【作者】 魏刚；

【导师】 郑俊民； 李三鸣；

【作者基本信息】 沈阳药科大学 ， 药剂学， 2002， 博士

【摘要】 眼部药物传递作为控制释放领域的重要分支一直备受人们的关注。眼睛的有效保护机制与高度敏感性促使人们探索开发安全合理的给药系统，同时又限制了许多药剂学手段的应用，为此类剂型的设计带来了极大的困难。环境敏感凝胶（in situ gel）是指以溶液状态给药后立即在用药部位发生相转变，形成的非化学交联的半固体制剂。该传递系统完美地融合了溶液与凝胶制剂的优点，特别适合用作眼部给药的载体。本文选择马来酸噻吗洛尔（TM）作为模型药物，采用多项新颖技术与方法，从研究药物的角膜透过性入手，考察水溶性聚合物在离体角膜表面的滞留能力，制备具有适宜相转变温度的体温敏感凝胶，运用动态流变学方法表征胶凝过程，解析其在生理／非生理条件下的状态，探讨凝胶中的药物释放、扩散行为与规律，并对体温敏感凝胶眼部应用后的消除动力学以及房水药物动力学进行研究。 噻吗洛尔透过离体角膜的扩散行为符合零级动力学特征，生理条件下测得表观渗透系数为1.43×10^-5 cm-s^-1。随着pH值升高，TM透过角膜的时滞缩短，累积透过量增加。计算得到游离型噻吗洛尔的角膜渗透系数为解离型的3.3倍。可促进药物经细胞内途径转运的渗透促进剂对TM具有显著增渗作用。0.05％去氧胆酸钠和1％泊洛沙姆188（P188）分别使TM的表观渗透系数增至1.88和1.55倍而未见体内外刺激性。进一步提高P188浓度抑制药物透过角膜。月桂氮卓酮（Azone）虽然显著增加TM的透过量，却对角膜组织造成损伤。金属离子络合剂EDTA可增加上皮细胞间通路的透过性，然而对TM经角膜渗透未见促进作用。上述结果表明，噻吗洛尔主要以分子状态经细胞内途径透过角膜，且角膜上皮是其扩散的主要屏障。 为比较水溶性聚合物的角膜滞留能力，评价溶液粘度对其角膜滞留时间的影响，本文采用束缚泡技术，以接触角的连续变化为指征，在模拟生理条件下考察聚合物从离体眼球表面解吸附的动力学过程。悬挂泡法测得兔眼角膜的接触角为38.2±1.6°，透明质酸钠（HA-Na）虽然不能降低溶液的表面张力，但却显示出最佳的角膜润湿性。聚合物的角膜滞留能力呈现显著差异，卡波姆和HA-Na吸附于离体眼球表面达15min以上，具有良好的生物粘附性。溶液粘度由12mPa·s增至50 mPa·s，卡波姆和HA-Na的角膜滞留时间分别延长10min和7min，而羧甲基纤维素钠的角膜滞留时间未受影响。体外实验结果提示，适当提高溶液粘度能够延缓生物粘附性聚合物从角膜表面消除。 本文首次报道具有适宜相转变温度的眼用体温敏感凝胶。泊洛沙姆407（P407）溶液的可逆胶凝行为呈现强烈的浓度依赖性，单独使用无法获得理想的胶凝温度。P188或聚乙二醇（PEG）可调节相转变温度，但加入不同分子量的PEG，P407溶液经模拟泪液稀释后失去胶凝能力。电解质、渗透压调节剂和粘膜粘附性聚合物可降低相转变温度。泊洛沙姆溶液温度敏感的胶凝行为与凝胶的胶束结构有关，胶凝温度取决于疏 沈阳药科大学博士学位论文 摘 要一水性聚氧丙烯（PPO）与亲水性聚氧乙烯（PEO）嵌段间的相互作用。 动态流变实验研究在正弦交变应力作用下凝胶的特定响应，提供粘弹性流体力学性质的重要信息。体温敏感凝胶的相转变表现为弹性模量呈指数增长，全部过程在6～7”C内完成，合并应用P188未改变胶凝机制。优化处方的相转变温度较单独使用P407升高9℃，低于25℃时为自由流动的液体，生理条件下转化为半固态凝胶，且在35℃经模拟泪液稀释前后具有最大凝胶强度。加入HA－Na后，凝胶强度与承受泪液稀释的能力减弱，提示其与泊洛沙姆的乙氧基单元形成氢键络合。 体温敏感凝胶稳定性良好，未见体内急性刺激性反应，符合眼部应用要求。 根据眼部用药的体内特征，采用无膜溶出模型，同时考察凝胶溶蚀及药物释放行为。泊洛沙姆凝胶中药物的释放完全受溶蚀控制，且二者均遵循零级动力学过程。处方组成确定的情况下，不同性质的药物具有恒定的释放速率。合并应用亲水性聚合物，药物释放先于凝胶溶蚀进行。实验因素（如释放面积、振荡频率）与处方因素 （如泊洛沙姆与HA－Na用量）可影响凝胶溶蚀与药物释放速率。边界层厚度与胶束通过边界层的传质系数，而并非凝胶强度，是决定凝胶溶蚀及药物释放速度的重要因素。 采用自由扩散模型研究了药物在凝胶中的扩散行为。药物经凝胶内部水性通道转运的过程符合 Fick机理。24h内仅有不足 10％的药物以扩散方式释放，普奈洛尔、TM和硫酸沙丁胺醇的扩散系数分别为 0．gi．l．32和 3．30x10‘6 cm’·s“‘。亲脂性强的药物可在凝胶的亲水／疏水区域间达到分配平衡，使其扩散受到阻滞。增加聚合物浓度，导致水性通道曲折程度和凝胶微粘度增大，是药物扩散系数减小的主要原因。 y一闪烁照相结果表明，滴眼液在眼部消除呈典型的先快后慢的两相模式，Zmin时仅有不足24％的放射性标记物残留在角膜表面。体温敏感凝胶在体给药后瞬间发生胶凝，显著延长标记物的角膜滞留时间，滞留效果优于HA－Na溶液，角膜区域放射活性一时间曲线下面积（AUC；。m；n）较对照溶?更多还原

【Abstract】 Wei Gang (Specialty: Pharmaceutics) Dissertation supervisor: Prof. Zheng Junmin and Li SanmingAs one of the important fields of controlled release, ophthalmic drug delivery has received extensive interests during the last two decades. The sensitivity and protection mechanisms of the eye promote more effective drug delivery systems with better compliancy to be developed, however, the applications of numerous pharmaceutical methods are limited simultaneously, which presents great challenge in designing ophthalmic dosage forms. In situ gels refer to the polymer solutions can be administrated as liquid, which undergo a phase transition to a non-crosslinked semisolid gel upon exposure to physiological environments. Most of the applications of the in situ gels are concerned with ophthalmic disease treatment for its convenient administration combined with the favorable ocular residence time, hi this dissertation, timolol maleate (TM) was selected as a model drug, and a series of relative researches were carried out, during which many novel techniques and methods have been used, including the drug permeability across isolated cornea, in vitro evaluation of the precorneal residence of water soluble polymers, development of in situ gels with modulated phase transition temperature, characterization of gelation process by dynamic rheological method, analyzing the states of the thermosetting vehicles under physiological and non-physiological conditions, drug release and diffusion, the dynamics of precorneal clearance and the pharmacokinetics in aqueous humor after the in situ gels applied topically.The diffusion behaviors of TM across isolated rabbit cornea possessed zero-order kinetic characteristic. At neutral media (pH 7.65), an apparent permeation coefficient of 1.43×10-5 cm.s-1 was found. When the pH varied from 6.65 to 9.20, the accumulative amount for timolol transcorneal penetration increased 1.3 times and the lag time shortened more than 19-folds. The calculated permeability coefficients of ionized and un-ionized timolol were 1.29×10-5 cm.s-1 and 4.22×10-5 cm.s-1, respectively. Penetration enhancers, which accelerate the drug transporting by intracellular pathway, showed significantly promoting activity. 0.05% sodium deoxycholate and 1% poloxamer 188 (P188) improved the apparent permeability of TM as much as 1.88 and 1.55 folds, respectively, without irritancy observed, but further increasing P188 concentration led to lower permeability. Azone caused corneal tissue damage although has showed maximum permeation enhancing effect. EDTA, a calcium ion chelator, may loosen tight intercellular junctions, however, no improvement was found for TM transcornealpermeation. The result indicated that timolol mainly penetrated corneal membrane as freebase by intracellular pathway, and comeal epithelium was the rate-limiting barrier.For the purpose of comparing the capability of some water soluble polymers to adhere to the ocular surface and evaluating the effect of solution viscosity on precomeal residence, captive bubble technique was used, with the consecutive change of contact angle interpreted as an indication of desorption process, to study the residence of those polymers on freshly enucleated rabbit eyes under physiological conditions. It was evidenced that the contact angle on mucin-coated corneal surface was 38.2?.6?measured by sessile bubble method, and sodium hyaluronate (HA-Na) had the most appropriate corneal wettability although not decreasing the surface tension. Significant difference in the corneal retentive capabilities was observed between five polymers. Carbopol and HA-Na, which adsorbed to isolated ocular surface more than 15 min, showed the optimum bioadhesive properties. When the solution viscosity increased from 12 mPa.s to 50 mPa.s, the residence times of Carbopol and HA-Na were prolonged by 10 min and 7 min, respectively, but that of sodium carboxymethylcellulose was not affected. The result suggested that moderately higher viscosity is beneficial to improve the ocular residence更多还原