Fig. 2.

Brush concentration profiles, nanoparticle sieving and growth dynamics. a Fluorescent profile of a planar HA brush and its intensity profile. b Fluorescent profile of spherical brush and its intensity profile. In both a, b the brush growth time is 4 h at 30 °C and the ionic strength 150 mM. c−e Cross-section of brush grown for 4 h on 8 µm microsphere (left) and the particle penetration intensity profile (right) for c 20 nm, 150 mM, d 200 nm, 150 mM and e 200 nm, 1.5 mM. Twenty nanometer particles show a distinct gradient within the brush while 200 nm particles remain excluded. Dextran (10 kDa, ~5 nm) is present in all cases (cyan) and shows an enhanced gradient in the low ionic strength swollen brush. f Dynamic growth of hyaluronan brushes generated by HA synthase (150 mM). The brush height reaches 2.62 ± 0.2 µm (st. dev.) in just 1 h (planar) in high ionic strength conditions. After 16 h the brush is 10.6 ± 1.0 µm (st. dev.). Measurements from individual brushes are shown in gray, averages and standard deviations are indicated in black. N_planar = 3 brushes, 12 regions per sample, except 16 h brush which is just one brush. The spherical brush plateaus at much earlier times (~5 h) at a final height of 4.3 ± 0.4 µm (st. dev.). N_spherical > 120 for spherical brush height measurements. All scale bars are 5 µm.