No abstract

In this study, the different encapsulation methods involving emulsification and coaxial electrospinning were both utilized to fabricate a series of core/sheath composite, nanoparticles (NPs) and Nanofibers (NFs) separately, for drug delivery on potential biological and therapeutic applications. Bovine serum albumin (BSA) was employed as an active pharmaceutical ingredient model for core; poly(L-lactic acid) (PLLA) and methoxy poly(ethyleneglycol)-Poly lactic acid (mPEG-PLA) were selected as the encapsulation matrix for sheath. Attributed to the optimized fabrication procedures, the obtained NPs and NFs had the small average diameters and narrow size distributions with uniform structures and smooth surface morphologies. Based on the drug release profiles, both the NPs provided a burst release process followed by a drug diffusion manner, while for the NFs, the drug diffusion was the predominant factor in drug release. In particular, the mPEG-PLA NFs were fabricated with excellent hydrophilicity and highly neutralized surface resulting in a sustained release of BSA over 10 days. In addition, mPEG-PLA NFs also provided a better zero-order drug release profiles during the release time from 8 to 72 h, and a one-dimensional Fickian diffusion pattern during the whole BSA release period. A cytotoxicity study suggested that the two drug delivery systems were both safe to cells. In conclusions, the synergism of PEGylation with coaxial electrospinning may be an effective way to retard the release of drugs in a more sustained manner.

Rigid polyurethane foams (RPUFs) were prepared with specific heteroaromatic and brominated benzyl polyols. The mechanical properties and thermal stability were studied using dynamic mechanical analysis (DMA) and thermogravimetric analysis (TG). The limiting oxygen index (LOI) was used to investigate the flame retardancy of the RPUFs. The results showed that the glass transition temperature (T g ) of the RPUF prepared by heteroaromatic polyol was 1828C, demonstrating an improved thermal stability for this specific heteroaromatic polyol. Brominated benzyl polyol exhibited less negative influence on mechanical properties of the RPUFs at the same time of improving the flame retardancy. The LOI values increased with an increase in the brominated polyol content to 27.5%, and the char-forming ability of the RPUF improved; the char residue rate reached 12.6% at 7008C, but it was only 6.2% without the flame retardant. Scanning electron microscope (SEM) and energy-dispersive spectrometry (EDS) verified that the mechanism of flame retardancy was due to a synergistic effect of the gas phase and the condensed phase.

In this paper, ceria (CeO 2 ) nanoparticle was prepared through ultrasonic combined with calcine method, which was further introduced into thermoplastic polyurethane matrix via one-step in situ bulk polymerization technique, and thus CeO 2 /thermoplastic polyurethane nanocomposites were obtained. SEM images revealed that CeO 2 nanoparticles (with size of $60 nm) are uniformly dispersed into thermoplastic polyurethane matrix, which can lead to an increase of degree of phase separation. The degree of phase separation values were calculated according to the ratio of the 1701 and 1727 cm À1 absorbance areas in FTIR spectra. Effects of CeO 2 amounts on thermoplastic polyurethane's properties including blood compatibility, cell viability, chemical resistance, mechanical and thermal property, and so on were discussed in detail. Additionally, possible interaction mechanism of thermoplastic polyurethane with nano CeO 2 is discussed initially.

Chronic wounds are prone to produce excessive reactive oxygen species (ROS), which are the main reason for multiple bacterial infections and ulcers at the wound. Therefore, regulating ROS is the key in the process of wound healing. Herein, a new type of thermosensitive hydrogels is developed to improve the scavenging efficiency of ROS and accelerate wound repair. Nano-CeO2 was uniformly dispersed on the surface of mesoporous silica (MSN). The nanocomposite particles were physically crosslinked with poly­(N-isopropylacrylamide) (PNIPAM) to form a MSN-CeO2@PNIPAM thermoresponsive hydrogel (PMCTH). The stability, temperature sensitivity, rheological properties, biocompatibility, and wound healing ability of the PMCTH were evaluated in detail. The results showed that the hydrogel could not only maintain the stability of the system for a long time with low biological toxicity but also have a phase transition temperature close to the human body temperature. In addition, the PMCTH was directly applied onto the skin surface. The MSN-CeO2 nanoparticles would be dispersed in the hydrogel to restrict ROS exacerbation effects and promoted the formation of blood vessels as well as surrounding tissues, accelerating the wound healing. More importantly, animal experiments showed that when the mass ratio of CeO2 to MSN was 40%, the wound healing rate reached up to 78% on the 10th day, which was far higher than that of other experimental groups. This study provides a new strategy and experimental basis for the applications of functional hydrogels in wound repair.