Gelatin nanocarriers assembled by a self-immolative cross-linker for targeted cancer therapy

With a number of outstanding properties, gelatin is an ideal candidate for assembling nanoplatforms in biomedical applications. Generally, gelatin nanocarriers are cross-linked by aldehydes to improve their stability in water solution. However, aldehydes could cause multiple toxicities and their cross-linking products are uncontrollable. Here, we first used a self-immolative cross-linker to assemble gelatin nanocarriers for the controlled release of drugs and targeted cancer therapy. The cross-linker contains a disulphide bridge and two symmetrical succinimidyl-esters, endowing it with multiple functions: 1) to cross-link the gelatin nanocarriers and thus improve their stability in water; 2) to conjugate the drug and tumor-targeting ligands with nanocarriers through covalent linkage; 3) to redox-responsively degrade the nanocarriers through hydrolysis of disulphide bridge; and 4) to produce traceless drug molecules through self-immolative reaction. Good biocompatibility and controllable drug release were demonstrated by in vitro experiments. Both qualitative and quantitative analyses confirmed the intracellular uptake of the nanocarriers by using doxorubicin (DOX) as a drug model and phenylboronic acid (PBA) as the targeting ligand. In vivo results demonstrated high therapeutic efficiency and low toxic side effects of the DOX loaded nanocarriers against artificial liver tumors.

PEGylated mesoporous silica core-shell redox-responsive nanoparticles for delivering paclitaxel to breast cancer cells

Controlling the drug release and restricting its presence in healthy organs is extremely valuable. In this study, mesoporous silica nanoparticles (MSN) as the core, loaded with paclitaxel (PTX), were coated with a non-porous silica shell functionalized with disulfide bonds. The nanoparticles were further coated with polyethylene glycol (PEG) via disulfide linkages. We analyzed the physicochemical properties of nanoparticles, including hydrodynamic size via Dynamic Light Scattering (DLS), zeta potential, X-ray Diffraction (XRD) patterns, Fourier-Transform Infrared (FTIR) spectra, and imaging through Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM). The drug release profile in two distinct glutathione (GSH) concentrations of 2 µM and 10 µM was measured. The cellular uptake of nanoparticles by MCF-7 cell line was determined using Confocal Laser Scanning Microscopy (CLSM) images and flow cytometry. Furthermore, the cell viability and the capability of nanoparticles to induce apoptosis in MCF-7 cell line were studied using the MTT assay and flow cytometry, respectively. Our investigations revealed that the release of PTX from the drug delivery system was redox-responsive. Also, results indicated an elevated level of cellular uptake and efficient induction of apoptosis, underscoring the promising potential of this redox-responsive drug delivery system for breast cancer therapy.

Multifunctional nanogel based on carboxymethyl cellulose interfering with cellular redox homeostasis enhances phycocyanobilin photodynamic therapy

The redox homeostasis defense mechanism of tumor cells is one of the prime reasons for the unsatisfactory effect of photodynamic therapy (PDT). So far, little attention has been paid to this obstacle. In this work, we reported a synthesizing simple yet versatile nanogel (BCPS), synthesized by cystamine dihydrochloride functionalized sodium carboxymethylcellulose (CMC-SS), bovine serum albumin, and Phycocyanobilin self-assembly. The BCPS reduced the levels of glutathione molecules by reacting with glutathione, thereby interfering with intracellular redox homeostasis and enhancing the sensitivity of tumor cells to PDT. The BCPS was shown to possess excellent serum stability, high blood compatibility, low toxic side effects, and higher reactive oxygen species (ROS) utilization. After irradiation, the BCPS could significantly increase intracellular ROS level by approximately 1.6-fold and decrease the IC50 to HeLa cells by approximately 1.5-fold, compared to the pre-functional drugs BCP. This proposed strategy, based on increasing the utilization rate of ROS in tumor cells is promising for application potentials in tumor therapy.

Redox-responsive microemulsion: Fabrication and application to curcumin encapsulation

HYPOTHESIS

Stimulus-responsive microemulsions have aroused significant attention because of their versatile and reversible switchability between stable and unstable states. However, most stimuli-responsive microemulsions are based on stimuli-responsive surfactants. We posit that the change in the hydrophilicity of a selenium-containing alcohol triggered by a mild redox reaction could also influence the stability of microemulsions and provide a new nanoplatform for the delivery of bioactive substances.

EXPERIMENTS

A selenium-containing diol (3,3'-selenobis(propan-1-ol), PSeP) was designed and used as a co-surfactant in a microemulsion with ethoxylated hydrogenated castor oil (HCO40), diethylene glycol monohexyl ether (DGME), 2-n-octyl-1-dodecanol (ODD) and water. The redox-induced transition in PSeP was characterized by ¹H NMR, ⁷⁷Se NMR, and MS. The redox-responsiveness of the ODD/HCO40/DGME/PSeP/water microemulsion was investigated through determination of a pseudo-ternary phase diagram, analysis by dynamic light scattering, and electrical conductivity, and its encapsulation performance was evaluated by determination of the solubility, stability, antioxidant activity, and skin penetrability of encapsulated curcumin.

FINDINGS

The redox conversion of PSeP enabled efficient switching of ODD/HCO40/DGME/PSeP/water microemulsions. Addition of oxidant (H₂O₂), oxidized PSeP into more hydrophilic PSeP-Ox (selenoxide), disrupting the emulsifying capacity of the combination of HCO40/DGME/PSeP, markedly reducing the monophasic microemulsion region in the phase diagram, and inducing phase separation in some formulations. Addition of reductant (N₂H₄·H₂O), reduced PSeP-Ox and restored the emulsifying capacity of the combination of HCO40/DGME/PSeP. In addition, PSeP-based microemulsions can significantly enhance the solubility in oil (by 23 times), stability, antioxidant capacity (DPPH∙ radical scavenging by 91.74 %), and skin penetrability of curcumin, showing clear potential for encapsulation and delivery of curcumin and other bioactive substances.

Green synthesis of quaternized chitosan nanogel using emulsion-photopolymerization as redox-responsive drug carrier

We report the green synthesis of trimethyl chitosan-functionalized poly(2-hydroxyethyl methacrylate) (PHEMA-TMC) nanogels via surfactant-free emulsion photopolymerization. TMC, a quaternized derivative of chitosan, was synthesized through methylation of chitosan, resulting in quaternary and tertiary amine groups as the main substitution products. TMC tertiary amine moiety and riboflavin (RF) acted as a redox photo-initiating system to generate free radicals for the polymerization under light irradiation. The effects of polymerization parameters such as irradiation time, concentrations of TMC and RF were investigated using MBA as crosslinker. Under the optimal condition of 1 % TMC, 4 % HEMA, 0.8 μM RF, 5 % MBA, and 4 h of polymerization time, the cationic PHEMA-TMC nanogel was synthesized with 76 % monomer conversion and an average diameter of about 106 nm. Moreover, the disulfide-crosslinked PHEMA-TMC nanogel was also synthesized using the disulfide dimethacrylate crosslinker, which exhibited a redox-induced degradation and release of encapsulated melatonin, potentially useful as a redox-responsive drug delivery carrier.

Linear-like polypeptide-based micelle with pH-sensitive detachable PEG to deliver dimeric camptothecin for cancer therapy

Nano drug delivery systems have made significant progress in delivering anticancer drugs camptothecin (CPT). However, many challenges for CPT delivery remain, including low drug loading efficiency, premature drug leakage, and poor cellular internalization. Herein, we report a novel dual-sensitive polypeptide-based micelle with remarkably high drug loading of CPT for cancer therapy. This self-assembled micelle possesses the following essential components for CPT: (1) pH-sensitive PEG (OHC-PEG-CHO) for prolonging blood circulation and allowing biocompatibility by shielding the cationic micelles, which can be detached under the tumor acidic microenvironment and facilitates the cellular uptake; (2) polypeptide polylysine-polyphenylalanine (PKF) synthesized via ring-opening polymerization for micelle formation and CPT analogue loading; (3) dimeric CPT (DCPT) with redox-sensitive linker for increasing CPT loading and ensuring drug release at tumor sites. Interestingly, the linear-like morphology of PEG-PKF/DCPT micelles was able to enhance their cellular internalization when compared with the spherical blank PKF micelles. Also, the anticancer efficacy of DCPT against lung cancer cells was significantly improved by the micelle formation. In conclusion, this work provides a promising strategy facilitating the safety and effective application of CPT in cancer therapy.

Tumor-targeted dual-starvation therapy based on redox-responsive micelle nanosystem with co-loaded LND and BPTES

The starvation therapy mediated by the lonidamine (LND) was limited by the low drug delivery efficiency, off-target effect and compensative glutamine metabolism. Herein, a hyaluronic acid (HA)-modified reduction-responsive micellar nanosystem co-loaded with glycolysis and glutamine metabolism inhibitor (LND and bis-2-(5-phenylacetmido-1,2,4-thiadiazol-2-yl)ethyl sulfide, BPTES) was constructed for tumor-targeted dual-starvation therapy. The in vitro and in vivo results collectively suggested that the fabricated nanosystem could effectively endocytosed by tumor cells via HA receptor-ligand recognition, and rapidly release starvation-inducers LND and BPTES in response to the GSH-rich intratumoral cytoplasm. Furthermore, the released LND and BPTES were capable of inducing glycolysis and glutamine metabolism suppression, and accompanied by significant mitochondrial damage, cell cycle arrest and tumor cells apoptosis, eventually devoting to the blockade of the energy and substance supply and tumor killing with high efficiency. In summary, HPPPH@L@B nanosystem significantly inhibited the compensatory glycolysis and glutamine metabolism via the dual-starvation therapy strategy, blocked the indispensable energy and substance supply of tumors, consequently leading to the desired tumor starvation and effective tumor killing with reliable biosafety.

Active targeting redox-responsive mannosylated prodrug nanocolloids promote tumor recognition and cell internalization for enhanced colon cancer chemotherapy

Despite the diversified therapeutic approaches for malignant tumors, chemotherapy remains the backbone of current cancer treatment. However, conventional chemotherapeutics was found to be associated with deficient recognition of tumor, low uptake efficiency, insolubility, short circulation, poor biocompatibility and low therapeutic outcomes. Herein, the active targeting redox-responsive mannosylated prodrug nanocolloids (HM NCs) were constructed for enhanced chemotherapy of colon cancer. HM NCs were prepared by the covalent cross-linking of 10-hydroxycamptothecin (HCPT) and mannose (MAN) via a redox-responsive cross-linker containing disulfide bonds, and modified with a moderate amount of polyethylene glycol (PEG). The large amount of mannose contained in HM NCs could actively target overexpressed mannose receptors on the surface of cancer cells and enhance cancer cell internalization through mannose receptor-mediated endocytosis. Owing to the combination of active targeting and the enhanced permeability and retention (EPR) passive targeting, HM NCs could effectively accumulate in tumors and high glutathione (GSH) in tumor microenvironment triggered cleavage of redox-responsive bonds and precise drug release. HM NCs exhibited superior antitumor activity both in vitro and in vivo and appreciably extended the mouse survival rate with good biocompatibility. The innovative HM NCs are expected to be conducive to overcoming the limitations of conventional chemotherapy for colon cancer and providing more choices for future clinical translation. STATEMENT OF SIGNIFICANCE: Despite the enhanced permeability and retention effect, the passive targeting can be interfered with by the complex biologic barriers in the body. In this study, an active targeting system (HM NCs) was constructed by covalent cross-linking of mannose and anticancer drug 10-hydroxycamptothecin via redox-responsive disulfide bonds for enhanced colon cancer chemotherapy. Mannosylation could promote hydrophilia and stability for prolonged blood circulation. Mannose could promote tumor recognition and cell internalization via mannose receptor-mediated endocytosis. High glutathione level could trigger the redox-responsive release of anticancer drugs and further induce cell apoptosis via DNA damage. The HM NCs exhibited superior antitumor activity both in vitro and in vivo and appreciably extended the mouse survival rate with good biocompatibility.

A redox-responsive dihydroartemisinin dimeric nanoprodrug for enhanced antitumor activity

Redox-responsive drug delivery system emerges as a hopeful platform for tumor treatment. Dihydroartemisinin (DHA) has been investigated as an innovative tumor therapeutic agent. Herein, a DHA dimeric prodrug bridged with disulfide bond as linker (DHA2-SS) has been designed and synthesized. The prepared prodrugs could self-assemble into nanoparticles (SS NPs) with high DHA content (> 90%) and robust stability. These SS NPs display sensitive redox responsive capability and can release DHA under the tumor heterogeneity microenvironment. SS NPs possess preferable antitumor therapeutic activity in contrast with free DHA. Moreover, the possible anti-cancer mechanism of SS NPs was investigated through RNA-seq analysis, bioinformatics and molecular biological method. SS NPs could induce apoptosis via mitochondrial apoptosis pathway, as well as glycolysis inhibition associate with the regulation of PI3K/AKT/HIF-1α signal path, which may offer an underlying therapeutic target for liver cancer. Our study highlights the potential of using redox responsive prodrug nanoparticles to treat cancer, meanwhile provides insights into the anti-cancer mechanism of DHA prodrug.

In vivo therapeutic evaluation of a novel bis-lawsone derivative against tumor following delivery using mesoporous silica nanoparticle based redox-responsive drug delivery system

Herein, we have evaluated the in vivo therapeutic efficacy and systemic toxicity profile of a synthetic anticancer compound [3,3'-((4-(trifluoromethyl)phenyl)methylene)bis(2-hydroxynaphthalene-1,4-dione)]. A multifunctional mesoporous silica nanoparticle (MSN) based drug delivery network was also fabricated which specifically showed targeting nature towards the cancer cell. The mesopores of silica nanoparticles were tagged with phenyl boronic acid (PBA) for targeted drug delivery into tumor tissue. 1j was then loaded inside the nanocarriers followed by pore blocking with gold nanoparticles (GN) to attain a redox-responsive controlled drug delivery pattern. The synthesized nanocarriers (1j@-MSN-PBA-GN) having mean diameter of ~86 nm exhibited a moderate 1j loading content of 13.68% with overall negative surface charge. Both the targeted and non-targeted nanoformulations were tested for their anticancer activities both in vitro and in vivo models, and found more effective as compared with free 1j treatment. However, the targeted nanoformulations showed higher therapeutic effect due to increased cellular internalization and caused mitochondria-dependent apoptosis in MCF-7 cells via oxidative stress. Besides, the targeted nanoformulation significantly inhibited in the development of solid tumor in comparison to non-targeted nanoformulations and free 1j as a consequence of increased internalization of the drug-candidate in tumor tissue. Therefore, this study proposes that 1j can be considered as a potent anti-carcinogenic compound in vivo and its therapeutic potential is further increased by using PBA functionalized and GN gated MSN-based controlled drug delivery system without showing any significant systemic toxicity.

pH-activated, mitochondria-targeted, and redox-responsive delivery of paclitaxel nanomicelles to overcome drug resistance and suppress metastasis in lung cancer

Background

Mitochondria play a role in the occurrence, development, drug resistance, metastasis, and other functions of cancer and thus are a drug target. An acid-activated mitochondria-targeting drug nanocarrier with redox-responsive function was constructed in the present study. However, whether this vector can precisely delivery paclitaxel (PTX) to enhance therapeutic efficacy in drug-resistant lung cancer is unknown.

Results

Acid-cleavable dimethylmaleic anhydride (DA) was used to modify pluronic P85-conjugated mitochondria-targeting triphenylphosphonium (TPP) using disulfide bonds as intermediate linkers (DA-P85-SS-TPP and DA-P-SS-T). The constructed nanocarriers demonstrated enhanced cellular uptake and selective mitochondrial targeting at extracellular pH characteristic for a tumor (6.5) and were characterized by extended circulation in the blood. TPP promoted the targeting of the DA-P-SS-T/PTX nanomicelles to the mitochondrial outer membrane to decrease the membrane potential and ATP level, resulting in inhibition of P-glycoprotein and suppression of drug resistance and cancer metastasis. PTX was also rapidly released in the presence of high glutathione (GSH) levels and directly diffused into the mitochondria, resulting in apoptosis of drug-resistant lung cancer cells.

Conclusions

These promising results indicated that acid-activated mitochondria-targeting and redox-responsive nanomicelles potentially represent a significant advancement in cancer treatment.

Graphic Abstarct

Redox-responsive hyaluronic acid-based nanoparticles for targeted photodynamic therapy/chemotherapy against breast cancer

Specific cellular uptake and sufficient drug release in tumor tissues are important for effective cancer therapy. Hyaluronic acid (HA), a skeleton material, could specifically bind to cluster determinant 44 (CD44) receptors highly expressed on the surface of tumor cells to realize active targeting. Cystamine (cys) is sensitive highly reductive environment inside tumor cells and was used as a connecting arm to connect docosahexaenoic acid (DHA) and chlorin e6 (Ce6) to the HA skeleton to obtain redox-sensitive polymer HA-cys-DHA/Ce6 (CHD). Nanoparticles were fabricated and loaded with chemotherapeutic drug docetaxel (DTX) by physical encapsulation. The prepared nanoparticles had significantly increased uptake by MCF-7 cells that overexpressed CD44 receptors, and DTX was effectively released at high reducing condition. Compared with mono-photodynamic therapy (PDT) or mono-chemotherapy, the prepared nanoparticles exhibited superior anti-tumor effect by inhibiting microtubule depolymerization, blocking cell cycle and generating reactive oxygen species (ROS). In vivo anti-tumor experiments proved that DTX/CHD nanoparticles had the best antitumor response versus DTX and CHD nanoparticles under near-infrared (NIR) irradiation. These studies revealed that redox-responsive DTX-loaded CHD nanoparticles held great potential for the treatment of breast cancer.

Protein corona precoating on redox-responsive chitosan-based nano-carriers for improving the therapeutic effect of nucleic acid drugs

Spontaneous formation of protein corona on chitosan-based nano-carriers is inevitable once they enter the blood, which is considered to be an important factor that weakens the delivery efficiency and therapeutic effect of nucleic acid drugs. For this, cyclic RGDyK peptide (cRGD) modified bovine serum albumin (BSA) was designed as a corona to precoat on redox-responsive chitosan-based nano-carriers (TsR NPs) before administration. The effects of the precoating corona on the pharmaceutical properties and delivery efficiency of the nano-carriers and the therapeutic effect of model siRNA (siVEGF) were investigated. The results showed that BSA-cRGD formed steady corona around TsR NPs, which enhanced targeting ability to cancer cells and reduced serum proteins adsorption. The Bc corona improved the stability and biocompatibility of TsR NPs, increased the intracellular uptake, facilitated the lysosomal escape and maintained their redox-sensitive responsiveness, resulting in enhanced gene silencing efficiency and anti-tumor proliferation effects both in vitro and in vivo.

Lung cancer chemotherapy using nanoparticles: Enhanced target ability of redox-responsive and pH-sensitive cisplatin prodrug and paclitaxel

Platinum-based combination therapy is more effective and less toxic, but lack of targeting, and is not capable to enrich in the tumor zone. To obstacle these drawbacks, prodrug and nanotechnology strategies have been investigated in this study. GSH-responsive and pH-responsive cisplatin prodrug was synthesized. Cisplatin prodrug and paclitaxel co-loaded nanoparticles: DDP-P/PTX NPs were constructed. The drug release behavior and cytotoxicity of nanoparticles was assessed in vitro. In vivo anticancer efficiency and toxicity were evaluated on lung cancer bearing mice animal model. DDP-P/PTX NPs had a nanoscale size of 112.9 ± 3.5 nm. A reduction and pH triggered drug release with a synergistic tumor cell inhibition ability was observed by DDP-P/PTX NPs. DDP-P/PTX NPs also exhibited high tumor distribution, low systemic toxicity and remarkable antitumor effects in vivo. DDP-P/PTX NPs could be applied as promising anticancer system for the treatment of NSCLC.

Redox-responsive prodrug for improving oral bioavailability of paclitaxel through bile acid transporter-mediated pathway

Most anticancer drugs are not orally bioavailable due to their undesirable physicochemical properties and inherent physiological barriers. In this study, a polymeric prodrug strategy was presented to enhance the oral bioavailability of BCS class IV drugs using paclitaxel (PTX) as the model drug. PTX was covalently conjugated with cholic acid-functionalized PEG by a redox-sensitive disulfide bond. Cholic acid-functionalized PEGylated PTX (CPP) achieved remarkably improved PTX solubility (>30,000-fold), as well as favorable stability under the physiological environment and controlled drug release in the tumor. Meanwhile, CPP could self-assemble into nanoparticles with an average size of 56.18 ± 2.06 nm and drug loading up to 17.6% (w/w). Then, permeability study on Caco-2 cell monolayers demonstrated that CPP obtained an approximately 4-fold increase by apical sodium-dependent bile acid transporter (ASBT) mediated transport, compared with Taxol®. Pharmacokinetic studies carried out in rats confirmed that the oral bioavailability of CPP was 10-fold higher than that of Taxol®. Finally, significant improvement in the antitumor efficacy of CPP against breast cancer was confirmed on MDA-MB-231 cells. In summary, this prodrug-based cascade strategy offers new ways for chemotherapeutic drugs whose oral delivery is limited by solubility and permeability, also endows drugs with the capacity of tumor-specific release.

Facile preparation of multi-stimuli-responsive degradable hydrogels for protein loading and release

Functional materials that can recognize the tumor microenvironment, characterized by acidic or reducing conditions, are needed for the designing of drug delivery carriers for cancer treatment. Hydrogels are potential protein drug carriers because they contain a large amount of water and stimuli-responsive functions can easily be introduced in them. However, it is difficult to introduce multi-stimuli-responsive functions and degradability at the same time. Here, we synthesized thermo- and pH-responsive hydrogels via a coupling reaction between poly(ethylene glycol) diglycidyl ether (PEGDE) and cystamine (CA). The prepared hydrogels showed lower critical solution temperature-type thermoresponsive behavior and pH-responsive swelling changes due to the protonation of secondary and/or tertiary amino groups arising from the crosslinking agent CA. Under reducing conditions, the hydrogels were degraded via the thiol exchange reaction in the presence of dithiothreitol or glutathione. The loading and release properties of FITC-labeled model proteins from the hydrogels were investigated. The loaded amount of the protein increased with decreasing molecular weight or hydrodynamic radius, which is based on the size of the network structure of the hydrogels. Notably, loaded proteins in the hydrogels were released only under reducing conditions, which mimic the tumor microenvironment. Thus, the prepared multi-responsive degradable hydrogels are expected to be used as functional drug delivery carriers for cancer treatment.

Recent advances in the redox-responsive drug delivery nanoplatforms: A chemical structure and physical property perspective

Poor water solubility, off-target toxicity, and small therapeutic window are among major obstacles for the development of drug products. Redox-responsive drug delivery nanoplatforms not only overcome the delivery and pharmacokinetic pitfalls observed in conventional drug delivery, but also leverage the site-specific delivery properties. Cleavable diselenide and disulfide bonds in the presence of elevated reactive oxygen species (ROS) and glutathione concentration are among widely used stimuli-responsive bonds to design nanocarriers. This review covers a wide range of redox-responsive chemical structures and their properties for designing nanoparticles aiming controlled loading, delivery, and release of hydrophobic anticancer drugs at tumor site.

Dual-responsive carboxymethyl cellulose/dopamine/cystamine hydrogels driven by dynamic metal-ligand and redox linkages for controllable release of agrochemical

The utilization of agrochemicals in crop production is often inefficient due to lack of appropriate carriers, raising in the significant concerns of ecological environment and public health. To enhance the efficiency of agrochemical delivery, a novel cellulose-based hydrogel was constructed in this work by cross-linking dopamine (DA)-modified carboxymethyl cellulose (CMC) with cystamine (CYS) in the presence of Fe³⁺ ions. The hydrogels displayed reversible sol-gel transitions upon exposure to stimulation of changes in pH and redox, leading to the controllable release of model agrochemical (6-benzyladenine). Compared with single-triggered condition, the hydrogel doubled the cumulative release when co-triggered by pH and redox. The dynamic metal/catechol complexation and disulfide bonding coexist in the hydrogel networks, enabling occurrence of dynamic reaction under a variety of environmental conditions. The finite element method (FEM) was employed to simulate the hydrogel to provide a theoretical insight into the tested drug delivery. Benefitting from the reversibly cross-linked networks and the excellent biodegradability of the hydrogels, we anticipate that this dual-responsive, polysaccharide-based hydrogel will offer diverse applications to reach the full potential in sustainable advancement of crop production.

siRNA and chemotherapeutic molecules entrapped into a redox-responsive platform for targeted synergistic combination therapy of glioma

Vascular endothelial growth factor (VEGF) has been implicated as the key regulator of tumor neovascularization. RNAi interference plays a critical role on down-regulation of VEGF, while single VEGF inhibition could not completely suppress angiogenesis and tumor growth; the effect of siRNA is temporary. To improve glioma therapy efficacy, an angiopep-2 (Ap) modified redox-responsive glycolipid-like copolymer co-delivering siVEGF and paclitaxel (PTX), termed as Ap-CSssSA/P/R complexes, was developed in this study. Ap modification significantly enhanced the distribution of Ap-CSssSA in glioma cells both in vitro and in vivo. Ap-CSssSA/P/R complexes could simultaneously deliver siVEGF and PTX into tumor cells, exhibiting great superiority in glioma growth suppression via receptor-mediated targeting delivery and cell apoptosis, accompanied with an obvious inhibition of neovascularization induced by VEGF gene silencing. The present study indicated that the combination delivery of siVEGF and PTX via Ap-modified copolymeric micelles presented a promising and safe platform for glioma targeted therapeutics.

Construction of redox-responsive tumor targeted cisplatin nano-delivery system for effective cancer chemotherapy

Cisplatin is one of the most widely used platinum-based anticancer chemotherapeutic drugs. However, its low solubility, serious side effects and the development of cisplatin resistance limit its further use in the clinic. Controlling the delivery and release of cisplatin at the targeted site efficiently is a meaningful way to overcome these undesirable side effects of cisplatin. Herein, a tumor targeted and stimuli responsive nano-delivery system for cisplatin was constructed using branched polyethyleneimine (BPEI) as the backbone, disulfide bond as the redox-responsive covalent linker and hyaluronic acid (HA) as targeting recognition unit which can bind selectively to the receptor of CD44, which is highly expressed on the A549 tumor cells. The cisplatin-polyethyleneimine conjugate BPEI-SS-Pt was prepared and the drug loading of cisplatin was up to 32.66 ± 0.06%. After optimized the coating weight ratio of HA and BPEI-SS-Pt, the nanoparticle delivery system HA-(BPEI-SS-Pt)-1/4 outperformed with smaller particle size of 159.0 ± 21.0 nm, narrow polydispersity index (PDI) of 0.069 ± 0.022 and higher cisplatin loading of 29.23 ± 0.18%, showing specific tumor-targeting ability and redox-responsive drug release manner. Moreover, for the treatment of cancer in vivo, it achieved more effective antitumor performance along with minor side effects and systemic toxicity compared with cisplatin which is of great significance for the chemotherapeutic drug in the clinic.

Redox-responsive nanoparticles from disulfide bond-linked poly-(N-ε-carbobenzyloxy-l-lysine)-grafted hyaluronan copolymers as theranostic nanoparticles for tumor-targeted MRI and chemotherapy

Redox-responsive theranostic nanoparticles based on poly-(N-ε-carbobenzyloxy-l-lysine) (PZLL) grafted hyaluronan (HA) (HA-g-SS-PZLL) copolymers were constructed for hepatocellular carcinoma diagnosis and therapy. These hyaluronan derivatives formed nanoparticles via a self-assembly process in aqueous solution at low concentration. Theranostic nanoparticles were obtained after loading hydrophobic doxorubicin (DOX) and superparamagnetic iron oxide (SPIO) into the core of the nanoparticles via a dialysis method. Theranostic nanoparticles exhibited redox triggered DOX release behavior, and faster DOX released from theranostic nanoparticles was detected under a reducing environment compared with slow DOX release under a normal physiological environment. Confocal laser scanning microscopy (CLSM), flow cytometry and Prussian blue staining against HepG2 cells demonstrated that HA-g-SS-PZLL theranostic nanoparticles were capable of delivering DOX and SPIO into the cells. The analysis of the anticancer effect revealed that the HA-g-SS-PZLL theranostic nanoparticles shown higher cytotoxicity against HepG2 cells than DOX-loaded HA-g-PZLL nanoparticles. In vitro T₂ magnetic resonance imaging (MRI) results exhibited that theranostic nanoparticles showed a good contrast enhancement effect, and the r₂ relaxivity value was approximately 231 Fe mM^-1 s^-1. Finally, the theranostic nanoparticles acted as nanoprobes for HepG2 tumor-bearing BALB/c mice for in vivo MRI. Therefore, HA-g-SS-PZLL copolymers have great potential as theranostic nanoparticles for tumor-targeted diagnosis and treatment.

Redox-responsive hollow mesoporous silica nanoparticles constructed via host-guest interactions for controllable drug release

A novel redox-responsive hollow mesoporous silica (HMS) was constructed by host-guest interaction between β-cyclodextrin modified hollow mesoporus silica nanoparticles (HMS@β-CD) and the ferrocene-containing amphiphilic block copolymer PEG-b-PMAFc (PPFc), the prepared HMS@β-CD@PPFc system was used to control drug delivery in targeted cancer therapy through redox stimulus. The self-assembled morphology was investigated by transmission electron microscopy (TEM) and dynamic light scattering (DLS). Intracellular localization of DOX-loaded HMS@β-CD@PPFc in A549 cells was further investigated by confocal laser scanning microscopy (CLSM), and the results indicated that DOX-loaded HMS@β-CD@PPFc was ingested by A549 cells effectively. Furthermore, the redox agent H₂O₂ was used to trigger the release of DOX. The cytotoxicity evaluated by MTT method indicated that HMS@β-CD@PPFc had good biocompatibility and was promising as the drug carrier.

Ultrasonic-assisted fabrication and release kinetics of two model redox-responsive magnetic microcapsules for hydrophobic drug delivery

The smart biocompatible carriers have an advantage in the high-efficiency delivery and stimuli-responsive release of drugs. This study describes two model magnetic microcapsules (MMC) fabricated by sonicating the hydrophobic drug-loaded oil phase in an albumin aqueous solution, where magnetic nanoparticles are either encapsulated into the core or embedded onto the albumin shell. The as-prepared MMC with magnetic shell (MS) or with magnetic core (MC) shows an appropriate dispersibility with a well-defined spherical morphology in water, an excellent magnetism-mediated shifting ability for targeted drug delivery, and a good biocompatibility for high-level cell viability. Moreover, both the two microcapsules also show a high efficiency to trap the hydrophobic drugs, where the embedding ratios are 87.41% for MMC-MS and 95.31% for MMC-MC, respectively. Meanwhile in current study, the release kinetics and mechanism reveal that the sulfhydryl-crosslinked shell structure endows the MMC with a redox-responsive behavior to release the contents for controlled drug release, and the release rate or the release amount can be adjusted by changing the dosage of reducing agent. Therefore, the MMC have great potential as a smart carrier of hydrophobic drugs for enhancing the therapeutic efficiency.

Preparation and characterization of redox-sensitive glutenin nanoparticles

In recent thirty years, protein-based nanoparticles have attracted considerable attention, and they are being widely used in the food, pharmaceutical, and biomedical fields. Wheat glutenin, an important natural vegetable protein, has been demonstrated to be nutritive and biocompatible. This study aimed to develop a new type of redox-sensitive protein nanoparticles. The glutenin nanoparticles (GNPs) were synthesized with glutenin concentrations (0.082%, 0.5%, and 0.83%) through the adoption of an antisolvent titration technique and the use of hydrogen peroxide (H₂O₂) oxidative cross-linking for different periods. At a glutenin concentration of 0.83% and oxidation time of 20 h, the obtained GNPs were spherical in shape and approximately 100-300 nm in size, as measured by transmission electron microscopy and dynamic light scattering. The formation of disulfide was confirmed by Raman spectroscopy. The turbidity values of the GNP suspensions were decreased by half after the addition of β-mercaptoethanol. Nile blue A, a model hydrophilic substance, was entrapped in the GNPs with 77.67% loading efficiency. The newly developed GNPs can be used as redox-responsive carriers for delivering hydrophilic active substances.

Fabrication of redox-responsive Bi(mPEG-PLGA)-Se2 micelles for doxorubicin delivery

Stimuli-responsive polymeric nanostructures have emerged as potential drug carriers for cancer therapy. Herein, we synthesized redox-responsive diselenide bond containing amphiphilic polymer, Bi(mPEG-PLGA)-Se₂ from mPEG-PLGA and 3,3'-diselanediyldipropanoic acid (DSeDPA) using DCC/DMAP as coupling agents. Due to its amphiphilic nature, Bi(mPEG-PLGA)-Se₂ self-assembled in to stable micelles in aqueous solution with a hydrodynamic size of 123.9 ± 0.85 nm. The Bi(mPEG-PLGA)-Se₂ micelles exhibited DOX-loading content (DLC) of 6.61 wt% and encapsulation efficiency (EE) of 54.9%. The DOX-loaded Bi(mPEG-PLGA)-Se₂ micelles released 73.94% and 69.54% of their cargo within 72 h upon treatment with 6 mM GSH and 0.1% H₂O₂, respectively, at pH 7.4 and 37 °C. The MTT assay results demonstrated that Bi(mPEG-PLGA)-Se₂ was devoid of any inherent toxicity and the DOX-loaded micelles showed pronounced antitumor activities against HeLa cells, 44.46% of cells were viable at maximum dose of 7.5 µg/mL. The cellular uptake experiment further confirmed the internalization of DOX-loaded Bi(mPEG-PLGA)-Se₂ micelles and endowed redox stimuli triggered drug release in cytosol and nuclei of cancer cells. Overall, the results suggested that the smart, biocompatible Bi(mPEG-PLGA)-Se₂ copolymer could serve as potential drug delivery biomaterial for the controlled release of hydrophobic drugs in cancer cells.

Polydopamine-Based Composite Nanoparticles with Redox-Labile Polymer Shells for Controlled Drug Release and Enhanced Chemo-Photothermal Therapy

Photothermal therapy (PTT) that utilizes phSUPPotothermal conversion agents (PTC) to ablate tumor under NIR light irradiation has attracted increasing attention due to its excellent therapeutic efficacy and improved target selectivity. Herein, a novel core-shell nanoparticle based on disulfide-crosslinked poly(methacrylic acid) (PMAA) layer coated polydopamine (PDA) particle has been successfully synthesized by precipitation polymerization. For these PDA@PMAA composite nanoparticles, PDA core exhibits high photothermal efficacy, meanwhile, the redox-labile PMAA shell serves as carriers to encapsulate anticancer drugs and selectively release them. Due to the characteristic of the disulfide bond, PMAA shell occurs at selective degradation as well as controlled drug release upon entering cancer cells. Moreover, the DOX-loaded PDA@PMAA nanoparticles demonstrated a synergistic effect, which shows a significantly improved inhibition effect against cancer cells by the combination of photothermal therapy and traditional chemotherapy with low drug dosage and short laser irradiation in an in vitro study.

Co-responsive smart cyclodextrin-gated mesoporous silica nanoparticles with ligand-receptor engagement for anti-cancer treatment

Combination of both internal- and external-stimuli responsive strategies in nanoplatforms can maximize therapeutic outcomes by overcoming drug efflux-mediated resistance and prolonging sustained release of therapeutic payloads in controlled and sequential manner. Here, we show a light/redox dual-stimuli responsive β-cyclodextrin (β-CD)-gated mesoporous silica nanoparticles (MSN) that can effectively load and seal the chemotherapeutics, doxorubicin (DOX), inside MSN with a dual-capped system. The primary gatekeeper was achieved by capping β-CD via a disulfide linkage. An azobenzene/galactose-grafted polymer (GAP) was introduced to functionalize the MSN surface through host-guest interaction. GAP not only served as a secondary non-covalent polymer-gatekeeper to further prevent molecules from leaking out, but also presented targeting ligand for engagement of the asialoglycoprotein receptor (ASGPR) on hepatocellular carcinoma (HepG2) cells. The controlled and stimuli release of DOX could be realized via dissociation of azobenzene moieties from β-CD cage upon UV-irradiation, followed by liberation with the endogenous glutathione. The in vitro studies verified the redox-sensitive DOX release behavior, and the UV irradiation could accelerate this process to trigger DOX burst from MSN-ss-CD/GAP. Notably, the DOX@MSN-ss-CD/GAP could more efficiently deliver DOX into HepG2 cells and demonstrate enhanced cytotoxicity as compared with HeLa and COS7 cells. The smart MSN-ss-CD/GAP delivery system holds the potential for universal therapeutic uses in both biomedical research and clinical settings.

Diselenide linkage containing triblock copolymer nanoparticles based on Bi(methoxyl poly(ethylene glycol))-poly(ε-carprolactone): Selective intracellular drug delivery in cancer cells

Redox-responsive diselenide bond containing triblock copolymer Bi(mPEG-SeSe)-PCL,Bi(mPEG-SeSe)-PCL was developed for specific drug release in cancer cells. Initially, ditosylated polycaprolactone was prepared via the reaction between polycaprolactone diol (PCL-diol) and tosyl chloride (TsCl). Next, Bi(mPEG-SeSe)-PCL was synthesized via the reaction between ditosylated polycaprolactone and sodium diselenide initiated poly (ethylene glycol) methyl ether tosylate. The synthesized amphiphilic triblock copolymer could self-assemble into uniform nanoparticles in aqueous medium and disassemble upon redox stimuli. The Bi(mPEG-SeSe)-PCL nanoparticles showed a DOX loading content of 5.1 wt% and a loading efficiency of 49%. In vitro drug release studies showed that about 62.4% and 56% of DOX was released from the nanoparticles during 72 h at 37 °C in PBS containing 2 mg/mL (6 mM) GSH and 0.1% H2O2, respectively, whereas only about 30% of DOX was released in PBS under the same conditions. The cell viability (MTT assays) results showed that the synthesized material was biocompatible with above 90% cell viability, and that the DOX-loaded Bi(mPEG-SeSe)-PCL nanoparticles had a high antitumor activity against HeLa cells and low antitumor activity against HaCaT cells, following a 24-h incubation period. Three-dimensional (3D) spheroids of HeLa cells were established for the evaluation of localization of the DOX-loaded nanoparticles into spheroids cells and the successfully inhibition of 3D tumor spheroid growth. The results indicated that the synthesized material Bi(mPEG-SeSe)-PCL was biocompatible and it could be a potential candidate for anticancer drug delivery system.

Redox-responsive chitosan oligosaccharide-SS-Octadecylamine polymeric carrier for efficient anti-Hepatitis B Virus gene therapy

DrzBC and DrzBS (10-23 DNAzyme) could block the expression of HBV e- and s- gene respectively. But the application of 10-23 DNAzyme was limited owing to the lack of appropriate delivery vehicles. Chitosan oligosaccharide-SS-Octadecylamine (CSSO), a redox-responsive nano-sized polymeric carrier, could self-aggregate and bind with DNA by electrostatic interaction at proper mass ratio. Compared with the traditional commercial carrier Lipo2000, CSSO exhibited lower cytotoxicity, efficient cellular uptake by targeting cells, and rapidly DNA released in cytoplasm after escaping from endosomes. Including the same DNA concentration, Lipo2000/(DrzBC or DrzBS) showed maximum inhibitory rate on HBeAg (47.29 ± 1.86%) and HBsAg (33.58 ± 0.72%) secretion after 48 h incubation, and then both decreased. In contrast, HBeAg secretion inhibition by CSSO/DrzBC and HBsAg secretion inhibition by CSSO/DrzBS were up to 73.86 ± 1.77% and 67.80 ± 2.51% at 48 h, and further increased to 83.83 ± 2.34% and 76.79 ± 2.18% at 72 h, respectively. CSSO is a promising redox-responsive polymeric carrier for efficient anti-Hepatitis B Virus gene therapy.

Redox/pH dual-stimuli responsive camptothecin prodrug nanogels for "on-demand" drug delivery

At present, chemotherapy remains to be one of the most important therapeutic approaches for malignant tumors. The tumor microenvironment(TME)-responsive intelligent drug delivery systems are still the hot research topics in delivering chemotherapeutic drugs. Camptothecin (CPT) possesses very strong antitumor activities, but its clinical application is hindered by its poor water-solubility and serious toxic side effects. Herein, a new intelligent and TME-responsive P(CPT-MAA) prodrug nanogel was developed for delivering CPT and reducing its side effects. P(CPT-MAA) prodrug nanogels were prepared with methacrylic acid (MAA), CPT monomer (CPTM) and N,N'-methylenebisacrylamide (Bis) via distillation-precipitation polymerization, in which CPT was covalently conjugated into the nanogels via redox-responsive disulfide linker. The as-prepared nanogels were spherical shapes with uniform size and narrow size distribution. With the help of redox-responsive property of disulfide linker and pH-responsive property of PMAA, the release of CPT from prodrug nanogels was redox/pH-dual dependent and could be accelerated by the increased concentration of GSH and the decreased pH value, which were favorable to realize the "on-demand" drug release in tumor cell and tumor tissue microenvironment. Furthermore, P(CPT-MAA) prodrug nanogels exhibited superior antitumor activity both in vitro and in vivo without observed side effects. Hence, the prepared P(CPT-MAA) prodrug nanogels may be a promise delivery system for chemotherapeutic agents.

A versatile strategy to create an active tumor-targeted chemo-photothermal therapy nanoplatform: A case of an IR-780 derivative co-assembled with camptothecin prodrug

Self-assembled nanovehicles of chemotherapy drug with photothermal agent are regarded as intriguing chemo-photothermal therapy nanoplatform. However, most of the drugs and photothermal agents have poor water solubility and poor interactions to drive the formation of self-assembled nanovehicles, which is a bottleneck of co-assembled drug/photothermal agent for cancer therapy. Here, we proposed a versatile strategy to create self-assembled chemo-photothermal therapy nanoplatform based on the chemical modification of photothermal agent and drug. The IR-780 and camptothecin (CPT) were chosen as the studied models since they are important photothermal agent and anticancer drug, both of which have such poor water solubility with strong itself molecular interactions that they cannot co-assemble together. IR-780 was modified with an active targeting ligand lactobionic acid (LA) to result in amphiphilic IR780-LA while CPT was modified into redox-sensitive prodrug CPT-ss-CPT through a disulfide linkage to realize its assembly. Well-defined nanoparticles (NPs) could be created through the co-assembling of IR780-LA and CPT-ss-CPT. The IR780-LA/CPT-ss-CPT nanoparticles were demonstrated to be an excellent fluorescence imaging-guided, redox-responsive and enhanced synergistic chemo-photothermal therapy nanoplatform against tumors. Specifically, our chemical modification strategy offers a universal way to create self-assembled chemo-photothermal therapy nanoplatform, which solves the bottleneck of co-assembled drug/photothermal agent for cancer therapy. STATEMENT OF SIGNIFICANCE: Self-assembled nanoparticles of chemotherapeutics with photothermic drugs are regarded as intriguing chemo-photothermal therapy nanoplatform. However, most drugs have too poor solubility and interactions to form into self-assembled nanoparticles. We proposed a versatile strategy to create co-assembled chemo-photothermal therapy nanoparticles based on the chemical modification of common drugs. The IR-780 was modified with an active targeting ligand LA to result in amphiphilic IR780-LA molecules, while CPT was modified into redox-sensitive prodrug CPT-ss-CPT through disulfide linkage. Well-defined IR780-LA/CPT-ss-CPT nanoparticles were created through the co-assembling of IR780-LA and CPT-ss-CPT. The nanoparticles were demonstrated to be an excellent fluorescence imaging-guided, redox-responsive, active targeting chemo-photothermal therapy nanoplatform against tumors. Our strategy offers a versatile way to construct smart chemo-photothermal therapy nanoplatform from common drugs.

Redox-responsive degradable prodrug nanogels for intracellular drug delivery by crosslinking of amine-functionalized poly(N-vinylpyrrolidone) copolymers

HYPOTHESIS

Facile approaches for the development of new tailored drug carriers are of high importance for the controlled administration of drugs. Herein we report a method for the synthesis of water-soluble reactive copolymers with well-defined architectures for fabrication of redox-sensitive degradable prodrug nanogels for intracellular drug release.

EXPERIMENTS

Primary amine-functionalized statistical copolymers were obtained by hydrolysis of poly(N-vinylpyrrolidone-co-N-vinylformamide) copolymers which were synthesized via Reversible Addition-Fragmentation chain-Transfer (RAFT) polymerization. Redox-sensitive degradable nanogels with varying crosslinking densities were synthesized with a redox-sensitive cross-linker. Doxorubicin (DOX) was loaded to form prodrug nanogels (DNG) with hydrodynamic radius from 142 nm to 240 nm.

FINDINGS

The nanogels demonstrated slower degradation and retarded drug release rate with increased crosslinking density in the presence of 10 mM reduced glutathione (GSH) at 37 °C. The in vitro release studies revealed that maximum 85% DOX was released in 24 h under a reductive environment. Intracellular drug release profiles in HeLa cells indicated that the DOX delivery rate was tunable via varying crosslinking density of the nanogels. Cell viability assay demonstrated that the blank nanogels were biocompatible in wide concentrations up to 0.5 mg/mL while the DOX-loaded nanogels displayed medium antitumor activity with IC50 (half-maximal inhibitory concentration) of 1.80 μg/mL, 2.57 μg/mL, 3.01 μg/mL for DNG5, DNG10 and DNG15 respectively.

Redox-responsive polymer inhibits macrophages uptake for effective intracellular gene delivery and enhanced cancer therapy

The development of advanced gene delivery carriers with stimuli-responsive release manner for tumor therapeutics is desirable, since they can exclusively release the therapeutic gene via their structural changes in response to the specific stimuli of the target site. Moreover, interactions between macrophages and drug delivery systems (DDSs) seriously impair the treatment efficiency of DDSs, thus macrophages uptake inhibition would to some extent improve the intracellular uptake of DDSs in tumor cells. Herein, a PEGylated redox-responsive gene delivery system was developed for effective cancer therapy. PEG modified glycolipid-like polymer (P-CSSO) was electrostatic interacted with p53 to form P-CSSO/p53 complexes, which exhibited an enhanced redox sensitivity in that the disulfide bond was degraded and the rate the plasmid released from P-CSSO was 2.29-fold that of nonresponsive platform (P-CSO-SA) in 10 mM levels of glutathione (GSH). PEGylation could significantly weaken macrophages uptake, while enhance the accumulation of P-CSSO in tumor cells both in vitro and in vivo. Compared with nonresponsive complexes (P-CSO-SA/p53) (59.2%) and Lipofectamine™ 2000/p53 complexes (52.0%), the tumor inhibition rate of P-CSSO/p53 complexes (77.1%) significantly increased, which was higher than CSSO/p53 complexes (69.9%). The present study indicates that tumor microenvironment sensitive and macrophages uptake suppressive P-CSSO/p53 is a powerful in vivo gene delivery system for enhanced anticancer therapy.

Advances in redox-responsive drug delivery systems of tumor microenvironment

With the improvement of nanotechnology and nanomaterials, redox-responsive delivery systems have been studied extensively in some critical areas, especially in the field of biomedicine. The system constructed by redox-responsive delivery can be much stable when in circulation. In addition, redox-responsive vectors can respond to the high intracellular level of glutathione and release the loaded cargoes rapidly, only if they reach the site of tumor tissue or targeted cells. Moreover, redox-responsive delivery systems are often applied to significantly improve drug concentrations in targeted cells, increase the therapeutic efficiency and reduce side effects or toxicity of primary drugs. In this review, we focused on the structures and types of current redox-responsive delivery systems and provided a comprehensive overview of relevant researches, in which the disulfide bond containing delivery systems are of the utmost discussion.

Anti-inflammatory polymersomes of redox-responsive polyprodrug amphiphiles with inflammation-triggered indomethacin release characteristics

Inflammation serves as a natural defense mechanism to protect living organisms from infectious diseases. Nonsteroidal anti-inflammatory drugs (NSAIDs) can help relieve inflammatory reactions and are clinically used to treat pain, fever, and inflammation, whereas long-term use of NSAIDs may lead to severe side effects including gastrointestinal damage and cardiovascular toxicity. Therefore, it is of increasing importance to configure new dosing strategies and alleviate the side effects of NSAIDs. Towards this goal, glutathione (GSH)-responsive disulfide bonds and hydrogen peroxide (H₂O₂)-reactive phenylboronic ester linkages were utilized as triggering moieties in this work to design redox-responsive prodrug monomers and polyprodrug amphiphiles based on indomethacin (IND) drug. Note that IND is a widely prescribed NSAID in the clinic. Starting from three types of redox-reactive IND prodrug monomers, redox-responsive polyprodrug amphiphiles were synthesized through reversible addition-fragmentation chain transfer (RAFT) polymerizations of prodrug monomers using poly(ethylene oxide) (PEO)-based macroRAFT agent. The resultant polyprodrug amphiphiles with high IND loading contents (>33 wt%) could self-assemble into polymersomes with PEO shielding coronas and redox-responsive bilayer membranes composed of IND prodrugs. Upon incubation with GSH or H₂O₂, controlled release of intact IND in the active form from polyprodrug polymersomes was actuated by GSH-mediated disulfide cleavage reaction and H₂O₂-mediated oxidation of phenylboronic ester moieties, respectively, followed by self-immolative degradation events. Furthermore, in vitro studies at the cellular level revealed that redox-responsive polymersomes could efficiently relieve inflammatory responses induced by lipopolysaccharide (LPS) in RAW264.7 macrophage cells.

Redox-responsive micelles for triggered drug delivery and effective laryngopharyngeal cancer therapy

In this study, we reported a redox-responsive drug delivery system (DDS) based on heparosan and deoxycholic acid conjugates (HSDs) for effective treatment of laryngopharyngeal carcinoma. The amphiphilic HSDs can self-assemble into stable nanoscale micelles in aqueous medium with favorable drug loading capacity for doxorubicin (DOX). The HSD micelles can exhibit glutathione (GSH)-triggered drug release behavior and reach a nearly 100% release rate in a high GSH level (10 mM) environment. Moreover, FaDu cancer cells can internalize HSD micelles by clathrin-mediated endocytosis, which is energy dependent, fast, and effective. The DOX@HSD induced inhibition of FaDu cancer cells can achieve a minimum of 10-fold selectivity relative to that of COS-7 normal cells. Overall, the redox-responsive DDSs show good biocompatibility and are promising in the clinical treatment of laryngopharyngeal carcinoma.

Layer-by-Layer Engineered Polymer Capsules for Therapeutic Delivery

Polymer capsules fabricated via layer-by-layer (LbL) assembly have emerged as promising carriers for therapeutic delivery. The versatile assembly technique allows an extensive choice of materials to be incorporated as constituents of the multilayers, which therefore endow capsules with specific properties and functionalities. This chapter describes protocols for fabrication of LbL-engineered poly(methacrylic acid) (PMA) capsules for applications in gene delivery, including (1) synthesis of building blocks, (2) cargo encapsulation, (3) multilayer film formation, (4) surface modification, and (5) cross-linking of multilayer films and dissolution of particle templates. DNA is adsorbed onto positively charged silica particle templates, followed by formation of polymer films via hydrogen-bonded multilayers of thiol-functionalized PMA and poly(N-vinylpyrrolidone) (PVP). The outer polymer membranes can be surface modified with copolymers of PMA and poly(ethylene glycol) (PEG). Upon film stabilization and dissolution of particle templates, disulfide-cross-linked DNA-loaded PMA capsules are obtained, which serve as therapeutic carriers that can degrade and facilitate cargo release in intracellular reducing environment.

mPEGylated solanesol micelles as redox-responsive nanocarriers with synergistic anticancer effect

We prepared an amphiphilic redox-responsive conjugate based on mPEGylated solanesol, solanesyl poly(ethylene glycol) dithiodipropionate (SPDP), along with its inert counterpart solanesyl poly(ethylene glycol) succinate (SPGS), which self-assembled in aqueous solution to form redox-responsive micelles. Used as efficient drug carriers for doxorubicin (DOX), the micelles acted as synergistic agents for cancer therapy. Dynamic light scattering (DLS) measurements showed that the SPDP micelles had average diameters of 111nm, which decreased to 88nm after the encapsulation of DOX. The mean diameters and size distribution of the disulfide-containing micelles changed obviously in the presence of the reducing agent glutathione (GSH), whereas no changes occurred in the case of redox-insensitive SPGS micelles. DOX could be loaded into both types of micelles, with drug loading content of about 4.0%. A significantly accelerated release of DOX was triggered by GSH for DOX-loaded SPDP micelles, compared with DOX-loaded SPGS micelles. Blank SPGS and SPDP micelles displayed higher inhibition of HeLa and MCF-7 cell proliferation but less cytotoxicity to normal L-02 cells at similar concentrations. Confocal microscopic observation indicated that a greater amount of DOX was delivered into the nuclei of cells following 9 or 12h incubation with DOX-loaded micelles. In vivo studies on H22-bearing Swiss mice demonstrated the superior anticancer activity of DOX-loaded SPDP micelles over free DOX and DOX-loaded SPGS micelles. All of the data presented here suggested that these SPDP micelles may have a dual function, as they are preferentially toxic for tumor cells alone and are efficient and safe carriers for anticancer drugs.

STATEMENT OF SIGNIFICANCE

Various nanoscale drug carriers were used to enhance therapeutic effect of many drugs. While, the metabolites of high quantities of carriers may cause additional short- or long-term toxicities. In this study, a new systems based on solanesol derivatives was developed for anticancer drug delivery. There are two features for this system. One is solanesol originated bioactivity of the carrier, which will synergistically facilitate therapeutic effect of the encapsulated drug. The other is the redox-responsive drug release behavior adaptable to the glutathione-rich atmosphere of tumor cell. All the hypothesis have been elucidated in this work through in vitro and in vivo studies. It was found that this drug delivery system may have a dual function, as they are preferentially toxic for tumor cells alone and are efficient and safe carriers for anticancer drugs.

Gene regulation of two ferredoxin:NADP+ oxidoreductases by the redox-responsive regulator SurR in Thermococcus kodakarensis

The redox-responsive regulator SurR in the hyperthermophilic archaea Pyrococcus furiosus and Thermococcus kodakarensis binds to the SurR-binding consensus sequence (SBS) by responding to the presence of elemental sulfur. Here we constructed a surR gene disruption strain (DTS) in T. kodakarensis, and identified the genes that were under SurR control by comparing the transcriptomes of DTS and parent strains. Among these genes, transcript levels of ferredoxin:NADP⁺ oxidoreductases 1 and 2 (FNOR1 and FNOR2) genes displayed opposite responses to surR deletion, indicating that SurR repressed FNOR1 transcription while enhancing FNOR2 transcription. Each promoter region contains an SBS upstream (uSBS) and downstream (dSBS) of TATA. In addition to in vitro binding assays, we examined the roles of each SBS in vivo. In FNOR1, mutations in either one of the SBSs resulted in a complete loss of repression, indicating that the presence of both SBSs was essential for repression. In FNOR2, uSBS indeed functioned to enhance gene expression, whereas dSBS functioned in gene repression. SurR bound to uSBS2 of FNOR2 more efficiently than to dSBS2 in vitro, which may explain why SurR overall enhances FNOR2 transcription. Further analyses indicated the importance in the distance between uSBS and TATA for transcriptional activation in FNOR2.

Fabrication of redox and pH dual-responsive magnetic graphene oxide microcapsules via sonochemical method

In this study, the biocompatible redox and pH dual-responsive magnetic graphene oxide microcapsules (MGOMCs) were prepared by a simple sonochemical method. The disulfide bonds cross-linked the wall of MGOMCs were formed from the hydrosulfuryl on the surface of thiolated graphene oxide, which was synthesized by functionalizing graphene oxide with cysteine, showed an excellent redox-responsive property to control drugs release. Moreover, oleic acid modified Fe₃O₄ nanoparticles were encapsulated into the microcapsules successfully with the hydrophobic drugs dispersed in the hydroxy silicone oil. The MGOMCs possess distinguished magnetic property and pH-responsive ability. Besides, the microcapsules could be engulfed by Hela cells successfully due to the appropriate size and flexible shell. The MGOMCs could be a good carrier for hydrophobic drugs, especially the anticancer drugs.

Enhanced Antiglioma Efficacy of Ultrahigh Loading Capacity Paclitaxel Prodrug Conjugate Self-Assembled Targeted Nanoparticles

Glioblastoma multiforme (GBM) presents one of the most lethal brain tumor with a dismal prognosis. And nanodrug delivery system (nano-DDS) have raised a lot of concern, while the conventional nanoformulations addressed many limitations, especially the low drug loading capacity and poor stability in vivo. Herein, we proposed PTX prodrug (PTX-SS-C₁₈) conjugate self-assembled nanoparticles (PSNPs) functionalized with Pep-1, glioma homing peptide, to overcome the blood brain tumor barrier (BBTB) via interleukin 13 receptor α2 (IL-13Rα2)-mediated endocytosis for targeting GMB. This nanocarrier was with ultrahigh drug loading capacity (56.03%) and redox-sensitivity to the up-expression of glutathione in glioma tumors. And compared with PEG-PSNPs, Pep-PSNPs could significantly enhance cellular uptake in U87MG cells via IL-13Rα2-mediated endocytosis. Enhanced cytotoxicity of Pep-PSNPs against U87MG cells and BCEC cells pretreated with glutathione monoester (GSH-OEt) confirmed that this nanosystem was sensitive to reduction environment, and there was significant difference between targeting and nontargeting groups in MTT assay. Real-time fluorescence image of intracranialU87MG glioma-bearing mice revealed that Pep-PSNPs could more efficiently accumulate at tumor site and improve the penetration. Furthermore, the ex vivo fluorescence imaging and corresponding semiquantitative results displayed that the glioma fluorescence intensity of Pep-PSNPs group was 1.74-fold higher than that of nontargeting group. Pep-PSNPs exhibited remarkable antiglioblastoma efficacy with an extended median survival time. In conclusion, Pep-PSNPs had a promising perspective as a targeting drug delivery system of PTX for glioma treatment.

Robust, active tumor-targeting and fast bioresponsive anticancer nanotherapeutics based on natural endogenous materials

The clinical success of cancer nanomedicines critically depends on availability of simple, safe and highly efficient nanocarriers. Here, we report that robust and multifunctional nanoparticles self-assembled from hyaluronic acid-g-poly(γ-benzyl-l-glutamate)-lipoic acid conjugates achieve a remarkably high loading (up to 25.8wt.%) and active targeted delivery of doxorubicin (DOX) to human breast tumor xenograft in vivo. DOX-loaded nanoparticles following auto-crosslinking (DOX-CLNPs) are highly stable with little drug leakage under physiological conditions while quickly release ca. 92% DOX in 30h under a cytoplasmic-mimicking reductive environment. The in vitro assays reveal that DOX-CLNPs possess a superior selectivity and antitumor activity to clinically used pegylated liposomal doxorubicin hydrochloride (DOX-LPs) in CD44 receptor overexpressing MCF-7 human breast cancer cells. Strikingly, DOX-CLNPs exhibit a superb tolerated dose of over 100mg DOX equiv./kg, which is more than 5 times higher than DOX-LPs, and an extraordinary breast tumor accumulation of 8.6%ID/g in mice. The in vivo therapeutic studies in MCF-7 human breast tumor-bearing nude mice show that DOX-CLNPs effectively inhibit tumor growth, improve survival rate, and significantly decrease adverse effects as compared to DOX-LPs. DOX-CLNPs based on natural endogenous materials with high drug loading, great stability and CD44-targetability are highly promising for precision cancer chemotherapy.

STATEMENT OF SIGNIFICANCE

We demonstrate that with rational design, simple and multifunctional anticancer nanotherapeutics can be developed to achieve highly efficient and targeted cancer chemotherapy. Doxorubicin-loaded multifunctional nanoparticles based on hyaluronic acid-g-poly(γ-benzyl-l-glutamate)-lipoic acid conjugates exhibit a high drug loading, superior stability, fast bioresponsivity, high tolerability, and obvious selectivity toward CD44-overexpressing tumors in vivo. These nanotherapeutics achieve effective tumor suppression, drastically improved survival rate and reduced side effects as compared to clinically used pegylated liposomal doxorubicin in MCF-7 human breast tumor-bearing nude mice. Unlike previously reported multifunctional nanomedicines, the present nanotherapeutics primarily based on natural endogenous materials are simple and straightforward to fabricate, which makes them potentially interesting for clinical translation.

Fully glutathione degradable waterborne polyurethane nanocarriers: Preparation, redox-sensitivity, and triggered intracellular drug release

Polyurethanes are important class of biomaterials that are extensively used in medical devices. In spite of their easy synthesis, polyurethanes that are fully degradable in response to the intracellular reducing environment are less explored for controlled drug delivery. Herein, a novel glutathione degradable waterborne polyurethane (WPU) nanocarrier for redox triggered intracellular delivery of a model lipophilic anticancer drug, doxorubicin (DOX) is reported. The WPU was prepared from polyaddition reaction of isophorone diisocyanate (IPDI) and a novel linear polyester polyol involving disulfide linkage, disulfide labeled chain extender, dimethylolpropionic acid (DMPA) using dibutyltin dilaurate (DBTDL) as a catalyst. The resulting polyurethane self-assembles into nanocarrier in water. The dynamic light scattering (DLS) measurements and scanning electron microscope (SEM) revealed fast swelling and disruption of nanocarriers under an intracellular reduction-mimicking environment. The in vitro release studies showed that DOX was released in a controlled and redox-dependent manner. MTT assays showed that DOX-loaded WPU had a high in vitro antitumor activity in both HDF noncancer cells and MCF- 7 cancer cells. In addition, it is found that the blank WPU nanocarriers are nontoxic to HDF and MCF-7 cells even at a high concentration of 2mg/mL. Hence, nanocarriers based on disulfide labeled WPU have appeared as a new class of biocompatible and redox-degradable nanovehicle for efficient intracellular drug delivery.

Effective co-delivery of doxorubicin and curcumin using a glycyrrhetinic acid-modified chitosan-cystamine-poly(ε-caprolactone) copolymer micelle for combination cancer chemotherapy

A glycyrrhetinic acid-modified chitosan-cystamine-poly(ε-caprolactone) copolymer (PCL-SS-CTS-GA) micelle was developed for the co-delivery of doxorubicin (DOX) and curcumin (CCM) to hepatoma cells. Glycyrrhetinic acid (GA) was used as a targeting unit to ensure specific delivery. Co-encapsulation of DOX and CCM was facilitated by the incorporation of poly(ε-caprolactone) (PCL) groups. The highest drug loading content was 19.8% and 8.9% (w/w) for DOX and CCM, respectively. The PCL-SS-CTS-GA micelle presented a spherical or ellipsoidal geometry with a mean diameter of approximately 110nm. The surface charge of the micelle changed from negative to positive, when the pH value of the solution decreased from 7.4 to 6.8. Meanwhile, it also exhibited a character of redox-responsive drug release and GA/pH-mediated endocytosis in vitro. In simulated body fluid with 10mM glutathione, the release rate in 12h was 80.6% and 67.2% for DOX and CCM, respectively. The cell uptake of micelles was significantly higher at pH 6.8 than pH 7.4. The combined administration of DOX and CCM was facilitated by PCL-SS-CTS-GA micelle. Results showed that there was strong synergic effect between the two drugs. The PCL-SS-CTS-GA micelle might turn into a promising and effective carrier for improved combination chemotherapy.

Multifunctional mesoporous silica nanoparticles modified with tumor-shedable hyaluronic acid as carriers for doxorubicin

In this paper, a CD44-targeted and redox-responsive drug delivery system based on mesoporous silica nanoparticles (MSNs) was synthesized by conjugating tumor-shedable hyaluronic acid (HA) on the surface of MSNs via disulfide bonds. Doxorubicin hydrochloride (DOX·HCl) was physically encapsulated into HA modified MSNs (MSNs/SS/HA@DOX) as a model drug. MSNs/SS/HA@DOX (40nm) had a high drug loading (14.1%) and redox-responsive drug release property. The cellular uptake behaviors of MSNs/SS/HA@DOX by HeLa and LO2 cells were evaluated by confocal laser scanning microscopy (CLSM) and flow cytometry (FCM). MSNs/SS/HA@DOX exhibited higher cellular uptake efficacy via CD44-mediated endocytosis by HeLa cells (CD44 over-expressed cells) than by LO2 cells (CD44 deficient cells). The in vitro cytotoxicity assay demonstrated that MSNs/SS/HA@DOX exhibited higher cytotoxicity to HeLa cells than to LO2 cells. These results indicated that MSNs/SS/HA@DOX might be promising as a multifunctional drug delivery system to improve the anti-tumor efficacy of chemotherapeutic drugs.

Intracellular Doxorubicin Delivery of a Core Cross-linked, Redox-responsive Polymeric Micelles

Redox-responsive micelles based on amphiphilic polyethylene glycol-polymethyl methacrylate with the introduction of disulfide containing cross-linked agent (mPEG-PMMA-SS) were developed for intracellular drug release. Benefiting from the amphiphilicity, mPEG-PMMA-SS could self-assembled into core cross-linked micelles in aqueous medium with tunable sizes (85-151 nm), appropriate zeta potential (-24.8 mV), and desirable critical micelle concentration (CMC) (0.18 mg/mL). Doxorubicin (DOX) could efficiently load into the micelles with satisfactory entrapment efficiency. As expected, the in vitro release studies displayed that DOX release from mPEG-PMMA-SS micelles was about 75% within 10h under tumor-relevant reductive condition, whereas only about 25% DOX was released in non-reductive medium. SRB assays indicated that these mPEG-PMMA-SS micelles were biocompatible and nontoxic up to a concentration of 50 μg/mL. The cytotoxicity studies and the intracellular drug delivery demonstrated that the drug release behavior in cells was related to the concentration of GSH in cytoplasm. Furthermore, the cell experiments using fluorescence microscopy showed clearly that DOX was delivered by micelles to the cytoplasm, released in cytoplasm under reductive environment, and then accumulated in cell nucleus. These results suggest that such redox-responsive micelles may develop into an efficient cytoplasmic delivery for hydrophobic anticancer drugs.

Selective redox-responsive drug release in tumor cells mediated by chitosan based glycolipid-like nanocarrier

The redox responsive nanocarriers have made a considerable progress in achieving triggered drug release by responding to the endogenous occurring difference between the extra- and intra- cellular redox environments. Despite the promises, this redox difference exists both in normal and tumor tissue. So a non-selective redox responsive drug delivery system may result in an undesired drug release in normal cells and relevant side-effects. To overcome these limitations, we have developed a chitosan based glycolipid-like nanocarrier (CSO-ss-SA) which selectively responded to the reducing environment in tumor cells. The CSO-ss-SA showed an improved reduction-sensitivity which only fast degraded and released drug in 10mM levels of glutathione (GSH). The CSO-ss-SA could transport the drug fast into the human ovarian cancer SKOV-3 cells and human normal liver L-02 cells by internalization, but only fast release drug in SKOV-3 cells. By regulating the intracellular GSH concentration in SKOV-3 cells, it indicated that the cellular inhibition of the PTX-loaded CSO-ss-SA showed a positive correlation with the GSH concentration. The CSO-ss-SA was mainly located in the liver, spleen and tumor in vivo, which evidenced the passive tumor targeting ability. Despite the high uptake of liver and spleen, drug release was mainly occurred in tumor. PTX-loaded CSO-ss-SA achieved a remarkable tumor growth inhibition effect with rather low dose of PTX. This study demonstrates that a smartly designed glycolipid-like nanocarrier with selective redox sensitivity could serve as an excellent platform to achieve minimal toxicity and rapid intracellular drug release in tumor cells.

Redox-responsive mesoporous silica as carriers for controlled drug delivery: a comparative study based on silica and PEG gatekeepers

Hybrid mesoporous silica nanoparticles (MSNs) modified with polymer polyethylene glycol (PEG) through the biodegradable disulfide bonds were prepared to achieve 'on demand' drug release. In this system, PEG chains were chosen as the representative gatekeepers that can block drugs within the mesopores of MSNs. After the addition of glutathione (GSH), the gatekeepers were removed from the pore outlets of MSNs, followed by the release of encapsulated drugs. In this research, the effects of grafting density of gatekeepers on the drug release and biocompatibility of silica carriers were also investigated. First, PEG modified MSNs were prepared by the condensation reaction between the carboxyl groups of MSN and the hydroxyl of PEG. The structure of the resultant MSN-SS-PEG was characterized by transmission electron microscopy (TEM), nitrogen adsorption/desorption isotherms analysis and Fourier transform infrared spectroscopy (FTIR). Rhodamine B (RhB) as the model drug was loaded into MSNs. The in vitro assay results indicated that RhB was released rapidly after the addition of 10 mM GSH; M1-SS-PEG had the best capping efficiency compared with M0.5 and M1.5 groups. Moreover, hemolysis assay, serum protein adsorption and cell viability test indicated that with the increase of PEG grafting density, the biocompatibility of silica carriers increased.