Biolens behavior of RBCs under optically-induced mechanical stress

Francesco Merola, Álvaro Barroso, Lisa Miccio, Pasquale Memmolo, Martina Mugnano, Pietro Ferraro, Cornelia Denz

In this work, the optical behavior of Red Blood Cells (RBCs) under an optically-induced mechanical stress was studied. Exploiting the new findings concerning the optical lens-like behavior of RBCs, the variations of the wavefront refracted by optically-deformed RBCs were further investigated. Experimental analysis have been performed through the combination of digital holography and numerical analysis based on Zernike polynomials, while the biological lens is deformed under the action of multiple dynamic optical tweezers. Detailed wavefront analysis provides comprehensive information about the aberrations induced by the applied mechanical stress. By this approach it was shown that the optical properties of RBCs in their discocyte form can be affected in a different way depending on the geometry of the deformation. In analogy to classical optical testing procedures, optical parameters can be correlated to a particular mechanical deformation. This could open new routes for analyzing cell elasticity by examining optical parameters instead of direct but with low resolution strain analysis, thanks to the high sensitivity of the interferometric tool. Future application of this approach could lead to early detection and diagnosis of blood diseases through a single-step wavefront analysis for evaluating different cells elasticity.

DOI

High-throughput linear optical stretcher for mechanical characterization of blood cells

Kevin B. Roth, Keith B. Neeves, Jeff Squier and David W. M. Marr

This study describes a linear optical stretcher as a high-throughput mechanical property cytometer. Custom, inexpensive, and scalable optics image a linear diode bar source into a microfluidic channel, where cells are hydrodynamically focused into the optical stretcher. Upon entering the stretching region, antipodal optical forces generated by the refraction of tightly focused laser light at the cell membrane deform each cell in flow. Each cell relaxes as it flows out of the trap and is compared to the stretched state to determine deformation. The deformation response of untreated red blood cells and neutrophils were compared to chemically treated cells. Statistically significant differences were observed between normal, diamide-treated, and glutaraldehyde-treated red blood cells, as well as between normal and cytochalasin D-treated neutrophils. Based on the behavior of the pure, untreated populations of red cells and neutrophils, a mixed population of these cells was tested and the discrete populations were identified by deformability.

DOI