Shuangjiang Yu

pH and reduction dual responsive polyurethane triblock copolymers for efficient intracellular drug delivery

A series of pH/reduction dual responsive poly(ethylene glycol)/polyurethane triblock copolymers containing tertiary amines and disulfide bonds are reported. The polyurethane block copolymers self-assembled into stable micelles in aqueous medium at pH 7.4, which responded rapidly to both a narrow pH change within the physiologically relevant pH range and a reduction environment mimicking the intracellular space. The in vitro drug release from doxorubicin (DOX)-loaded polyurethane micelles was significantly accelerated by reducing the pH or by addition of an intracellular reducing agent, glutathione (GSH). Confocal laser scanning microscopy (CLSM) and flow cytometry measurements revealed that the intracellular drug release from the DOX-loaded nanoparticles was increased in the HeLa cells with enhanced intracellular GSH level. In addition, even though the polyurethane block copolymers exhibited good cytocompatibility, the DOX-loaded polyurethane micelles displayed efficient growth inhibition of HeLa and HepG2 cells, which showed a dependence on the intracellular GSH concentration. Owing to their unique responsiveness to dual biological stimuli, the biocompatible and bioreducible polyurethane block copolymers have the potential to serve as a versatile platform for intracellular drug delivery.

Disulfide Cross-Linked Polyurethane Micelles as a Reduction-Triggered Drug Delivery System for Cancer Therapy

Nanoscale carriers that stably load drugs in blood circulation and release the payloads in desirable sites in response to a specific trigger are of great interest for smart drug delivery systems. For this purpose, a novel type of disulfide core cross-linked micelles, which are facilely fabricated by cross-linking of poly(ethylene glycol)/polyurethane block copolymers containing cyclic disulfide moieties via a thiol-disulfide exchange reaction, are developed. A broad-spectrum anti-cancer drug, doxorubicin (DOX), is loaded into the micelles as a model drug. The drug release from the core cross-linked polyurethane micelles (CCL-PUMs) loaded with DOX is suppressed in normal phosphate buffer saline (PBS), whereas it is markedly accelerated with addition of an intracellular reducing agent, glutathione (GSH). Notably, although DOX-loaded CCL-PUMs display lower cytotoxicity in vitro compared to either free DOX or DOX-loaded uncross-linked polyurethane micelles, the drug-loaded CCL-PUMs show the highest anti-tumor efficacy with reduced toxicity in vivo. Since enhanced anti-tumor efficacy and reduced toxic side effects are key aspects of efficient cancer therapy, the novel reduction-responsive CCL-PUMs may hold great potential as a bio-triggered drug delivery system for cancer therapy.

Intracellular pH-sensitive PEG-block-acetalated-dextrans as efficient drug delivery platforms.

Intracellular pH-sensitive micelles of PEG-block-acetalated-dextran (PEG-b-AC-Dex) were prepared and used for acid-triggered intracellular release of anticancer drug. The hydrodynamic radii (Rh) of PEG-b-AC-Dex micelles could increase after incubation in PBS solution at pH 5.5. Based on the pH-responsive Rh variation behavior, it was expected that the PEG-b-AC-Dex micelles should be interesting for intracellular drug delivery. Thus, doxorubicin (DOX), a wide-spectrum anticancer drug, was loaded into the micelles and the pH-dependent release of the payload DOX was tested in vitro. The in vitro drug release profiles showed that only a small amount of the loaded DOX was released in PBS solution at pH 7.4, while up to about 90% of the loaded DOX could be quickly released in PBS solution at pH 5.5. Compared to pH-insensitive PEG-PLA micelles, the PEG-b-AC-Dex micelles displayed a faster drug release behavior in tumor cells. Moreover, higher cellular proliferation inhibition efficacy was achieved toward tumor cells. These features suggested that DOX could be efficiently loaded and delivered into tumor cells in vitro by the intracelluar pH-sensitive micelles, leading to enhanced inhibition of tumor cell proliferation. Therefore, the pH-sensitive micelles may provide a promising carrier for acid-triggered drug release for cancer therapy.

Reduction-responsive cross-linked micelles based on PEGylated polypeptides prepared via click chemistry

This study aims to develop novel reduction-responsive cross-linked micelles (CMs) based on poly(ethylene glycol)-block-poly(γ-propargyl-L-glutamate) (PEG-PPLG) by click chemistry. 1H NMR spectroscopy, IR spectroscopy, dynamic light scattering (DLS) and transmission electron microscopy (TEM) were performed to confirm the successful construction of the CMs. Doxorubicin (DOX) was loaded into the CMs as a model anticancer drug. The DOX-loaded CMs could hold the drug under physiological conditions, and release the payload quickly in the presence of glutathione (GSH). Confocal laser scanning microscopy (CLSM) and flow cytometry measurements revealed that the intracellular drug release from the DOX-loaded CMs was increased in the HeLa cells with an enhanced intracellular GSH level. In vitro methyl thiazolyl tetrazolium (MTT) assays indicated that the CMs were biocompatible, and DOX-loaded CMs showed higher cellular proliferation inhibition towards GSH-pretreated HeLa cells than non-pretreated cells. Due to their unique responsiveness, the biocompatible CMs show promise for the intracellular delivery of chemotherapeutic drugs in cancer therapy.

pH-Responsive Poly(ethylene glycol)/Poly(L-lactide) Supramolecular Micelles Based on Host-Guest Interaction.

pH-responsive supramolecular amphiphilic micelles based on benzimidazole-terminated poly(ethylene glycol) (PEG-BM) and β-cyclodextrin-modified poly(L-lactide) (CD-PLLA) were developed by exploiting the host-guest interaction between benzimidazole (BM) and β-cyclodextrin (β-CD). The dissociation of the supramolecular micelles was triggered in acidic environments. An antineoplastic drug, doxorubicin (DOX), was loaded into the supramolecular micelles as a model drug. The release of DOX from the supramolecular micelles was clearly accelerated as the pH was reduced from 7.4 to 5.5. The DOX-loaded PEG-BM/CD-PLLA supramolecular micelles displayed an enhanced intracellular drug-release rate in HepG2 cells compared to the pH-insensitive DOX-loaded PEG-b-PLLA counterpart. After intravenous injection into nude mice bearing HepG2 xenografts by the tail vein, the DOX-loaded supramolecular micelles exhibited significantly higher tumor inhibition efficacy and reduced systemic toxicity compared to free DOX. Furthermore, the DOX-loaded supramolecular micelles showed a blood clearance rate markedly lower than that of free DOX and comparable to that of the DOX-loaded PEG-b-PLLA micelles after intravenous injection into rats. Therefore, the pH-responsive PEG-BM/CD-PLLA supramolecular micelles hold potential as a smart nanocarrier for anticancer drug delivery.

In situ formed reactive oxygen species–responsive scaffold with gemcitabine and checkpoint inhibitor for combination therapy

A ROS-responsive hydrogel scaffold controls release of gemcitabine and immune checkpoint inhibitor for enhanced antitumor activity. An antitumor two-step Although cancer immunotherapy can be quite effective, it has a variety of drawbacks. Most patients still do not achieve remission, whereas those who respond to therapy often experience immune-related side effects. Wang et al. address both of these concerns by maximizing drug access to tumors and minimizing systemic exposure. To achieve this, the authors designed a hydrogel that they inject at the site of a tumor, where it forms a scaffold for sequential release of drugs. A cytotoxic chemotherapy is released first, killing some cancer cells before the release of most of an immune checkpoint inhibitor, which then stimulates antitumor immunity. With this approach, the authors demonstrate efficacy in mouse models of primary tumors, as well as those that recur after surgery. Patients with low-immunogenic tumors respond poorly to immune checkpoint blockade (ICB) targeting the programmed death-1 (PD-1)/programmed death-ligand 1 (PD-L1) pathway. Conversely, patients responding to ICB can experience various side effects. We have thus engineered a therapeutic scaffold that, when formed in situ, allows the local release of gemcitabine (GEM) and an anti–PD-L1 blocking antibody (aPDL1) with distinct release kinetics. The scaffold consists of reactive oxygen species (ROS)–degradable hydrogel that releases therapeutics in a programmed manner within the tumor microenvironment (TME), which contains abundant ROS. We found that the aPDL1-GEM scaffold elicits an immunogenic tumor phenotype and promotes an immune-mediated tumor regression in the tumor-bearing mice, with prevention of tumor recurrence after primary resection.

Interleukin-15 and cisplatin co-encapsulated thermosensitive polypeptide hydrogels for combined immuno-chemotherapy

&NA; In situ‐forming thermosensitive hydrogels based on poly(ethylene glycol)‐poly(&ggr;‐ethyl‐L‐glutamate) diblock copolymers (mPEG‐b‐PELG) were prepared for the co‐delivery of interleukin‐15 (IL‐15) and cisplatin (CDDP). The polypeptide‐based hydrogels as local drug delivery carriers could reduce the systemic toxicity, degrade thoroughly within 3 weeks after subcutaneous injection into rats and display an acceptable biocompatibility. When incubated with mouse melanoma B16 cells, only the CDDP‐treated groups had significant effects on the S phase cell‐cycle arrest in melanoma cells. After a single peritumoral injection of the hydrogel containing IL‐15/CDDP in C57BL/6 mice inoculated with B16F0‐RFP melanoma cells, the dual drug‐loaded hydrogels displayed synergistic anticancer efficacy, which was resulted from a combination of CDDP‐mediated S arrest and IL‐15/CDDP‐induced recovery of CD8+ T cell and NK cell populations to reduce immunosuppression and enhance antitumor immunity. Hence, the as‐prepared thermosensitive polypeptide hydrogels for localized and sustained co‐delivery of IL‐15 and CDDP may have potential for efficient treatment of melanoma. Graphical abstract The mechanism for synergistic antitumor effects of coadministration of IL‐15 and CDDP released from the mPEG‐b‐PELG hydrogels. Figure. No caption available.

pH‐Triggered Charge‐Reversal Polyurethane Micelles for Controlled Release of Doxorubicin

A series of pH-triggered charge-reversal polyurethane copolymers (PS-PUs) containing methoxyl-poly(ethylene glycol) (mPEG), carboxylic acid groups, and piperazine groups is presented in this work. The obtained PS-PUs copolymers can form into stable micelles at pH 7.4, which response to a narrow pH change (5.5-7.5) and show a tunable pH-triggered charge-reversal property. Doxorubicin (DOX) is encapsulated into the PS-PU micelles as a model drug. The drug release of DOX-loaded PS-PU micelles shows an obviously stepped-up with reducing the pH. Meanwhile, it is found that the charge-reversal property can improve the cellular uptake behavior and intracellular drug release in both HeLa cells and MCF-7 cells. Additionally, the time-dependent cytotoxicity of the DOX-loaded PS-PU micelles is confirmed by MTT assay. Attributed to the tunable charge-reversal property through changing the molar ratio of piperazine/carboxyl, the PS-PU micelles will be a potential candidate as an intelligent drug delivery system in future studies.

pH and reduction dual responsive cross-linked polyurethane micelles as an intracellular drug delivery system

Nano-vehicles that exhibit enhanced stability in blood circulation while spontaneously releasing therapeutic cargos at pathological sites in response to specific biological triggers are of interest for on-demand drug delivery. In this work, disulfide cross-linked polyurethane micelles (CL-PUMs) that respond to pH change and an intracellular reducing agent were developed. The micelles were prepared by cross-linking of poly(ethylene glycol)–polyurethane multiblock copolymers containing tertiary amino and cyclic disulfide moieties via a thiol–disulfide exchange reaction. The CL-PUMs tended to swell or decompose under a weakly acidic environment or in the presence of an intracellular reducing agent, glutathione (GSH), likely owing to the protonation of the tertiary amino groups and cleavage of the disulfide cross-linking bonds. The doxorubicin (DOX)-loaded CL-PUMs suppressed the initial burst release at pH 7.4 without GSH, while they displayed a triggered drug release manner in response to an acidic environment and GSH. It was found that the intracellular DOX release of the DOX-loaded CL-PUMs in HepG2 cells was accelerated by an acidic environment or enhanced intracellular GSH concentration. Moreover, the time-dependent cytotoxicity against HepG2 and HeLa cells of the DOX-loaded CL-PUMs was confirmed by an MTT assay. Overall, due to the enhanced stability, selective swelling and decomposition properties in response to intracellular micro-environments, the pH- and reduction-sensitive polyurethane cross-linked nano-carriers can serve as a potential system for intracellular drug delivery.

ε-Methacryloyl-L-lysine based polypeptides and their thiol–ene click functionalization

Facile synthesis of biopolymers that facilitate versatile post-polymerization modification is of great interest for biotechnological and biomedical applications. In this study, a methacryloyl-substituted L-lysine N-carboxyanhydride (LysMA-NCA) monomer was designed and synthesized, and methacryloyl-functionalized polypeptides were prepared through the ring opening polymerization (ROP) of the L-lysine-based monomer. The post-polymerization functionalization of the methacryloyl-containing polypeptides with various thiol-containing molecules was achieved with high efficiency through facile radical-mediated thiol–ene chemistry. Moreover, a block copolypeptide bearing both methacryloyl and alkynyl pendants was developed through successive ROP of LysMA-NCA and γ-propargyl-L-glutamate (PPLG-NCA). The sequential modification of the block copolypeptide with hydrophilic and hydrophobic molecules, respectively, was achieved by the successive alkyne–azido and thiol–ene “click” reactions. Overall, the facile synthesis of polypeptides bearing functional substituents and their versatile post-polymerization modification may serve as a useful platform for the development of various functional polymers.