Fabrication and characterization of heparin-grafted poly-L-lactic acid-chitosan core-shell nanofibers scaffold for vascular gasket.

Electrospun nanofibers were widely studied to be applied as potential materials for tissue engineering. A new technology to make poly-l-lactic acid/chitosan core/shell nanofibers from heterologous solution by coaxial electrospinning technique was designed for vascular gasket. Chitosan surface was cross-linked by genipin and modified by heparin. Different ratios of PLA/CS in heterologous solution were studied to optimize the surface morphology of fibers. Clean core-shell structures formed with a PLA/CS ratio at 1:3. Superior biocompatibility and mechanical properties were obtained by optimizing the core-shell structure morphology and surface cross-linking of chitosan. UE7T-13 cells grew well on the core-shell structure fibers as indicated by methylthiazolyldiphenyl-tetrazolium bromide (MTT) results and scanning electron microscopy (SEM) images. Compared with the pure PLA fiber meshes and commercial vascular patch, PLA/CS core-shell fibers had better mechanical strength. The elastic modulus was as high as 117.18 MPa, even though the yield stress of the fibers was lower than that of the commercial vascular patch. Attachment of red blood cell on the fibers was evaluated by blood anticoagulation experiments and in vitro blood flow experiments. The activated partial thromboplastin time (APTT) and prothrombin time (PT) value from PLA/CS nanofibers were significantly longer than that of pure PLA fibers. SEM images indicated there were hardly any red blood cells attached to the fibers with chitosan coating and heparin modification. This type of fiber mesh could potentially be used as vascular gasket.

[Effects of cleaners on the color stability of prosthesis silicone rubbers].

OBJECTIVE: To evaluate the effect of different cleaners on the color stability of two silicone rubbers used for maxillofacial prosthesis, and to provide recommendations for clinical use. METHODS: Thirty skin-color columniform specimens (12 mm diameter, 10 mm height) of two silicone rubber (A:A-2000; Z:ZY-1) were prepared, randomly divided into 6 groups according to the table of random number, and cleaned with the following solutions: isopropyl alcohol (I), three kinds of denture cleaners (P: Polident, S: Steradent, C: Cleansoft) and distilled water (D), simulating the total immersion time of 1 year (1, 15, 10, 3 and 10 min each time respectively). Control group was kept in dark place without treatment. The L(*), a(*), b(*) value were tested before and after immersion. Then color difference value was calculated. RESULTS: Color differences were different among groups. Color difference in group I (A: 2.15, Z: 2.00) were significantly greater than that in any other group. There were no significant differences between groups using denture cleaner P (A: 0.36, Z: 0.36), C (A: 0.42, Z: 0.37) and S (A: 0.33, Z: 0.38), and group D (A: 0.22, Z: 0.23). CONCLUSIONS: Isopropyl alcohol causes the most severe fading, and denture cleaners and distilled water cause obscure fading.