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Graft Length (graft + length)

Distribution by Scientific Domains

Polymers and Materials Science	71%
Medical Sciences	28%

Selected Abstracts

Controlled synthesis of amphiphilic biodegradable polylactide-grafted dextran copolymers

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2004
Cécile Nouvel
Abstract The whole controlled synthesis of novel amphiphilic polylactide (PLA)-grafted dextran copolymers was achieved. The control of the architecture of such biodegradable and potentially biocompatible copolymers has required a three-step synthesis based on the "grafting from" concept. The first step consisted of the partial silylation of the dextran hydroxyl groups. This protection step was followed by the ring-opening polymerization of D,L -lactide initiated from the remaining OH functions of the partially silylated polysaccharide. The third step involved the silylether group deprotection under very mild conditions. Based on previous studies, in which the control of the first step was achieved, this study is focused on the last two steps. Experimental conditions were investigated to ensure a controlled polymerization of D,L -lactide, in terms of grafting efficiency, graft length, and transesterification limitation. After polymerization, the final step was studied in order to avoid degradation of both polysaccharide backbone and polyester grafts. The chemical stability of dextran backbone was checked throughout each step of the synthesis. PLA-grafted dextrans and PLA-grafted (silylated dextrans) were proved to adopt a core-shell conformation in various solvents. Furthermore, preliminary experiments on the potential use of these amphiphilic grafted copolymers as liquid/liquid interface stabilizers were performed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2577,2588, 2004 [source]

Effect of poly(acrylic acid)-g-PCL microstructure on the mechanical properties of starch/PCL blend compatibilized with poly(acrylic acid)-g-PCL

POLYMER ENGINEERING & SCIENCE, Issue 3 2001
Chang-Hyeon Kim
Poly(acrylic acid)-g-polycaprolactone (PAA-g-PCL) graft copolymer was synthesized and starch/PCL blends compatibilized with PAA-g-PCL were prepared. The mechanical properties of the starch/PCL blends compatibilized with various PAA-g-PCLs that have different graft degrees and graft lengths were investigated. As the graft degree of the PAA-g-PCLs that have the same graft length increased, the modulus and the strength of the blends decreased. However, the elongation at break and the tensile toughness of the blends showed a maximum at a certain graft degree (10.8 mol%) owing to the better compatibilizing effect compared to the low (3.9 mol%) and the high (23.4 mol%) graft degree of PAA-g-PCL. It was also found that the modulus and the strength of the blends increased with the increase of graft length of the PAA-g-PCLs that have the same graft degree (,11 mol%). However, the blend compatibilized with the short graft length (M.W. of PCL graft: 530) exhibited the highest value of the elongation at break and the tensile toughness. This result is attributed to the self-crystallization of PAA-g-PCL in the blend that has longer PCL grafts. [source]

Alcohol Pretreatment of Small-diameter Expanded Polytetrafluoroethylene Grafts: Quantitative Analysis of Graft Healing Characteristics in the Rat Abdominal Aorta Interposition Model

ARTIFICIAL ORGANS, Issue 7 2009
Erman Pektok
Abstract Long-term patency rates of small-diameter expanded polytetrafluoroethylene (ePTFE) vascular prostheses are unsatisfactory. Treatment of ePTFE grafts by alcohol before implantation was reported to increase hydrophilic properties, yielding better endothelialization and cellular in-growth, thus improving graft healing. The effect of alcohol pretreatment on ePTFE grafts and postoperative healing characteristics of wet ePTFE grafts were evaluated in this study. Ten sterile ePTFE grafts (2 mm ID, 30 µ thru-pore, 12 mm long) were implanted in the infrarenal aorta of male Sprague-Dawley rats (324,380 g). Five grafts were treated with ethanol 70% and soaked with saline solution before implantation (wet); five nontreated grafts served as control. All rats were sacrificed after digital subtraction angiography and sampling of the graft for histological investigation after 3 weeks. Histomorphometric analysis was performed for endothelial coverage, cellular in-growth, and intimal hyperplasia. All grafts were patent at the end of 3 weeks in both groups. Histological evaluation revealed significantly better endothelial coverage and prominent infiltration by fibroblasts and lymphocytes in the wet group. Endothelial coverage (31.03 ± 10.61% vs. 13.03 ± 9.46%, P = 0.03) and cellular infiltration of grafts (50.91 ± 8.55% vs. 39.29 ± 10.70%, P = 0.11) were higher in the wet group. Area of intimal hyperplasia per graft length was also higher in the wet group (5.32 ± 4.75 µm2/µm vs. 2.69 ± 3.41 µm2/µm, P = 0.36). Wetting of ePTFE grafts with ethanol 70% pretreatment before implantation might have a beneficial effect on long-term patency of small-diameter vascular grafts due to facilitated graft healing. [source]

Donor-site morbidity in buccal mucosa urethroplasty: lower lip or inner cheek?

BJU INTERNATIONAL, Issue 4 2005
Stefan Kamp
Authors from Germany debate the issue as to whether the donor site for oral mucosa used in urethroplasty should be taken from the inner cheek or the lower lip, using morbidity as a deciding factor. As a result of their study they have changed their technique, now using the inner cheek as the donor site whenever possible. OBJECTIVE To evaluate donor-site complications of buccal mucosa urethroplasty and whether there is a difference in morbidity between harvesting the mucosa graft from the inner cheek or the lower lip. PATIENTS AND METHODS Twenty-four consecutive patients with recurrent urethral strictures were treated with buccal mucosa urethroplasty in our department between September 2002 and April 2004. In 12 patients the graft was harvested from the lower lip or cheek and lower lip (group 1), and in 12 patients from the cheek (group 2). The mean (range) age of patients was 51 (26,66) years in group 1 and 53 (32,75) years in group 2. The mean (range) graft length was 6.2 (2,16) cm in group 1 and 5.7 (2,13) cm in group 2. All patients were followed up using a mailed questionnaire that asked about pain, numbness, difficulties in mouth opening or ingestion, and satisfaction, monthly for the first 3 months and then every 6 months. The mean (range) follow-up was 12.5 (6,23) months. RESULTS There were no bleeding complications or disturbances in wound healing. All of the patients reported numbness in the area of the mental and buccal nerves, and graft-site tenderness after surgery. In group 1, the pain lasted for a mean (range) of 5.9 (0.5,22) months, compared to 1 (0.1,7) months in group 2 (P = 0.022). Perioral numbness lasted for a mean (range) of 10.3 (0.5,23) months in group 1 and 0.85 (0.1,3) months (P = 0.0027) in group 2. There were no statistically significant differences in problems with mouth opening or food intake between the two groups, but the patients in group 1 seemed to be less satisfied (6/12 patients satisfied) than those in group 2 (11/12 patients satisfied). CONCLUSIONS Buccal mucosa graft harvesting from the lower lip and the inner cheek are both feasible, but harvesting from the lower lip resulted in a significantly greater long-term morbidity, which resulted in a lower proportion of satisfied patients. This seems to be due to a long-lasting neuropathy of the mental nerve. We therefore have changed our technique entirely from lower lip to inner cheek graft harvesting, whenever possible. [source]

Synthesis and Characterisation of Poly[oligo(, -caprolactone)L -malate- graft -poly(L -lactide)]

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 7 2010
Christian Hahn
Abstract Graft copolyesters with a PCL backbone and PLLA side chains were successfully prepared in three steps avoiding transesterification. First , -caprolactone was polymerised with 1,6-hexane diol as initiator to obtain hydroxytelechelic oligo(, -caprolactone)s. These diols were then subjected,in the second step,to polycondensation with L -malic acid yielding in linear poly[oligo(, -caprolactone)L -malate] having secondary hydroxyl functions in the side chain. For both reactions scandium triflate Sc(OTf)3 was used as a catalyst. In the third step various amounts of L -lactide were grafted from the polymer backbone using Zn(oct)2 as catalyst. The successful reaction was confirmed by NMR and SEC (size exclusion chromatography) analysis. Further the thermal properties of the graft copolymers with different graft lengths were determined via differential scanning calorimetry. [source]