posted on 2021-09-16, 16:15authored byCarolyn J. Moll, Giulia Giubertoni, Lennard van Buren, Jan Versluis, Gijsje H. Koenderink, Huib J. Bakker
Hyaluronan is a biopolymer
that is essential for many biological
processes in the human body, like the regulation of tissue lubrication
and inflammatory responses. Here, we study the behavior of hyaluronan
at aqueous surfaces using heterodyne-detected vibrational sum-frequency
generation spectroscopy (HD-VSFG). Low-molecular-weight hyaluronan
(∼150 kDa) gradually covers the water–air interface
within hours, leading to a negatively charged surface and a reorientation
of interfacial water molecules. The rate of surface accumulation strongly
increases when the bulk concentration of low-molecular-weight hyaluronan
is increased. In contrast, high-molecular-weight hyaluronan (>1
MDa)
cannot be detected at the surface, even hours after the addition of
the polymer to the aqueous solution. The strong dependence on the
polymer molecular weight can be explained by entanglements of the
hyaluronan polymers. We also find that for low-molecular-weight hyaluronan
the migration kinetics of hyaluronan in aqueous media shows an anomalous
dependence on the pH of the solution, which can be explained from
the interplay of hydrogen bonding and electrostatic interactions of
hyaluronan polymers.