Ya Liu

Folate-modified-chitosan-coated liposomes for tumor-targeted drug delivery

In this study, a folate-modified–chitosan-coated liposome (FCCL) was prepared for tumor-targeted drug delivery. The folate–chitosan conjugates were characterized using 1H NMR and infrared spectrum analysis. The properties of folate–chitosan-coated liposomes (FCCLs) were studied and compared with those of traditional liposomes and chitosan-coated liposomes (CCLs). FCCLs were spherical in shape with a classic core–shell structure. Compared with conventional liposomes, FCCLs had larger size (average diameter: 182.0xa0nm), higher zeta potential (10.1xa0mV), prolonged drug release behaviors (55.76xa0% after 24xa0h), and better physical stability when stored at 25xa0°C, all similar to the properties of CCLs. With fluorescein as a model drug, fluorescein-loaded liposomes, CCLs, and FCCLs were prepared and their tumor targeting ability was evaluated according to the in vitro cellular uptake of fluorescein loaded nanoparticles by MCF-7 and HUVEC cells. Results demonstrated that FCCLs had a significant higher uptake by folate receptor positive cells (MCF-7) as compared to traditional liposomes and CCLs, which indicated that the FCCLs were promising nano-carriers for tumor-targeted drug delivery.

Hydroxybutyl chitosan thermo-sensitive hydrogel: a potential drug delivery system

Drug delivery mediated by hydrogel has shown great promise in controlled drug release field. We report here the development of a hydroxybutyl chitosan (HBC) thermo-sensitive gel to deliver doxorubicine hydrochloride (DOX·HCl) for cancer treatment. Concentrated HBC aqueous solution could transform into hydrogel within 30xa0s after injection under physiological temperature in non-chemical fashion. The properties of the HBC gels including chemical structure, surface morphology, and rheologic properties were studied. Gelation temperature and gelation time of HBC could be adjusted by HBC concentrations. The gel erosion rate in vivo was faster than solubilization rate in vitro. The mild inflammatory response caused by implantation of the hydrogel was acceptable. The DOX·HCl (1xa0mg/ml) loaded HBC gels displayed slow release rates that were independent of the HBC concentration, and significantly reduced viability of 4T-1 cells compared with the HBC gels after 1xa0day incubation. These results indicate that thermo-sensitive HBC hydrogels have promising potential as an injectable drug carrier for pharmaceutical applications.

Surface charge effect on mucoadhesion of chitosan based nanogels for local anti-colorectal cancer drug delivery

To develop more effective anticancer mucoadhesive drug delivery system for the treatment of colorectal cancer, chitosan based nanogels (NGs) were prepared by electrostatic interaction between chitosan (CS) and carboxymethyl-chitosan (CMCS). By respectively using tripolyphosphate (TPP) and CaCl2 as ionic crosslinker, two well-characterized doxorubicin hydrochloride (DOX) loaded NGs with opposite zeta potential (DOX:CS/CMCS/TPP NGs, -32.6±1.1 mV and DOX:CS/CMCS/Ca2+ NGs, +31.8±0.9 mV) were obtained. Compared with DOX:CS/CMCS/TPP NGs, DOX:CS/CMCS/Ca2+ NGs were taken up to a greater extent by colorectal cancer cells, resulting in greater reduction in percentage of cell viability. Owing to high binding capability to mucin and inhibited paracellular transport by colon, DOX:CS/CMCS/Ca2+ NGs exhibited improved mucoadhesion and limited permeability. This is beneficial to prolong the contact time of formulation onto intestinal mucosa and improved local drug concentration. The results provided evidence DOX:CS/CMCS/Ca2+ NGs to be exciting and promising for the treatment of colorectal cancer.

Biocompatibility, cellular uptake and biodistribution of the polymeric amphiphilic nanoparticles as oral drug carriers

Oleoyl-carboxymethyl-chitosan (OCMCS) was synthesized and were soluble at neutral pH. The critical micelle concentration (CMC) of OCMCS in deionized water was 0.021 mg/ml. OCMCS nanoparticles were successfully prepared via self-assembly with mean diameter of 215.34 nm, zeta potential of 19.26 mV and an almost spherical shape as determined by electron microscopy. The OCMCS nanoparticles showed low erythrocyte membrane-damaging effect. The MTT survival assay indicated no significant cytotoxicity to Caco-2 cells and MEFs cells. The uptake of FITC labeled OCMCS nanoparticles by Caco-2 cells was confirmed via confocal laser scanning microscope (CLSM). In vivo toxicity assays were performed via histopathological evaluation, and no specific anatomical pathological changes or tissue damage was observed in the tissues of carps. The extent of tissue distribution and retention following oral administration of FITC-OCMCS nanoparticles was analyzed for 3 days. After 3 days, the nanoparticles remained detectable in the muscle, heart, kidney, liver, intestine, and spleen. The results showed that 34.32% of the particles were localized in the liver, 18.79% in the kidney, and 17.36% in the heart. The lowest percentage was observed in the muscle. These results implied that OCMCS nanoparticles had great potential to be applied as safe carriers for the oral administration of protein drugs.

Positive/negative surface charge of chitosan based nanogels and its potential influence on oral insulin delivery.

To develop insulin delivery system for the treatment of diabetes, two insulin-loaded nanogels with opposite zeta potential (-15.94 ± 0.449 mV for insulin:CMCS/CS-NGs(-) and +17.15 ± 0.492 mV for insulin:CMCS/CS-NGs(+)) were obtained. Ex vivo results showed that the nanogels with opposite surface charge exhibited different adhesion and permeation in specific intestinal segments. There was no significant differences in adhesion and permeation in rat duodenum, but in rat jejunum, insulin:CMCS/CS-NGs(-) exhibited enhanced adhesion and permeation, which were about 3 folds (adhesion) and 1.7 folds (permeation) higher than insulin:CMCS/CS-NGs(+). These results demonstrated that the surface charge property of nanogels determined the absorption sites of CMCS/CS-NGs in small intestine. In vivo study, the blood glucose level in insulin:CMCS/CS-NGs(-) group had 3 mmol/L lower than insulin:CMCS/CS-NGs(+) group during 1h to 11h after the oral administration, which demonstrated that negative insulin:CMCS/CS-NGs had a better management of blood glucose than positive ones.

Preparation and evaluation of oleoyl-carboxymethy-chitosan (OCMCS) nanoparticles as oral protein carriers.

Oleoyl-carboxymethy chitosan (OCMCS) nanoparticles based on chitosan with different molecular weights (50, 170 and 820xa0kDa) were prepared by self-assembled method. The nanoparticles had spherical shape, positive surface charges and the mean diameters were 157.4, 274.1 and 396.7xa0nm, respectively. FITC-labeled OCMCS nanoparticles were internalized via the intestinal mucosa and observed in liver, spleen, intestine and heart following oral deliverance to carps (Cyprinus carpio). Extracellular products (ECPs) of Aeromonas hydrophila as microbial antigen was efficiently loaded to form OCMCS–ECPs nanoparticles and shown to be sustained release in PBS. Significantly higher (Pxa0<xa00.05) antigen-specific antibodies were detected in serum after orally immunized with OCMCS-ECPs nanoparticles than that immunized with ECPs alone and non-immunized in control group in carps. These results implied that amphiphilic modified chitosan nanoparticles had great potential to be applied as carriers for the oral administration of protein drugs.

In vitro evaluation of mucoadhesion and permeation enhancement of polymeric amphiphilic nanoparticles.

Oleoyl-carboxymethy-chitosan (OCMCS) nanoparticles based on chitosan with various molecular weights were prepared using coacervation process, which demonstrated particle size of 150-350 nm, zeta potential of 10-20 mV, and high encapsulation efficiency of fluorescein isothiocyanate dextran (FD4). OCMCS nanoparticles were found to be adsorbed onto the excised carp intestinal mucosa, the extent of adsorption increased with increasing chitosan molecular weight. In comparison to FD4 solution, OCMCS nanoparticles promoted FD4 transport through excised carp intestinal mucosa by 3.26-6.52 folds, which were observed via fluorescence microscope. The OCMCS nanoparticulate systems that interacted with the Caco-2 cells decreased the transepithelial electric resistance (TEER) and induced increasing the apparent permeability coefficient (Papp) of FD4 by 3.61-6.32 folds. Cytotoxicity studies in Caco-2 monolayers verified the safety of the delivery system. The improvement of mucoadhesive ability and permeability enable the OCMCS nanosystems suitable carriers for the intestinal absorption of protein drugs.

Biomaterials based on N,N,N-trimethyl chitosan fibers in wound dressing applications.

In the present work, N,N,N-trimethyl chitosan (TMC) fibers were synthesized successfully and the resulting quaternized materials were characterized by FTIR. The designed TMC fibers with different degree of quaternization achieved high water absorption capability. In antibacterial activity study, TMC fibers showed high antibacterial activity than chitosan fibers against the gram-negative bacteria Escherichia coli (>63%) and gram-positive bacteria Staphylococcus aureus (>99%). TMC fibers exhibited no obvious cytotoxicity to mouse embryo fibroblast cells with low extraction concentrations (<0.05g/mL). In animal wound healing test, TMC2 fibers could significantly enhance wound re-epithelialization and contraction compared with the control (chitosan fibers). In conclusion, TMC fibers have a potential to be used as wound dressing materials.

Surface fluid-swellable chitosan fiber as the wound dressing material.

The objective of this study was to develop a novel surface fluid-swellable chitosan (SFSC) fiber for potential wound dressing. The SFSC fiber was successfully prepared by surface modification of chitosan fiber with succinic anhydride, which was characterized by FTIR and solid-state (13)C NMR. The SFSC fiber exhibited better water absorption capacity (approx. 2980%) and stronger antibacterial activities (both above 90%) against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) than chitosan fiber (both below 75%). The cell viability was more than 90% after treated with the SFSC fiber extract, which demonstrated that SFSC fiber had low cytotoxicity towards mouse embryo fibroblasts (MEFs). The SFSC fiber could promote wound healing with advanced development of granulation tissue and epithelial coverage compared with the control (gauze-covered) group. The results indicated that SFSC fiber had great potential to be used as wound dressing material.

Investigation of gelling behavior of thiolated chitosan in alkaline condition and its application in stent coating

The gelling behaviors of thiolated chitosan (TCS) in alkaline condition were investigated. Thioglycolic acid was conjugated onto chitosan backbone through amide bond formation. The variations of thiol group content were monitored in presence of H2O2 or different pH values (pH 7.0, 8.0, 9.0) in dialysis mode. Different from the decreasing thiol group content upon time in acidic condition, increasing amount of thiol groups was detected in alkaline pH during 120 min dialysis attributed to alkaline hydrolysis of intra-molecular disulfide bonds. The extent of which was larger at higher pH values. Higher degree of thiolation, thiomer concentration or pH values promoted gelation of TCS. Entanglement and coagulation of chitosan molecule chains and re-arrangement of disulfide bonds acted closely and dynamically in the gelation process. Disulfide bonds, especially inter-molecular type, are formed by synergetic effects of thiol/disulfide interchange and thiol/thiol oxidation reactions. TCS coated vascular stent displayed wave-like microstructure of parallel ridges and grooves, which favored HUVECs adhesion and proliferation. The biocompatibility, peculiar morphology and thiol moieties of TCS as stent coating material appear application potential for vascular stent.