Enhanced biocompatibility of polyphosphazenes achieved by radiation grafting

Hierarchical Polyphosphazene@Molybdenum Disulfide Hybrid Structure for Enhancing the Flame Retardancy and Mechanical Property of Epoxy Resins

A novel polyphosphazene (PZS) microsphere@molybdenum disulfide nanoflower (MoS₂) hierarchical hybrid architecture was first synthesized and applied for enhancing the mechanical performance and flame retardancy of epoxy (EP) resin via a cooperative effect. Herein, using PZS microsphere as the template, a layer of MoS₂ nanoflowers were anchored to PZS spheres via a hydrothermal strategy. The well-designed PZS@MoS₂ exhibits excellent fire retardancy and a reinforcing effect. The obtained PZS@MoS₂ significantly enhanced the flame-retardant performance of EP composites, which can be proved by thermogravimetric and cone calorimeter results. For instance, the incorporation of 3 wt % PZS@MoS₂ brought about a 41.3% maximum reduction in the peak heat-release rate and decreased by 30.3% maximum in the total heat release, accompanying the higher graphitized char layer. With regard to mechanical property, the storage modulus of EP/PZS@MoS₂3.0 in the glassy state was dramatically increased to 22.4 GPa in comparison with that of pure EP (11.15 GPa). It is sensible to know that the improved flame-retardant performance for EP composites is primarily assigned to a physical barrier effect of the MoS₂ nanoflowers and the polyphosphazene structure has an positive impact on promoting char formation in the condensed phase.

Surface functionalization of polypropylene devices with hemocompatible DMAAm and NIPAAm grafts for norfloxacin sustained release

To improve the hemocompatibility and elution of antimicrobial agents for medical devices, N,N′-dimethylacrylamide (DMAAm) and N-isopropylacrylamide (NIPAAm) were sequentially grafted onto polypropylene (PP) films. Various (PP-g-DMAAm)-g-NIPAAm grafts were prepared using different time periods of irradiation while keeping the radiation dose constant. The hydrogel layer that formed on the surface of the PP was temperature-responsive (shifted from 32°C for NIPAAm to 37°C for the copolymer). The (PP-g-DMAAm)-g-NIPAAm films adsorbed serum albumin but not fibrinogen and had significantly lower hemolytic and thrombogenic activity. The DMAAm promoted the loading of norfloxacin (13.3 μg cm—2) when the hydrogel layer was swollen; as the NIPAAm shrank, a sustained delivery (∼6 h) occurred at body temperature. These functionalized PP films have potential as hemo- and cyto-compatible materials for medical devices and drug delivery products.

Cell adhesion on polytetrafluoroethylene modified by UV-irradiation in an ammonia atmosphere

We report on the modification of polytetrafluoroethylene (PTFE) by exposure to the ultraviolet (UV) light of a Xe(2)*-excimer lamp at a wavelength of 172 nm in an ammonia atmosphere. Typical treatment times were up to 30 min. Subsequently, the samples were grafted with the amino acid alanine from an aqueous solution. The samples were characterized by means of optical transmission spectroscopy, laser-induced fluorescence and contact-angle measurements. We studied the adhesion of rat aortic smooth muscle cells (SMC) and mouse fibroblasts (3T3 cells) to the modified polymer samples using an in vitro technique, where the population density and spread of adhering cells is determined 24 h after seeding by image analysis. For both cell types the exposure of PTFE to UV-light in an ammonia atmosphere resulted in a significant increase in the number of adhering cells and in the size of their spreading area. The grafting with alanine enhanced this effect. Additional experiments with human endothelial cells (HEC) also demonstrated improved adhesion to modified PTFE. Thus, PTFE modified by our method appears to be a promising material for fabrication of artificial vascular prostheses and implants or for cultivation of skin substitutes.