Multidepth screening of living cells using optical waveguides

Adhesion kinetics of human primary monocytes, dendritic cells, and macrophages: Dynamic cell adhesion measurements with a label-free optical biosensor and their comparison with end-point assays

“…An instrument capable of resolving dynamic mass redistributions at the subcellular level 59,60 would enable the behavior of individual cells to be monitored and thus cell-to-cell variations in a seemingly homogeneous population to be studied. A biosensor combining high-throughput detection with multimode waveguides could be used for the depth profiling of cell refractive index variations, 39 so the direction of dynamic mass redistributions inside cells could be determined. Highthroughput label-free biosensors equipped with flow-through microfluidics 61,62 would enable the real-time monitoring of cellular mechanotransduction and could make many cellular assays more biologically relevant by enabling (1) a more controlled stimulation of cells with different substances, and (2) cell behavior to be studied under flow, so the in vivo conditions of red blood cells, various immune cells, and tumor cells circulating in the blood stream could be better approximated.…”

“…Evanescent field-based optical biosensors, including surface plasmon resonance (SPR), 36,37 optical waveguide lightmode spectroscopy (OWLS), 28,[38][39][40] photonic crystal biosensors, 41 grating coupling interferometry, 42,43 and resonant waveguide grating (commonly recognized as Epic) 44,45 biosensors, are considered to be especially straightforward means to monitor surface adhesion. First, they are sensitive only in a $150 nm thick layer closest to the substratum, exactly where establishment and maturation of anchorage and spreading occurs.…”

Integrated Biophotonics with CYTOP

“…Here, CYTOP plays a crucial role in extending the range of possible penetration depths of the excitation field, controlled by varying the waveguide core layer thickness and/or refractive index. For the same reason, so-called reverse symmetry waveguides fabricated on special low-index porous glass substrates (n = 1.2) have been developed and used for refractive index sensing, as well as bacterial and cell monitoring applications [25][26][27]. For a completely symmetric three-layer waveguide there is no cutoff thickness for the core layer and any penetration depth of the evanescent field into the sample solution can, in principle, be realized.…”

Sample handling in surface sensitive chemical and biological sensing: A practical review of basic fluidics and analyte transport

“…First, the introduction and deposition of the cells should ideally result in their uniform distribution on the sensor surface. Second, a sensing area coverage of somewhat more than 50% (typically meaning 2000-6000 deposited eukaryotic cells/mm 2 ) is necessary to allow the relative adhesion strength to be determined; in OWLS-based cytometry, the refractive index change in the evanescent field at 50% coverage is a quantitative measure of cellsubstratum adhesivity [46,67,73]. However, there is an upper limit to the desirable cell density; in order to allow uniformly distributed cells to have enough space for all of them to spread the formation of multilayers or that of cell aggregates should be avoided.…”