Huang Steven H, Sheth Saahil, Jain Era, Jiang Xuefeng, Zustiak Silviya P, Yang Lan
Opt Express. 2018 Jan 8;26(1):51-62. doi: 10.1364/OE.26.000051.
Whispering gallery mode (WGM) resonators are compact and ultrasensitive devices, which enable label-free sensing at the single-molecule level. Despite their high sensitivity, WGM resonators have not been thoroughly investigated for use in dynamic biochemical processes including molecular diffusion and polymerization. In this work, the first report of using WGM sensors to continuously monitor a chemical reaction (i.e. gelation) in situ in a hydrogel is described. Specifically, we monitor and quantify the gelation dynamics of polyacrylamide hydrogels using WGM resonators and compare the results to an established measurement method based on rheology. Rheology measures changes in viscoelasticity, while WGM resonators measure changes in refractive index. Different gelation conditions were studied by varying the total monomer concentration and crosslinker concentration of the hydrogel precursor solution, and the resulting similarities and differences in the signal from the WGM resonator and rheology are elucidated. This work demonstrates that WGM alone or in combination with rheology can be used to investigate the gelation dynamics of hydrogels to provide insights into their gelation mechanisms.
回音壁模式（WGM）谐振器是紧凑且超灵敏的器件，能够在单分子水平上实现无标记传感。尽管WGM谐振器具有高灵敏度，但尚未针对其在包括分子扩散和聚合在内的动态生化过程中的应用进行深入研究。在这项工作中，描述了首次使用WGM传感器原位连续监测水凝胶中化学反应（即凝胶化）的报告。具体而言，我们使用WGM谐振器监测并量化聚丙烯酰胺水凝胶的凝胶化动力学，并将结果与基于流变学的既定测量方法进行比较。流变学测量粘弹性的变化，而WGM谐振器测量折射率的变化。通过改变水凝胶前体溶液的总单体浓度和交联剂浓度研究了不同的凝胶化条件，并阐明了WGM谐振器信号与流变学信号中由此产生的异同。这项工作表明，单独使用WGM或与流变学结合使用可用于研究水凝胶的凝胶化动力学，以深入了解其凝胶化机制。
