Jing Chang

Cooperative Hierarchical Self-Assembly of Peptide Dendrimers and Linear Polypeptides into Nanoarchitectures Mimicking Viral Capsids †

Supramolecular self-assembly is regarded as ubiquitous and essential phenomenon during the early stages of life. In the past decade, self-assembly inspired from nature has been evolved as an effective and practical strategy for nanoarchitecture fabrication. With respect to the formation of soft matter, advances were achieved in the selfassembly of linear polymers, but the selfassembly of spherical macromolecules such as dendrimers is still at an early stage. The regulation of dispersive dendrimers into ordered nanoarchitectures as potential biomacromolecules remains challenging research work. Peptide dendrimers possess not only the general characteristics of typical dendrimers, but also certain unique properties of globular proteins. Initiating hierarchical self-assembly of globular or linear polypeptides may provide a powerful approach to fabricate supramolecular structures with transfer or delivery functions in medical applications as virosomes in cellular environment. Most dendrimers lack the driving forces for self-assembly; therefore, chemical or physical interactions were explored as driving forces. Herein, we report a novel approach to regulate the cooperative selfassembly of peptide dendrimers and linear polypeptides into capsid-like nanostruc-

Pharmacokinetics and biodegradation mechanisms of a versatile carboxymethyl derivative of chitosan in rats: in vivo and in vitro evaluation.

Carboxymethyl chitosan (CM-chitosan), which is a water-soluble derivative of chitosan, has attracted much attention as a new biomedical material. The safety study of this material was persuasive for its potential application. The present study was conducted to assess the tissue distribution, pharmacokinetics, biodegradation mechanism, and excretion of CM-chitosan in rats. After the rats were intraperitoneally injected at the dose of 50 mg/kg, the fluorescein isothiocyanate (FITC)-labeled CM-chitosan was absorbed rapidly and distributed to different organs, including liver, spleen, and kidney. The highest level of CM-chitosan was found in liver. It was at the level of 1.6 +/- 0.6 mg/liver and made up approximately 10-22% of the total injected FTC-CM-chitosan. Urinary excretion was the predominant way of excretion of FITC-labeled CM-chitosan, and 85% of the dose was excreted in urine over the period of 11 days. The molecular weights of body distributed FTC-CM-chitosan and urinary excreted FTC-CM-chitosan were analyzed by gel chromatography. The results indicated that the FTC-CM-chitosan was degraded in abdominal dropsy. The absorbed CM-chitosan forms were found with a relatively high molecular weight (approximately 300 kDa), whereas the molecular weight of the urinary excreted FTC-CM-chitosan was less than 45 kDa. In vitro research revealed that the CM-Chi was also degradable in plasma and homogenate of liver. The CM-chitosan with a molecular weight of approximately 800k was thoroughly degraded to a small molecule after it was incubated in homogenate of liver at 37 degrees C for 24 h. The results suggested that the liver plays a central role in biodegradation of CM-chitosan. The excellent biodegradability of CM-chitosan could potentially contribute to the clinical applications. The results also provide important clues for further modification of CM-chitosan as the postsurgical and other biomedical materials.

Investigation of the skin repair and healing mechanism of N-carboxymethyl chitosan in second-degree burn wounds

N‐carboxymethyl chitosan (NCMC) was synthesized with the modification of chitosan; the substitution degree was measured by titration. The biocompatibility and degradability of the NCMC were studied in vivo and the results showed that the NCMC was nontoxic and biocompatible. The in vivo degradation rate of NCMC in musculature was faster than that in subcutaneous tissue due to the relatively high lysozyme concentration. The NCMC was used as biomaterial to heal deep second‐degree burn wounds. The wound size reduction, histological examination, and the quantification of transforming growth factor‐β1, tumor necrosis factor‐α and interleukin‐8 protein levels, and Smad3 gene expression were measured to evaluate the healing effects. The results demonstrated that the NCMC was efficient in accelerating wound healing via activating transforming growth factor‐β1/Smad3 signaling pathway.

Effects of pH-sensitive chain length on release of doxorubicin from mPEG-b-PH-b-PLLA nanoparticles

Background Two methoxyl poly(ethylene glycol)-poly(L-histidine)-poly(L-lactide) (mPEG-PH-PLLA) triblock copolymers with different poly(L-histidine) chain lengths were synthesized. The morphology and biocompatibility of these self-assembled nanoparticles was investigated. Methods Doxorubicin, an antitumor drug, was trapped in the nanoparticles to explore their drug-release behavior. The drug-loaded nanoparticles were incubated with HepG2 cells to evaluate their antitumor efficacy in vitro. The effects of poly(L-histidine) chain length on the properties, drug-release behavior, and antitumor efficiency of the nanoparticles were investigated. Results The nanoparticles were pH-sensitive. The mean diameters of the two types of mPEG-PH- PLLA nanoparticle were less than 200 nm when the pH values were 5.0 and 7.4. The nanoparticles were nontoxic to NIH 3T3 fibroblasts and HepG2 cells. The release of doxorubicin at pH 5.0 was much faster than that at pH 7.4. The release rate of mPEG45-PH15-PLLA82 nanoparticles was much faster than that of mPEG45-PH30-PLLA82 nanoparticles at pH 5.0. Conclusion The inhibition effect of mPEG45-PH15-PLLA82 nanoparticles on the growth of HepG2 cells was greater than that of mPEG45-PH30-PLLA82 nanoparticles when the concentration of encapsulated doxorubicin was less than 15 μg/mL.

Functionalization of biodegradable hyperbranched poly(α,β-malic acid) as a nanocarrier platform for anticancer drug delivery

Multiple functionalization of nanoparticles has attracted great interest in drug delivery. In this paper, biodegradable poly(α,β-malic acid) with a hyperbranched architecture was synthesized via the polycondensation of L-malic acid, the functionalized poly(α,β-malic acid) was used as a nanocarrier platform with the immobilization of poly(ethylene glycol) (PEG) for long circulation, cinnamyl alcohol (CIN) for introducing π–π stacking interactions and 1-(3-aminopropyl)imidazole (API) for pH-sensitivity. The conjugates self-assembled into nanoparticles to load anticancer drug doxorubicin (DOX). The morphology, mean size and size distribution, drug release profile and in vitro anticancer activity of DOX loaded nanoparticles were studied. The results showed that the mean size of the nanoparticles was below 200 nm, the drug loading content was higher than 10 wt% and it increased with increasing CIN content because of the π–π stacking interaction between DOX and the carriers. The drug release of the nanoparticles was faster in the medium with pH 6.0 compared to pH 7.4. The nanoparticles exhibited an endosomal escape function to accelerate the release of DOX in cancer cells, which resulted in low IC50s to kill 4T1 breast cancer cells and HepG2 liver cancer cells in vitro.

Chain length effect on drug delivery of chrysin modified mPEG–PCL micelles

Four chrysin modified mPEG–PCL block copolymers with different chain lengths of mPEG and PCL blocks were synthesized and self-assembled into micelles to load the anticancer drug doxorubicin (DOX). The effect of block chain length on drug delivery was investigated. The four block copolymers were characterized by 1H NMR, GPC and DSC. The drug loading contents of all the micelles were higher than 20%, the mPEG2k–PCL5k–CHS micelles showed the highest drug loading content and encapsulation efficiency of 26.8% and 93%, respectively. The micelles were spherical with the size increasing after drug encapsulation, and the mean size of the drug loaded micelles was around 100 nanometers. π–π stacking interactions between the micelles and DOX was invoked. The mPEG2k–PCL5k–CHS micelles exhibited the best profile for sustained-release. The cellular uptake and IC50 revealed that the DOX loaded mPEG2k–PCL5k–CHS micelles showed the best anticancer activity in vitro.

Modulation of liver L-γ-glutamyl-L-cysteinylglycine homeostasis by N-acetyl-glucosamine-thiazolidine-4(R)-carboxylic acid in mice.

Abstract:The properties of modulating liver L-&ggr;-glutamyl-L-cysteinylglycine (GSH) homeostasis by thiazolidine derivative N-acetyl-glucosamine-thiazolidine-4(R)-carboxylic acid (GlcNAcCys) and the underlying mechanisms were investigated in L-buthionine-[S,R]-sulfoximine (BSO)-induced mice liver GSH depletion model. The data show that BSO (6 mmol/kg body weight; intraperitoneally) significantly decreased liver total sulfhydryl and GSH concentrations when compared with control. When mice were treated with different doses of GlcNAcCys (200, 400, 900 mg/kg body weight; intraperitoneally, respectively), total sulfhydryl and GSH concentrations were significantly increased when measured 6 hours after treatment. The activities of GSH-associated enzymes were also measured. Liver glutathione S-transferase (GST) activities were significantly decreased by BSO compared with the control, and GlcNAcCys significantly increased GST activity. Moreover, reverse-transcriptase polymerase chain reaction data indicated that GlcNAcCys could significantly induce glutamylcysteine ligase catalytic subunit c mRNA transcription. The mRNA levels of transcription factors c-jun and c-fos were increased by BSO administration but were decreased back to normal after the administration of GlcNAcCys. In a conclusion, GlcNAcCys can modulate liver GSH homeostasis, which may be related to its ability to induce glutamylcysteine ligase catalytic subunit transcription. GlcNAcCys has potential hepatoprotective properties by increasing GSH content, increasing GST activity.

Purification, characterization of Chondroitinase ABC from Sphingomonas paucimobilis and in vitro cardiocytoprotection of the enzymatically degraded CS-A

An extracellular chondroitinase ABC (ChSase ABC) produced by Sphingomonas paucimobilis was purified to homogeneity through ammonium sulfate precipitation, DEAE-Sepharose Fast Flow and Sephadex G-100 chromatography. The molecular weight was 82.3u202fkDa. It showed specific lyase activity toward chondroitin sulfate A (CS-A), CS-B, CS-C and hyaluronan (HA). Using CS-A as substrate, the specific activity was 98.04u202fU/mg, the maximal reaction rate (Vmax) and Michaelis-Menten constant (Km) were 0.49u202fμmol/min/ml and 0.79u202fmg/ml, respectively. Highest activity was obtained at pHu202f6.5 and 40u202f°C, and Hg2+ could strongly inhibit the enzyme activity. Mass spectrometry analysis indicated CS-A was degraded to unsaturated disaccharides by ChSase ABC. In vitro cytotoxic tests showed that CS-A oligosaccharide at the concentration of 50 and 100u202fμg/ml could promote the proliferation of normal H9c2 myocardial cells, decrease the damage induced by isoproterenol (ISO) and accelerate the recovery of cells injured by ISO. These findings suggested that ChSase ABC from Sphingomonas paucimobilis could be a promising tool for the structural analysis and bioactive oligosaccharide preparation of glucosaminoglycans.

Construction and characterization of Gal-chitosan graft methoxy poly (ethylene glycol) (Gal-CS-mPEG) nanoparticles as efficient gene carrier

In the present study, galactosylated chitosan (Gal-CS) was conjugated with methoxy poly(ethylene glycol) (mPEG) as a hydrophilic group. The structure of Gal-CS-mPEG polymer was characterized and the nanoparticles (NPs) were prepared using ironic gelation method. The study was designed to investigate the characteristics and functions of Gal-CS-mPEG NPs. The morphology of Gal-CS-mPEG NPs was observed by SEM and it was a compact and spherical shape. The size of the NPs was approximately 200 nm in diameter under the ideal process parameters. The interaction between Gal-CS-mPEG NPs and pDNA, and the protection of pDNA against DNase I and serum degradation by Gal-CS-mPEG NPs were evaluated. Agarose gel electrophoresis results showed that Gal-CS-mPEG NPs had strong interaction with pDNA at the weight ratio of 12:1, 4:1 and 2:1 and could protect pDNA from DNase I and serum degradation. Gal-CS-mPEG NPs exhibited high loading efficiency and sustainable in vitro release. The blood compatibility studies demonstrated that Gal-CS-mPEG NPs had superior compatibility with erythrocytes in terms of aggregation degree and hemolysis level. Gal-CS-mPEG NPs showed no cytotoxicity on L929 cells, which is a normal mouse connective tissue fibroblast, but showed inhibitory effects on the proliferation of Bel-7402 cells, which is a liver cancer cell line. In conclusion, Gal-CS-mPEG NP is a bio-safe and efficient gene carrier with potential application in gene delivery.

ARGININE- AND ACRYLONITRILE-MODIFIED CHITOSAN NANOPARTICLES FOR ANTICANCER DRUG DELIVERY

Chitosan (CS) is an excellent natural biodegradable and biocompatible polymer for biomedical applications, however, its poor solubility in water or organic solvents limits its applications in drug delivery. In order to resolve this problem, chitosan was modified with acrylonitrile (AN) and arginine (Arg), the modified chitosan (AN–CS–Arg) was characterized by 1H NMR and Fourier transform infrared (FTIR). The AN–CS–Arg was self-assembled into nanoparticles to encapsulate anticancer drug doxorubicin (DOX). The size and morphology of the blank and drug-loaded AN–CS–Arg (AN–CS–Arg/DOX) nanoparticles were measured by dynamic light scattering (DLS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The mean size of both blank and AN–CS–Arg/DOX nanoparticles were around 50 nm and 170 nm, respectively. The drug-loading content was about 12%. The release profile of AN–CS–Arg/DOX nanoparticles was investigated in vitro, 80% encapsulated DOX could be released within 80 h. The AN–CS–Arg nanoparticles were nontoxic to both NIH 3T3 fibroblasts and HepG2 cancer cells. The cellular uptake of the AN–CS–Arg nanoparticles was trafficked via Confocal Laser Scanning Microscopy and Flow Cytometry, both results showed that the AN–CS–Arg nanoparticles could be internalized in HepG2 cells efficiently. The IC50 of AN–CS–Arg/DOX nanoparticles to HepG2 cancer cells was 10.0 μg/mL. The AN–CS–Arg nanoparticles are potential carriers for anticancer drug delivery.