Browsing by Author "Yang, Xiao"

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    A unique biomimetic modification endows polyetherketoneketone scaffold with osteoinductivity by activating cAMP/PKA signaling pathway
    (AAAS, 2022) Yuan, Bo; Zhang, Yuxiang; Zhao, Rui; Lin, Hai; Yang, Xiao; Zhu, Xiangdong; Zhang, Kai; Mikos, Antonios G.; Zhang, Xingdong
    Osteoinductivity of a biomaterial scaffold can notably enhance the bone healing performance. In this study, we developed a biomimetic and hierarchically porous polyetherketoneketone (PEKK) scaffold with unique osteoinductivity using a combined surface treatment strategy of a sulfonated process and a nano bone-like apatite deposition. In a beagle intramuscular model, the scaffold induced bone formation ectopically after 12-week implantation. The better bone healing ability of the scaffold than the original PEKK was also confirmed in orthotopic sites. After culturing with bone marrow–derived mesenchymal stem cells (BMSCs), the scaffold induced osteogenic differentiation of BMSCs, and the new bone formation could be mainly depending on cell signaling through adenylate cyclase 9, which activates the cyclic adenosine monophosphate/protein kinase A signaling cascade pathways. The current work reports a new osteoinductive synthetic polymeric scaffold with its detailed molecular mechanism of action for bone repair and regeneration.
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    Extraordinary light-induced local field, angular momentum and force near metallic nanoparticles
    (2017-08-10) Yang, Xiao; Nordlander, Peter
    The intense local field induced near metallic nanostructures provides strong enhancements for surface enhanced spectroscopies, a major focus of plasmonics research over the past decade. Here we show several different nanoantennas for SEIRA detection, which exhibit an order of magnitude greater SEIRA sensitivity than previous record-setting designs. We also consider that plasmonic nanoparticles can induce remarkably large electromagnetic field gradients near their surfaces, which can excite dipole-forbidden transitions in nearby atoms or molecules and provide unique spectroscopic fingerprinting for chemical and bimolecular sensing. We introduce the concept of the local angular momentum (LAM) vector as a useful figure of merit for the design of nanostructures that provide large field gradients. Finally, we introduce a new technique that can demonstrate the mapping of electromagnetic forces between a nanoscale tip and an optically excited sample consisting of plasmonic nanostructures with an imaging platform based on atomic force microscopy.
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    Photoinduced force mapping of plasmonic nanostructures
    (American Chemical Society, 2016) Tumkur, Thejaswi U.; Yang, Xiao; Cerjan, Benjamin; Halas, Naomi J.; Nordlander, Peter; Thomann, Isabell; Laboratory for Nanophotonics; Rice Quantum Institute
    The ability to image the optical near-fields of nanoscale structures, map their morphology and concurrently obtain spectroscopic information, all with high spatiotemporal resolution, is a highly sought-after technique in nanophotonics. As a step towards this goal, we demonstrate the mapping of electromagnetic forces between a nanoscale tip and an optically excited sample consisting of plasmonic nanostructures, with an imaging platform based on atomic force microscopy. We present the first detailed joint experimental-theoretical study of this type of photo-induced force microscopy. We show that the enhancement of near-field optical forces in gold disk dimers and nanorods follows the expected plasmonic field enhancements, with strong polarization sensitivity. We then introduce a new way to evaluate optically-induced tip-sample forces by simulating realistic geometries of the tip and sample. We decompose the calculated forces into in-plane and out-of-plane components and compare the calculated and measured force enhancements in the fabricated plasmonic structures. Finally, we show the usefulness of photo-induced force mapping for characterizing the heterogeneity of near-field enhancements in precisely e-beam fabricated nominally alike nanostructures - a capability of widespread interest for precise nanomanufacturing, SERS and photocatalysis applications.