2. Unlike the DOX-loaded non-crosslinked micelles (DOX@NCMs) which exhibited initial burst release, DOX@CCMs demonstrated a sustained release profile in vitro where 71.7% of the encapsulated DOX was released within 72 h. In addition, the in vitro fluorescent microscope images and flow cytometry analysis confirmed the efficient cellular internalization of DOX@CCMs. The in vitro cytotoxicity test on HaCaT, MDCK, and HeLa cell lines reiterated the cytocompatibility (≥82% cell viability) of the mPEG-P(LA-DSeDEA)-PCL copolymer and DOX@CCMs selectively inhibit the viabilities of 48.85% of HeLa cells as compared to 15.75% of HaCaT and 7.85% of MDCK cells at a maximum dose of 10 µg/mL. Overall, all these appealing attributes make CCMs desirable as nanocarriers for the delivery and controlled release of DOX in tumor cells.

An overview of nanogel-based vaccines

Introduction: The development of more efficacious vaccines, especially subunit vaccines administered via non-invasive routes, is a priority in vaccinology. Nanogels are materials that can meet the requirements to serve as efficient vaccine delivery vehicles (in terms of thermo-sensitivity, biocompatibility, and pH-responsiveness; among others); thus there is a growing interest in exploring the potential of nanogels for vaccine development. Areas covered: Herein, a critical analysis of nanogel synthesis methodologies is presented and nanogel-based vaccines under development are summarized and placed in perspective. Promising vaccine candidates based on nanogels have been reported for cancer, obesity, and infectious diseases (mainly respiratory diseases). Some of the candidates were administered by mucosal routes which are highly attractive in terms of simple administration and induction of protective responses at both mucosal and systemic levels. Expert opinion: The most advanced models of nanogel-based vaccines comprise candidates against cancer, based on cholesteryl pullulan nanogels evaluated in clinical trials with promising findings; as well as some vaccines against respiratory pathogens tested in mice thus far. Nonetheless, the challenge for this field is advancing in clinical trials and proving the protective potential in test animals for many other candidates. Implementing green synthesis approaches for nanogels is also required.

Recent advances in stimuli-responsive polymeric micelles via click chemistry

Stimuli-responsive polymeric micelles via click chemistry are divided into six major sections (temperature, light, ultrasound, pH, enzymes, and redox).

pH-Responsive reversibly cross-linked micelles by phenol–yne click via curcumin as a drug delivery system in cancer chemotherapy

pH-sensitive reversibly cross-linked micelles by phenol–yne click via curcumin (Cur) using mPEG-b-PHEMA-5HA are developed by combining drug loading and cross-linking as a drug delivery system.

Near-infrared light-responsive, diselenide containing core-cross-linked micelles prepared by the Diels–Alder click reaction for photocontrollable drug release application

We report a facile and efficient preparation of a NIR-triggered micelle system for a drug vehicle.

A mini review of the synthesis of poly-1,2,3-triazole-based functional materials

Most recent advances of the synthesis of poly-1,2,3-triazole-based functional materials.