Combining Whispering‐Gallery Mode Optical Biosensors with Microfluidics for Real‐Time Detection of Protein Secretion from Living Cells in Complex Media

Abstract

The noninvasive monitoring of protein secretion of cells responding to drug treatment is an effective and essential tool in latest drug development and for cytotoxicity assays. In this work, a surface functionalization method is demonstrated for specific detection of protein released from cells and a platform that integrates highly sensitive optical devices, called whispering-gallery mode biosensors, with precise microfluidics control to achieve label-free and real-time detection. Cell biomarker release is measured in real time and with nanomolar sensitivity. The surface functionalization method allows for antibodies to be immobilized on the surface for specific detection, while the microfluidics system enables detection in a continuous flow with a negligible compromise between sensitivity and flow control over stabilization and mixing. Cytochrome c detection is used to illustrate the merits of the system. Jurkat cells are treated with the toxin staurosporine to trigger cell apoptosis and cytochrome c released into the cell culture medium is monitored via the newly invented optical microfluidic platform.

Whispering Gallery Mode Optical Microresonators: Structures and Sensing Applications

“…In 2018, Chen et al. combined WGM with microfluids to monitor the secretion and specific binding of cytochrome C in real time and proposed a biotin–streptavidin sandwich method, which candetect almost any biomarker.…”

Label-Free Optical Resonator-Based Biosensors

“…WGM biosensors are highly sensitive to changes in the surface conditions and refractive index, and they have been developed for single-molecule detection [ 20 , 21 , 115 ], pico- to atto-molar scale detection [ 21 , 112 , 113 , 116 , 117 , 118 , 119 , 120 , 121 ], and monitoring biological processes [ 122 , 123 , 124 , 125 , 126 ] or enzymatic reactions [ 127 , 128 ]. In recent studies, researchers have also taken advantage of geometric modifications [ 129 , 130 ] and material doping [ 116 , 118 , 119 , 131 , 132 , 133 , 134 ] to improve the Q-factors and sensitivity of WGM-based resonators.…”

“…These are typically based on microbubbles, microspheres, or microdroplets. Some notable modifications were label-free surface functionalization [ 120 , 123 , 137 , 138 ], doping [ 118 , 119 ], and self-referencing [ 111 , 120 ].…”

“…In another work, acrylate microspheres were used for label-free, real-time detection toward testing drugs/treatments using a non-invasive approach [ 123 ]. Cytochrome C (Cyt-C) is released by Jurkat cells in the body as a response to staurosporine, an anti-cancer drug.…”

Reusable, Non-Invasive, and Ultrafast Radio Frequency Biosensor Based on Optimized Integrated Passive Device Fabrication Process for Quantitative Detection of Glucose Levels

“…Moreover, another key factor limiting the application of electrochemical sensors is the fact that the electrolytes need to be replenished on a regular basis, which significantly increase burden to subsequent costs [30][31][32]. With regard to optical biosensors, it needs a long settling time for detection and is highly susceptible to change the test results for ambient light [33][34][35][36][37][38][39][40][41]. Recently, a biosensor based on radio frequency (RF) techniques has attracted enormous attention and is regarded as a promising and competitive candidate for implementing third-generation glucose biosensors [42][43][44][45][46][47].…”