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Study of Surface Modification of Polyglycolic Acid Scaffold and Its Application in Islet Culture and Transplantation

Author: SongChun
Tutor: HuangYuDong
School: Harbin Institute of Technology
Course: Chemical Engineering and Technology
Keywords: Polyglycolic acid Polylysine Surface modification islet cells diabetes
CLC: O632.5
Type: PhD thesis
Year: 2009
Downloads: 17
Quote: 0
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Abstract


Polyglycolic acid (PGA), as a medical biologically-adaptive polymer approvedby FDA, is one of the most studied bio-degradation materials. This research aimed toimprove the adhesion of PGA scaffold via re-modifying the surface materials of PGAscaffolds and to provide better adhesion condition for islet cells on PGA scaffoldswith implication for PGA scaffolds to be applied in the fields of islet culture in vitroand transplantation.The effect of treating power and time on the PGA holder performance was wasstudied with XPS analysis, mechanical analysis and wetting ability analysis. Theresults indicated that the mechanical performance and the wetting ability of PGAholder were better when the treating power was240W and treating time was4min.The effect of different concentration coatings of sucrose, L-glutaminic acid andpoly-lysine acid on the PGA holder performances were carried on throughmechanical analysis and wetting ability analysis, respectively. It is found that theperformance and wetting ability of PGA treated by poly-lysine acid (2mg/ml) werebetter than those of PGA holder treated by other coatings. In the end, the plasma andthe poly-lysine acid coating were combined to treat PGA. The mechanicalperformances and wetting ability of PGA holder was better than that of PGA holdertreated by either single. Thus, the method that plasma and the poly-lysine acidcoating method was employed in order to improve the wetting ability between PGAholder and culture fluid and further increase the adhesion of PGA scaffolds and cells..Islet cells on the modified PGA scaffolds were cultured in vitro (stasis andmicrogravity culture, respectively) and observed under inverted microscope. Theresult showed that the islet cells which were in good shape and well growth adheredtightly to the scaffold with less dead cells. Dithizon (DTZ) staining results indicatedthat the purity of islet cells on PGA scaffolds was quite high. Acridine Orange (AO)and Propidium Iodide (PI) fluorescence double-staining method and radioimmunitydetection results demonstrated that survival rates and insulin contents of islet cells onPGA scaffolds were relatively high. MTT detection results showed thatbio-compatibility between PGA scaffold materials and islet cells was excellent.Observations under scanning electron microscopy (SEM) exhibited that islet cellscould grow adhesively to PGA scaffolds and large interspaces between islet cellshelped islet cells acquire nutrition sufficiently and enabled islet cells to exhibit goodmorphology. Under laser confocal microscopy, green islet β and red α cells were clearly seen on PGA scaffolds.The islet cells were co-cultured with PGA scaffolds for five days in vitro andthen PGA-islet grafts were transplanted into the muscle of diabetic wistar rats toobserve the treatment effect of PGA-islet graft. The blood glucose and serum insulincontent results indicated that PGA-islet graft in PGA-microgravity culture group canrecover blood glucose and serum insulin content to the normal condition. Observationunder SEM and confocal microscopy, pathological detection results as well showedthat islet cells on PGA scaffolds were in good shape, the bio-compatibility betweenislet cells and PGA scaffolds was good, extracellular matrix like reticular fibers wasformed and visible between islet cells. In addition, interspaces around PGA-islet werelarge and no islet cells were crushed in muscular tissues. Nascent capillary were seenbetween PGA scaffolds and red cells were visible around islet cells, which indicatedsufficient blood supply and plenitudinous nutrition supply to islet cells in the muscles.After30days’ transplantation, PGA fiber scaffolds began to collapse, PGA pieces andits degradable products had no harm to body.After porcine islet cells and PGA scaffolds were co-cultured, the quality,biological characteristics of porcine islet cells survival in vitro and bio-compatibilitywere studied. Compare with the islet cells in the static condition, the AO-PIfluorescence double staining results showed that PGA scaffold can improve theviability of porcine islet cells and increase survival rates of porcine islet cells.Radioimmunity detection result demonstrated high insulin releasing index of porcineislet cells on PGA scaffolds and MTT detection result showed good bio-compatibilityPGA scaffold and porcine islet cells had. Observations under the inverted microscopyand immunofluorescence microscopy indicated that porcine islet cells on PGAscaffold exhibited good morphology and adhesive growth.The experimental results demonstrated that PGA scaffold was acted asextracellular matrix, providing good culture condition for islet cells in vitro.Especially, the PGA-microgravity culture condition was a better choice for islet cellsin vitro survival and transplantation in vivo.

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CLC: > Mathematical sciences and chemical > Chemistry > Polymer chemistry ( polymer ) > Carbon - chain polymers > Of polymers of unsaturated acids and their derivatives
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