Using graphene oxide (GO) as both a reducing agent and a support, a two-step method was used to fabricate GO decorated with Au-Ag alloy nanoparticles with an Au-rich shell. The material exhibited excellent catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol in water at room temperature and its activity was superior to that of GO decorated with Au-Ag alloy nanoparticles that was prepared by a one-step method and GO decorated with either Au or Ag nanoparticles alone.
Structural colors: Poly(N-isopropyl acrylamide) based microgel photonic crystals are fabricated by using a new method called "high-temperature-induced hydrophobic assembly". The assembling conditions affect the water content of the crystals, thus determining their structural color (see image). The obtained photonic crystals are sensitive to solvents, and the reversible changes in their color can be observed with the naked eye.
The bone-repairing composite material CS/PLLA was fabricated by mixing poly-L-lactic acid (PLLA) and calcium sulfate hemihydrate (CSH). The structure of the composite was analyzed with Infrared spectroscope, X-ray diffraction, and scanning electron microscope. The results indicated that the crystal pattern of calcium sulfate was affected by the addition of PLLA. PLLA part impacted the development of calcium sulfate dihydrate (CSD) crystal by slowing the conversion from CSH to CSD, so the composites are actually composed of CSH, CSD, and PLLA. The absorbing test in vitro showed that CS/PLLA composite absorbed more slowly than pure CS, suggesting the addition of PLLA can adjust the absorption rate of CS to meet different requirements. The pH value changes of the media had similar trends for different composites during the absorbing test of CS/PLLA samples in aqueous medium, which was connected to the absorption of calcium sulfate. The absorption of calcium sulfate in a certain time left a porous PLLA scaffold that will enable cells to further grow in. The surface of CS/PLLA pellets was inoculated with human osteoblasts, and the primary results showed that the osteoblasts could attach and spread on the surface, which will stimulate our desire for further study.
A novel hybrid biomaterial composed of calcium sulfate (CS) and gelatin (GEL) was prepared with the potential of being used as bone filler or scaffold owing to its osteoconduction. Such composite biomaterial, cross-linked or un-cross-linked, could provide a suitable absorbing rate and prevent the CS crystals migrating from the implant for tissue engineering. The structure of the composite was analyzed with infrared (IR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicated that the crystal pattern of CS was affected by the addition of GEL. The GEL part affected the development of the CS dihydrate (CSD) crystal by slowing the conversion from CS hemihydrate (CSH) to CSD; thus, the composite actually contained CSD, CSH and GEL. The compressive strength of the CS/CLGEL composite was also investigated. The compressive strength was correlated to the weight proportions of CS in the CS/cross-linked GEL (CS/CLGEL) composite, and the highest compressive strength of 82 MPa was obtained for the composite containing 40 wt% CS. The in vitro absorption test and the SEM results showed that a porous scaffold was formed in situ with the absorption of CS in the CS/CLGEL composite in a certain time. Therefore, the CS/CLGEL composite material can be used as an in situ porous scaffold with a high initial mechanical strength, and the remaining porous GEL scaffold will enable further in-growth of cells. Human osteoblasts were cultured in contact with the CS/CLGEL composite and the primary results suggested that human osteoblasts could attach and spread on the surface of CS/CLGEL films. The preliminary animal model experiment was operated for assessing the potential of the CS/CLGEL composite as a biodegradable bone substitute. The primary results showed that the CS/CLGEL composite filler could promote new bone in-growth, which will stimulate further study.
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