磁性奈米材料用於抑制人類降鈣素聚集

Abstract

根據文獻紀錄目前約有三十多種人類胜肽或蛋白質聚集形成類澱粉蛋白纖維，而此些類澱粉蛋白纖維存在又與人類疾病關係密切，可惜的是目前並沒有治癒類澱粉蛋白變性病的方法，因此抑制類澱粉蛋白聚集成為最重要的治療策略。人類降鈣素是由32個胺基酸所組成的激素肽，透過甲狀腺濾泡旁細胞(亦稱C細胞)分泌，主要功能為調節體內鈣離子濃度與維持骨骼結構，因此可應用於治療骨相關疾病。然而，人類降鈣素因聚集速度較快易於形成類澱粉蛋白纖維導致降低其生物利用度及治療活性。目前選擇用聚集速度較慢的鮭魚降鈣素做成的鼻噴劑來當作治療藥物，但其與人類降鈣素的胺基酸序列差異甚大，導致具有免疫反應相關問題，而能有效抑制人類降鈣素形成類澱粉蛋白聚集並維持其治療活性成為最重要的研究課題。磁性奈米材料因具有較高生物相容性、低毒性、獨特的磁性以及其他等優點，因此於各個領域皆廣泛地發展成為具有潛力的材料，此外亦有些許的研究是關於磁性奈米材料抑制類澱粉蛋白纖維的探討，並且發現此奈米材料抑制人類降鈣素聚集的文獻甚少。本研究中，我們透過化學共沉澱法製備出氧化鐵奈米粒子，並且利用不同方法(如共價鍵與吸附)將小分子包覆於氧化鐵奈米粒子的表面，再觀察其對於人類降鈣素形成類澱粉蛋白纖維的影響。經由硫磺素-T動力學和穿透式電子顯微鏡證明Dopamine-Fe3O4及Dihydrocaffeic acid@Fe3O4這兩種材料皆能有效抑制人類降鈣素聚集以及可降解其類澱粉蛋白纖維，透過此些實驗結果，我們期望能再以人類降鈣素為有效成份的劑型開發中，尋求可用來穩定人類降鈣素的藥物賦形劑添加物。According to pervious research literature, it has been discovered that more than thirty species of human peptides or proteins would aggregate to form amyloid fibrils and associated with some human diseases. Unfortunately, there is no cure for amyloid diseases now, it is important to develop therapeutic strategies which can be used to inhibit amyloid aggregation. Human calcitonin (hCT) is a hormone peptide which contains thirty-two amino acids and it is secreted by parafollicular cells (also known as C cells) in the human body. In principle, this hormone can regulate the concentration of calcium in human body and also can be used to treat bone-related diseases. However, hCT aggregates quickly in aqueous solution and forms amyloid fibril which would reduce bioavailability and therapeutic activity of the peptide. The currently strategy is use salmon calcitonin (sCT) in a nasal spray as a treatment drug which has less aggregation propensity then human calcitonin. However, the sequence of sCT is quite different to that of hCT and sometimes will lead to immune response problems, it is important to prevent hCT aggregation and maintain its therapeutic activity. Magnetic nanomaterials have been widely developed as potential materials for various fields due to their high biocompatibility, low toxicity, and unique magnetic properties and easy to functionalize. So far, only a few studies utilized magnetic nanomaterials to treat other amyloidogenic proteins, but not for hCT.In this study, we prepared iron oxide nanoparticles by chemical co-precipitation by use different methods such as covalent bonding and adsorption to coating small molecules on the surface of iron oxide nanoparticles. Later, we tested their effects on hCT aggregation. By ThT kinetic assay and images which collected from transmission electron microscope, we found that both Dopamine-Fe3O4 and Dihydrocaffeic acid@Fe3O4 can inhibit hCT amyloid formation and dissociate preformed hCT amyloid fibrils. It appears to be one of the most promising ways to stabilizes hCT in solution condition.