Abstract We report a label-free liquid crystal (LC)-based biosensor for sensitive detection of arsenic (III) ions (As3+) in aqueous solutions, using an arsenic-binding aptamer (Ars-3 aptamer) as a molecular recognition element. In this sensing system, the cationic surfactant, cetyltrimethylammonium bromide (CTAB), was employed to induce a homeotropic orientation of the LCs at the aqueous/LC interface, a result of the self-assembly of CTAB molecules. In the absence of As3+, the addition of Ars-3 aptamers disturbed the self-assembly of CTAB at the aqueous/LC interface, due to interactions between CTAB and the Ars-3 aptamers, causing an orientational transition of LCs from homeotropic to planar. In the presence of As3+, the specific binding of the Ars-3 aptamers with As3+ led to the formation of an aptamer-As3+ complex, resulting in a conformational change of the aptamer. This change weakened the interaction between CTAB and the aptamer at the interface, causing the orientation of the LCs to remain unchanged in a homeotropic state. The changes in the orientation of the LCs caused by the interactions between the Ars-3 aptamer, As3+, and CTAB were simply converted and observed under a polarized light microscope as a shift between a bright and a dark image. A low detection limit of 50 nM (~3.7 ppb) was obtained, which is well below the maximum permissible level of As3+ in drinking water (133 nM) set by the US Environmental Protection Agency and the World Health Organization. Other chemical species (heavy metal ions) did not induce these changes, and thus, the biosensor was highly specific for As3+ ion sensing. The potential application of the developed sensor for As3+ detection in tap water was also demonstrated. Therefore, this LC-based biosensor is a promising platform for simple, rapid, label-free determination of As3+ concentration in aqueous samples with high selectivity and sensitivity.

中文翻译：

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使用 ssDNA 作为识别探针，基于无标记液晶检测 As(III) 离子

摘要 我们报告了一种基于无标记液晶 (LC) 的生物传感器，使用砷结合适体 (Ars-3 适体) 作为分子识别元件，用于灵敏检测水溶液中的砷 (III) 离子 (As3+)。在该传感系统中，阳离子表面活性剂十六烷基三甲基溴化铵 (CTAB) 用于在水/LC 界面诱导 LC 的垂直取向，这是 CTAB 分子自组装的结果。在没有 As3+ 的情况下，由于 CTAB 和 Ars-3 适配体之间的相互作用，Ars-3 适配体的添加干扰了 CTAB 在水/LC 界面的自组装，导致 LC 从垂直到平面的取向转变。在 As3+ 存在下，Ars-3 适配体与 As3+ 的特异性结合导致形成适配体-As3+ 复合物，导致适体的构象变化。这种变化削弱了 CTAB 与界面处适体之间的相互作用，导致 LC 的取向在垂直状态下保持不变。由 Ars-3 适配体、As3+ 和 CTAB 之间的相互作用引起的 LC 取向的变化被简单地转换并在偏光显微镜下观察为明暗图像之间的偏移。获得了 50 nM (~3.7 ppb) 的低检测限，远低于美国环境保护署和世界卫生组织设定的饮用水中 As3+ 的最大允许水平 (133 nM)。其他化学物质（重金属离子）不会引起这些变化，因此，生物传感器对 As3+ 离子传感具有高度特异性。还展示了开发的用于检测自来水中 As3+ 的传感器的潜在应用。因此，这种基于 LC 的生物传感器是一种有前途的平台，可以简单、快速、无标记地以高选择性和灵敏度测定水性样品中的 As3+ 浓度。