Microparticle shape, as a tunable design parameter, holds much promise for controlling drug-release kinetics from polymeric microparticulate systems. In this study we hypothesized that the intensity and duration of a local nerve block can be controlled by administration of bupivacaine-loaded stretch-induced anisotropic poly(lactic-co-glycolic acid) microparticles (MPs). MPs of size 27.3 ± 8.5 μm were synthesized by single emulsion method and subjected to controlled stretching force. The aspect ratio of the anisotropic–bupivacaine MPs was quantified, and bupivacaine release was measured in vitro. The anisotropic MPs were administered as local nerve block injections in rats, and the intensity and duration of local anesthesia was measured. Bupivacaine-loaded anisotropic MPs used in this study were ellipsoid in shape and exhibited increased surface pores in comparison to spherical MPs. Anisotropic MPs exhibited a higher rate of bupivacaine release in vitro, and showed significantly (P < 0.05) stronger sensory nerve blocking as compared to spherical bupivacaine MPs, even though the duration of the nerve block remained similar. This study demonstrates the utility of stretch-induced anisotropic MPs in controlling drug release profiles from polymeric MPs, under both in vitro and in vivo conditions. We show that shape, as a tunable design parameter, could play an important role in engineering drug-delivery systems.

中文翻译：

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用于神经阻滞麻醉中不同药物释放的各向异性微粒

微粒形状作为一个可调节的设计参数，对于控制聚合物微粒系统的药物释放动力学具有很大的前景。在这项研究中，我们假设局部神经阻滞的强度和持续时间可以通过施用布比卡因拉伸诱导的各向异性聚乳酸-乙醇酸微粒 ( MPs ) 来控制。通过单乳液法合成尺寸为 27.3 ± 8.5 μm 的 MPs，并受到控制的拉伸力。量化各向异性-布比卡因 MP 的纵横比，并在体外测量布比卡因释放. 各向异性 MPs 作为大鼠局部神经阻滞注射给药，并测量局部麻醉的强度和持续时间。本研究中使用的载有布比卡因的各向异性 MP 呈椭圆形，与球形 MP 相比，表面孔隙增加。与球形布比卡因 MPs 相比，各向异性 MPs在体外表现出更高的布比卡因释放率，并且表现出显着 ( P < 0.05) 更强的感觉神经阻滞，尽管神经阻滞的持续时间保持相似。本研究证明了拉伸诱导的各向异性 MP在体外和体内控制聚合物 MP 药物释放曲线方面的效用条件。我们表明，形状作为一个可调设计参数，可以在工程药物输送系统中发挥重要作用。