Guojun Song

Fabrication and characterization of nano-composite scaffold of PLLA/silane modified hydroxyapatite

In order to improve the interfacial connection of hydroxyapatite (HAP) to poly-l-lactic acid (PLLA), gamma-methacryloxypropyl-trimethoxysilane (gamma-MPS) was used as a coupling agent to modify the surface of nano-HAP (NHAP) particles. The FTIR and XPS results showed gamma-MPS was successfully bonded on the surface of NHAP. Silane modified nano-HAP (MNHAP) and PLLA were fabricated to nano-composite scaffold by a thermally induced phase separation method. The characterization of the composite scaffold showed that the scaffold had a nano-fibrous PLLA network (fiber size 100-800 nm), an interconnective microporous structure (1-8 microm) and high porosity (>90%). MNHAP was homogeneously distributed in the scaffold, also partly set in the nano-PLLA fibers. As a result, the compressive modulus and the protein adsorption of PLLA/MNHAP (80:20, w/w) composite scaffold increased to 4.2-fold and 2.8-fold compared with those of a pure PLLA scaffold. Incorporating MNHAP into PLLA network also buffered the pH reduction and reduced the weight loss in vitro degradation significantly.

Fabrication of PLLA/β-TCP nanocomposite scaffolds with hierarchical porosity for bone tissue engineering

Polymer and ceramic composite scaffolds play a crucial role in bone tissue engineering. In an attempt to mimic the architecture of natural extracellular matrix (ECM), poly(l-lactic acid)/β-tricalcium phosphate (PLLA/β-TCP) nanocomposite scaffolds with a hierarchical pore structure were fabricated by combining thermal induced phase separation and salt leaching techniques. The nanocomposite scaffold consisted of a nanofibrous PLLA matrix with a highly interconnected, high porosity (>93%) hierarchical pore structure with pore diameters ranging from 500nm to 300μm and a homogeneously distributed β-TCP nanoparticle phase. The nanofibrous PLLA matrix had a fiber diameter of 70-300nm. The nanocomposite scaffolds possess three levels of hierarchical structure: (1) porosity; (2) nanofibrous PLLA struts comprising the pore walls; and (3) β-TCP nanoparticle phase. The β-TCP nanoparticle phase improved the mechanical properties and bioactivity of the PLLA matrix. The nanocomposite scaffolds supported MG-63 osteoblast proliferation, penetration, and ECM deposition, indicating the potential of PLLA/β-TCP nanocomposite scaffolds with hierarchical porosity for bone tissue engineering applications.

Fabrication of Nano-fibrous PLLA Scaffold Reinforced with Chitosan Fibers

In this study, a nano-fibrous PLLA scaffold reinforced by micro-scale chitosan fibers was fabricated using thermally-induced phase separation (TIPS). The morphology, porosity, mechanical performance and pH changes in in vitro degradation of the scaffold were also investigated. Results showed that the mechanical properties of the scaffold increased with the amount of chitosan fibers embedded, and the pH in in vitro degradation of the scaffold changed more slowly than that of the pure nano-fibrous PLLA scaffold without chitosan fibers. The new composite scaffold might be a very promising scaffold for tissue engineering.

Fabrication of nano-fibrous poly(l-lactic acid) scaffold reinforced by surface modified chitosan micro-fiber

To mimic the fibrillar structure of natural extracellular matrix and optimize the chemical composition of the scaffold, a nano-fibrous poly(L-lactic acid) (PLLA) scaffold reinforced by surface modified chitosan micro-fiber (MCTSF) was fabricated using the thermally induced phase separation method. The composite scaffold has a novel structure comprised of a nano-matrix with reinforcing micro-fibers, in which the nano-fibrous PLLA matrix promotes cell adhesion and proliferation, while the MCTSF provides the mechanical support and adjusts the biocompatibility. The morphology of the composite scaffold showed a nano-fibrous PLLA matrix (100-500 nm fiber diameter), an interconnected microporous structure (1.0-8.0 μm pore size), and high porosity (>90%). MCTSF were homogeneously distributed in the composite scaffold and had intimate interactions with PLLA matrix. As a result, the compressive modulus of PLLA/MCTSF (100:40, w/w) increased 4.7-fold compared with that of a pristine PLLA scaffold. The prepared composite scaffold also showed good properties including buffering the acidic degradation of PLLA during in vitro degradation, enhanced protein adsorption capacity, and good cytocompatibility, suggesting that the PLLA/MCTSF composite scaffolds are potential candidate materials in tissue engineering.

Synthesis and flocculation performance of a chitosan-acrylamide-fulvic acid ternary copolymer

The flocculant made from natural polymers gained prominence in recent years due to its eco-friendliness and low cost. In this study, two natural polymers of chitosan and fulvic acid were successfully grafted with a synthetic monomer of acrylamide as a new type of flocculant. The prepared chitosan-acrylamide-fulvic acid (CAMFA) exhibited an excellent capacity to remove three typical dyes, the color removal ratios were 97.0%, 91.6%, and 38.2%, respectively, at the dosage of 283mg/L for 100mg/L of acid blue 113, reactive black 5 and methyl orange. The main flocculation mechanisms were charge neutralization and bridging effect. CAMFA showed nice flocculation performance with solubility in pure water, high removal efficiency, broad pH effectiveness scope, and a wide flocculation window. The ternary copolymer based on natural polymers is a promising candidate as a flocculant from the perspective of effectiveness, operation simplicity and cost.

Fabrication and biocompatibility of poly(l-lactic acid) and chitosan composite scaffolds with hierarchical microstructures

The scaffold microstructure is crucial to reconstruct tissue normal functions. In this article, poly(l-lactic acid) and chitosan fiber (PLLA/CTSF) composite scaffolds with hierarchical microstructures both in fiber and pore sizes were successfully fabricated by combining thermal induced phase separation and salt leaching techniques. The composite scaffolds consisted of a nanofibrous PLLA matrix with diameter of 50-500nm, and chitosan fibers with diameter of about 20μm were homogenously distributed in the PLLA matrix as a microsized reinforcer. The composite scaffolds also had high porosity (>94%) and hierarchical pore size, which were consisted of both micropores (50nm-10μm) and macropores (50-300μm). By tailoring the microstructure and chemical composition, the mechanical property, pH buffer and protein adsorption capacity of the composite scaffold were improved significantly compared with those of PLLA scaffold. Cell culture results also revealed that the PLLA/CTSF composite scaffolds supported MG-63 osteoblast proliferation and penetration.

The effect of fiber size and pore size on cell proliferation and infiltration in PLLA scaffolds on bone tissue engineering

The scaffold microstructure has a great impact on cell functions in tissue engineering. Herein, the PLLA scaffolds with hierarchical fiber size and pore size were successfully fabricated by thermal-induced phase separation or combined thermal-induced phase separation and salt leaching methods. The PLLA scaffolds were fabricated as microfibrous scaffolds, microfibrous scaffolds with macropores (50–350 µm), nanofibrous scaffolds with micropores (100 nm to 10 µm), and nanofibrous scaffolds with both macropores and micropores by tailoring selective solvents for forming different fiber size and pre-sieved salts for creating controlled pore size. Among the four kinds of PLLA scaffolds, the nanofibrous scaffolds with both macropores and micropores provided a favorable microenvironment for protein adsorption, cell proliferation, and cell infiltration. The results further confirmed the significance of fiber size and pore size on the biological properties, and a scaffold with both micropores and macropores, and a nanofibrous matrix might have promising applications in bone tissue engineering.

Preparation of pure chitosan film using ternary solvents and its super absorbency.

Chemical modification and graft copolymerization were commonly adopted to prepare super absorbent materials. However, physical microstructure of pure chitosan film was optimized to improve the water uptake capacity in this study. Chitosan films with micro-nanostructure were prepared by a ternary solvent system. The optimal process parameters are 1% acetic acid water solution: dioxane: dimethyl sulfoxide=90: 2.5: 7.5 (v/v/v) with chitosan concentration at 1.25% (w/v). The water uptake capacity of the chitosan film prepared under the optimal process parameters was 896g/g. The prepared chitosan films also exhibited high water uptake capacity in response to external stimuli such as temperature, pH and salt. This finding may provide another way for improving the water absorbency. The pure chitosan film may find potential applications especially in the fields of hygienic products and biomedicine due to its super water absorbency and nontoxicity.