Omer Muhammad, Park Soo-Young
Department of Polymer Science, Kyungpook National University, #1370 Sangyuk-dong, Buk-gu, Daegu, 702-701, South Korea.
Anal Bioanal Chem. 2014 Sep;406(22):5369-78. doi: 10.1007/s00216-014-7900-y. Epub 2014 Jul 1.
The interface between nematic liquid crystal, 4-cyano-4'-pentylbiphenyl (5CB), and water in a transmission electron microscopy (TEM) grid cell coated with QP4VP-b-LCP (quaternized poly(4-vinylpyridine) (QP4VP) and poly(4-cyanobiphenyl-4'-oxyundecylacrylate) (LCP)) was examined for protein and DNA detection. QP4VP-b-LCP was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. Quaternization of P4VP with iodomethane (CH3I) made it a strong cationic polyelectrolyte and allowed QP4VP-b-LCP to form complexes with oppositely charged biological species. Several proteins, such as bovine serum albumin (BSA), hemoglobin (Hb), α chymotrypsinogen-A (ChTg), and lysozyme (LYZ), were tested for nonspecific protein detection. By injecting the protein solutions into the TEM grid cell, the initial homeotropic orientation of the TEM grid cell changed to a planar orientation above their isoelectric points (PIs) due to electrostatic interactions between QP4VP (+charge) and proteins (-charge), which did not occur below the PIs of the tested proteins. Their minimum concentrations at which the homeotropic to planar configurational change (H-P change) occurred were 0.01, 0.02, 0.03, and 0.04 wt.% for BSA, ChTg, Hb, and LYZ, respectively. One of the strong anionic polyelectrolytes, deoxyribonucleic acid (DNA) (due to the phosphate deoxyribose backbone) was also tested. A H-P change was observed with as little as 0.0013 wt.% salmon sperm DNA regardless of the pH of the cell. A H-P change occurred in 5CB and was observed by polarized optical microscopy. This simple and inexpensive setup for nonspecific biomaterial detection provides the basic idea for developing effective selective biosensors by introducing specific binding groups, such as the aptamer and antibody.
在涂有QP4VP-b-LCP（季铵化聚（4-乙烯基吡啶）（QP4VP）和聚（4-氰基联苯-4'-氧基十一烷基丙烯酸酯）（LCP））的透射电子显微镜（TEM）网格池中，研究了向列型液晶4-氰基-4'-戊基联苯（5CB）与水之间的界面用于蛋白质和DNA检测。QP4VP-b-LCP通过可逆加成-断裂链转移（RAFT）聚合反应合成。用碘甲烷（CH3I）对P4VP进行季铵化使其成为强阳离子聚电解质，并使QP4VP-b-LCP与带相反电荷的生物物种形成复合物。测试了几种蛋白质，如牛血清白蛋白（BSA）、血红蛋白（Hb）、α-胰凝乳蛋白酶原-A（ChTg）和溶菌酶（LYZ）用于非特异性蛋白质检测。通过将蛋白质溶液注入TEM网格池，由于QP4VP（带正电荷）与蛋白质（带负电荷）之间的静电相互作用，TEM网格池最初的垂直取向在其等电点（PI）以上变为平面取向，而在测试蛋白质的PI以下则不会发生这种情况。对于BSA、ChTg、Hb和LYZ，发生垂直向平面构型变化（H-P变化）的最低浓度分别为0.01、0.02、0.03和0.04 wt.%。还测试了一种强阴离子聚电解质脱氧核糖核酸（DNA）（由于磷酸脱氧核糖主链）。无论细胞的pH值如何，仅用0.0013 wt.%的鲑鱼精DNA就观察到了H-P变化。5CB中发生了H-P变化，并通过偏光显微镜观察到。这种用于非特异性生物材料检测的简单且廉价的装置为通过引入特异性结合基团（如适体和抗体）开发有效的选择性生物传感器提供了基本思路。
