The Lubricity of Mucin Solutions Is Robust toward Changes in Physiological Conditions

Abstract

Abstract：Solutions of manually purified gastric mucins have been shown to be promising lubricants for biomedical purposes, where they can efficiently reduce friction and wear. However, so far, such mucin solutions have been mostly tested in specific tribological settings, i.e. in combination with different material pairings; variations in the composition of the lubricating fluid have not been systematically explored yet. We here fill this gap and determine the viscosity, adsorption behavior, and lubricity of porcine gastric mucin solutions on hydrophobic surfaces at different pH levels, mucin and salt concentrations and in the presence of other proteins. We demonstrate that mucin solutions provide excellent lubricity even at very low concentrations of 0.01 % (w/v), over a broad range of pH levels and even at elevated ionic strength. Furthermore, we provide mechanistic insights into mucin lubricity, which help explain how certain variations in physiologically relevant parameters can limit the lubricating potential of mucin solutions. Our results motivate that solutions of manually purified mucin solutions can be powerful biomedical lubricants, e.g. serving as artificial joint fluids for viscosupplementation, as eye drops or mouth spray, or as a personal lubricant for intercourse.

Bioinspired Dopamine/Mucin Coatings Provide Lubricity, Wear Protection, and Cell‐Repellent Properties for Medical Applications

“…As reported previously, [ 10f,21 ] the tribological properties of a steel‐on‐PDMS tribo‐paring lubricated with simple buffer are very poor; the very high coefficient of friction (COF) μ we measure here in the boundary lubrication and mixed lubrication regime ( Figure a) underscores this. In part, this bad tribological performance is due to the inability of hydrophobic PDMS to interact well with a water‐based lubricant.…”

“…We test this idea by exploring another material combination, that is, coated steel probed with a polyetheretherketone (PEEK) counter body. This choice is motivated by three aspects: first, steel is a material which is widely used in biomedical applications but—compared to hydrophobic polymer materials—only allows for low levels of passive mucin adsorption [ 21 ] ; second, PEEK is often employed as a counter material for biotribological tests [ 1d,8 ] ; third, with this particular set of experiments, we aim to mimic highly challenging conditions in the boundary lubrication regime where a high contact pressure is expected to entail asperity‐to‐asperity contact and thus significant wear formation. In other words, the chances of the coating to provide protective properties are rather low.…”

Smart Biopolymer‐Based Multi‐Layers Enable Consecutive Drug Release Events on Demand

“…Interestingly, exposing the multi‐layer construct to a physiological NaCl solution induces a slight frequency shift (Figure 3b and Figure S5a, Supporting Information), which can be attributed to a conformational change of mucin molecules from a rather extended state to a more condensed state. [ 29 ] However, this event is fully reversible, which demonstrates that the full multi‐layer is still present when the NaCl is removed. In contrast, when the system is exposed to a GlcNAc, an irreversible increase in the recorded resonance frequency is detected (Figure 3b and Figure S5b, Supporting Information), which indicates a permanent loss of adsorbed mass.…”

“…The adsorption properties of multi‐layers on hydrophobic PDMS surfaces were studied by quartz crystal microbalance with dissipation monitoring (QCM‐D) using a qcell T‐Q2 platform (3T‐Analytik, Tuttlingen, Germany) as described in a previous study. [ 29 ] Since QCM‐D is a very sensitive technique to detect adsorbed molecules, [ 36 ] lower biomolecule concentrations were used here for conducting the coating process in situ: mucin (0.2 mg mL −1 ) and lectin (0.1 mg mL −1 ) solutions were prepared in 20 m m HEPES buffer (pH = 7.4). A dopamine solution (4 mg mL −1 ) was prepared in 50 m m Tris buffer (pH = 8.5).…”

Double-Cross-Linked Networks Based on Methacryloyl Mucin

“…[ 7 ], these products are often purified through chromatography [ 5 , 9 , 10 ], thus increasing the actual price of the starting material. Nevertheless, the complexity of their structure proved to be appealing, and mucins have been studied for their use as carriers for bioactive species [ 11 , 12 ], coatings with improved tribological performance [ 13 , 14 , 15 ], and antifouling properties [ 16 , 17 , 18 , 19 ]. Furthermore, to obtain chemically cross-linked stable hydrogels, protocols describing the modification of other natural macromolecules (such as gelatin [ 20 , 21 ] or chitosan [ 22 , 23 ]) have been used to modify mucin, and they allow for its subsequent polymerization in a manner similar to that performed for synthetic polymers.…”