Browsing by Author "Tushar K. Ghosh, Committee Member"

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    Concurrent and Sequential Surface Modification of Electrospun Polymer Micro/Nano-Fibers
    (2009-04-23) Sun, Xiaoyu; Orlin D. Velev, Committee Member; Tushar K. Ghosh, Committee Member; Saad A. Khan, Committee Member; Richard J. Spontak, Committee Chair
    Surface modification of nano-fibers with bioactive functional groups has become an arresting research area in recent decades, which provides possibility for the invention of bioactive materials for textiles and biomedical applications e.g. tissue engineering. The major objective of this research is to develop a novel single-step processing route for the production of synthetic fibers possessing specific bioactive surface functionalities at nano/submicron scale. Unlike traditional sequential surface modification of nanofibers, sequence-defined oligo-peptide that carries biofunctionality was synthesized separately before incorporated onto the electrospun fibers as surface functionalities by a single-step spinning process, so as to avoid the effect from chemical synthesis on fiber processing. As one of the most widely-used technologies for the production of polymeric nanofibers, electrospinning was chosen to achieve the single-step surface modification. Conventional homopolymer in conjunction with the biofunctional oligopeptide-incorporated block copolymer were co-electrospun. Nanofibers at submicron scale with surface enrichment of block copolymer were achieved due to phase separation caused by polarizability difference under static electric field. The surface segregation of peptide block was proved by the nitrogen enrichment measured from X-ray Photoelectric Spectroscopy (XPS). The proposed mechanism is discussed based on mainly the model homopolymer system of polyethylene oxide (PEO), and extended to the ternary polymer blends composed of thermoplastic polymethyl methacrylate (PMMA), PEO and block copolymer. The surface modification technique introduced deep insight into the electrospinning process with its effect to the polymer blends microphase separation, and leads to a promising perspective for biomaterial engineers to produce nanofibers with certain surface bio-functional groups.
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    Reinforcing Effect of a Cyanoacrylate Adhesive on Surgical Suture Knots
    (2009-04-16) Samson, Genevieve; Tushar K. Ghosh, Committee Member; Hechmi Hamouda, Committee Member; Martin W. King, Committee Co-Chair; Bhupender S. Gupta, Committee Co-Chair
    Despite the latest polymer materials and surgical suturing techniques, the knot will always be the weakest point of the tied suture loop. In theory, the knot must be as small as possible to prevent an excessive amount of tissue reaction and a delay in healing. There have been reports suggesting that topical cyanoacrylate adhesives could have a reinforcing effect on a surgeon’s knot. Such an outcome could lead to the elimination of knot slippage and the unsatisfactory performance of some surgical knots. The main purpose of this study was to determine if cyanoacrylate adhesive could have a significant reinforcing effect on typical suture types and sizes when tied as a surgeon’s knot. The second aim was to evaluate if the cyanoacrylate adhesive could replace an additional throw in the surgeon’s knot so as to achieve an equivalent mechanical performance. The topical cyanoacrylate adhesive LiquiBand® was combined with six different suture materials (TicronTM, SurgidacTM, Ethilon*, Nurolon*, BiosynTM and PDS*II) in four different sizes (USP 5-0, USP 3-0, USP 0 and USP 1). The surgeon’s knot (2=1) with and without one (2=1=1) and two additional throws (2=1=1=1) were tied in a reproducible way and mechanically tested. Six dependent variables were used to evaluate the performance of each knot with and without adhesive. The performance criteria were: the force at loop failure, the maximum loop-holding force, the loop holding capacity, the knot efficiency, the knot elongation efficiency and the loop distraction. From the results and from scanning electron microscopic observations of the reinforced knots, the cyanoacrylate adhesive was found to significantly improve the knot performance. The improvement was superior with braided sutures and with absorbable polymer sutures. The reinforcement was more significant with thicker suture sizes and with the plain surgeon’s knot. Finally, it was found that, according to the six performance criteria, the cyanoacrylate adhesive could not replace an additional throw in the surgeon’s knot.