Redox-sensitive Nanogels Research Articles

Impact of Glutathione Modulation on Stability and Pharmacokinetic Profile of Redox‐Sensitive Nanogels

Nanoparticles degradable upon external stimuli combine pharmacokinetic features of both small molecules as well as large nanoparticles. However, despite promising preclinical results, several redox responsive disulphide-linked nanoparticles failed in clinical translation, mainly due to their unexpected in vivo behavior. Glutathione (GSH) is one of the most evaluated antioxidants responsible for disulfide degradation. Herein, the impact of GSH on the in vivo behavior of redox-sensitive nanogels under physiological and modulated conditions is investigated. Labelling of nanogels with a DNA-intercalating dye and a radioisotope allows visualization of the redox responsiveness at the cellular and the systemic levels, respectively. In vitro, efficient cleavage of disulphide bonds of nanogels is achieved by manipulation of intracellular GSH concentration. While in vivo, the redox-sensitive nanogels undergo, to a certain extent, premature degradation in circulation leading to rapid renal elimination. This instability is modulated by transient inhibition of GSH synthesis with buthioninsulfoximin. Altered GSH concentration significantly changes the in vivo pharmacokinetics. Lower GSH results in higher elimination half-life and altered biodistribution of the nanogels with a different metabolite profile. These data provide strong evidence that decreased nanogel degradation in blood circulation can limit the risk of premature drug release and enhance circulation half-life of the nanogel.

Abstract 3099: pH-regulated hydrophilicity/hydrophobicity-, surface charge-reversible and redox sensitive nanogels for anticancer drug delivery

Abstract Long circulation in blood, enhanced tumor accumulation and penetration, efficient cellular internalization and intracellular drug release are major challenges in the development of ideal anticancer drug delivery systems. Although several strategies have been reported to improve therapeutic efficacy, they mainly meet one or a few features which can not circumvent all the barriers. Here the stimuli-responsive zwitterionic nanogels were developed to overcome the sequential physiological barriers in cancer chemotherapy. The nanogels were constructed via a simple precipitation polymerization method by using temperature-sensitive monomer N-isopropylacrylamide (NIPAM) pH-responsive monomer methylallyl amine (MAA) and betaine-based zwitterionic monomer sulfobetaine methacrylate (SBMA) with in vivo anti-protein adsorption property as comonomers, and disulfide bonds-containing N, N'-bis(acryloyl) cystamine (BAC) as crosslinker. Volume phase transition temperature (VPTT) and surface charge of the prepared nanogels were precisely controlled by altering the feeding molar ratio of these comonomers. Remarkably, The nanogels possess ultra-pH sensitive hydrophilicity/hydrophobicity reversible property, in which the nanogels were hydrophilic in the blood (pH 7.4, 37 °C) for prolonged circulation, while they were rapidly switched to hydrophobic with similar size and surface charge at acidic tumor pH, resulting in enhanced tumor accumulation and penetration and strong internalization by normal cancer cells and CSCs. For efficient lysosomal escape and intracellular drug release, the nanogels were positively charged at lysosome pH, which allowed them to be transported into the cytosol where the loaded cargo DOX was released from the nanogels with the introduction of intracellular high GSH concentration to exert cytotoxicity. This study indicated that pH-dependent hydrophilicity/hydrophobicity-, surface charge-reversible and redox sensitive nanogels might be used as potential carriers for anticancer drugs, which provided a foundation for designing an effective drug delivery system for cancer therapy. Note: This abstract was not presented at the meeting. Citation Format: Hao Yang, Qin Wang, Fuying Li, Yanhong Zhu, Lu Gan, Xiangliang Yang. pH-regulated hydrophilicity/hydrophobicity-, surface charge-reversible and redox sensitive nanogels for anticancer drug delivery [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3099. doi:10.1158/1538-7445.AM2017-3099

Enhance chemotherapy efficacy and minimize anticancer drug side effects by using reversibly pH- and redox-responsive cross-linked unimolecular micelles

Chemotherapy side effects elimination while keeping the original therapeutic advantages has been of extensive interest over last decades. We herein develope a new pH and redox-sensitive nanogel for glutathione-mediated intracellular drug delivery employing disulfide crosselinked unimolecular micelles. We developed H40-polycaprolactone-b-polyacrylic acid-b′-methoxy poly(ethylene glycol)/poly(ethylene glycol)-folate (i.e., H40-PCL-(b-PAA-b′-MPEG/PEG-FA)2) unimolecular micelles with targeting moieties on the periphery. It was then crosslinked with cystamine in order to generate a pH and redox-sensitive nanogel. Dynamic light scattering (DLS) was performed to study pH-dependent nanogel sizes. We applied Paclitaxel, a hydrophobic anticancer drug, into delivery system and examined triggered release behaviors at different pHs upon DTT buffer exposure. Our results demonstrated that DTT presence as reductive agent within acidic environment is essential for drug release. This may potentially reduce unwanted drug release at non-cancerous acidic tissues leading to eliminated side effects. We examined biocompatibility and cytotoxicity of free nanogel and PTX-loaded nanogel to normal and cancer HeLa cells using MTT assay. Nanogel HeLa cell uptake was confirmed by Fluorescein loading into the gel followed by fluorescent microscope imaging. Our novel strategy would have profound implications in both enhanced chemotherapy efficacy and minimized side effects.

Hydrophilicity/Hydrophobicity reversable and redox-sensitive nanogels for anticancer drug delivery.

Long circulation in the blood, efficient cellular internalization, and intracellular drug release in the tumor cells are major challenges in the development of ideal anticancer drug delivery systems. In this paper, hydrophilicity/hydrophobicity reversable and redox-sensitive poly(oligo(ethylene glycol) methacrylates-ss-acrylic acid) (P(OEGMAs-ss-AA)) nanogels were constructed as drug carriers for cancer therapy. The nanogels underwent a pH-dependent hydrophilic/hydrophobic change. The nanogels were hydrophilic under physiological conditions (pH 7.4, 37 °C), resulting in fewer opsonization of proteins and less phagocytosis by macrophage RAW264.7 cells, while they were hydrophobic in the tumor tissues (pH 6.5, 37 °C), resulting in strong internalization by Bel7402 cells. The doxorubicin (DOX) release from DOX-loaded nanogels was increased in intracellular reductive and lysosome acidic environments. DOX-loaded nanogels exhibited higher cellular proliferation inhibition to GSH-OEt-pretreated Bel7402 cells at pH 6.5 than to unpretreated cells at pH 7.4. Further studies showed that the loaded DOX and nanogels were internalized into the cells together via both lipid raft/caveolae- and clathrin-mediated endocytic pathways. After internalization, the DOX-loaded nanogels were transported via the specific route in endo/lysosomal system. The loaded DOX was released from the nanogels with the introduction of intracellular GSH and entered the nucleus. This study indicated that the hydrophilicity/hydrophobicity reversable and redox-sensitive nanogels might be used as potential carriers for anticancer drugs, which provided a foundation for designing an effective drug delivery system for cancer therapy.

Composite supramolecular nanoassemblies with independent stimulus sensitivities

Nanoscale assemblies with stimuli-sensitive features have attracted significant attention due to implications in a variety of areas ranging from materials to biology. Recently, there have been excellent developments in obtaining nanoscale structures that are concurrently sensitive to multiple stimuli. Such nanostructures are primarily focused on a single nanostructure containing an appropriate combination of functional groups within the nanostructure. In this work, we outline a simple approach to bring together two disparate supramolecular assemblies that exhibit very different stimuli-sensitive characteristics. These composite nanostructures comprise a block copolymer micelle core and nanogel shell, both of which can preserve their respective morphology and stimulus sensitivities. The block copolymer is based on poly(2-(diisopropylamino)ethylmethacrylate-b-2-aminoethylmethacrylate hydrochloride), which contains a pH-sensitive hydrophobic block. Similarly, the redox-sensitive nanogel is derived from a poly(oligoethyleneglycolmonomethylethermethacrylate-co-glycidylmethacrylate-co-pyridyldisulfide ethylmethacrylate) based random copolymer. In addition to the independent pH-response of the micellar core and redox-sensitivity of the nanogel shell in the composite nanostructures, the synergy between the micelles and the nanogels have been demonstrated through a robust charge generation in the nanogels during the disassembly of the micelles. The supramolecular assembly and disassembly have been characterized using transmission electron microscopy, dynamic light scattering, zeta potential measurements, fluorescence spectroscopy and cellular uptake.

Delivery of doxorubicin in vitro and in vivo using bio-reductive cellulose nanogels.

A methacrylation strategy was used to functionalize carboxymethyl cellulose and prepare redox-sensitive cellulose nanogels which contained disulfide bonds. Dynamic light scattering, zeta potential and electron microscopy were utilized to characterize these nanogels. It was found that these nanogels had a spherical morphology with a diameter of about 192 nm, and negative surface potential. These redox-sensitive nanogels were stable against high salt concentration but de-integrated in the reducing environment containing glutathione. When doxorubicin (DOX) was loaded into the nanogels, a high drug loading content (36%) and a high encapsulation efficiency (83%) were achieved. Confocal laser scanning microscopy and co-localization images showed that DOX-loaded nanogels were internalized by the cancer cells through endocytosis and the DOX could be delivered into the nucleus. Near-infrared fluorescence imaging biodistribution examination indicated that the nanogels could passively target to the tumor area by the EPR effect and had a significantly prolonged circulation time. In vivo antitumor evaluation found that DOX-loaded nanogels exhibited a significantly superior antitumor effect than the free DOX by combining the tumor volume measurement and the examination of cell apoptosis and proliferation in tumor tissues.

Redox-Responsive Alginate Nanogels with Enhanced Anticancer Cytotoxicity

Although doxorubicin (Dox) has been widely used in the treatment of different types of cancer, its insufficient cellular uptake and intracellular release is still a limitation. Herein, we report an easy process for the preparation of redox-sensitive nanogels that were shown to be highly efficient in the intracellular delivery of Dox. The nanogels (AG/Cys) were obtained through in situ cross-linking of alginate (AG) using cystamine (Cys) as a cross-linker via a miniemulsion method. Dox was loaded into the AG/Cys nanogels by simply mixing it in aqueous solution with the nanogels, that is, by the establishment of electrostatic interactions between the anionic AG and the cationic Dox. The results demonstrated that the AG/Cys nanogels are cytocompatible, have a high drug encapsulation efficiency (95.2 ± 4.7%), show an in vitro accelerated release of Dox in conditions that mimic the intracellular reductive conditions, and can quickly be taken up by CAL-72 cells (an osteosarcoma cell line), resulting in higher Dox intracellular accumulation and a remarkable cell death extension when compared with free Dox. The developed nanogels can be used as a tool to overcome the problem of Dox resistance in anticancer treatments and possibly be used for the delivery of other cationic drugs in applications beyond cancer.

Metal Coordinative-crosslinked Polysaccharide Nanogels with Redox Sensitivity

Abstract Metal coordinative-crosslinked nanogels were prepared by introducing a metal–ligand to a hydrophilic polysaccharide. The redox couple of Co(II) and Co(III) was utilized for construction of a redox-sensitive nanogel system. This is a new method for the preparation of hybrid nanogels with dual network structures of both physically and coordinative-crosslinking points.