Sequential delivery of chlorhexidine acetate and bFGF from PLGA-glycol chitosan core-shell microspheres.

Wound treatment should meet the challenge both of preventing infection and promoting wound healing. To design a sequential delivery system for wound healing, PLGA-glycol chitosan (GC) core-shell microspheres containing chlorhexidine acetate (CHA) at the GC shell and bFGF in the core of PLGA microspheres were fabricated using emulsion-solvent evaporation method. SEM showed that the microspheres were all spherical in shape with a smooth surface. The average size of PLGA-GC microspheres increased due to the GC coating on the surface. The results of release profiles and fluorescence images indicated that PLGA-GC microspheres had an ability to deliver drugs in sequence. The CHA was rapidly released, whereas the proteins presented a sustained release. The release behavior could be modulated by changing the GC amount. Antibacterial assay and cell proliferation tests suggested that the released CHA and bFGF retained their antimicrobial activity and bioactivity during preparation. The microspheres exhibited non-cytotoxicity against 3T3 cells and had a good biocompatibility. These results demonstrated that PLGA-GC core-shell microspheres could be a promising controlled release system of delivering drugs and proteins in sequence for wound healing.

Fish collagen-based scaffold containing PLGA microspheres for controlled growth factor delivery in skin tissue engineering.

To design a scaffold controlled release system for skin tissue engineering, fish collagen/chitosan/chondroitin sulfate scaffolds were fabricated by freeze-drying and incorporated with bFGF-loaded PLGA microspheres (MPs). SEM showed that the scaffolds exhibited an interconnected porous structure, and the spherical MPs were uniformly distributed into the scaffolds. The higher swelling and degradation rate of scaffolds/MPs could lead to a higher diffusion rate of MPs from the scaffolds, causing an increase in the protein release. The release rate of proteins could be adjusted by the size of MPs and the ratio of collagen to chitosan of scaffolds. Circular dichroism spectroscopy and MTT of bFGF after release indicated that the released bFGF retained its structural integrity and bioactivity during preparation. Cell proliferation and in vivo evaluation results suggested that the scaffolds/MPs had a good biocompatibility and an ability to promote fibroblast cell proliferation and skin tissue regeneration. These results demonstrated that this scaffold/MP controlled release system has the potential for skin tissue engineering.

Preparation and biological evaluation of chitosan-collagen-icariin composite scaffolds for neuronal regeneration.

In this study the chitosan/collagen/icariin composite scaffolds for nerve regeneration were produced by blending and crosslinking chitosan with collagen and icariin. The microstructure of the composite scaffolds was observed by scanning electron microscopy. 3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide and attachment assays were conducted, respectively, to investigate the biocompatibility of the scaffolds. Cell cultural tests showed that the channel-structured porous scaffolds acted as a positive factor to support connective nerve cell growth. After culture, cells showed a clear flow trend to move close to the composite scaffolds in culture solution, arranging in spiral-like, and aligned parallel to the orientation of the channel structure on the surface of scaffolds. When compared to pure chitosan and chitosan/collagen scaffolds, Schwann cells and PC12 cells on the chitosan/collagen/icariin composite scaffolds exhibited the greatest proliferation and longest average neurite length. These results suggested that the chitosan/collagen/icariin composite scaffolds are potential cell carriers in nerve tissue engineering.

In situ fabrication of nano-hydroxyapatite in a macroporous chitosan scaffold for tissue engineering.

A chitosan (CS)/hydroxyapatite (HAP) nanohybrid scaffold with high porosity and homogeneous nanostructure was fabricated through a bionic treatment combined with thermally-induced phase separation. The nano-HAP particles were formed in situ in the scaffold at room temperature instead of mechanically mixing the powders with the polymer component. The scaffold was macroporous with a pore size of about 100-136 microm. The nano-sized HAP particles with diameters of 90-200 nm were scattered homogeneously in the interactively connective pores. Both the improvement of the compressive modulus and yield strength of the scaffolds showed that the in situ nano-HAP particles reinforced the microstructure of the scaffold. The in vitro bioactivity study carried out in simulated body fluid (SBF) indicated good mineralization activity. The crystallization phenomenon suggested that the nano-HAP particles have positive impacts on directing apatite crystallization in the scaffold and led to the good bioactivity of the nanohybrid scaffold.

Self-organization of hydroxyapatite nanorods through oriented attachment.

The oriented attachment of hydroxyapatite (HAP) nanorods was achieved through a hydrothermal treatment. The nanorods were arranged in order along the c-axis of the HAP. These formed ca. 3.5 slip-shaped pores between the rods. High-resolution transmission electron (HRTEM) also revealed that single crystals of HAP may grow in the [0 0 2] direction of the HAP structure. This work extends the understanding of the potential for using biomimetic principles to synthesize bone-like composite materials.

[Imaging features of lung carcinoma, pulmonary tuberculoma, and inflammatory pseudotumor on helical incremental dynamic CT scan--a report of 44 cases].

BACKGROUND & OBJECTIVE: Lung carcinoma, pulmonary tuberculoma, and inflammatory pesudotumor are the most common solitary pulmonary nodules (SPN). Computed tomography (CT) is the major diagnostic examination of them. Most recent reports focused on their morphologic features on CT. The differential diagnoses are still difficult. This study was to explore their imaging features on helical incremental dynamic CT scan according to the differences of their hematal supply, and get more information for the diagnosis and differential diagnosis. METHODS: Incremental dynamic CT scan was performed on 115 cases of solitary pulmonary nodule. Of the 44 cases proved by postoperative pathology, 30 were lung carcinoma, 7 were pulmonary tuberculoma, and 7 were inflammatory pesudotumor. RESULTS: Of the 30 cases of lung carcinoma, 7 were mildly enhanced, 14 were moderately enhanced, 5 were highly enhanced, 2 were remarkably enhanced, and 7 were not enhanced; 9 had peak enhancement began at 18-28 s after injection, 17 began at 30-39 s, and 4 began at 40-44 s, with an average time of 32 s. Of the 7 cases of tuberculoma, 5 were not enhanced, and 2 were cricoid enhanced. All the 7 cases of inflammatory pesudotumor were remarkably enhanced, with the peak enhancement value of over 100 Hu in all cases; the peak enhancements began at 26 s, 28 s, 30 s, 32 s, 33 s, 110 s, and 122 s, respectively, after injection. CONCLUSION: Helical incremental dynamic CT is helpful in differential diagnoses of lung carcinoma, pulmonary tuberculoma, and inflammatory pesudotumor.