Mingxian Liu

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.

Chitosan/halloysite nanotubes bionanocomposites: Structure, mechanical properties and biocompatibility

Incorporation of nanosized reinforcements into chitosan usually results in improved properties and changed microstructures. Naturally occurred halloysite nanotubes (HNTs) are incorporated into chitosan for forming bionanocomposite films via solution casting. The electrostatic attraction and hydrogen bonding interactions between HNTs and chitosan are confirmed. HNTs are uniformly dispersed in chitosan matrix. The tensile strength and Youngs modulus of chitosan are enhanced by HNTs. The storage modulus and glass transition temperature of chitosan/HNTs films also increase significantly. Blending with HNTs induces changes in surface nanotopography and increase of roughness of chitosan films. In vitro fibroblasts response demonstrates that both chitosan and chitosan/HNTs nanocomposite films are cytocompatibility even when the loading of HNTs is 10%. In summary, these results provide insights into understanding of the structural relationships of chitosan/HNTs bionanocomposite films in potential applications, such as scaffold materials in tissue engineering.

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.

Chitin-natural clay nanotubes hybrid hydrogel

Novel hybrid hydrogel was synthesized from chitin NaOH/urea aqueous solution in presence of halloysite nanotubes (HNTs) via crosslinking with epichlorohydrin. Fourier transform infrared (FT-IR) spectra and atomic force microscopy (AFM) results confirmed the interfacial interactions in the chitin-HNTs hybrid hydrogel. The compressive strength and shear modulus of chitin hydrogel were significantly increased by HNTs as shown in the static compressive experiment and rheology measurement. The hybrid hydrogels showed highly porous microstructures by scanning electron microscopy (SEM). The swelling ratio of chitin hydrogel decreased because of the addition of HNTs. The malachite greens absorption experiment result showed that the hybrid hydrogel exhibited much higher absorption rate than the pure chitin hydrogel. The prepared hybrid hydrogel had potential applications in waste treatment and biomedical areas.

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.

Electrospun composite nanofiber membrane of poly(l-lactide) and surface grafted chitin whiskers: Fabrication, mechanical properties and cytocompatibility.

To improve both the mechanical properties and cytocompatibility of poly(l-lactide) (PLLA), rod-like chitin whiskers (CHWs) were prepared, and subsequently surface modified with l-lactide to obtain grafted CHWs (g-CHWs). Then, CHWs and g-CHWs were further introduced into PLLA matrix to fabricate CHWs/PLLA and g-CHWs/PLLA nanofiber membranes by electrospinning technique. Morphologies and properties of the CHWs and g-CHWs were characterized. The surface-grafted PLLA chains played an important role in improving interfacial interaction between the whiskers and PLLA matrix. The g-CHWs dispersed more uniformly in matrix than CHWs, and the as-prepared g-CHWs/PLLA nanofiber membrane showed relative smooth and uniform fiber. As a result, the tensile strength and modulus of the g-CHWs/PLLA nanofiber membrane were obviously superior to those of the pure PLLA and CHWs/PLLA nanofiber membranes. Cells culture results indicated that g-CHWs/PLLA nanofiber membrane is more effectively in promoting MC3T3-E1 cells adhesion, spreading and proliferation than pure PLLA and CHWs/PLLA nanofiber membrane.

Tough and highly stretchable polyacrylamide nanocomposite hydrogels with chitin nanocrystals

Chitin nanocrystals (CNCs) that were 10-20 nm wide and 100-500 nm long were synthetized via acidolysis and characterized with various methods. To avoid the flocculation of CNCs in the initiator solution during acrylamide polymerization, chitosan was selected as a surface modifier. The chitosan-modified CNCs were employed as multifunctional crosslinkers for the polyacrylamide (PAAm) nanocomposite (NC) hydrogels. The NC gels were tough and stretchable; for example, the maximum tensile strength and the elongation at break of the NC gels were 90 kPa and 3070%, respectively. The dynamic shear modulus of the NC gels was also significantly higher than that of the PAAm. The NC gels were nearly free of residual strain after 2000% elongation. The microstructures of all NC gels were porous, with a pore size of 20-100 μm. The maximum equilibrium swelling degree of the NC gels was 3800%. The improvement in the properties of the NC gels is attributed to the good dispersion of CNCs and the interfacial interactions in the composites. This work developed PAAm NC hydrogels with CNCs for application as absorbent or biomedical material due to the high mechanical properties, high absorb ability and good biocompatibility of CNCs and explored new applications for CNCs as well.

Chitosan-chitin nanocrystal composite scaffolds for tissue engineering.

Chitin nanocrystals (CNCs) with length and width of 300 and 20nm were uniformly dispersed in chitosan (CS) solution. The CS/CNCs composite scaffolds prepared utilizing a dispersion-based freeze dry approach exhibit significant enhancement in compressive strength and modulus compared with pure CS scaffold both in dry and wet state. A well-interconnected porous structure with size in the range of 100-200μm and over 80% porosity are found in the composite scaffolds. The crystal structure of CNCs is retained in the composite scaffolds. The incorporation of CNCs leads to increase in the scaffold density and decrease in the water swelling ratio. Moreover, the composite scaffolds are successfully applied as scaffolds for MC3T3-E1 osteoblast cells, showing their excellent biocompatibility and low cytotoxicity. The results of fluorescent micrographs images reveal that CNCs can markedly promote the cell adhesion and proliferation of the osteoblast on CS. The biocompatible composite scaffolds with enhanced mechanical properties have potential application in bone tissue engineering.

Antibacterial activity and cytocompatibility of chitooligosaccharide-modified polyurethane membrane via polydopamine adhesive layer

The aim of this study was to provide a convenient surface modification method for polyurethane (PU) membrane and evaluate its influence on hydrophilicity, antibacterial activity and cell functions, which are the most important factors for wound dressings. For this purpose, chitooligosaccharide (COS) was modified onto the surface of PU membrane based on the self-polymerization of dopamine (DOPA). Surface composition, morphology, hydrophilicity and surface energy of the original and modified PU membranes were characterized. Surface roughness and hydrophilicity of the PU membrane were obviously increased by modified with polydopamine (PDOPA) and COS. Antibacterial experiment against Escherichia coli and Staphylococcus aureus indicated that antibacterial activity of PU membrane increased only slightly by modified with PDOPA, but increased significantly by further modified with COS. Cells culture results revealed that COS-functionalized PU membrane is more beneficial to the adhesion and proliferation of NIH-3T3 cells compared to the original and PDOPA-modified PU membranes.