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BMP-2 Immoblized in BCP-Chitosan-Hyaluronic Acid Hybrid Scaffold for Bone Tissue Engineering
Nath, Subrata Deb,Abueva, Celine,Sarkar, Swapan Kumar,Lee, Byong Taek Materials Research Society of Korea 2014 한국재료학회지 Vol.24 No.12
In this study, we fabricated a novel micro porous hybrid scaffold of biphasic calcium phosphate (BCP) and a polylectrolyte complex (PEC) of chitosan (CS) and hyaluronic acid (HA). The fabrication process included loading of CS-HA PEC in a bare BCP scaffold followed by lypophilization. SEM observation and porosimetry revealed that the scaffold was full of micro and macro pores with total porosity of more than 60 % and pore size in the range of $20{\sim}200{\mu}m$. The composite scaffold was mechanically stronger than the bare BCP scaffold and was significantly stronger than the CS-HA PEC polymer scaffold. Bone morphogenetic growth factor (BMP-2) was immobilized in CS-HA PEC in order to integrate the osteoinductive potentiality required for osteogenesis. The BCP frame, prepared by sponge replica, worked as a physical barrier that prolonged the BMP-2 release significantly. The preliminary biocompatibility data show improved biological performance of the BMP-2 immobilized hybrid scaffold in the presence of rabbit bone marrow stem cells (rBMSC).
Nath, Narayan Chandra Deb,Ahammad, A. J. Saleh,Sarker, Subrata,Rahman, Md. Mahbubur,Lim, Sung-Su,Choi, Won-Youl,Lee, Jae-Joon American Scientific Publishers 2012 Journal of nanoscience and nanotechnology Vol.12 No.7
<P>The multi-walled carbon nanotubes (MWCNTs), electrophoretically deposited on fluorine-doped tin oxide (FTO), were employed as charge-collecting channels in the TiO2 photoelectrode of dye-sensitized solar cells (DSSCs) fabricated at 200 degrees C. The CNT-networks at the conducting substrate increased the charge collection efficiency of the porous TiO2 film, while the short circuit current increased up to ca. 43% under optimized condition. However, the significant decrease in the open-circuit voltage (Voc) up to ca. 132 mV resulted in the failure of the overall cell efficiency improvement. Findings reveal that the transfer process for the back electron is mainly responsible for the significant Voc drop when the MWCNTs were deposited at the electron-collecting substrate of the photoelectrode. The study demonstrates that electrophoretic deposition of MWCNTs on charge collecting substrate would be applicable to introduce an effective charge-collecting channel for the fabrication of flexible DSSCs under low temperature sintering condition.</P>
Sarker, Subrata,Nath, Narayan Chandra Deb,Rahman, Md. Mahbubur,Lim, Sung-Su,Ahammad, A. J. Saleh,Choi, Won-Youl,Lee, Jae-Joon American Scientific Publishers 2012 Journal of Nanoscience and Nanotechnology Vol.12 No.7
<P>Using a doctor-blade method, a highly viscous titanium dioxide (TiO2) paste was deposited on a glass substrate coated with fluorine doped tin oxide (FTO). The paste was mainly composed of commercially available TiO2 nanoparticles (P25) and hydroxypropyl cellulose (HPC) as organic filler. Varying the content of HPC in the TiO2 paste changed the physical properties of the mesoporous TiO2 layer, particularly its porosity and surface area. From the quantification of dyes on Ti2, layer and the electrochemical impedance spectroscopy (EIS) study of the dye-sensitized solar cells (DSSCs), the surface area of the TiO2 film was found to have decreased. This came with the increase of HPC content while the porosity of the film increased, consistent with the concurrent decrease of short-circuit current density (Jsc) and efficiency (eta). The increased porosity greatly affected the electron transport through the TiO2 film by decreasing the coordination number of the TiO2 particles resulting to a decrease of the electron diffusion coefficient.</P>
A Series of N-Alkylimidazolium Propylhexanamide Iodide for Dye-Sensitized Solar Cells
임성수,Subrata Sarker,Sunyoung Yoon,Narayan Chandra Deb Nath,김영준,전흥배,이재준 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.5
We report a series of novel imidazolium iodides based ionic liquids (NMIPHI, NAIPHI, and NBIPHI) with different functional groups for the development of a quasi-solid type electrolyte for dye-sensitized solar cells (DSSCs). The diffusion coefficients of redox ions (I− and I3 −) are dependent on the molecular weight and it was higher for lighter salts. Among the three ionic liquids, NMIPHI showed highest efficiency of 4.18% when it was used in a liquid electrolyte of a DSSC with ca. 6 μm thick TiO2 mesoporous film. Even though the efficiency was ca. 19% lower than that obtained from a liquid electrolyte composed of PMII. When NMIPHI was mixed with PMII with a molar ratio of 1:1 in a solvent free electrolyte, the efficiency of the DSSCs was enhanced compared to that based on pristine PMII.
Kim, Woo Seok,Nath, Subrata Deb,Bae, Jun Sang,Padalhin, Andrew,Kim, Boram,Song, Myeong Jin,Min, Young Ki Materials Research Society of Korea 2014 한국재료학회지 Vol.24 No.6
In this experiment, a highly porous scaffold of biphasic calcium phosphate (BCP) was prepared using the spongereplica method. The BCP scaffold was coated with 58S bioactive glass (BG) and sintered for a second time. The resulting scaffold was coated with gelatin (Gel) and cross-linked with [3-(3-dimethyl aminopropyl) carbodiimide] and N-Hydroxysuccinamide (EDC-NHS). The initial average pore size of the scaffold ranged from 300 to $700{\mu}m$, with more than 85 % porosity. The coating of BG and Gel had a significant effect on the scaffold-pore size, decreasing scaffold porosity while increasing mechanical strength. The material and surface properties were evaluated by means of several experiments involving scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) and X-ray diffraction (XRD). Cytotoxicity was evaluated using MTT assay and confocal imaging of MC3T3-E1 pre-osteoblast cells cultured in vitro. Three types of scaffold (BCP, BCP-BG and BCP-BG-Gel) were implanted in a rat skull for in vivo evaluation. After 8 weeks of implantation, bone regeneration occurred in all three types of sample. Interestingly, regeneration was found to be greater (geometrically and physiologically) for neat BCP scaffolds than for two other kinds of composite scaffolds. However, the other two types of scaffolds were still better than the control (i.e., defect without treatment).
A Series of N-Alkylimidazolium Propylhexanamide Iodide for Dye-Sensitized Solar Cells
Lim, Sung-Su,Sarker, Subrata,Yoon, Sun-Young,Nath, Narayan Chandra Deb,Kim, Young-Jun,Jeon, Heung-Bae,Lee, Jae-Joon Korean Chemical Society 2012 Bulletin of the Korean Chemical Society Vol.33 No.5
We report a series of novel imidazolium iodides based ionic liquids (NMIPHI, NAIPHI, and NBIPHI) with different functional groups for the development of a quasi-solid type electrolyte for dye-sensitized solar cells (DSSCs). The diffusion coefficients of redox ions ($I^-$ and $I_3{^-}$) are dependent on the molecular weight and it was higher for lighter salts. Among the three ionic liquids, NMIPHI showed highest efficiency of 4.18% when it was used in a liquid electrolyte of a DSSC with $ca$. 6 ${\mu}m$ thick $TiO_2$ mesoporous film. Even though the efficiency was $ca$. 19% lower than that obtained from a liquid electrolyte composed of PMII. When NMIPHI was mixed with PMII with a molar ratio of 1:1 in a solvent free electrolyte, the efficiency of the DSSCs was enhanced compared to that based on pristine PMII.
Lee, Ga In,Nath, Narayan Chandra Deb,Sarker, Subrata,Shin, Weon Ho,Ahammad, A. J. Saleh,Kang, Jeung Ku,Lee, Jae-Joon The Royal Society of Chemistry 2012 Physical chemistry chemical physics Vol.14 No.15
<P>Here, we find that doping <I>sp</I><SUP>2</SUP> selective nitrogen, N <I>sp</I><SUP>2</SUP>, into carbon nanotube (CNT) channels induces a positive shift in the Fermi level of TiO<SUB>2</SUB> photoelectrodes. It is found that this results in the large diffusion coefficient of solar driven electrons for increasing the photocurrent as well as in the low recombination rate for improving open circuit voltage with 0.74 V, which could not be overcome by using pristine CNT channels with 0.66 V.</P> <P>Graphic Abstract</P><P>The Fermi energy level tuning of a photoanode by N(<I>sp</I><SUP>2</SUP>)-doped carbon nanotube channels was found to prevent the open circuit voltage decay suffering from the use of pristine CNTs. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2cp40279c'> </P>
Addition of Hydroxyapatite to Toothpaste and Its Effect to Dentin Remineralization
Sadiasa, Alexander,Jang, Dong-Woo,Nath, Subrata Deb,Seo, Hyung Seok,Yang, Hyn Mo,Lee, Byong Taek Materials Research Society of Korea 2013 한국재료학회지 Vol.23 No.3
In this study, hydroxyapatite (HAp) was incorporated into toothpaste and its effect on the remineralization and restoration of dental enamel was evaluated. Different sets of toothpaste were incorporated with HAp levels of 0%, 5%, 10 %, and 15 %. The filler particles of the resulting toothpaste samples were observed via SEM and XRD and compared with compositions of several commercially available toothpastes, showing that the HAp was successfully incorporated into the toothpaste samples. Different sets of human enamel were inflicted with lesions and then treated with the different fabricated toothpaste samples for five minutes three times a day for seven days. During the treatment, the teeth were subjected to demineralization and remineralization cycles to simulate the effect of natural saliva. The surface of the enamel samples were observed using SEM before and after one week of treatment, showing the formation of HAp layers on the surfaces of the enamel samples. The effect of the toothpaste on the lesions was observed using an inverted light microscope and the lesion depth was found to decrease as the concentration of HAp in the toothpaste used increased. HAp was successfully incorporated in the toothpaste and its presence was found to lessen lesion depths and improve tooth remineralization.