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Stabilization of gold nanoparticles by hydrophobically-modified polycations
Remant Bahadur, K. C.,Aryal, Santosh,Bhattarai, Shanta Raj,Bhattarai, Narayan,Kim, Chi Hun,Kim, Hak Yong Informa UK (TaylorFrancis) 2006 Journal of Biomaterials Science. Polymer Edition Vol.17 No.5
<P>Surface-modified gold nanoparticles have pronounced benefits in the biomedical field due to their significant interaction with delivery materials. In the present study we used hydrophobically-modified polycations (i.e., N-acylated chitosan) to stabilize gold nanoparticles. Aliphatic hydrophobic groups, having carbon chains of different lengths, were first grafted onto the backbone of chitosan by N-acylation with fatty-acid chlorides in order to increase its hydrophobicity. Gold nanoparticles stabilized with native chitosan and N-acylated chitosan were prepared by the graft-onto approach. Chemical modification and its quantification were studied by Fourier-transform infrared (FT-IR) spectroscopy. Further, the stabilized gold nanoparticles were characterized by different physico-chemical techniques such as UV-Vis, FT-IR, TEM, TGA and DLS. Spectral studies of gold nanoparticles show the backbone and the side chain functional groups of chitosan were not cleaved during the conjugation process. TEM observations revealed that the modified chitosan gold nanoparticles were well dispersed and spherical in shape with average size around 10-12 nm in triply-distilled water at pH 7.4, whereas the native chitosan gold nanoparticles appeared as clusters with 9.9 nm as average diameter and were dispersed only in dilute HCl. The size of modified chitosan gold nanoparticles varied depending on the length of grafting molecules.</P>
Remant, Bahadur K.C.,Kim, Kwan-Woo,Bhattarai, Shanta Raj,Kim, Hak-Yong,Lee, Duck-Rae The Korean Fiber Society 2007 Fibers and polymers Vol.8 No.2
Electrospinning is a versatile process used to prepare micro- and nano-sized fibers from various polymer solution. Here, we dealt with the variation in the morphology of nylon 6 electrospun nanofibers and their polymorphism depending on the type and physical state of the collectors. SEM study showed that the fiber diameter was increased from 80 to 103 nm while it was collected in water bath. Similarly the fiber diameter and bonding was increased 103 to 115 nm with the temperature whereas it was linearly decreased 103 to 90 nm with the conductivity of the water bath. Spectroscopic analysis (FT-Raman, FT-IR) showed that the polymorphism of nylon 6 depended on the types of collector (aluminum sheet and water bath). Nylon 6 electrospun nanofibers display the ${\gamma}-phase$ while collected in aluminum sheet and ${\alpha}-phase$ while collection in water bath. The extent of transformation from ${\gamma}$- to ${\alpha}$-phase was linearly increased with temperature and conductivity of the water bath.
Remant Bahadur, K. C.,Aryal, Santosh,Raj Bhattarai, Shanta,Seob Khil, Myung,Kim, Hak Yong Wiley Subscription Services, Inc., A Wiley Company 2007 Journal of applied polymer science Vol.103 No.4
<P>Amphiphilic triblock copolymers composed of poly(p-dioxanone) (PPDO) and poly(ethylene glycol) (PEG) were synthesized by ring opening polymerization of PDO initiated through dihydroxyl-terminated PEG in the presence of stannous 2-ethylhexanoate [Sn(oct)<SUB>2</SUB>] as a catalyst. Polymeric nanoparticles were prepared in an aqueous medium (triple distilled water and phosphate buffer pH 7.4) by cosolvent evaporation technique at room temperature (25°C). Stability of nanoparticles was significantly enough in triple distilled water when compared with the phosphate buffer. Core-shell geometry of polymeric nanoparticles was characterized by <SUP>1</SUP>H-NMR spectroscopy and further confirmed by spectrophotometric analysis using pyrene as a probe. Variation in physicochemical characteristics of polymeric nanoparticles with the fraction of PPDO was investigated through the analysis of microscopic, spectroscopic, and light scattering techniques. Critical micelle concentration of polymer in triple distilled water decreased from 2.3 × 10<SUP>−</SUP><SUP>3</SUP> to 4.7 × 10<SUP>−</SUP><SUP>3</SUP>. Atomic force microscopic observation revealed that polymeric nanoparticles were spherical and uniform with smooth textured of around 50–68 nm diameter. Dynamic light scattering and electrophoretic light scattering measurements showed a mono-disperse size distribution of around 113–171 nm hydrodynamic diameters and negative zeta (ζ)-potential (−4.00 to −5.87 mV), respectively. The investigation showed a significant effect of polymeric composition on the physicochemical characteristic of polymeric nanoparticles. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2695–2702, 2007</P>
Observation of dielectric relaxation modes in chiral smectic Cliquid crystal mixture
Rajbir Singh,V.K. Agarwal,K.K. Raina,B. Bahadur 한국물리학회 2005 Current Applied Physics Vol.5 No.6
The dielectric parameters in the frequency range 50Hz to 1MHz have been measured in a SmC* liquid crystal mixture in planaralignment. The relaxation frequency (fr), distribution parameter (a) and dielectric strength (de) have been evaluated and their cor-responding values were found to be 206.62Hz, 0.06 and 114.6 respectively. The Goldstone mode, domain mode, soft mode and anewrelaxation mode have been observed..
Malignant Neoplasm Burden in Nepal - Data from the Seven Major Cancer Service Hospitals for 2012
Pun, Chin Bahadur,Pradhananga, Kishore K,Siwakoti, Bhola,Subedi, Krishna,Moore, Malcolm A Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.18
In Nepal, while no population based cancer registry program exists to assess the incidence, prevalence, morbidity and mortality of cancer, at the national level a number of hospital based cancer registries are cooperating to provide relevant data. Seven major cancer diagnosis and treatment hospitals are involved, including the BP Koirala Memorial Cancer hospital, supported by WHO-Nepal since 2003. The present retrospective analysis of cancer patients of all age groups was conducted to assess the frequencies of different types of cancer presenting from January 1st to December 31st 2012. A total of 7,212 cancer cases were registered, the mean age of the patients being 51.9 years. The most prevalent age group in males was 60-64 yrs (13.6%), while in females it was 50-54 yrs (12.8%). The commonest forms of cancer in males were bronchus and lung (17.6%) followed by stomach (7.3%), larynx (5.2%) and non Hodgkins lymphoma (4.5%). In females, cervix uteri (19.1%) and breast (16.3%), were the top ranking cancer sites followed by bronchus and lung (10.2%), ovary (6.1%) and stomach (3.8%). The present data provide an update of the cancer burden in Nepal and highlight the relatively young age of breast and cervical cancer patients.
Aryal, Santosh,Bahadur K. C, Remant,Bhattarai, Shanta Raj,Prabu, P.,Kim, Hak Yong Royal Society of Chemistry 2006 Journal of materials chemistry Vol.16 No.48
<P>The growth of hydroxyapatite (HA) on self-assembled collagen gold nanoparticles is presented for the first time by employing wet chemistry at ambient conditions, and we obtained near-quantitative yields of composite. Transmission electron microscopy reveals that the gold nanoparticles are well dispersed with an average diameter of 4 nm, which was further supported by the strong surface plasmon band (SPB) at 527 nm in the UV-vis spectra. The band broadening, shifting and flattening after the addition of HA precursors suggests the formation of HA aggregates. FT-IR spectroscopy confirms that the characteristic functionalities of collagen are intact even after the conjugation with gold nanoparticles, which renders the formation of randomly aggregated quarter-moon-like HA. Microscopic and crystallographic study at this stage further confirms its crystallographic structure that the HA particles aligned with their crystallographic <I>c</I>-axes preferentially parallel to the orientation of collagen on the gold nanoparticles with an elemental composition resembling that of natural HA. The result showed that gold nanoparticles with collagen form an efficient matrix for the growth of HA and the mineralized collagen can be potentially applied in bone tissue repair and regeneration.</P> <P>Graphic Abstract</P><P>Gold nanoparticles with collagen form an efficient matrix for the growth of hydroxyapatite and the mineralized collagen can be potentially applied in bone tissue repair and regeneration. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b608300e'> </P>