Institute of Bioengineering and Nanotechnology, 31 Biopolis Way, The Nanos, Singapore 138669, Singapore.
Biomaterials. 2013 Oct;34(32):7971-9. doi: 10.1016/j.biomaterials.2013.07.005. Epub 2013 Jul 21.
Hydrophobic modification of low molecular weight (LMW) polyethylenimine (PEI) is known to increase gene transfection efficiency of LMW PEI. However, few studies have explored how the conjugated hydrophobic groups influence the properties of the modified LMW PEI mainly due to difficulties in obtaining well defined final product compositions and limitations in current chemical synthesis routes. The aim of this study was to modify LMW PEI (Mn 1.8 kDa, PEI-1.8) judiciously with different hydrophobic functional groups and to investigate how hydrophobicity, molecular structure and inclusion of hydrogen bonding properties in the conjugated side groups as well as the conjugation degree (number of primary amine groups of PEI-1.8 modified with hydrophobic groups) influence PEI-1.8 gene transfection efficiency. The modified polymers were characterized for DNA binding ability, particle size, zeta potential, in vitro gene transfection efficiency and cytotoxicity in SKOV-3 human ovarian cancer and HepG2 human liver carcinoma cell lines. The study shows that modified PEI-1.8 polymers are able to condense plasmid DNA into cationic nanoparticles, of sizes ~100 nm, whereas unmodified polymer/DNA complexes display larger particle sizes of 2 μm. Hydrophobic modification also increases the zeta potential of polymer/DNA complexes. Importantly, modified PEI-1.8 shows enhanced transfection efficiency over the unmodified counterpart. Higher transfection efficiency is obtained when PEI-1.8 is modified with shorter hydrophobic groups (MTC-ethyl) as opposed to longer ones (MTC-octyl and MTC-deodecyl). An aromatic structured functional group (MTC-benzyl) also enhances transfection efficiency more than an alkyl functional group (MTC-octyl). An added hydrogen-bonding urea group in the conjugated functional group (MTC-urea) does not enhance transfection efficiency over one without urea (MTC-benzyl). The study also demonstrates that modification degree greatly influences gene transfection, and ~100% substitution of primary amine groups leads to significantly lower gene transfection efficiency. These findings provide insights to modification of PEI for development of effective and non-cytotoxic non-viral vectors.
低分子量（LMW）聚亚乙基亚胺（PEI）的疏水性修饰已知可提高 LMW PEI 的基因转染效率。然而，由于难以获得具有明确最终产物组成的修饰 LMW PEI，以及当前化学合成途径的局限性，很少有研究探索共轭疏水性基团如何影响修饰的 LMW PEI 的性质。本研究旨在明智地用不同的疏水性官能团修饰 LMW PEI（Mn 1.8 kDa，PEI-1.8），并研究疏水性、分子结构以及共轭侧基中氢键性质的包含程度以及修饰度（用疏水性基团修饰的 PEI-1.8 的伯胺基团数）如何影响 PEI-1.8 的基因转染效率。修饰聚合物的 DNA 结合能力、粒径、Zeta 电位、体外基因转染效率和 SKOV-3 人卵巢癌细胞系和 HepG2 人肝癌细胞系的细胞毒性进行了表征。研究表明，修饰的 PEI-1.8 聚合物能够将质粒 DNA 凝聚成阳离子纳米颗粒，粒径约为 100nm，而未修饰的聚合物/DNA 复合物显示出 2μm 的较大粒径。疏水性修饰还增加了聚合物/DNA 复合物的 Zeta 电位。重要的是，修饰的 PEI-1.8 显示出比未修饰的对应物更高的转染效率。当 PEI-1.8 用较短的疏水性基团（MTC-ethyl）修饰时，会获得更高的转染效率，而不是用较长的疏水性基团（MTC-octyl 和 MTC-deodecyl）修饰。在共轭官能团中添加氢键脲基团（MTC-urea）不会比没有脲基团（MTC-benzyl）提高转染效率。该研究还表明，修饰度极大地影响基因转染，而伯胺基团的约 100%取代会导致基因转染效率显著降低。这些发现为开发有效且非细胞毒性的非病毒载体修饰 PEI 提供了思路。
