Xuejiao Zhang

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

A novel pH and redox dual-responsive prodrug nanogel was prepared by an inverse nanoprecipitation method, which is mild and surfactant free, and based on a thiol-disulfide exchange reaction and thiol-Michael addition reaction. Highly biocompatible hyperbranched polyglycerol (hPG) was cross-linked with disulfide bonds, to obtain biodegradable nanogels, which could be degraded under intracellular reductive conditions. Doxorubicin (DOX) was conjugated to the biodegradable nanogel matrix via an acid-labile hydrazone linker. This is the first dual-responsive prodrug nanogel system that shows very low unspecific drug leaching, but efficient intracellular release of the payload triggered by the intracellular conditions. Two different prodrug nanogels were prepared with a size of approximately 150nm, which is big enough to take the advantage of the enhanced permeation and retention (EPR) effect in tumor tissue. Cell culture analysis by microscopy and flow cytometry revealed that the prodrug nanogels were efficiently internalized by tumor cells. Distinct release profiles of DOX were achieved by adjusting the nanogel architecture, and online detection of cytotoxicity showed that, unlike free DOX, the dual-responsive prodrug nanogels exhibited a delay in the onset of toxicity, indicating the different uptake mechanism and the need for prodrug activation to induce cell death.

Surfactant free preparation of biodegradable dendritic polyglycerol nanogels by inverse nanoprecipitation for encapsulation and release of pharmaceutical biomacromolecules.

In this paper we report a novel approach to generate biodegradable polyglycerol nanogels on different length scales. We developed a mild, surfactant free inverse nanoprecipitation process to template hydrophilic polyglycerol nanoparticles. In situ crosslinking of the precipitated nanoparticles by bioorthogonal copper catalyzed click chemistry allows us to obtain size defined polyglycerol nanogels (100-1000nm). Biodegradability was achieved by the introduction of benzacetal bonds into the net points of the nanogel. Interestingly, the polyglycerol nanogels quickly degraded into low molecular weight fragments at acidic pH values, which are present in inflamed and tumor tissues as well as intracellular organelles, and they remained stable at physiological pH values for a long time. This mild approach to biodegradable polyglycerol nanogels allows us to encapsulate labile biomacromolecules such as proteins, including the therapeutic relevant enzyme asparaginase, into the protein resistant polyglycerol network. Enzymes were encapsulated with an efficacy of 100% and after drug release, full enzyme activity and structural integrity were retained. This new inverse nanoprecipitation procedure allows the efficient encapsulation and release of various biomacromolecules including proteins and could find many applications in polymer therapeutics and nanomedicine.

Amphiphilic Random Glycopolymer Based on Phenylboronic Acid: Synthesis, Characterization, and Potential as Glucose-Sensitive Matrix

This study is devoted to developing amphiphilic, random glycopolymers based on phenylboronic acid, which self-assemble to form nanoparticles (NPs), as a glucose-sensitive agent. Maleimide-glucosamine was copolymerized with 3-acryl aminophenylboronic acid in methanol at 70 degrees C. Using the nanoprecipitation method, NPs with a narrow size distribution were successfully generated. Transmission electron microscopic analysis showed that the NPs were well dispersed as individual, spherically shaped particles. The swelling behavior of the NPs and the in vitro release profiles of insulin at different glucose concentrations revealed definite glucose sensitivity of the glycopolymers. Further, circular dichroism spectroscopy demonstrated that the overall tertiary structure of the released insulin was not altered compared with standard insulin. The analysis of relative cell proliferation suggested that the glycopolymer NPs had good biocompatibility. The glycopolymers that responded to changes in the glucose concentration of the surrounding environment are being aimed for use in self-regulated insulin delivery.

A hydrotropic β-cyclodextrin grafted hyperbranched polyglycerol co-polymer for hydrophobic drug delivery

The development of successful formulations for poorly water soluble drugs remains a longstanding, critical, and challenging issue in cancer therapy. A β-cyclodextrin (CD) functionalized hyperbranched polyglycerol (HPG) has been prepared as a potential water insoluble drug carrier. The HPG-g-CD molecules could self-assemble into multimolecular spherical micelles in water, the size of which ranged from 200 to 300 nm, with good dispersity. A high loading capacity and high encapsulation efficiency of paclitaxel, as a model, were obtained. The release profiles of different co-polymer compositions showed a burst release followed by continuous extended release. Furthermore, MTT analysis showed that HPG-g-CD had good biocompatibility, indicating that HPG-g-CD may be considered a promising hydrophobic drug delivery system.

Synthesis and physicochemical characterization of a novel amphiphilic polylactic acid-hyperbranched polyglycerol conjugate for protein delivery

Amphiphilic copolymers with polylactic acid (PLA) chains grafted onto hyperbranched polyglycerol (HPG) have been synthesized and characterized. The copolymer nanoparticles with corona and core structure were formed by self-assembly in aqueous solution. The loading capacity and association efficiency were up to 23% and 86%, respectively. Protein release profiles with different copolymer compositions and BSA concentrations all showed a burst effect followed by a continuous release phase. The released BSA from the copolymer nanoparticles remained in its original structure over a period of 4 days, as testified by circular dichroism spectroscopy. Furthermore, cell viability research suggested good biocompatibility of the copolymer nanoparticles, which have a promising potential for protein delivery system.

Hydrotropic Polymeric Mixed Micelles Based on Functional Hyperbranched Polyglycerol Copolymers as Hepatoma-Targeting Drug Delivery System

Mixed copolymer nanoparticles (NPs) self-assembled from β-cyclodextrin-grafted hyperbranched polyglycerol (HPG-g-CD) and lactobionic acid (LA)-grafted hyperbranched polyglycerol (HPG-g-LA) were applied as carriers for a hydrophobic antitumor drug, paclitaxel (PTX), achieving hepatocellular carcinoma-targeted delivery. The resulting NPs exhibited high drug loading capacity and substantial stability in aqueous solution. In vitro drug release studies demonstrated a controlled drug release profile with increased release at acidic pH. Remarkably, tumor proliferation assays showed that PTX-loaded mixed copolymer NPs inhibited asialoglycoprotein (ASGP) receptor positive HepG2 cell proliferation in a concentration-dependent manner in comparison with ASGP receptor negative BGC-823 cells. Moreover, the competition assay demonstrated that the small molecular LA inhibited the cellular uptake of the PTX-loaded mixed copolymer NPs, indicating the ASGP receptor-mediated endocytosis in HepG2 cells. In addition, the intracellular uptake tests by confocal laser scanning microscopy showed that the mixed copolymer NPs were more efficiently taken up by HepG2 cells compared with HPG-g-CD NPs. These results suggest a feasible application of the mixed copolymer NPs as nanocarriers for hepatoma-targeted delivery of potent antitumor drugs.

Disulfide cross-linked biodegradable polyelectrolyte nanoparticles for the oral delivery of protein drugs

Polyelectrolyte nanoparticles were prepared by mixing chitosan (CS) and polyaspartic acid functionalized with cysteamine (PASP–CA) under mild conditions. The nanoparticles (NPs) included thiol moieties that were cross-linked to render the NPs stable at physiological pH. It was demonstrated that reacting the thiol moieties to form disulfide bonds led to improved stability. NPs without disulfide bonds were readily deconstructed at physiological pH. The disulfide bond cross-linked NPs can remain more stable in physiological pH solution and decrease the loss of protein drugs caused by simulating the gastric pH environment, and can release the drugs in the simulated pH environment of the intestine. This approach has potential for the in vivo application of NPs for the oral delivery of protein drugs.

Functionalized nanogels carrying an anticancer microRNA for glioblastoma therapy

Glioblastoma Multiforme (GBM) is one of the most aggressive forms of all cancers. The median survival with current standard-of-care radiation and chemotherapy is about 14months. GBM is difficult to treat due to heterogeneity in cancer cell population. MicroRNA-based drugs have rapidly become a vast and burgeoning field due to the ability of a microRNA (miRNA) to target many genes involved in key cellular pathways. However, in vivo delivery of miRNA remains a crucial challenge for its therapeutic success. To bypass this shortcoming, we designed polymeric nanogels (NGs), which are based on a polyglycerol-scaffold, as a new strategy of miRNA delivery for GBM therapy. We focused on miR-34a, which is known for its key role in important oncogenic pathways and its tumor suppression ability in GBM and other cancers. We evaluated the capability of six NG derivatives to complex with miR-34a, neutralize its negative charge and deliver active miRNA to the cell cytoplasm. Human U-87 MG GBM cells treated with our NG-miR-34a nano-polyplexes showed remarkable downregulation of miR-34a target genes, which play key roles in the regulation of apoptosis and cell cycle arrest, and induce inhibition of cells proliferation and migration. Administration of NG-miR-34a nano-polyplexes to human U-87 MG GBM-bearing SCID mice significantly inhibited tumor growth as opposed to treatment with NG-negative control miR polyplex or saline. The comparison between different polyplexes highlighted the key features for the rational design of polymeric delivery systems for oligonucleotides. Taken together, we expect that this new therapeutic approach will pave the way for safe and efficient therapies for GBM.

Amphiphilic polylactic acid‐hyperbranched polyglycerol nanoparticles as a controlled release system for poorly water‐soluble drugs: physicochemical characterization

Objectives  Quercetin was applied as a model drug to evaluate the potential application of amphiphilic polylactic acid‐hyperbranched polyglycerol (HPG‐PLA) nanoparticles as carriers for poorly water‐soluble drugs.

Size Effect on the Cytotoxicity of Layered Black Phosphorus and Underlying Mechanisms

A systematic cytotoxicity study of layered black phosphorus (BP) is urgently needed before moving forward to its potential biomedical applications. Herein, bulk BP crystals are synthesized and exfoliated into layered BP with different lateral size and thickness. The cytotoxicity of as-exfoliated layered BP is evaluated by a label-free real-time cell analysis technique, displaying a concentration-, size-, and cell type-dependent response. The IC50 values can vary by 40 and 30 times among the BP sizes and cell types, respectively. BP-1 with the largest lateral size and thickness has the highest cytotoxicity; whereas the smallest BP-3 only shows moderate toxicity. The sensitivity of three tested cell lines follows the sequence of 293T > NIH 3T3 > HCoEpiC. Two possible mechanisms for BP to induce cytotoxicity are proposed and verified: (1) the generation of intracellular reactive oxygen species (ROS) is detected by a ROS sensitive probe using the inverted fluorescence microscopy and flow cytometry; (2) the interaction of layered BP and model cell membrane is examined by quartz crystal microbalance with dissipation, illustrating the disruption of cell membrane integrity especially by the largest BP-1. This systematic study of BPs cytotoxicity will shed light on its future biomedical and environmental applications.