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Sunghyen Hwang,Mitsugu Todo 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.7
Regeneration of articular layered tissues consisting of cartilage and cancellous bone has been a critical issue in orthopedics. Tissue engineering technology for such large-scale damaged layered tissue may be developed by using layered scaffold with stem cells. In this study, therefore, a novel multi-layer scaffold consisting of a porous poly (ε-caprolactone) (PCL) layer for cartilage regeneration and a porous composite layer of poly (L-lactic acid) (PLLA) and hydroxyapatite (HAp) for bone regeneration was developed. The microstructure of the scaffold was characterized by a field emission scanning electron microscope (FE-SEM). Compression tests were also performed to understand the stress-strain behavior. FE-SEM observation clearly showed that an interlayer exists between the PCL and the composite layers. The compressive stress-strain relation is characterized by a stepwise behavior including the first and the second steps. The first modulus corresponding to the first step is mainly related to the deformation of the PCL layer; on the other hand, the second modulus is related to both solidified PCL layer and the composite layer and increases with increase of HAp content of the composite layer. It is also found that the classical mechanics theory and three-dimensional finite element model can predict the first modulus reasonably well.
Alam, Mohammad K.,Rahman, Mohammed M.,Elzwawy, Amir,Torati, Sri Ramulu,Islam, Mohammad S.,Todo, Mitsugu,Asiri, Abdullah M.,Kim, Dojin,Kim, CheolGi Elsevier 2017 ELECTROCHIMICA ACTA Vol.241 No.-
<P><B>Abstract</B></P> <P>A facile and cost effective chemical reduction method is employed for the preparation of reduced graphene oxide/hydroxyapatite (rGO/HAp) nanocomposites. The transmission electron microscopy images revealed that the HAp flakes are well decorated on the surface of rGO. The morphological structure of the as-synthesized rGO/HAp nanocomposites was confirmed through X-ray diffraction, Fourier transform infrared spectroscopy and Raman spectroscopy, while the composition and thermal stability were analyzed by energy dispersive spectra and thermogravimetric analysis, respectively. Furthermore, the effect of rGO/HAp nanocomposites for the proliferation of Human Mesenchymal Stem Cell (hMSC) was performed to confirm the biocompatibility. A selective chemical sensor based on rGO/HAp modified glassy carbon electrode (GCE) for sensitive detection of Bis-phenol A (BPA) has been developed. Several important parameters controlling the performance of the BPA chemi-sensor were investigated and optimized at room conditions. The rGO/HAp/Nafion/GCE sensor offers a fast response and highly sensitive BPA detection. Under the optimal conditions, a linear range from 0.2nmolL<SUP>−1</SUP> to 2.0mmolL<SUP>−1</SUP> for the detection of BPA was observed with the detection limit of 60.0pmolL<SUP>−1</SUP> (signal-to-noise ratio, at an SNR of 3) and sensitivity of 18.98×10<SUP>4</SUP> μA.L/μmol.m<SUP>2</SUP>. Meanwhile, the fabricated chemi-sensor showed an excellent, specific and selective recognition to target BPA molecules among coexistence of other analytes in the buffer system. This novel effort initiated a well-organized way of efficient rGO/HAp/Nafion/GCE sensor development and practically analyzed the real hazardous environmental pollutants at room conditions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Simple chemical reduction method was used for preparation of reduced graphene oxide/hydroxyapatite (rGO/HAp) nanocomposites. </LI> <LI> The rGO/HAp nanocomposites exhibited good biocompatibility with hMSCs. </LI> <LI> Selective chemical sensor based on rGO/HAp nanocomposites was developed for detection of Bis-phenol A. </LI> <LI> The fabricated rGO/HAp/Nafion/GCE sensor exhibited good detection limit of 60pmolL<SUP>−1</SUP>. </LI> </UL> </P>