Pica Karen, Tchao Ruy, Ofner Clyde M
Department of Pharmaceutical Sciences, Philadelphia College of Pharmacy, University of the Sciences in Philadelphia, 600 South 43rd Street, Philadelphia, Pennsylvania, USA.
J Pharm Sci. 2006 Sep;95(9):1896-908. doi: 10.1002/jps.20572.
Gelatin-methotrexate microspheres for intra-tumor administration have possibilities for minimizing systemic toxicities of methotrexate (MTX) and overcoming its resistance. Gelatin-MTX conjugates prepared by a carbodiimide reaction were crosslinked with glutaraldehyde to form microspheres (MTX:gelatin molar ratios of 2:1, 15:1, and 21:1). Microspheres were evaluated under in vitro tumor conditions at pH 6.5 and 37 degrees C with and without Cathepsin B (Cat B). Some microspheres were capped with an ethanolamine/cyanoborohydride procedure. SEM of broken microspheres revealed a hollow shell structure. Superficial Cat B degradation influenced some free MTX release but produced no conjugate fragment release. HPLC measured release of fragments (<10 kDa) was very little and release of free MTX was small. However, higher drug load microspheres released less free MTX than lower drug load, a substantial lag phase of free MTX release from capped microspheres changed to an initial rapid release in uncapped microspheres, and fragments were only released from uncapped microspheres. Opened unstable Schiff base crosslinks in uncapped microspheres may allow enzyme to produce conjugate fragments not observed in capped microspheres. Free MTX release may occur from dissolved uncrosslinked conjugate within the hollow microspheres. Important relationships and observations are described that will be useful for gelatin and perhaps other proteinaceous microspheres.
用于肿瘤内给药的明胶-甲氨蝶呤微球有可能将甲氨蝶呤（MTX）的全身毒性降至最低并克服其耐药性。通过碳二亚胺反应制备的明胶-MTX缀合物与戊二醛交联以形成微球（MTX与明胶的摩尔比为2:1、15:1和21:1）。在体外肿瘤条件下，于pH 6.5和37℃、有和没有组织蛋白酶B（Cat B）的情况下对微球进行评估。一些微球采用乙醇胺/氰基硼氢化钠方法进行封端。破碎微球的扫描电子显微镜显示为中空壳结构。表面Cat B降解影响了一些游离MTX的释放，但未产生缀合物片段的释放。高效液相色谱法测定的片段（<10 kDa）释放量非常少，游离MTX的释放量也很小。然而，载药量较高的微球释放的游离MTX比载药量较低的微球少，封端微球中游离MTX释放的显著滞后阶段在未封端微球中变为初始快速释放，并且片段仅从未封端微球中释放。未封端微球中开放的不稳定席夫碱交联可能使酶产生在封端微球中未观察到的缀合物片段。游离MTX的释放可能来自中空微球内溶解的未交联缀合物。描述了一些重要的关系和观察结果，这些对于明胶以及可能其他蛋白质微球将是有用的。
