RESUMEN
Platelets are anucleate cells that play an important role in wound closure following vessel injury. Maintaining a constant platelet volume is critical for platelet function. For example, water-induced swelling can promote procoagulant activity and initiate thrombosis. However, techniques for measuring changes in platelet volume such as light transmittance or impedance techniques have inherent limitations as they only allow qualitative measurements or do not work on the single-cell level. Here, we introduce high-speed scanning ion conductance microscopy (HS-SICM) as a new platform for studying volume regulation mechanisms of individual platelets. We optimized HS-SICM to quantitatively image the morphology of adherent platelets as a function of time at scanning speeds up to 7 s/frame and with 0.1 fL precision. We demonstrate that HS-SICM can quantitatively measure the rapid swelling of individual platelets after a hypotonic shock and the following regulatory volume decrease (RVD). We found that the RVD of thrombin-, ADP-, and collagen-activated platelets was significantly reduced compared to non-activated platelets. Applying the Boyle van't Hoff relationship allowed us to extract the non-osmotic volume and volume fraction on a single-platelet level. Activation by thrombin or ADP, but not by collagen, resulted in a decrease of the non-osmotic volume, likely due to a release reaction, leaving the total volume unaffected.
RESUMEN
Imaging and probing liquid-liquid interfaces at the micro- and nanoscale are of high relevance, for example, in materials science, surface chemistry, and microfluidics. However, existing imaging techniques are limited in resolution, average over large sample areas, or interact with the sample. Here, we present a method to quantify the shape, stiffness, and interface tension of liquid droplets with the scanning ion conductance microscope (SICM), providing submicrometer resolution and the ability to perform noncontact mechanical measurements. We show that we can accurately image the three-dimensional shape of micrometer-sized liquid droplets made of, for example, decane, hexane, or different oils. We then introduce numerical models to quantitatively obtain their stiffness and interface tension from SICM data. We verified our method by measuring the interface tension of decane droplets changing under the influence of surfactants at different concentrations. Finally, we use SICM to resolve the dissolution dynamics of decane droplets, showing that droplet shape exhibits different dissolution modes and stiffness continuously increases while the interface tension remains constant. We thereby demonstrate that SICM is a useful method to investigate liquid-liquid interfaces on the microscale with applications in materials or life sciences.