Preparation of ROS-responsive core crosslinked polycarbonate micelles with thioketal linkage

Herein, we prepared novel reactive oxygen species (ROS) responsive core crosslinked (CCL/TK) polycarbonate micelles conveniently by click reaction between amphiphilic diblock copolymer poly(ethylene glycol)-poly(5-methyl-5-propargylxycar-bonyl-1,3-dioxane-2-one) (PEG-PMPC) with pendant alkynyl group and thioketal containing azide derivative bis (2-azidoethyl) 3, 3'- (propane-2, 2-diylbis (sulfanediyl)) dipropanoate (TK-N₃). The CCL/TK micelles were obtained with small size of 146.4 nm, showing excellent stability against dilution and high doxorubicin (DOX) loading. In vitro toxicity tests demonstrated that the obtained CCL/TK micelles have good biocompatibility and low toxicity with cell viability above 95 %. Furthermore, DOX-loaded CCL/TK micelles showed significantly superior toxicity with IC₅₀ values for HeLa and MCF-7 cells about 3.74 μg/mL and 3.91 μg/mL, respectively. Confocal laser scanning microscope (CLSM) and flow cytometry showed excellent internalization efficiency and intracellular drug release of DOX-loaded CCL/TK micelles. The obtained ROS-responsive CCL/TK micelles showed great potential for anticancer drug delivery.

Influence of Core Cross-Linking and Shell Composition of Polymeric Micelles on Immune Response and Their Interaction with Human Monocytes

Block copolymer micelles have received increasing attention in the last decades, in particular for their appealing properties in nanomedicine. However, systematic investigations of the interaction between polymeric micelles and immune cells are still rare. Therefore, broader studies comparing the structural effects remain inevitable for a comprehensive understanding of the immune response and for the design of efficient, nonimmunogenic delivery systems. Here, we present novel block copolymer micelles with the same hydrophobic core, based on a copolymer of BA and VDM, and various hydrophilic shells ranging from common PEG derivatives to morpholine-based materials. The influence of these shells on innate immune responses was studied in detail. In addition, we investigated the impact of micelle stability by varying the cross-linking density in the micellar core. Surprisingly, whereas different shells had only a minor impact on immune response, micelles with reduced cross-linking density considerably enhanced the release of cytokines from isolated human monocytes. Moreover, the uptake of non-cross-linked micelles by monocytes was significantly higher as compared to cross-linked materials. Our study emphasizes the importance of the micellar stability on the interaction with the immune system, which is the key for any stealth properties in vivo. Polymers based on morpholines result in a similar low response as the PEG derivative and may represent an interesting alternative to the common PEGylation.

Reduction responsive and surface charge switchable polyurethane micelles with acid cleavable crosslinks for intracellular drug delivery

Previously we synthesized redox sensitive polyurethane micelles, core crosslinked by diisocyanates (PU-CCL).

Biodegradable polyurethane micelles with pH and reduction responsive properties for intracellular drug delivery

Polyurethane micelles with disulfide linkage located at the interface of hydrophilic shell and hydrophobic core (PU-SS-I) have been shown enhanced drug release profiles. However, the payloads could not be released completely. The occurrence of aggregation of hydrophobic cores upon shedding hydrophilic PEG coronas was considered as the reason for the incomplete release. To verify the above hypothesis and to develop a new polyurethane based micelles with dual stimuli respond properties and controllable location of pH and reduction responsive groups in the PU main chains, a tertiary amine was incorporated into the hydrophobic core PU-SS-I, which resulted polyurethane with both reduction and pH sensitive properties (PU-SS-N). Biodegradable polyurethane with only disulfide linkages located between the hydrophilic PEG segment and the hydrophobic PCL segments (PU-SS-I) and polyurethane with only pH sensitive tertiary amine at the hydrophobic core (PU-N-C) were used as comparisons. Paclitaxel (PTX) was chosen as mode hydrophobic drug to evaluate the loading and redox triggered release profiles of the PU micelles. It was demonstrated that PU-SS-N micelles disassembled instantly at the presence of 10mM GSH and at an acidic environment (pH=5.5), which resulted the nearly complete release (~90%) of the payloads within 48h, while about ~70% PTX was released from PU-SS-I and PU-SS-N micelles at neutral environment (pH=7.4) with the presence of 10mM GSH. The rapid and complete redox and pH stimuli release properties of the PU-SS-N nanocarrier will be a promising anticancer drug delivery system to ensure sufficient drug concentration to kill the cancer cells and to prevent the emergency of MDR. The in vitro cytotoxicity and cell uptake of the PTX-loaded micelles was also assessed in H460 and HepG2 cells.

Size changeable nanosystems for precise drug controlled release and efficient overcoming of cancer multidrug resistance

Herein we demonstrate the rational design of a size changeable nanosystem for precise drug controlled release and efficient overcoming of cancer multidrug resistance in cancer cells by enhancing the cellular uptake and inhibiting the expression of ABC family proteins.

Surface charge switchable and core cross-linked polyurethane micelles as a reduction-triggered drug delivery system for cancer therapy

The core cross-linked polyurethane micelles with redox sensitive and pH-responsive surface charge switchable properties were prepared by using diisocyanates as crosslinkers and studied as anticancer drug carriers.

Photosensitizer cross-linked nano-micelle platform for multimodal imaging guided synergistic photothermal/photodynamic therapy

The multifunctional nano-micelle platform holds great promise to enhance the accuracy and efficiency of cancer diagnosis and therapy. In this work, an amphiphilic poly[(poly(ethylene glycol) methyl ether methacrylate)-co-(3-aminopropyl methacrylate)]-block-poly(methyl methacrylate) (P(PEGMA-co-APMA)-b-PMMA) block copolymer was synthesized by successive RAFT polymerizations and subsequent chemical modification. Then the multifunctional micelles with high solubility in physiological environments were developed by a self-assembly and crosslinking processes. The photosensitizer segment, 5,10,15,20-tetrakis (4-carboxyphenyl) porphyrin (TCPP), serves as a tetra-functional cross-linker, photodynamic agent, fluorescence indicator, as well as magnetic resonance (MR) contrast agent after labelling with manganese ions (Mn(2+)), while IR825 simultaneously locating in the interior of the fabricated micelles contributed to the photoacoustic (PA) imaging ability and the photothermal effect. The prepared nanoparticles show great stability in a physiological environment with uniform morphology and diameters of around 80 nm as disclosed by stability investigation, TEM and DLS analysis. IR825@P(PEGMA-co-APMA)-b-PMMA@TCPP/Mn nanoparticles displayed high in vivo tumor uptake with a long blood circulation half-life (∼3.64 h) by the EPR effect after intravenous (i.v.) injection, as revealed by fluorescence, MR and PA imaging models. In vivo anti-tumor effects were achieved via a combined photothermal and photodynamic therapy without noticeable dark toxicity, and this strategy was able to induce a remarkably improved synergistic therapeutic effect to both superficial and deep regions of tumors under mild conditions compared with either single photothermal or photodynamic mechanisms.

Functionalized Pluronic-b-poly(ε-caprolactone) based nanocarriers of paclitaxel: solubilization, antiproliferative efficacy and in vivo pharmaceutic kinetics

Novel paclitaxel (PTX) nanocarriers were developed based on the Pluronic-based pentablock copolymer and their pharmaceutical behaviours were thoroughly evaluated.

Synthesis, characterization and self-assembly behavior of zwitterionic amphiphilic triblock copolymers bearing pendant amino acid residues

Zwitterionic amphiphilic triblock copolymers bearing pendant amino acid residues PAGE/cys-b-PCL-b-PEG were synthesized and characterized. The self-assembly behavior of the copolymers was studied.

Self-assembled pH-responsive hyaluronic acid-g-poly((L)-histidine) copolymer micelles for targeted intracellular delivery of doxorubicin

Hyaluronic acid (HA) was conjugated with hydrophobic poly(l-histidine) (PHis) to prepare a pH-responsive and tumor-targeted copolymer, hyaluronic acid-g-poly(l-histidine) (HA-PHis), for use as a carrier for anti-cancer drugs. The effect of the degree of substitution (DS) on the pH-responsive behaviour of HA-PHis copolymer micelles was confirmed by studies of particles of different sizes. In vitro drug release studies demonstrated that doxorubicin (DOX) was released from HA-PHis micelles in a pH-dependent manner. In vitro cytotoxicity assays showed that all the blank micelles were nontoxic. However, MTT assay against Michigan Cancer Foundation-7 (MCF-7) cells (overexpressed CD44 receptors) showed that DOX-loaded micelles with a low PHis DS were highly cytotoxic. Cellular uptake experiments revealed that these pH-responsive HA-PHis micelles taken up in great amounts by receptor-mediated endocytosis and DOX were efficiently delivered into cytosol. Moreover, micelles with the lowest DS exhibited the highest degree of cellular uptake, which indicated that the micelles were internalized into cells via CD44 receptor-mediated endocytosis and the carboxylic groups of HA are the active binding sites for CD44 receptors. Endocytosis inhibition experiments and confocal images demonstrated that HA-PHis micelles were internalized into cells mainly via clathrin-mediated endocytosis and delivered to lysosomes, triggering release of DOX into the cytoplasm. These results confirm that the biocompatible pH-responsive HA-PHis micelles are a promising nanosystem for the intracellular targeted delivery of DOX.

Fluorescence imaging enabled biodegradable photostable polymeric micelles

Amphiphilic biodegradable photoluminescent polymers (ABPLPs) composed of a biodegradable fluorescent polymer and methoxy poly (ethyleneglycol) demonstrate intrinsic bright, tunable, and stable fluorescence emission. ABPLP micelles elicit minor cellular toxicity and can be used for cell and tissue imaging both in vitro and in vivo.

Facile fabrication of reduction-responsive nanocarriers for controlled drug release

An amphiphilic multiblock poly(ether–ester) containing multiple thiols was facilely synthesized by “one-pot” polycondensation, and was used to prepare reduction-responsive core-crosslinked micelles for controlled drug release.