Journal: Scientific Reports

Article Title: Single-cell adhesion force kinetics of cell populations from combined label-free optical biosensor and robotic fluidic force microscopy

doi: 10.1038/s41598-019-56898-7

Figure Lengend Snippet: The optical biosensor measurement workflow and results. ( a ) Schematic of the measurement workflow. The cancer cells are pipetted into the custom well containing the array of 2 × 2 mm optical sensors. After sedimentation cells adhere to the functionalized sensor surface that is illuminated from below (yellow-green arrow) and reflects only a certain resonant wavelength (red arrow). The evanescent field (red shadow above the sensor) penetrates into the surface structures of the cell such as the integrins, the membrane, the actin filaments and the additional proteins that make up the adhesion site (top right drawing). ( b , c ) Photographs showing the custom-made biosensor insert holder (in a hand, and placed into the Epic Cardio device) with two circular wells optimized for subsequent FluidFM BOT measurements. The large area of each well contains twelve 2 × 2 mm 2 biosensors simultaneously read out, and allows for navigating later with the FluidFM BOT probe over centimeter wide surfaces. ( d ) Photograph of the Epic Cardio biosensor insert. The 2 × 2 mm 2 sensor areas are visible as colorful squares due to light diffraction on the embedded grating. ( e ) Raw WS signal image of a single sensor area at t = 90 min (color bar at top right corner). Individual cells are well separable as the pixel size is 25 × 25 µm 2 . ( f ) Comparison of different thresholding strategies of recorded biosensor images. The top left part shows the original biosensor image with a 3 rd degree interpolation. The bottom left and right pictures show the effect of applying a constant threshold of 1000 and 300 picometers respectively: the former underestimates the cell areas, while the latter overshoots and creates unrealistic interconnected cells. It is apparent that the introduced unique thresholding (top right image) gives a better agreement with the original image and the cell perimeter can be determined accurately. ( g ) Fused image of the biosensor signal and the brightfield picture, showing a clear correspondence between the two overlapping modalities. Moreover, it is observable that cells with similar area can produce distinct WS amplitudes, thus our IWS (incorporating both size and WS of the cell) is indeed a suitable measure of cell adhesion. On the upper part, the original resolution biosensor data was used, while the lower image is a 4 th degree interpolated picture. ( h ) The Voronoi tessellation of a sensor area. Red dots indicate the local maxima of the signal that were taken as the generators of the tesselation. Red edges separate the individual segments belonging to the generator included within them. During evaluation, a cell-specific threshold calculated from the maximal pixel value was applied individually in every segment. ( i ) Area matching segmentation: the combined optical biosensor and brightfield picture shows how the segmented cell perimeter (red) approximates the actual cell perimeter measured on the microscope image (black) after setting the optimal threshold.

Article Snippet: The Epic Cardio imager biosensor (Corning Inc., Corning, NY, USA) used in our experiments accepts 384-well Society for Biomolecular Screening (SBS) standard format biosensor microplates.

Techniques: Sedimentation, Membrane, Comparison, Microscopy

Journal: Scientific Reports

Article Title: Single-cell adhesion force kinetics of cell populations from combined label-free optical biosensor and robotic fluidic force microscopy

doi: 10.1038/s41598-019-56898-7

Figure Lengend Snippet: Calibration of the biosensor signal by FluidFM BOT measurements ( a ) Demonstration of the developed methodology: Individual cells are first let to spread and adhere in the biosensor device while their IWS signal is recorded. ( b ) Afterwards, the same single-cells are detached from the surface and their force-distance curves are measured using the FluidFM BOT device. ( c , d ) Correlation between the IWS signal and adhesion energies as well as IWS signal and adhesion forces measured in the experiments on the same single-cells. The linear correlation coefficients were determined as C = 0.8607 for the adhesion energy- and C = 0.8945 for the adhesion force versus the IWS recorded by the optical biosensor. ( e ) Corresponding brightfield microscopy images are also taken in order to facilitate the thresholding of the Cardio imager data. The scale bars represent 100 µm. (S, M and L marks a typical Small, Medium and Large sized cell, respectively.)

Article Snippet: The Epic Cardio imager biosensor (Corning Inc., Corning, NY, USA) used in our experiments accepts 384-well Society for Biomolecular Screening (SBS) standard format biosensor microplates.

Techniques: Microscopy

Journal: Scientific Reports

Article Title: Single-cell adhesion strength and contact density drops in the M phase of cancer cells

doi: 10.1038/s41598-021-97734-1

Figure Lengend Snippet: Comparative table to overview the capabilities of different cell adhesion measurement techniques 36 .

Article Snippet: The Epic Cardio RWG imager biosensor (Corning Inc., Corning, NY, USA) was used in our experiments which accepts 384-well Society for Biomolecular Screening (SBS) standard format biosensor microplates.

Techniques: In Situ

Journal: Scientific Reports

Article Title: Single-cell adhesion strength and contact density drops in the M phase of cancer cells

doi: 10.1038/s41598-021-97734-1

Figure Lengend Snippet: Schematic representation of the adhesion strength measurements on single cells using a computer-controlled micropipette and the high-resolution RWG biosensor (Single-Cell RWG) , . ( A ) Region of interest (ROI) of RGD-displaying Petri dish surface containing HeLa Fucci cells is scanned, then cells are automatically detected and selected for measurement. The developed device automatically adjusted the vacuum in a syringe connected to a micropipette with 70 micron opening, positioned the micropipette above the targeted cell and opened the fluidic valve. Adhesion characteristics of cells were evaluated by calculating the ratio of still adhering cells after the application of subsequent suction force steps on hundreds of cells. ( B ) Incident light is coupled into the biosensor chip through the waveguide grating and penetrates into a 150 nm depth into the sample (adhering cell) on the chip surface in the form of an evanescent field (red shadow above the waveguide surface). Thus field is ideal to monitor the cell-substratum contact zone. Biochemical or cellular events, such as cell adhesion change the local refractive index inside the evanescent field, resulting in a wavelength shift of the reflected light. Due to the large spatial resolution, individual cells are clearly visible on the recorded wavelength shift map. The wavelength shift is sensitive to nanometer scale changes in the cell adhesion contacts (perpendicular to the sensor surface). Such tiny variations are not resolvable by traditional optical microscopy.

Article Snippet: The Epic Cardio RWG imager biosensor (Corning Inc., Corning, NY, USA) was used in our experiments which accepts 384-well Society for Biomolecular Screening (SBS) standard format biosensor microplates.

Techniques: Refractive Index, Microscopy