Characterizing electrostatic interactions between glycosaminoglycans and cationic

摘要本修订提案描述了小分子与带负电荷的多糖在离体和体内模型中的结合机制，并将其发现应用于开发用于关节软骨成像的新型X射线计算机断层扫描（CT）造影剂。具体地说，我们扩展了我们最近的报告(J. Am。化学。Soc。浙江农业学报，2009,31 (1):2469-2471；骨关节炎与软骨，2010,18,184- 191；中华骨外科杂志，2011,29 (2):444 - 444；骨关节炎和软骨，2011年，出版/在线)使用阳离子碘造影剂对关节软骨中带负电荷的糖胺聚糖（GAGs）进行CT成像。目前临床上，软骨不使用CT成像，一些研究小组正在探索使用已知的CT造影剂，这些造影剂具有全阴离子电荷，用于成像GAGs。我们假设，由于阳离子造影剂的亲和力或带负电荷的GAGs，使用阳离子造影剂将导致更敏感的软骨成像技术。重要的是，我们有初步的数据表明，这些阳离子碘化造影剂以GAG浓度依赖的方式结合GAG，可以通过x射线CT用于软骨的离体和体内成像。本课题的具体目标是：目标1：合成一系列阳离子、阴离子和中性碘化CT造影剂；目标2：确定CT造影剂对离体软骨组织中存在的GAG的动力学和结合亲和力；目标3：确定CT衰减与GAG浓度的相关性并建立定量关系；(A)对兔膝关节前交叉韧带（ACL）横断前后进行连续体内对比增强计算机断层扫描（CECT）成像，以证明与牺牲后直接测量相比，使用阳离子对比剂进行CECT测量软骨GAG进行性变化的能力。(B)对新西兰白兔进行药代动力学/毒性研究。这些研究的成功完成将导致：1)用于定量测量GAG的高灵敏度软骨CT显像剂的结构-活性关系和设计要求的发展；2)健康软骨和退化软骨的活体成像；3)给药后造影剂的药代动力学特征；4)收集可靠的数据进行分析、讨论和进一步的假设生成。

DESCRIPTION (provided by applicant): Abstract This revised proposal describes the mechanism of binding in ex vivo, and in vivo models between small molecules and negatively charged polysaccharides, and applies its findings to the development of new X- ray computed tomography (CT) contrast agents for imaging articular cartilage. Specifically, we expand on our recent reports (J. Am. Chem. Soc., 2009, 131, 2469-2471; Osteoarthritis and Cartilage, 2010, 18, 184- 191; J. Orthopaedic Res., 2011, 29, 704-709; Osteoarthritis and Cartilage, 2011, in press/on line) of using cationic iodinated contrast agents for CT imaging of negatively-charged glycosaminoglycans (GAGs) in articular cartilage. Clinically today, cartilage is not imaged using CT and several research groups are exploring the use of known CT contrast agents, which possess an overall anionic charge, to image GAGs. We hypothesize that the use of a cationic contrast agent will result in a more sensitive technique for imaging cartilage due to its affinity or the negatively-charged GAGs. Importantly, we have preliminary data demonstrating that these cationic iodinated contrast agents bind GAG in a GAG concentration dependent manner and can be used for ex vivo and in vivo imaging of cartilage via X-ray CT. The specific aims of this proposal are: Aim 1: Synthesize a series of cationic, anionic, and neutral iodinated CT contrast agents, Aim 2: Determine the kinetics and binding affinities of the CT contrast agents to GAGs present in ex vivo cartilage tissue, Aim 3: Ascertain the correlation of CT attenuation vs. GAG concentration and develop a quantitative relationship, Aim 4: (A) Perform serial in vivo contrast enhanced computed tomography (CECT) imaging of rabbit knees before and after anterior cruciate ligament (ACL) transection to demonstrate the ability of CECT using cationic contrast agents to measure progressive changes in cartilage GAG compared to direct measurements after sacrifice, (B) Perform pharmacokinetic/toxicity studies in New Zealand White rabbits. Successful completion of these studies will result in: 1) the development of structure-activity relationships and design requirements for highly sensitive cartilage CT imaging agents for quantitative measurements of GAG; 2) imaging of healthy and degraded cartilage in vivo; 3) the pharmacokinetic profile of the contrast agent after administration; and 4) collection of robust data for analysis, discussion, and further hypothesis generation.