Zhe Yang

Micelles of enzymatically synthesized PEG-poly(amine-co-ester) block copolymers as pH-responsive nanocarriers for docetaxel delivery.

A series of PEGylated poly(amine-co-ester) terpolymers were successfully synthesized in one step via lipase-catalyzed copolymerization of ω-pentadecalactone (PDL), diethyl sebacate (DES), and N-methyldiethanolamine (MDEA) comonomers in the presence of poly(ethylene glycol) methyl ether as a chain-terminating agent. The resultant amphiphilic poly(ethylene glycol)-poly(PDL-co-MDEA-co-sebacate) (PEG-PPMS) block copolymers consisted of hydrophilic PEG chain segments and hydrophobic random PPMS chain segments, which self-assembled in aqueous medium to form stable, nanosized micelles at physiological pH of 7.4. Upon decreasing the medium pH from 7.4 to 5.0, the copolymer micelles swell significantly due to protonation of the amino groups in the micelle PPMS cores. Correspondingly, docetaxel (DTX)-encapsulated PEG2K-PPMS copolymer micelles showed gradual sustained drug release at pH of 7.4, but remarkably accelerated DTX release at acidic pH of 5.0. The drug-loaded micelle particles were readily internalized by SK-BR-3 cancer cells and, compared to free DTX drug, DTX-loaded micelles of the copolymers with optimal compositions exhibited enhanced potency against the cells. Biodegradable PEG-PPMS copolymer micelles represent a new type of promising, pH-responsive nanocarriers for anticancer drug delivery, and the drug release rate from the micelles can be systematically controlled by both pH and the copolymer composition.

PEGylated poly(amine-co-ester) micelles as biodegradable non-viral gene vectors with enhanced stability, reduced toxicity and higher in vivo transfection efficacy

Nanosized micelles based on cationic, amphiphilic poly(ethylene glycol)-poly(ω-pentadecalactone-co-N-methyldiethyleneamine-co-sebacate) (PEG-PPMS) block copolymers have been successfully developed to serve as a new type of biodegradable non-viral vectors for DNA delivery. PEG-PPMS copolymers with various compositions were synthesized in one step via lipase-catalyzed copolymerization of ω-pentadecalactone (PDL), N-methyldiethanolamine (MDEA) and diethyl sebacate (DES) with poly(ethylene glycol) methyl ether (MeO-PEG-OH). The effects of PEG molecular weight, PEG and PDL contents on the biological properties (including the gene transfection efficiency) of the copolymer micelles were investigated. The LucDNA-loaded micelles formed from the copolymers with 30-50 wt% PEG showed high stability in serum-containing aqueous medium, which is in sharp contrast to rapid aggregation of LucDNA/PPMS polyplex particles. The conjugation of PEG to PPMS chains significantly reduces the cytotoxicity and hemolysis activity of the PEG-PPMS micelles. Compared to PEG-free PPMS, the micelles of PEG-PPMS copolymers with optimal compositions (e.g., 42%PEG5K-PPMS-10%PDL and 42%PEG5K-PPMS-20%PDL) exhibited enhanced capability to condense and protect DNA. Although the optimized micelles showed comparable or slightly lower gene transfection efficacy than the reference PPMS in vitro, the efficiency of LucDNA/42%PEG5K-PPMS-20%PDL micelles in transfecting tumor cells in mice was twice as high as that of LucDNA/PPMS polyplex particles due to their strong DNA condensation ability and excellent stability under physiological conditions. The PEG-PPMS micelle system with improved properties is a family of potentially promising non-viral vectors for in vivo delivery of therapeutic genes to treat tumors.

Enzymatic synthesis of poly(ω-pentadecalactone-co-butylene-co-3,3′-dithiodipropionate) copolyesters and self-assembly of the PEGylated copolymer micelles as redox-responsive nanocarriers for doxorubicin delivery

Biodegradable copolyesters bearing disulfide functional groups in the main chain have been successfully synthesized by lipase-catalyzed copolymerization of lactone with disulfide-containing diester and diol. When poly(ethylene glycol) methyl ether (MeO-PEG-OH) was added as a chain terminating agent, the corresponding amphiphilic PEG-polyester block copolymers were formed. NMR analyses of the synthesized poly(ω-pentadecalactone-co-butylene-co-3,3′-dithiodipropionate) (PPBD) and PEG-PPBD copolymers indicate that the repeat unit distributions in PPBD chains or PPBD segments of PEG-PPBD chains are nearly statistically random. These new functional polyesters possess low toxicity and their hydrophobicity can be systematically adjusted by varying the lactone content in the polymers. In aqueous medium, the amphiphilic PEG-PPBD block copolymers self-assembled readily to form nanosized micelles that are capable of serving as efficient redox-responsive nanocarriers for anticancer drug delivery. The addition of D,L-dithiothreitol (DTT) reductant into the medium caused substantial swelling of the PEG-PPBD micelles and effectively triggered a fast drug release from the doxorubicin (DOX)-loaded micelles. Consistently, an in vitro cytotoxicity study revealed that the efficacy of DOX-loaded PEG-PPBD micelles against HepG2 cancer cells is enhanced by intracellular glutathione (GSH) after the internalization of the micelles by the cells.

Hybrid nanoparticles coated with hyaluronic acid lipoid for targeted co-delivery of paclitaxel and curcumin to synergistically eliminate breast cancer stem cells

Conventional chemotherapy drugs such as paclitaxel (PTX) can effectively inhibit tumor growth by killing the majority of the proliferating cancer cells; however, it also results in multi-drug resistance (MDR) and facilitates the conversion of non-cancer stem cells (non-CSCs) to cancer stem cells (CSCs), which are considered the reason for chemotherapy resistance, relapse, and metastasis. Thus, exploring combination therapy with multiple chemotherapeutics is considered as a promising approach for simultaneously eliminating CSCs and non-CSCs. Here, we fabricated a bCSC (breast cancer stem cell)-targeting co-delivery system (HA-hybrid NPs) by attaching a lipoid (HA-HDA) to the surface of hydrophobic PLGA nanoparticles to co-deliver the widely used chemotherapy agent, PTX, and the selective inhibitor of CSCs, curcumin (CUR). This co-delivery system was capable of targeting bCSCs via an interaction between HA and the CD44 receptor on the membrane of bCSCs, and it could efficiently eliminate the bCSC population, decrease the mammosphere formation of bCSCs, and inhibit the migration of bCSCs. Most importantly, HA-hybrid co-delivered NPs exhibited enhanced anti-tumor efficacy by synergistically inhibiting the growth of both non-bCSCs and bCSCs on MCF7 xenografted tumor models. Taken together, the results of this study demonstrate that this bCSC-targeted HA-hybrid NP provides a potential strategy for enhancing breast cancer therapeutic efficiency.

pH and redox dual-responsive multifunctional gene delivery with enhanced capability of transporting DNA into the nucleus

Stimuli-responsive gene delivery vectors based on physiologically triggered structure changing have been recently recognized as a new therapeutic agent for their excellent performance in vivo. Herein, we present an intelligent gene delivery system based on the octa-arginine peptides (R8)-conjugated polyamino acid derivatives noted as PPCRC (PVIm-(PAsp-Cystamine-R8)-Cholesteryl), which processed pH responsive, surface charge-switching, intracellular redox-responsive and enhanced nucleus import of gene together. Due to the imidazole group in the PPCRC backbone, the DNA/PPCRC polyplexes not only exhibited the enhanced buffering capacity in the endosome after endocytosis, but also displayed the reversible surface charge from negative to positive with decreasing the pH value form pH 7.4 to pH 6.5-6.8, which would promote the cell membrane binding and cellular uptake. The disulfide bond for R8 peptides conjugation in the polymer side chain could be rapidly cleaved under reductive conditions, facilitating DNA release in the cytoplasm. Subsequently, the DNA would be still associated with the R8 peptides, which would promote the intracellular nucleus import of DNA. The luciferase gene expression level of COS-7 cells transfected by DNA/PPCRC polyplexes was almost 2000 folds higher than cells transfected by DNA/PPCC polyplexes (without R8 peptides modification) in growth-arrested cell model. Nearly 10 folds enhanced gene transfection efficiency was found on human bone mesenchymal stem cells (hBMSCs) using the same strategy, which revealed that this intelligent vector can be also utilized in transfection of non-dividing cells. Intravenous injection of the DNA/PPCRC polyplexes also achieved the effective transfection in subcutaneous tumor model. Taken together, PPCRC vector has great potential for both dividing and non-dividing cells transfection and in vivo gene delivery application.

Thermo- and pH-dual responsive polymeric micelles with upper critical solution temperature behavior for photoacoustic imaging-guided synergistic chemo-photothermal therapy against subcutaneous and metastatic breast tumors

Chemo-photothermal therapy shows great potential for inhibiting tumor growth. However, achieving maximal chemo-photothermal synergistic efficacy is challenging because of the low efficiency of controllable chemo-drug release in response to external or internal triggers. Thus, a nano-delivery system that could effectively achieve photothermal therapy and dual stimuli-responsive (heat and pH) drug release to inhibit both primary breast tumor growth and metastases is required. Methods: Herein, a thermo- and pH-responsive polymer (mPEG-PAAV) with an upper critical solution temperature (UCST) was synthesized to fabricate a DOX- and IR780-loaded micellar system. After systematic studies of the photothermal performance and controllable drug release of mPEG-PAAV micelles/IR780+DOX under NIR irradiation at different pH values, their chemo-photothermal synergetic therapy efficacies were also estimated both in in vitro and in vivo. Results: Because of the photothermal conversion of mPEG-PAAV micelle/IR780+DOX (~200 nm, 3.82 mV), high local temperature could be induced at the tumor site under NIR laser irradiation. This hyperthermia not only produced an enhanced tumor necrosis, but also broke down the micelles under the decreased pH environment, resulting in rapid DOX release and enhanced intracellular drug accumulation after NIR laser irradiation. In addition, photoacoustic imaging (PAI) of mPEG-PAAV/IR780+DOX micelle was adopted to monitor the morphology and micro-vascular distribution of the tumor tissue, which could also guide the chemo-photothermal therapy. Most importantly, the systemic administration of mPEG-PAAV micelles/IR780+DOX combined with NIR laser irradiation could simultaneously eliminate the 4T1 breast tumor and thoroughly suppress lung metastasis without any obvious adverse effects. Conclusion: Herein, a pH- and thermo-dual responsive UCST micelle system was developed for delivering IR780 and DOX, which could achieve NIR laser-controlled drug release and PA imaging guidance for chemo-photothermal synergistic therapy of both primary breast tumors and their metastases.

Nanotechnology for Cancer Therapy Based on Chemotherapy

Chemotherapy has been widely applied in clinics. However, the therapeutic potential of chemotherapy against cancer is seriously dissatisfactory due to the nonspecific drug distribution, multidrug resistance (MDR) and the heterogeneity of cancer. Therefore, combinational therapy based on chemotherapy mediated by nanotechnology, has been the trend in clinical research at present, which can result in a remarkably increased therapeutic efficiency with few side effects to normal tissues. Moreover, to achieve the accurate pre-diagnosis and real-time monitoring for tumor, the research of nano-theranostics, which integrates diagnosis with treatment process, is a promising field in cancer treatment. In this review, the recent studies on combinational therapy based on chemotherapy will be systematically discussed. Furthermore, as a current trend in cancer treatment, advance in theranostic nanoparticles based on chemotherapy will be exemplified briefly. Finally, the present challenges and improvement tips will be presented in combination therapy and nano-theranostics.

Cargo-Free Nanomedicine with pH Sensitivity for Codelivery of DOX Conjugated Prodrug with SN38 To Synergistically Eradicate Breast Cancer Stem Cells

As a result of their ability to transform into bulk cancer cells and their resistance to radiotherapy and chemotherapy, cancer stem cells (CSCs) are currently considered as a major obstacle for cancer treatment. Application of multiple drugs using nanocarriers is a promising approach to simultaneously eliminate noncancer stem cells (non-CSCs) and CSCs. Herein, to employ the advantages of nanomedicine while avoiding new excipients, pH-responsive prodrug (PEG-CH═N-DOX) was employed as the surfactant to fabricate cargo-free nanomedicine for codelivery of DOX conjugated prodrug with SN38 to synergistically eradicate breast cancer stem cells (bCSCs) and non-bCSCs. Through the intermolecular interaction between DOX and SN38, PEG-CH═N-DOX and SN38 were assembled together to form a stable nanomedicine. This nanomedicine not only dramatically enhanced drug accumulation efficiency at the tumor site but also effectively eliminated bCSCs and non-bCSCs, which resulted in achieving a superior in vivo tumor inhibition activity. Additionally, the biosafety of this nanomedicine was systematically studied through immunohistochemistry, blood biochemistry assay, blood routine examination, and metabolomics. The results revealed that this nanomedicine significantly reduced the adverse effects of DOX and SN38. Therefore, this simple yet efficient nanomedicine provided a promising strategy for future clinical applications.

Insufficient fumarase contributes to generating reactive oxygen species in Dahl salt sensitive rats

Dahl SS rats exhibit greater levels of renal medullary oxidative stress and lower levels of fumarase activities. Fumarase insufficiencies can increase reactive oxygen species (ROS), the mechanism of which, however, is not clear. A proteomic analysis indicated fumarase knockdown in HK-2 cells resulted in changes in the expression or activity of NADPH oxidase, mitochondrial respiratory chain complex I and III, ATP synthase subunits, and α-oxoglutarate dehydrogenase, all of which are sites of ROS formation. Meantime, the activities of key antioxidant enzymes such as G6PD, 6PGD, GR, GPx and GST increased significantly too. The apparent activation of antioxidant defense appeared insufficient as glutathione precursors, glutathione and GSH/GSSG ratio were decreased. SS rats exhibited changes in redox metabolism similar to HK-2 cells with fumarase knockdown. Supplementation with fumarate and malate, the substrate and product of fumarase, increased and decreased, respectively, blood pressure and the levels of H2O2 and MDA in kidney tissues of SS rats. These results indicate fumarase insufficiencies cause a wide range of changes at several sites of ROS production and antioxidant mechanisms.

Multifunctional Cargo-Free Nanomedicine for Cancer Therapy

Nanocarriers encapsulating multiple chemotherapeutics are a promising strategy to achieve combinational chemotherapy for cancer therapy; however, they generally use exotic new carriers without therapeutic effect, which usually suffer from carrier-related toxicity issues, as well as having to pass extensive clinical trials to be drug excipients before any clinical applications. Cargo-free nanomedicines, which are fabricated by drugs themselves without new excipients and possess nanoscale characteristics to realize favorable pharmacokinetics and intracellular delivery, have been rapidly developed and drawn much attention to cancer treatment. Herein, we discuss recent advances of cargo-free nanomedicines for cancer treatment. After a brief introduction to the major types of carrier-free nanomedicine, some representative applications of these cargo-free nanomedicines are discussed, including combination therapy, immunotherapy, as well as self-monitoring of drug release. More importantly, this review draws a brief conclusion and discusses the future challenges of cargo-free nanomedicines from our perspective.