State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China; School of Applied Chemistry and Engineering, University of Science and Technology of China, Hefei 230026, China.
State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China.
J Chromatogr A. 2023 Nov 8;1710:464427. doi: 10.1016/j.chroma.2023.464427. Epub 2023 Oct 4.
Crosslinking of chitosan chains in dilute solution by natural crosslinker genipin leads to biocompatible nanogels. Here we investigated the reaction kinetics between chitosan and genipin in a 200 mM acetate buffer at 37 °C, and the structural and conformational evolutions of the nanogels during the crosslinking reaction by multi detection asymmetric flow field-flow fractionation (AF4). Upon crosslinking by genipin, the z-average hydrodynamic radius R of the chitosan chains increased from 26 nm to 130 nm, while the weight average molar mass M increased from 2.0 × 10 g/mol to 1.8 × 10 g/mol. The crosslinking reaction appeared to be first-order and size-dependent. In particular, the intrachain crosslinking reaction was preferentially for nanogels having the larger size, leading to formation of branched chains/nanogels having a wide range of molar masses between 10 and 10 g/mol but a similar radius of gyration R ∼ 40 nm. For the largest nanogel fractions with M > 2.0 × 10 g/mol, both R and R showed a scaling relation with exponent 1/3 and a structure parameter R/R = 0.74, as expected for the hard sphere particle. The reaction was accompanied by a reduction of charge density and an increase in hydrophobicity of chitosan nanogels, which plays a key role in the formation of uniform size nanogels with chain density ρ(R) up to 0.45 g/cm.
壳聚糖链在稀溶液中通过天然交联剂京尼平交联生成生物相容性纳米凝胶。在这里，我们研究了 37°C 200mM 醋酸盐缓冲液中壳聚糖和京尼平之间的反应动力学，以及通过多检测不对称流场流分离（AF4）在交联反应过程中纳米凝胶的结构和构象演变。用京尼平交联后，壳聚糖链的 z 均水力半径 R 从 26nm 增加到 130nm，而重均摩尔质量 M 从 2.0×10 g/mol 增加到 1.8×10 g/mol。交联反应似乎是一级和尺寸依赖性的。特别是，链内交联反应优先发生在尺寸较大的纳米凝胶上，导致支化链/纳米凝胶的形成，其摩尔质量在 10 到 10 g/mol 之间变化，但回转半径 R 相似，约为 40nm。对于 M>2.0×10 g/mol 的最大纳米凝胶分数，R 和 R 都表现出与指数 1/3 的标度关系和结构参数 R/R=0.74，这与硬球粒子的预期一致。反应伴随着壳聚糖纳米凝胶电荷密度的降低和疏水性的增加，这在形成链密度 ρ(R)高达 0.45g/cm 的均匀尺寸纳米凝胶方面起着关键作用。
