Changren Zhou

Chitosan–halloysite nanotubes nanocomposite scaffolds for tissue engineering

This work developed novel chitosan-halloysite nanotubes (HNTs) nanocomposite (NC) scaffolds by combining solution-mixing and freeze-drying techniques, and aimed to show the potential application of the scaffolds in tissue-engineering. The hydrogen bonding and electrostatic attraction between chitosan and HNTs were confirmed by spectroscopy and morphology analysis. The interfacial interactions resulted in a layer of chitosan absorbed on the surfaces of HNTs. The determination of mechanical and thermal properties demonstrated that the NC scaffolds exhibited significant enhancement in compressive strength, compressive modulus, and thermal stability compared with the pure chitosan scaffold. But the NC scaffolds showed reduced water uptake and increased density by the incorporation of HNTs. All the scaffolds exhibited a highly porous structure and HNTs had nearly no effect on the pore structure and porosity of the scaffolds. In order to assess cell attachment and viability on the materials, NIH3T3-E1 mouse fibroblasts were cultured on the materials. Results showed that chitosan-HNTs nanocomposites were cytocompatible even when the loading of HNTs was 80%. All these results suggested that chitosan-HNTs NC scaffolds exhibited great potential for applications in tissue engineering or as drug/gene carriers.

Functionalized halloysite nanotube by chitosan grafting for drug delivery of curcumin to achieve enhanced anticancer efficacy

Halloysite nanotubes (HNTs) have a unique tubular structure in nanoscale, and have shown potential as novel carriers for various drugs. Coating the nanotubes with a hydrophilic polymer shell can significantly decrease the toxicity and provide colloidal stability during blood circulation. Here, we synthesized chitosan grafted HNTs (HNTs-g-CS) and investigated their potential as a nano-formulation for the anticancer drug curcumin. The structure and properties of HNTs-g-CS were characterized using water contact angle, zeta-potential, Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and transmission electron microscopy (TEM) techniques. HNTs-g-CS exhibit a maximum 90.8% entrapment efficiency and 3.4% loading capacity of curcumin, which are higher than those of raw HNTs. HNTs-g-CS also show no obvious hemolytic phenomenon and good stability in serum. The cumulative release ratio of curcumin from HNTs-g-CS/curcumin at cell lysate after 48 hours is 84.2%. The curcumin loaded HNTs-g-CS show specific toxicity to various cancer cell lines, including HepG2, MCF-7, SV-HUC-1, EJ, Caski and HeLa, and demonstrate an inhibition concentration of IC50 at 5.3-192 μM as assessed by cytotoxicity studies. The anticancer activity of this nanoformulation is extremely high in EJ cells compared with the other cancer cell lines. The cell uptake of HNTs-g-CS is confirmed by fluorescence microscopy. Flow cytometric analysis of curcumin loaded HNTs-g-CS shows that curcumin loaded HNTs-g-CS increase apoptosis on EJ cells. The content of ROS created by HNTs-g-CS/curcumin is more than that of free curcumin. All these results suggest that HNTs-g-CS are potential nanovehicles for anticancer drug delivery in cancer therapy.

In vitro evaluation of alginate/halloysite nanotube composite scaffolds for tissue engineering

In this study, a series of alginate/halloysite nanotube (HNTs) composite scaffolds were prepared by solution-mixing and freeze-drying method. HNTs are incorporated into alginate to improve both the mechanical and cell-attachment properties of the scaffolds. The interfacial interactions between alginate and HNTs were confirmed by the atomic force microscope (AFM), transmission electron microscope (TEM) and FTIR spectroscopy. The mechanical, morphological, and physico-chemical properties of the composite scaffolds were investigated. The composite scaffolds exhibit significant enhancement in compressive strength and compressive modulus compared with pure alginate scaffold both in dry and wet states. A well-interconnected porous structure with size in the range of 100-200μm and over 96% porosity is found in the composite scaffolds. X-ray diffraction (XRD) result shows that HNTs are uniformly dispersed and partly oriented in the composite scaffolds. The incorporation of HNTs leads to increase in the scaffold density and decrease in the water swelling ratio of alginate. HNTs improve the stability of alginate scaffolds against enzymatic degradation in PBS solution. Thermogravimetrica analysis (TGA) shows that HNTs can improve the thermal stability of the alginate. The mouse fibroblast cells display better attachment to the alginate/HNT composite than those to the pure alginate, suggesting the good cytocompatibility of the composite scaffolds. Alginate/HNT composite scaffolds exhibit great potential for applications in tissue engineering.

Stripe-like Clay Nanotubes Patterns in Glass Capillary Tubes for Capture of Tumor Cells

Here, we used capillary tubes to evaporate an aqueous dispersion of halloysite nanotubes (HNTs) in a controlled manner to prepare a patterned surface with ordered alignment of the nanotubes . Sodium polystyrenesulfonate (PSS) was added to improve the surface charges of the tubes. An increased negative charge of HNTs is realized by PSS coating (from -26.1 mV to -52.2 mV). When the HNTs aqueous dispersion concentration is higher than 10%, liquid crystal phenomenon of the dispersion is found. A typical shear flow behavior and decreased viscosity upon shear is found when HNTs dispersions with concentrations higher than 10%. Upon drying the HNTs aqueous dispersion in capillary tubes, a regular pattern is formed in the wall of the tube. The width and spacing of the bands increase with HNTs dispersion concentration and decrease with the drying temperature for a given initial concentration. Morphology results show that an ordered alignment of HNTs is found especially for the sample of 10%. The patterned surface can be used as a model for preparing PDMS molding with regular micro-/nanostructure. Also, the HNTs rough surfaces can provide much higher tumor cell capture efficiency compared to blank glass surfaces. The HNTs ordered surfaces provide promising application for biomedical areas such as biosensors.

In vitro evaluation of random and aligned polycaprolactone/gelatin fibers via electrospinning for bone tissue engineering.

Scaffold, as an essential element of tissue engineering, should provide proper chemical and structural cues to direct tissue regeneration. In this study, aligned and random polycaprolactone (PCL)/gelatin fibrous scaffolds with different mass ratio were electrospun. Chemical, structural, and mechanical properties of PCL/gelatin fibrous scaffolds were characterized by FTIR and tensile measurements. The average diameters of different groups were between 334.96u2009±u200941.43u2009nm and 363.78u2009±u200950.49u2009nm. Blending PCL with gelatin increased the mechanical properties of the scaffolds. The cell culture results demonstrated that the mass ratio of PCL and gelatin showed no obvious effects on cell behavior, whereas the cell growth behavior was affected by the fibers orientation. Higher elongation ratio, enhanced cell proliferation and elevated alkaline phosphatase activity were observed for cells cultured on aligned fibers. The findings in our research provide insightful information for the design and fabrication of scaffolds for bone tissue engineering.

A surface molecularly imprinted electrospun polyethersulfone (PES) fiber mat for selective removal of bilirubin

Electrospinning has been widely recognized as a facile and scalable method for fabricating fibrous materials, which could be used as adsorption materials because of their high surface area. Surface molecular imprinting based on adsorption materials has shown excellent adsorption performance, including large binding capacity, a fast adsorption rate and selective adsorption. In this study, electrospinning and surface molecular imprinting were used together to prepare a surface molecularly imprinted electrospun polyethersulfone (PES) fiber mat (PES@MIP). The mat was prepared by self-polymerization of dopamine (as a functional monomer) on the electrospun PES fiber mat surface in weak alkaline aqueous solution in the presence of a template, bilirubin. The results indicated that a polydopamine coating was formed on the PES fiber mat surface successfully, and the template bilirubin could be removed. The adsorption performance of PES@MIP was investigated in detail, showing a higher adsorption capacity (184.24 mg g-1), faster adsorption kinetics and a short adsorption equilibrium time of 2 h, as well as a good selectivity toward bilirubin with an imprinting factor (IF) of 1.4. In addition, the selectivity coefficient (α) of PES@MIP toward cholesterol and testosterone could be calculated to be 1.11 and 1.43. Also, both adsorption kinetic and isotherm models were used to analyze the adsorption process. Besides, the dynamic adsorption indicated that PES@MIP adsorbed much more bilirubin, and had a shorter equilibrium time of about 40 minutes for bilirubin removal. In addition, PES@MIP had a much lower hemolysis ratio and exhibited a little anticoagulant property compared to the original PES fiber mat. Therefore, this work provided a new strategy to build practical PES@MIP for bilirubin adsorption.

Rapid biomimetic mineralization of collagen fibrils and combining with human umbilical cord mesenchymal stem cells for bone defects healing.

Collagen biomineralization is regulated by complicated interactions between the collagen matrix and non-collagenous extracellular proteins. Here, the use of sodium tripolyphosphate to simulate the templating functional motif of the C-terminal fragment of non-collagenous proteins is reported, and a low molecular weight polyacrylic acid served as a sequestration agent to stabilize amorphous calcium phosphate into nanoprecursors. Self-assembled collagen fibrils served as a fixed template for achieving rapid biomimetic mineralization in vitro. Results demonstrated that, during the mineralization process, intrafibrillar and extrafibrillar hydroxyapatite mineral with collagen fibrils formed and did so via bottom-up nanoparticle assembly based on the non-classical crystallization approach in the presence of these dual biomimetic functional analogues. In vitro human umbilical cord mesenchymal stem cell (hUCMSC) culture found that the mineralized scaffolds have a better cytocompatibility in terms of cell viability, adhesion, proliferation, and differentiation into osteoblasts. A rabbit femoral condyle defect model was established to confirm the ability of the n-HA/collagen scaffolds to facilitate bone regeneration and repair. The images of gross anatomy, MRI, CT and histomorphology taken 6 and 12weeks after surgery showed that the biomimetic mineralized collagen scaffolds with hUCMSCs can promote the healing speed of bone defects in vivo, and both of the scaffolds groups performing better than the bone defect control group. As new bone tissue formed, the scaffolds degraded and were gradually absorbed. All these results demonstrated that both of the scaffolds and cells have better histocompatibility.

In vitro degradation and cytocompatibility of g-MgO whiskers/PLLA composites

In vitro degradation properties and cytocompatibility of surface-grafted magnesia whiskers/poly(l-lactide) (g-MgO–Ws/PLLA) composite films which obtained by solution casting method were studied in this work. In vitro degradation experiments of the samples were carried out in a PBS solution at 37xa0°C with a pH of 7.4. Changes in weight, pH value, crystallization and melting behaviors, surface morphology and chemical composition, and tensile property of the g-MgO–Ws/PLLA composite films with the degradation time were characterized, from which the related degradation mechanism of the composite was concluded. Results showed that the weight loss of the g-MgO–Ws/PLLA composite films was slightly higher than that of the neat PLLA. The alkaline g-MgO–Ws can neutralize the acidity of degradation products of PLLA to some extent and maintain the tensile properties of the films well in the early degradation stage compared with neat PLLA. With the degradation, the crystallinity of PLLA matrix increased first and then decreased. In vitro cell culture results, based on the optical density value, alkaline phosphate (ALP) activity measurement, field emission scanning electron microscope, and confocal laser scanning microscopy observation, revealed that the g-MgO–Ws/PLLA composite films were not only in favor of cells adhesion, spreading, and proliferation, but also can significantly upregulate the ALP activity and promote the osteogenic differentiation of MC3T3-E1 cells compared with the neat PLLA film.

Liposomes coated with thiolated chitosan as drug carriers of curcumin

Liposome is one of a promising delivery system to improve water solubility, stability, and bioavailability of curcumin. But its instability is not favorable for long-circulating treatment, controlled release or conservation. To overcome the disadvantages, thiol derivatised chitosan (CSSH) were synthesized and utilized to coat liposomes. The CSSH coated curcumin liposomes (Cur-Lip-CSSH) had an encapsulation efficiency (EE) of 93.95%, a drug loading (DL) of 7.95%, an average particle size of 406.0nm, and a positive zeta-potential of 36.6mV, which were all higher than that of Cur-Lip. Cur-Lip-CSSH showed slower in vitro release than Cur-Lip at pH5.5 and pH7.4, and the higher retention of curcumin would be remained for the following uptake of cells. The stability of the both liposomes at 4°C was almost the same, but Cur-Lip-CSSH displayed a higher stability at room temperature and higher temperature by DSC characterization. Curcumin can inhibit the growth of cancer cells under certain conditions. MCF-7 cell line was used to study its inhibition and proliferation after treating with curcumin and Cur-Lip-CSSH. Treatment of MCF-7 with curcumin and Cur-Lip-CSSH showed dose and time dependent cytotoxicity, with growth suppression at 200μM, 72h, obviously. These results indicate that the proper coating of liposomes is able to improve the stability of liposomes and the Lip-CSSH can function as potential drug delivery system.

Polyethyleneimine grafted short halloysite nanotubes for gene delivery

Inorganic nanoparticles have attracted much attentions in gene delivery because of their desirable characteristics including low toxicity, well-controlled characteristics, high gene delivery efficiency, and multi-functionalities. Here, natural occurred halloysite nanotubes (HNTs) were developed as a novel non-viral gene vector. To increase the efficiency of endocytosis, HNTs were firstly shortened into an appropriate size (~200nm). Then polyethyleneimine (PEI) was grafted onto HNTs to bind green fluorescence protein (GFP) labeled pDNA. The structure and physical-chemical properties of PEI grafted HNTs (PEI-g-HNTs) were characterized by various methods. PEI-g-HNTs show lower cytotoxicity than PEI. PEI-g-HNTs are positively charged and can bind DNA tightly at designed N/P ratio from 5:1 to 40:1. PEI-g-HNTs/pDNA complexes show much higher transfection efficiency towards both 293T and HeLa cells compared with PEI/pDNA complexes at the equivalent N/P ratio. The transfection efficiencies of PEI-g-HNTs/pDNA complex towards HeLa cell can reach to 44.4% at N/P ratio of 20. PEI-g-HNTs/pDNA complexes possess a higher GFP protein expression than PEI/pDNA from simple western immunoblots. So, PEI-g-HNTs are potential gene vectors with good biocompatibility and high transfection efficiency, which have promising applications in cancer gene therapy.