Department of Fibre and Polymer Technology, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, SE-100 44 Stockholm, Sweden.
Department of Chemistry, School of Engineering Sciences in Chemistry, Biotechnology, and Health, KTH Royal Institute of Technology, Stockholm SE-100 44, Sweden.
ACS Nano. 2021 Mar 23;15(3):5341-5354. doi: 10.1021/acsnano.0c10893. Epub 2021 Mar 5.
Protein nanofibrils (PNFs) have been prepared by whey protein fibrillation at low pH and in the presence of different metal ions. The effect of the metal ions was systematically studied both in terms of PNF suspension gelation behavior and fibrillation kinetics. A high valence state and a small ionic radius (., Sn) of the metal ion resulted in the formation of hydrogels already at a metal ion concentration of 30 mM, whereas an intermediate valence state and larger ionic radius (Co, Ni, Al) resulted in the hydrogel formation occurring at 60 mM. A concentration of 120 mM of Na was needed to form a PNF hydrogel, while lower concentrations showed liquid behaviors similar to the reference PNF solution where no metal ions had been introduced. The hydrogel mechanics were investigated at steady-state conditions after 24 h of incubation/gelation, revealing that more acidic (smaller and more charged) metal ions induced . 2 orders of magnitude higher storage modulus as compared to the less acidic metal ions (with smaller charge and larger radius) for the same concentration of metal ions. The viscoelastic nature of the hydrogels was attributed to the ability of the metal ions to coordinate water molecules in the vicinity of the PNFs. The presence of metal ions in the solutions during the growth of the PNFs typically resulted in curved fibrils, whereas an upper limit of the concentration existed when oxides/hydroxides were formed, and the hydrogels lost their gel properties due to phase separation. Thioflavin T (ThT) fluorescence was used to determine the rate of the fibrillation to form 50% of the total PNFs (), which decreased from 2.3 to . 0.5 h depending on the specific metal ions added.
蛋白质纳米原纤维（PNFs）可以通过在低 pH 值和存在不同金属离子的条件下使乳清蛋白发生纤维化来制备。系统研究了金属离子对 PNF 悬浮液凝胶化行为和纤维化动力学的影响。金属离子的高价态和小离子半径（例如 Sn）导致在金属离子浓度为 30 mM 时就形成水凝胶，而中等价态和较大离子半径（例如 Co、Ni、Al）导致在金属离子浓度为 60 mM 时才形成水凝胶。需要 120 mM 的 Na 才能形成 PNF 水凝胶，而较低的浓度表现出类似于未引入金属离子的参考 PNF 溶液的液体行为。在孵育/凝胶化 24 小时后，在稳态条件下研究了水凝胶的力学性能，结果表明，与酸性较小（带电量较小，半径较大）的金属离子相比，更酸性（带电量更小，半径更小）的金属离子在相同金属离子浓度下诱导的储能模量高 2 个数量级。水凝胶的粘弹性性质归因于金属离子在 PNF 附近配位水分子的能力。在 PNF 生长过程中，溶液中存在金属离子通常会导致纤维弯曲，而当形成氧化物/氢氧化物时，存在浓度上限，并且由于相分离，水凝胶会失去其凝胶特性。使用硫黄素 T（ThT）荧光来确定形成总 PNF 的 50%所需的纤维化速率（），其取决于添加的特定金属离子，从 2.3 减少到 0.5 h。
