A biomimetic device combining microfluidics with nanotechnology allows studying the adhesion of erythrocytes to blood vessels.

SAFFIOTI, N.A.; LEAL DENIS MF; HERLAX V; SCHWARZBAUM P; PALLAROLA D.

Congreso; 20th IUPAB Congress, 45th Annual SBBf Meeting, and 50th Annual SBBq Meeting; 2021

Erythrocytes under pathological conditions undergo eryptosis, a process characterized by biochemical and morphological changes such as phosphatidylserine (PS) exposure to the external layer of the plasma membrane. Eryptotic erythrocytes adhere to the endothelial cells (EC), which may have an important role in bacterial infections and malaria. The adhesion mechanism is unknow, however PS has been proposed as an important mediator as the EC express PS receptors. To understand the adhesion mechanism, we designed a device that combines microfluidics with nanostructured surfaces to mimic the capillary architecture and the protein expression of the EC. Microfluidic chips were prepared in PDMS using moulds fabricated by photolithography. Nanostructured surfaces were synthesized by block copolymer lithography and consisted of a glass surface covered with 7 nm diameter gold nanoparticles (AuNP), arranged in a quasi-hexagonal array. The microfluidic chip was adhered to the nanostructured surface by an O2 plasma treatment. The AuNP were modified with a polyethylene glycol chain (PEG) that binds to the AuNP by a thiol in one extreme and has a nitriloacetic group (NTA) in the other. The NTA binds proteins expressing a His-Tag. The surface not occupied by AuNP was covered with PLL-g-PEG. We corroborated the specific AuNP functionalization by quartz microbalance and fluorescence microscopy using a GFP-His Tag. Then, we studied the erythrocytes adhesion to a device functionalized with Annexin V at different flows. Two conditions that promote eryptosis, incubation at 50° or incubation with ionomycin, significantly increased the adhesion of erythrocytes up to 1,5 dyn/cm2 in comparison with normal erythrocytes. However, eryptotic erythrocytes also adhered to a device functionalized with PEG without NTA groups. This indicates that erythrocytes adhesion may not be mediated only by PS receptors. Future experiments will test the ability of different proteins expressed by the EC to elicit erythrocyte adhesion.