A prodrug hydrogel with tumor microenvironment and near-infrared light dual-responsive action for synergistic cancer immunotherapy

The antitumor immune response induced by chemotherapy has attracted considerable attention. However, the immunosuppressive tumor microenvironment hinders the immune activation effect of cancer chemotherapy. TGF-β plays a key role in driving tumor immunosuppression and can prevent effective antitumor immune response through multiple roles. In this study, a dual-responsive prodrug micelle (PAOL) is designed to co-deliver LY2109761 (a TGF-β receptor I/II inhibitor) and oxaliplatin (OXA, a conventional chemotherapy) to remodel tumor microenvironment and trigger immunogenic cell death (ICD) to induce antitumor immunity response. Under hypoxia tumor environment, the polyethylene glycol shell of the micelle cleavages, along with the release of LY2109761 and OXA prodrug. Cytotoxic effect of OXA is then activated by glutathione-mediated reduction in tumor cells and the activated OXA significantly enhances tumor immunogenicity and promotes intratumoral accumulation of cytotoxic T lymphocytes. Meanwhile, TGF-β blockade through LY2109761 reprograms tumor microenvironment by correcting the immunosuppressive state and regulating tumor extracellular matrix, which further maintaining OXA induced immune response. Therefore, due to the capability of boosting tumor-specific antitumor immunity, the bifunctional micelle presents markedly synergistic antitumor efficacies and provides a potent therapeutic strategy for chemoimmunotherapy of solid tumors.

The incidence and progression of inflammatory bowel disease are closely related to oxidative stress caused by excessive production of reactive oxygen species (ROS). To develop an efficacious and safe nanotherapy against inflammatory bowel diseases (IBD), we designed a novel pH/ROS dual-responsive prodrug micelle GC-B-Que as an inflammatory-targeted drug, which was comprised by active quercetin (Que) covalently linked to biocompatible glycol chitosan (GC) by aryl boronic ester as a responsive linker. The optimized micelles exhibited well-controlled physiochemical properties and stability in a physiological environment. Time-dependent NMR spectra traced the changes in the polymer structure in the presence of H2O2, confirming the release of the drug. The in vitro drug release studies indicated a low release rate (<20 wt %) in physiological conditions, but nearly complete release (>95 wt % after 72 h incubation) in a pH 5.8 medium containing 10 μM H2O2, exhibiting a pH/ROS dual-responsive property and sustained release behavior. Importantly, the negligible drug release in a simulated gastric environment in 1 h allowed us to perform intragastric administration, which has potential to achieve the oral delivery by mature enteric-coating modification in future. Further in vivo activities and biodistribution experiments found that the GC-B-Que micelles tended to accumulate in intestinal inflammation sites and showed better therapeutic efficacy than the free drugs (quercetin and mesalazine) in a colitis mice model. Typical inflammatory cytokines including TNF-α, IL-6, and iNOS were significantly suppressed by GC-B-Que micelle treatment. Our work promoted inflammatory-targeted delivery and intestinal drug accumulation for active single drug quercetin and improved the therapeutic effect of IBD. The current study also provided an alternative strategy for designing a smart responsive nanocarrier for a catechol-based drug to better achieve the target drug delivery.

A novel strategy for the preparation of dual-responsive prodrug nanogels was proposed by Diels-Alder reaction. Firstly, poly(styrene-alt-maleic anhydride) copolymers were functionalized with furfuryl amine and hydrazine in a simple one-pot reaction. Secondly, doxorubicin (DOX) was further incorporated to copolymer via hydrazone linkage in the presence of dithiobismaleimidoethane as a cross-linking agent resulted in prodrug nanogels. The prodrug nanogels were stable under physiological condition while the disintegration of nanogels was taken place and DOX released rapidly in the redox medium. The prodrug nanogels presented strong toxicity towards HepG2 cell line, whereas they had almost no inhibition in HEK293 normal cell line. The results suggest that DOX conjugate-based nanogels would be a potential candidate for efficient drug nanocarrier.

Poly (isopropyl-oxazoline) micelle nanocarrier as dual-responsive prodrug for targeted doxorubicin delivery

Nanoparticle-based tumor immunotherapy has emerged to show great potential for simultaneously regulating the immunosuppressive tumor microenvironment, reducing the unpleasant side effects, and activating tumor immunity. Herein, an excipient-free glutathione/pH dual-responsive prodrug nanoplatform is reported for immunotherapy, simply by sequentially liberating 5-aminolevulinic acid and immunogenically inducing doxorubicin drug molecules, which can leverage the acidity and reverse tumor microenvironment. The obtained nanoplatform effectively boosts the immune system by promoting dendritic cell maturation and reducing the number of immune suppressive immune cells, which shows the enhanced adjunctive effect of anti-programmed cell death protein 1 therapy. Overall, the prodrug-based immunotherapy nanoplatform may offer a reliable strategy for improving synergistic antitumor efficacy.

Multidrug resistance (MDR) is one of the major obstacles for tumor therapy. Intake by receptor-mediated endocytosis enables molecules to bypass ABC transporter efflux, which is the primary mechanism of MDR. Here, we developed a novel pH/enzyme dual-responsive polypeptide prodrug to reverse multidrug resistance. This drug is composed of pH/MMP2-sensitive nanoparticles (MSNPs) self-assembled from mPEG-peptide-DOX. MSNPs can overcome sequential physiological barriers of multidrug resistance by prolonging the circulation time through PEGylation, enhancing tumor accumulation through passive targeting, increasing tumor penetration by enzyme-sensitive PEG deshielding, bypassing ABC transporter efflux by undergoing receptor-mediated endocytosis, and inducing sufficient DOX release from nanoparticles triggered by lysosomal pH. The reversal of MDR by MSNPs was evaluated in MCF-7/ADR cells and nude mice bearing tumors consisting of MCF-7/ADR cells. Both in vitro and in vivo studies showed that the MSNPs can effectively reverse MDR. Thus, MSNPs may constitute a potentially promising strategy for overcoming MDR in clinical applications.

Redox dual-responsive paclitaxel-doxorubicin heterodimeric prodrug self-delivery nanoaggregates for more effective breast cancer synergistic combination chemotherapy

In recent years, intelligent polymeric micelles with multifunctions are in urgent demand for cancer diagnosis and therapy. Herein, pH and redox dual-responsive prodrug micelles with aggregation-induced emission (AIE) active cellular imaging and charge conversion have been prepared for combined chemotherapy and bioimaging based on a novel doxorubicin-conjugated amphiphilic PMPC-PAEMA-P (TPE- co-HD)-ss-P (TPE- co-HD)-PAEMA-PMPC copolymer. The doxorubicin is conjugated via a pH cleavable imine linkage and can be packed in the hydrophobic core along with the glutathione (GSH)-sensitive disulfide bond. The DOX-conjugated inner core is sealed with a pH-responsive PAEMA as the "gate", which would rapidly open in the acidic condition, following the drug release and charge conversion-mediated acceleration of endocytosis. After an efficient internalization, the disulfide bond can be cleaved by the high concentration of GSH causing the further accelerated drug release. Meanwhile, intracellular drug delivery can be traced due to the AIE behavior of micelles. Moreover, great tumor inhibition in vitro and in vivo has been demonstrated for these DOX-conjugated micelles. This smart prodrug micelle system would be a desirable drug carrier for cancer therapy and bioimaging.

Facile preparation of pH/reduction dual-responsive prodrug microspheres with high drug content for tumor intracellular triggered release of DOX

A facile approach has been developed to prepare novel biocompatible and biodegradable pH/reduction dual-responsive oxidized alginate-doxorubicin (mPEG-OAL-DOX/Cy) prodrug nanohydrogels for tumor-specific intracellular triggered release of anticancer drug doxorubicin (DOX), by conjugating DOX via acid-labile Schiff base linkage into the alginate nanohydrogels crosslinked with bioreducible disulfide bonds. The uniform prodrug nanohydrogels, which were prepared with the oxidized alginate (OAL) with an oxidation degree of 20.0%, PEGylation degree of 7.5 mol%, and crosslinking degree of 94.0%, showed a favorable DOX content (22.7 ± 0.4%) with an average hydrodynamic diameter of about 170 nm. They released DOX rapidly in lower pH media mimicking the tumor microenvironment with a cumulative DOX release rate of 58.4% within 58 h with a sustained release behavior in long term release resulting from their nanohydrogel-micelle transformation, while the premature leakage under the simulated physiological conditions was only 15.5%. The MTT assay demonstrated that the mPEG-OAL-DOX/Cy prodrug nanohydrogels exhibited enhanced inhibitory efficiency against SKOV3 cells, in comparison with free DOX.

Direct chemical grafted curcumin on halloysite nanotubes as dual-responsive prodrug for pharmacological applications

In this study, thermal and redox dual sensitive nanogels based on N-vinylcaprolactam (VCL) and N-succinimidyl methacrylate (Suma) crosslinked with diallyl disulfide were synthesized via a facile and straightforward method. The reactive succinimide groups were mainly located in the nanogel shell which increases considerably their accessibility for conjugation reactions. Doxorubicin (DOX) was successfully loaded into the nanogel through two different routes. Approximately 91.3% of DOX molecules were covalently bound to the nanogel network via coupling with succinimide groups under mild conditions to obtain prodrug nanogels, while 8.7% of DOX molecules were captured into the nanogels via electrostatic interactions with the -COOH group from the hydrolyzed ester groups of the nanogels. The DOX-loaded nanogels demonstrated volume phase transition temperature (VPTT) near human physiological temperature. The nanogels shrink near body temperature, which could help lock the drug molecules stably in blood circulation. The conjugation of DOX molecules in nanogels avoided premature unspecific drug release under physiological conditions. The small amount of physically loaded DOX (due to electrostatic interactions) could be partially released as free DOX due to the increasing acidic conditions in the endosome/lysosome pathway. The chemically conjugated DOX was released in the form of a prodrug polymer triggered by the high concentration of glutathione in the cytosol that induced nanogel degradation. The present drug delivery system exhibits a sustainable delivery profile in the intracellular release study and high antitumor activity. We are convinced that the thermal and reduction dual-responsive prodrug nanogels have tremendous potential in controlled drug release.

Biomimic pH/reduction dual-sensitive reversibly cross-linked hyaluronic acid prodrug micelles for targeted intracellular drug delivery

A dual-responsive drug delivery system simulating an AND logic gate is developed by core-cross-linking of a disulfide-containing anticancer prodrug with Cu(2+) for safe and efficient delivery of anticancer drugs. These prodrug nanoparticles are stable and exhibit nearly no premature drug release, and allow a fast drug release under simulated intracellular conditions, realizing a precise drug delivery towards cell nuclei.

A facile approach for dual-responsive prodrug nanogels based on dendritic polyglycerols with minimal leaching