可逆性溶胶凝胶外文翻译(编辑修改稿)

可逆性溶胶凝胶外文翻译(编辑修改稿)内容摘要：

ed the properties of various polymer solutions from the viewpoint of rheology. The present study aimed at assessing the effect of the position of a thermosetting gel solution vehicle on its rheological properties. Furthermore, rheological properties were pared among different solutions, with the other in situ gelling systems for ophthalmic use as control. Experimental Materials Four different kinds of methylcellulose (MC), that is, Metolose (SM 15, 25, 400, 1500) by ShinEtsu Chemical (Japan) were used. Polyethylene glycol 1000 (mean molecular weight 950– 1050), 4000 (mean molecular weight 2600– 3800), 6000 (mean molecular weight 7300– 9300) (to be abbreviated to PEG 1000, 4000, 6000) and sodium citrate dihydrate (SC) were special grhemical Industries (Japan), and Poloxamer 407 used was Lutrol F127 by BASF (Japan). Timolol maleate was purchased from Industrie Chemiche Italiane (Italy), ketotifen fumarate from Kyowa Yakuhin Kogyo (Japan), Ofloxacin from Sigma (Japan), and betamethasone sodium phosphate from Sicor (France). The other reagents used were all special class grade on the market. Simulated tear fluid was prepared by adding distilled water to g of sodium chloride, g of sodium bicarbonate, and g of calcium chloride dihydrate until the total volume of solution reached 100 mL according to the preparation described by Rozier et al Preparation of thermosetting gel vehicle The thermosetting gel vehicle was prepared according to the method described in a previous paper with slight modification [6]. A hot slurry was prepared by adding g of MC to 50 mL of distilled water heated to 90 _C with stirring and allowing it to disperse sufficiently. The slurry was cooled to 5 _C and mixed with a solution of g SC in 30 mL distilled water, then with a solution of varying amounts (2– 10 g) of PEG in 15 mL distilled water. The mixture was stirred until it became transparent. After adjusting its pH with 3 N hydrochloric acid, the mixture was made up to 100 mL with distilled water, and used as the thermosetting gel vehicle. The drug was added after addition of PEG. Preparation of various in situ gelling solutions A hot slurry was prepared by adding MC ( g of SM15 and g of SM 400) to 50 mL of distilled water heated to 90 _C with stirring and allowing it to disperse sufficiently. The slurry was cooled to 5 _C, mixed with a solution of g SC in 30 mL distilled water, then with a solution of g PEG 4000 in 15 mL distilled water. The mixture was stirred until it became transparent. After adjusting its pH to with 3 N hydrochloric acid, the mixture was made up to 100 mL with distilled water and used as the thermosetting gelling solution. Gellan gum solution was prepared by dissolving g gellan gum in 90 mL of M Tris maleate buffer solution (pH ), then mixing it with g mannitol. The resultant solution was made up to 100 mL with M Tris maleate buffer solution (pH ) [8]. Poloxamer solution was prepared by dissolving 25 g poloxamer in 70 mL of So168。 rensen buffer solution (pH ), which was acplished by allowing the mixture to stand at 5 _C for 24 h, then mixing it with g mannitol, and making up the resultant solution to 100 mL with So168。 rensen buffer solution (pH ). Measurement of gelling temperature by the test tube inversion method The reversible sol– gel transition temperature for thermosetting gel solution was measured by the test tube inversion method. A 5 mL portion of sample was placed in a glass test tube (12 mm outer diameter, mm inner diameter), then the test tube was allowed to stand for 5 min in a constant temperature bath and was then inverted. The temperature at which the sample did not flow out on inversion was used as the reversible sol– gel transition temperature. Results and discussion Effect of PEG on reversible sol– gel transition temperature Several methods are known for measuring the reversible sol– gel transition temperature, such as the test tube inversion method, falling ball method,。