Microfluidics to innovate in reproductive medicine

VERONICA I. MARCONI

Congreso; SIMPOSIO NANOMED-AR-Nanomedicine; 2021

CHARLA INVITADANowadays it is well known in the physics community that many microswim- mers prefer to swim along walls, but the specific orientation, dynamics or ad- hesion to surfaces for each specie is a complicated issue, still unrevealed. Par- ticularly, ?pushers? swimmers, as E. Coli bacteria or sperm cells are found more likely following surfaces. This produce an excess of population density which presumably plays a crucial role in the development of bacteria biofilms. Sperms cells are believed to follow the boundaries as an orientation mechanisms through the fertilisation in the complex live environment of the female reproduc- tive track. Under laboratory conditions, microfluidics devices had been essential in order to characterise the microswimmer behaviour near surfaces. Recently we have reported human sperm velocity recovery under ultraconfined condi- tions, with a nice agreement between model and experiments [1]. We proposed a model of the sperm motility including cells lateral heading and torque that aligns them close to the walls. In this work we explore even further our sperm model over torque and cell internal noise: from the cellular individual dynamics, as their statistics of char- acteristic times close to the walls, to the population dynamics, as the spatial distribution. We study linear and cubic torque dependence with the orientation angle relative to the surfaces. The calculated characteristic times of spermatic cells swimming along walls are residence, alignment and escape times. A wide range of torque intensity and rotational diffusion coefficient were swept. We find a region in parameter space where the residence times are reduced, although for large torque it diverges. Although the wall accumulation is a population aver- age, it presents a similar behaviour to residence times. At relevant biological and physical scales for micro-swimmers, the residence time and the wall accu- mulation are reduced up to one order of magnitude when the torque is present. [1] M. A. Bettera Marcat, M. N. Gallea, G. L. Min ̃o, M. A. Cubilla, A. J. Banchio, L. C. Giojalas, V. I. Marconi, and H. A. Guidobaldi, Hitting the wall: Human sperm velocity recovery under ultra- confined conditions, Biomicrofluidics 14, 024108(2020) https://doi.org/10.1063/1.5143194