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Hydrophilic nanofibrous structure of polylactide; fabrication and cell affinity
Bhattarai, Shanta Raj,Bhattarai, Narayan,Viswanathamurthi, Periasamy,Yi, Ho Keun,Hwang, Pyoung Han,Kim, Hak Yong Wiley Publishers 2006 Journal of Biomedical Materials Research Part A Vol. No.
<P>Microstructure and architecture of the scaffolds along with the surface chemistry exert profound effect on biological activity (cell distribution, proliferation, and differentiation). For the biological activity, scaffolds in tissue engineering have been widely designed. The objective of this study was to develop hydrophilic nanofibrous structure of polylactides (PLLA) polymer in the form of nonwoven mat by electrospinning technique, and further evaluate the fibroblast NIH3T3 cell proliferation, morphology, and cell–matrix interaction. Hydrophilicity of the PLLA fibers was improved by adding small fraction of low molecular weight polyethylene glycol (PEG) into the electrospinning solution. Four different ratio types (100/0, 80/20, 70/30, and 50/50) of PLLA/PEG electrospun matrices were fabricated, and the pore characteristics, tensile properties, contact angle, and hydrolytic degradation were observed. Furthermore, scanning electron microscope (SEM) and fluorescence actin staining images were used for micro-observation of cell–matrix interaction and cell morphology. It was found that the electrospun mat of PLLA/PEG (80/20), composed of fibers with diameters in the range 540–850 nm, majority of pore diameter less than 100 μm, tensile strength 8 MPa, elongation 150%, porosity more than 90%, and improved hydrophilicity with slow hydrolytic degradation, is favorable for biological activity of NIH3T3 fibroblast cell. Based on these results, the correct composition of PLLA and PEG in the porous electrospun matrix (i.e., PLLA/PEG (80/20)) will be a better candidate rather than other compositions of PLLA/PEG as well as hydrophobic PLLA for application in tissue engineering. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2006</P>
Carbon nanotubes assisted biomimetic synthesis of hydroxyapatite from simulated body fluid
Aryal, Santosh,Bhattarai, Shanta Raj,K.C., Remant Bahadur,Khil, Myung Seob,Lee, Duck-Rae,Kim, Hak Yong Elsevier 2006 Materials science & engineering. properties, micro Vol.426 No.1
<P><B>Abstract</B></P><P>Synthesis of hydroxyapatite (HA) using carboxylated carbon nanotubes were investigated using simulated body fluid (SBF) similar to physiological condition and products tailored to have chemistry found to mimic natural bone. Composites were synthesized under ambient condition and physiological temperature (37°C). Former results the formation of dense net over carbon nanotubes even after 21 days of reaction, a hierarchy assemblies, whereas later results the formation of large crystals after 7 days of reaction. Physico-chemical characterization of composite material showed that the nucleation of HA initiates through the carboxyl group. Different parameters like temperature and reaction time were found to control the crystallization of HA. After 7 days of reaction, the crystal becames denser and directs towards the single plane; (002), thereby showing its phase purity. The result showed that the carboxylated carbon nanotubes were capable to nucleate HA from SBF, which can be used as a biomaterial for the modification of implant materials.</P>
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>
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>
Bajgai, Madhab Prasad,Aryal, Santosh,Bhattarai, Shanta Raj,Bahadur, K. C. Remant,Kim, Kawn-Woo,Kim, Hak Yong Wiley Subscription Services, Inc., A Wiley Company 2008 Journal of applied polymer science Vol.108 No.3
<P>The main objective of the present work was to fabricate poly(ε-caprolactone) grafted dextran (PGD) electrospun matrix (matrix) and to investigate the scaffold potential in tissue engineering application. In this work, at first we synthesized PGD polymer via ring opening polymerization (ROP), and with predetermined electrospinning conditions, nanofibrous matrix with high molecular weight PGD (PGD-50, M<SUB>w</SUB> = 45,500) has been successfully fabricated for the first time. Mouse osteoblast like cells, MC3T3 was used to test biocompatibility, assays of cell adhesion, survival, and effects on cell morphology of the matrix. The data demonstrate that PGD-50 matrix represent a suitable substrate for supporting cell proliferation, process outgrowth and migration and as such would be a good material for artificial extra cellular matrix. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008</P>