Lateral Microscope Enables the Direct Observation of Cellular Interfaces and Quantification of Changes in Cell...

The ability to observe cell adhesion processes in real-time remains a grand challenge in basic biology and medicine. Toward this goal, we have developed a lateral optical microscope that allows direct observation of cell-substrate interactions in real-time on any substrate-transparent, opaque, or coated-without requiring labels or specialized optical components. We demonstrate the use of our lateral microscope by quantifying dynamic changes in cell morphology during the first 90 min of adhesion to various materials. Specifically, we determined the rates of change in contact angle of HeLa, 3T3, HEK293, and MDA-MB-231 cells on five different substrates: glass, collagen-coated glass, Nylon, PTFE, and collagen-alginate hydrogels. We used these rates of change to compare adhesion of different cell lines on each surface, and to rank the adhesion-promoting capacities of the five surfaces for each cell line. For HeLa, 3T3, and HEK293 cells, we observed maximal rates of change in contact angle (0.058 min^-1) on collagen-coated glass substrates. All five cell lines exhibited minimal rates of change (0.006 min^-1) on PTFE. Lateral microscopy also revealed a unique morphology among MDA-MB-231 breast cancer cells during initial adhesion, which we quantified using measurements of changes in cell height. Our lateral microscope will not only enable more comprehensive, quantitative studies of cell adhesion to inform the development of biomaterials but will ultimately assist in advancing our understanding of many important biological processes and discovering new behaviors related to cell adhesion.