SCIENCE & TECHNOLOGY
from the SCENEs FROM THE MATERIALS SCENE
OYSTER SHELL COMPOSITE STIMULATES BONE GROWTH Some surgeries, such as tumor removal, and extreme injuries can create gaps in bone that are too large to heal naturally. To help regrow that bone, researchers report a new formulation for bone cement that combines calcium sulfate with oyster shell powder (ACS Appl. Mater. Interfaces 2014, DOI: 10.1021/am501448t). Yue Shen, a doctor of orthopedics at Zhejiang University
FROM THE BIOLOGICAL SCENE
SUGAR MIMIC HELPS STEM CELLS DIFFERENTIATE
School of Medicine, in China, and colleagues used oyster shell because it mineralizes similar to human bone and contains signaling molecules that enhance bone growth. The team tested calcium sulfate composites with varying amounts of oyster shell powder. They implanted the composites in 8-mm-diameter holes in the femurs of 24 live rabbits. After eight weeks, the team looked for new bone growth. The composite containing 18% oyster powder by weight
amide polymer. The team also added a long phospholipid tail so that the molecule could slip into cell membranes. They added the mimic to cells lacking heparan sulfate. After six days, cells treated with the mimic and fibroblast growth factor 2 changed into neural rosettes, flowerlike structures that form
J. AM. CHEM. SOC.
During embryogenesis, growth factors bind to receptors on embryonic stem cells, triggering the cells to differentiate. Sometimes long chains of sugars dangling from proteins on the cells help these growth factors bind. Researchers have now synthesized a molecular mimic of these sugardecorated proteins to direct mouse emResearchers added a fluorescently labeled sugar mimic to mouse embryonic stem cells (left). The mimic, along bryonic stem cells with fibroblast growth factor 2, triggered the cells to toward nerve cells differentiate into a neural rosette (right). (J. Am. Chem. Soc. 2014, DOI: 10.1021/ ja505012a). The mimic, designed by when stem cells become precursors Kamil Godula of the University of Cali- to nerve cells. The number of rosettes fornia, San Diego, and his colleagues, increased when cells were treated with consists of a disaccharide unit from more mimic. Cells treated with just the heparan sulfate attached to a polyacryl- growth factor did not differentiate.
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CEN.ACS.ORG
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AUGUST 18, 2014
Bone cements that include calcium sulfate and powdered oyster shell stimulate more bone growth than calcium sulfate alone.
performed the best. It stimulated the growth of almost twice as much new bone as the pure calcium sulfate. James H. Henderson, a biomedical engineer at Syracuse University, says that although the results are promising, the composites should undergo more tests, including a study of whether the oyster shell might elicit an immune response.
FRO M THE ANA LYTICAL SCENE
OPTICAL METHOD MEASURES GRAPHENE QUALITY To make graphene on an industrial scale, manufacturers need rapid ways to monitor the quality of the material. Scientists in Taiwan have shown that spectroscopic ellipsometry, a method long used for measuring the thickness of semiconductor thin films, can provide such information more quickly than current methods, such as Raman spectroscopy (Anal. Chem. 2014, DOI: 10.1021/ ac501557c). In ellipsometry, researchers shine a beam of light through a film, and the substrate holding the film reflects it back. Defects in the film change the polarization of the reflected light. Hsuen-Li Chen of National Taiwan University and colleagues used chemical vapor deposition to make graphene films with varying amounts of defects. The team found that more defects in the films led to greater changes in the polarization of the reflected light. Ellipsometry can scan a 1-cm2 sheet of graphene in under a minute, Chen says, whereas Raman would take more than an hour. Also, because ellipsometry allows researchers to perform two measurements at once—quality and thickness—it could translate to higher throughput in a production setting.
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