[Study of the preparation of silk fibroin gel and its morphology as drug release matrix in vitro and in vivo].

Silk fibroin (SF)/sodium alginate (SA) hydrogels can be used as drug injection materials. Homogenate was prepared by centrifugation of the pig myocardial extracellular matrix (PMM) and its modification of SF gel material. This paper observes and compares the different components SF, SF/SA, SF/SA/PMM to illustrate the SF/SA/PMM ternary material as a drug delivery composition material. This ternary material can shorten the gel time, and can make the gel form to be maintained better. Meanwhile, it makes the internal structure of the gel looser so that the hole wall becomes thinner and more conducive to the drug release. In addition, it has good biocompatibility proved by pathological analysis, and is able to enhance the mesenchymal stem cells growth activity, which has great significance in carrying out drug control release.

Fabrication of biocompatible Zn-cysteine nanowires and their application in selective fluorescence detection of Cu2+.

Novel Zn-cysteine complex nanowires were successfully fabricated by a facile self-assembly method at room temperature. They were innovatively used as fluorescence probes for the detecting of Cu2+, one of the most important physiological ions related with the neurobiology and general cell biology. A high fluorescence response was obtained, with a detecting limit of 2.1 x 10(-6) mol/L. This work offers a simple and quick strategy to fabricate analytic tools. As-synthesized probes have the advantages of high sensitivity, selectivity and good biocompatibility. They show promising applications as biological probes and assembled ion responsive devices.

Cytocompatibility and blood compatibility of multifunctional fibroin/collagen/heparin scaffolds.

An applicable matrix used in tissue engineering should not only have suitable mechanical properties, porous structures and biocompatibility that facilitate the adhesion, growth and proliferation of tissue cells, but also have the ability to release bioactive factors to provide a more conducive and inductive environment for tissue growth. Because of the harsh preparation conditions and deficiency of mechanical properties, it is still difficult for fibroin and collagen matrices to possess these multifunctional properties. In this research, we successfully prepared fibroin/collagen hybrid scaffolds containing heparin that possess multifunctional properties under mild conditions. These scaffolds maintain outstanding mechanical properties and porous structures of fibroin-based scaffolds. Furthermore, the scaffolds keep the bioactivity of collagen, becoming delivering systems that release heparin slowly to make the scaffolds blood compatible. Compared with fibroin/collagen scaffolds, the scaffolds containing heparin further facilitate the growth of HepG2 cells since a more complex, dynamic environment was formed to promote the cell growth. Considering the mild aqueous preparation environment without crosslinking reaction, besides promoting the progress in blood contacting tissue engineering, our research has also opened a door to prepare various multifunctional fibroin/collagen hybrid matrices that combine the advantages of fibroin and collagen.

Preparation of novel saw-toothed and riblike alpha-Si3N4 whiskers.

alpha-Si(3)N(4) whiskers with novel saw-toothed and riblike structures have been synthesized in a high yield by a carbothermal reduction and nitridation route. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), and selected-area electron diffraction (SAED). The results show that the saw-toothed whiskers with one smooth surface and another toothlike surface have lengths about several tens of microns and widths in the range of 600-1200 nm. The riblike whiskers are composed of Si(3)N(4) rod-arrays, which grow closely packed perpendicular to the central axial whiskers with uniform diameter and length. The growth mechanism of the products can be considered as a combination of VS mechanism and secondary epitaxial nucleation process. The photoluminescence (PL) spectrum of the whiskers shows a strong blue light emission peak at 406 nm and a weak peak at 485 nm, suggesting their potential applications in light and electron emission devices.

The biocompatibility of silk fibroin films containing sulfonated silk fibroin.

Sulfonation reaction may be an effective method for preparation of heparin-like materials. However, no sulfonated polymer based on protein backbone was used for improving the blood compatibility of biomaterials. In this study, the biocompatibility of new kind of composite materials films obtained by blending silk fibroin (SF) with sulfonated silk fibroin (SSF) was evaluated. The anticoagulant activity was characterized with prothrombin time (PT), activated partial thromboplastin time (APTT), and thrombin time (TT), which all increased remarkably, the clot times exceeded the measurement limit of clot detection instrument. Its platelet adhesion was also investigated as another parameter of blood compatibility. The cell compatibility of composite films was evaluated through cell morphologies on the films and cell viability by methyl thiazolyl tetrazolium (MTT) assay. Tensile strength and elongation at break of the composite films reached to 44.6 MPa and 50.3%, respectively. All these results indicated that SF/SSF composite film was a potential material for blood-contact materials and tissue engineering matrix.

A novel solvent system for blending of polyurethane and heparin.

To improve the blood-compatibility of polyurethane, the co-solvent of tetrahydrofuran and water, a new solvent system for blending polyurethane and heparin, was proposed. After solvent casting, heparin was blended in a polyurethane film. The ATR-FTIR was used to analyze the surface chemical element and the contact angle was measured to investigate the hydrophilicity of the surface of the PUs. As the amount of heparin increased, the surface hydrophilicity was increased and all the clot times exceeded the measurement limit of the clot detection instrument when the heparin loaded on the polyurethane films was 3%, 5% and 7%. After the films were immersed in the phosphate buffered saline for 30 days, the activated partial thromboplastin time and thrombin time still exceeded the measurement limit of the clot detection instrument.

A novel three-dimensional tubular scaffold prepared from silk fibroin by electrospinning.

Effects of electrospinning parameters (including voltage, collection distance, solution concentration and flow rate) on the morphology and diameter distribution of regenerated SF (silk fibroin) fiber were investigated. Afterward, SF tubular scaffold composed of homogenous fibers was fabricated at voltage of 18kV, collection distance of 18cm, concentration of 37%, and flow rate of 0.15mL/min. After methanol treatment, SF tubular scaffold showed tensile strength of 3.57MPa and porosity of 80.85%. It is satisfied that our work offers a simple method to fabricate seamless and porous tubular scaffold from SF without any additives and organic solvents. Furthermore, the results suggest that this tubular scaffold shows promising applications in small-diameter vascular graft.

Study on the preparation of collagen-modified silk fibroin films and their properties.

Blended films were prepared from a silk fibroin (SF) solution by adding a small amount of type I collagen (<5%). The mechanical properties of the wet films modified by collagen were improved obviously. The elongation at break reached 42%, and the smaller contact angles revealed that modified films had better hydrophilicity. 1% heparin was also added to modify the SF films to further improve the in vitro antithrombogenecity. The internal structure of the modified SF films was investigated with scanning electron microscopy, x-ray diffraction and Fourier transform infrared attenuated total reflection spectroscopy. The result indicates that the addition of a small amount of collagen and heparin did not change their conformation.

Blood compatibility of polyurethane immobilized with acrylic acid and plasma grafting sulfonic acid.

Sulfonic and carboxyl groups can effectively improve the blood compatibility of polyurethane. But it is difficult to obtain an optimum ratio of the two groups. In this article, polyurethane (PU) was dissolved with acrylic acid in a tetrahydrofuran solution and then spread on the glass plate to produce a film. At the same time, acrylic acid partly polymerized and immobilized with the PU films. The films (PU-AA) were exposed to sulfur dioxide plasma to graft sulfonic acid group on its surfaces. Through adjusting the quantity of acrylic acid and the plasma reaction condition, the antithrombin of polyurethane can be improved. The surface-modified PUs were characterized by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscope (XPS) and a contact angle goniometer. The blood compatibility of the films was examined by using thrombin time (TT), activated partial thromboplastin time (APTT) and prothrombin time (PT). The TT and APTT were significantly prolonged for the surface-modified films of PU-AA by sulfur dioxide plasma and only APTT was elongated for PU-AA. The results suggest that sulfonic acid and acrylic acid have the different effect on the blood compatibility of surface-modified PUs.

The preparation of insoluble fibroin films induced by degummed fibroin or fibroin microspheres.

Blending degummed fibroin (DF) or insoluble fibroin microspheres with concentrated fibroin solution, the insoluble films were obtained through drying the solution at 40-45 degrees C. The conformation of silk fibroin films was analyzed by infrared spectrum and X-ray diffractometry. The results demonstrated that beta-sheet conformation increased rapidly when the degummed silk or insoluble microspheres blended with fibroin, while the pure SF membrane was mainly composed of alpha/random coil conformation when the other conditions kept same. This suggested that fibroin microspheres and degummed fibroin could induce the formation of beta-sheet crystal and the insoluble films, without methanol after-treatment, could be obtained at approximately room temperature. Although the fibroin films blending with DF had many protuberances, the films containing fibroin microspheres had the smooth surface and could be used effectively in biotechnological materials and biomedical application.