School of Applied Chemical Engineering, Polymeric Nano Materials Laboratory, Kyungpook National University, Daegu 41566, Republic of Korea.
ACS Sens. 2021 Mar 26;6(3):1039-1048. doi: 10.1021/acssensors.0c02269. Epub 2021 Jan 17.
Monodispersed cross-linked poly(acrylic acid) (PAA) droplets (PAA X-droplets), prepared using the microfluidic method with in situ ultraviolet curing, were used as small spherical sensors to simultaneously detect both Ca and Mg in human saliva and serum. The PAA X-droplet treated with KOH (PAA X-droplet) was used as a reference droplet because of its highly swollen state. The PAA X-droplets shrunk in response to the presence of divalent metal ions (Ms) by forming a bridged structure of COO-M-OOC. The sizes of the PAA X-droplets were precisely and dynamically monitored in the poly(dimethylsiloxane) (PDMS) channel with passing time when the aqueous metal-ion solutions were flowing at a controlled flow rate. The sizes of the PAA X-droplets continuously decreased to the saturated constant size. The saturated size of the PAA X-droplet did not change; however, the speed of size reduction increased with an increase in the concentration of the divalent metal ion. The saturated size was studied using the saturated diameter ratio () with respect to the initial diameter of the PAA X-droplet before the metal-ion treatment, and the speed of the size reduction was investigated using the inverse time to reach half the saturated diameter reduction (). Ca and Mg exhibited values of 75.9 and 83.6%, respectively, when the flow rate was 5 μL min, regardless of the metal concentration. The s for the Ca and Mg linearly increased with an increase in their concentrations. The of the aqueous Ca/Mg mixture solution had a linear relationship with φ [= /( + ), where and are the molar concentrations of Ca and Mg, respectively]. The of the aqueous Ca, Mg mixture solution was calculated by adding the individual s of pure aqueous Ca and Mg solutions. Using the and of the Ca/Mg mixture aqueous solution, the individual C and in the mixture solution were successfully calculated. This method was applied to the human saliva and serum in which the major metal ions are Ca and Mg, and other metal ions existed in undetectable amounts by the PAA X-droplets. This method is simple, cost-effective, and highly accurate and solves the hurdles of separating the interference effect of a Mg ion when a Ca ion is measured in biofluids.
使用微流控方法原位紫外光固化制备的单分散交联聚丙烯酸（PAA）液滴（PAA X-液滴）被用作小型球形传感器，同时检测人唾液和血清中的 Ca 和 Mg。用 KOH 处理的 PAA X-液滴（PAA X-液滴）因其高度溶胀状态而被用作参考液滴。PAA X-液滴响应二价金属离子（Ms）的存在，通过形成 COO-M-OOC 的桥接结构而收缩。当含有金属离子的水溶液以受控流速流动时，PAA X-液滴的尺寸在通过 PDMS 通道时被精确且动态地监测。当金属离子存在时，PAA X-液滴的尺寸连续减小至饱和恒定尺寸。PAA X-液滴的饱和尺寸不变；然而，随着二价金属离子浓度的增加，尺寸减小的速度增加。通过相对于金属离子处理前 PAA X-液滴的初始直径的饱和直径比（）研究饱和尺寸，通过达到饱和直径减小一半的逆时间（）研究尺寸减小的速度。当流速为 5 μL min 时，Ca 和 Mg 的 值分别为 75.9%和 83.6%，而与金属浓度无关。随着浓度的增加，Ca 和 Mg 的 s 线性增加。水合 Ca/Mg 混合溶液的 与 φ [= /( + )，其中 和 分别是 Ca 和 Mg 的摩尔浓度]呈线性关系。水合 Ca、Mg 混合溶液的 可以通过添加纯水溶液的 Ca 和 Mg 溶液的各自 s 来计算。使用 Ca/Mg 混合水溶液的 ，成功计算了混合溶液中各自的 C 和 。该方法应用于人唾液和血清中，其中主要金属离子为 Ca 和 Mg，而其他金属离子的含量可以用 PAA X-液滴检测不到。该方法简单、经济高效、高度准确，并解决了在生物流体中测量 Ca 离子时分离 Mg 离子干扰效应的难题。
