Fig. 2: Cholesterol SCLs dynamically adapt to the polarity of their environment.
From: Entropic repulsion of cholesterol-containing layers counteracts bioadhesion
a,b, Contact time-dependent interaction forces (determined by AFM-based force spectroscopy) between a hydrophobic colloidal probe (a) (∅10 µm silica bead modified with a hydrophobic silane) or individual E. coli cells (b) (attached to a ∅10 µm silica bead) and cholesterol SCLs or thiocholesterol and thiocholenic acid SAMs. Experiments were performed at 37 °C. a,b, Mean ± s.e.m. Data were obtained from at least three independent experiments. Regressions are the best-fit solutions for a third-order process indicating formation of bonds at the probe cell–SCL interface following \(\frac{{\rm{d}}\sigma }{{\rm{d}}t}=-\,k{\sigma }^{3}\) (for details see Supplementary Note 1). The interaction force was assumed to be directly correlated to the surface concentration of formed bonds, σ. Coefficients of determination (R2) for fits are shown. c, Representative images showing the dynamic contact angles of water on the surface of a cholesterol SCL. The high advancing contact angle (θadv, blue box) reflects a hydrophobic surface. Following immediate withdrawal of the droplet (no resting period, green box), a slightly reduced but still high receding contact angle (θrec) was observed. No receding of the three-phase contact line was observed when the water droplet was withdrawn after a 20 s resting period (red box). d, During the 20 s resting period, oscillations in the three-phase contact line between the initial advancing angle (93°) and an approximately 10° lower angle were observed.
