Food and Drug Department, University of Parma, Italy.
Food and Drug Department, University of Parma, Italy; Current address: Pharmacy Service, University Hospital of Parma, Italy.
Int J Pharm. 2017 Apr 15;521(1-2):214-221. doi: 10.1016/j.ijpharm.2017.02.044. Epub 2017 Feb 20.
Apart from molecular weight and net surface charge, there are other macromolecule-related factors that could, in principle, influence their diffusion across biological tissues, such as shape, conformability, water solubility and surface charge distribution. Lysozyme and cytochrome c, proteins with comparable molecular weight, isoelectric point and net surface charge in physiological conditions (approx. +7.8), are suitable model compounds for comparative studies, in particular to find out if other properties can have a role in the permeation across the sclera. The comparison between lysozyme and cytochrome c permeability was conducted by studying the permeation across the sclera and the choroid-Bruch's membrane and the diffusion across a hyaluronan gel-matrix. Melanin binding tests and the measurement of the electroosmosis flow during transscleral iontophoresis allowed for the evaluation of macromolecules affinity for the ocular tissues. Finally, anodal iontophoresis was applied to further confirm the interaction of the two proteins with the sclera. The data here collected show that two proteins with very similar MW, p K and charge can display very different diffusion properties across biological barriers. In particular, these differences can be attributed to a different interaction with specific components of ocular tissues: while the interaction with melanin and collagen fibers is apparently the same for the two molecules, a relevant difference was found in case of hyaluronic acid. Considering also literature evidences, the important parameters that can be responsible for this different affinity are molecular shape (spherical for cytochrome c vs prolate for lysozyme) and a combination of hydrophobic and electrostatic interactions that depends on the surface charge distribution. The interactions between sclera components and lysozyme are relatively strong and were not altered by the application of electric current.
除分子量和净表面电荷外，还有其他与大分子相关的因素可能会影响它们在生物组织中的扩散，例如形状、顺应性、水溶性和表面电荷分布。溶菌酶和细胞色素 c 是在生理条件下（约+7.8）具有可比分子量、等电点和净表面电荷的蛋白质，是进行比较研究的合适模型化合物，特别是为了确定其他性质是否在巩膜渗透中起作用。通过研究巩膜和脉络膜-布鲁赫膜的渗透以及透明质酸凝胶基质的扩散，对溶菌酶和细胞色素 c 的通透性进行了比较。黑色素结合试验和经皮离子电渗时的电渗流测量可评估大分子对眼组织的亲和力。最后，应用阳极离子电渗法进一步证实了这两种蛋白质与巩膜的相互作用。这里收集的数据表明，两种分子量、p K 和电荷非常相似的蛋白质在穿过生物屏障时可以显示出非常不同的扩散特性。特别是，这些差异可以归因于与眼部组织特定成分的不同相互作用：虽然两种分子与黑色素和胶原纤维的相互作用显然相同，但在透明质酸的情况下发现了明显的差异。同时考虑到文献证据，可能导致这种不同亲和力的重要参数是分子形状（细胞色素 c 为球形，溶菌酶为长形）和取决于表面电荷分布的疏水和静电相互作用的组合。巩膜成分与溶菌酶之间的相互作用相对较强，电流的应用并未改变它们。
