Department of Materials Science and Engineering, University of Delaware, Newark, Delaware 19716, United States.
Bioconjug Chem. 2011 Oct 19;22(10):1946-53. doi: 10.1021/bc200148v. Epub 2011 Sep 26.
Addition chemistries are widely used in preparing biological conjugates, and in particular, maleimide-thiol adducts have been widely employed. Here, we show that the resulting succinimide thioether formed by the Michael-type addition of thiols to N-ethylmaleimide (NEM), generally accepted as stable, undergoes retro and exchange reactions in the presence of other thiol compounds at physiological pH and temperature, offering a novel strategy for controlled release. Model studies ((1)H NMR, HPLC) of NEM conjugated to 4-mercaptophenylacetic acid (MPA), N-acetylcysteine, or 3-mercaptopropionic acid (MP) incubated with glutathione showed half-lives of conversion from 20 to 80 h, with extents of conversion from 20% to 90% for MPA and N-acetylcysteine conjugates. After ring-opening, the resultant succinimide thioether did not show retro and exchange reactions. The kinetics of the retro reactions and extent of exchange can be modulated by the Michael donor's reactivity; therefore, the degradation of maleimide-thiol adducts could be tuned for controlled release of drugs or degradation of materials at time scales different than those currently possible via disulfide-mediated release. Such approaches may find a new niche for controlled release in reducing environments relevant in chemotherapy and subcellular trafficking.
加成化学反应广泛应用于制备生物缀合物，特别是马来酰亚胺-巯基加合物已被广泛应用。在这里，我们表明，在生理 pH 值和温度下，在其他巯基化合物存在的情况下，通过硫醇与 N-乙基马来酰亚胺（NEM）的迈克尔型加成形成的顺丁烯二酰亚胺硫醚会发生反式和交换反应，为控制释放提供了一种新策略。对与 4-巯基苯乙酸（MPA）、N-乙酰半胱氨酸或 3-巯基丙酸（MP）偶联的 NEM 的模型研究（1H NMR、HPLC），在与谷胱甘肽孵育时显示出从 20 到 80 小时的转化半衰期，MPA 和 N-乙酰半胱氨酸缀合物的转化率从 20%到 90%不等。开环后，所得的顺丁烯二酰亚胺硫醚不会发生反式和交换反应。反式反应的动力学和交换程度可以通过迈克尔供体的反应性来调节；因此，可以调整马来酰亚胺-巯基加合物的降解，以实现药物的控制释放或在不同于目前通过二硫键介导释放的时间尺度上的材料降解。此类方法可能会在与化疗和亚细胞运输相关的还原环境中为控制释放找到新的应用领域。
