Water Sorption and Structural Properties of Human Airway Mucus in Health and Muco-Obstructive Diseases

Muco-obstructive diseases change airway mucus properties, impairing mucociliary transport and increasing the likelihood of infections. To investigate the sorption properties and nanostructures of mucus in health and disease, we investigated mucus samples from patients and cell cultures (cc) from healthy, chronic obstructive pulmonary disease (COPD), and cystic fibrosis (CF) airways. Atomic force microscopy (AFM) revealed mucin monomers with typical barbell structures, where the globule to spacer volume ratio was the highest for CF mucin. Accordingly, synchrotron small-angle X-ray scattering (SAXS) revealed more pronounced scattering from CF mucin globules and suggested shorter carbohydrate side chains in CF mucin and longer side chains in COPD mucin. Quartz crystal microbalance with dissipation (QCM-D) analysis presented water sorption isotherms of the three types of human airway mucus, where, at high relative humidity, COPD mucus had the highest water content compared to cc-CF and healthy airway mucus (HAM). The higher hydration of the COPD mucus is consistent with the observation of longer side chains of the COPD mucins. At low humidity, no dehydration-induced glass transition was observed in healthy and diseased mucus, suggesting mucus remained in a rubbery state. However, in dialyzed cc-HAM, a sorption-desorption hysteresis (typically observed in the glassy state) appeared, suggesting that small molecules present in mucus suppress the glass transition.

Heteromultivalent Ligand Display on Reversible Self-Assembled Monolayers (rSAMs): A Fluidic Platform for Tunable Influenza Virus Recognition

We report on the design of heteromultivalent influenza A virus (IAV) receptors based on reversible self-assembled monolayers (SAMs) featuring two distinct mobile ligands. The principal layer building blocks consist of α-(4-amidinophenoxy)alkanes decorated at the ω-position with sialic acid (SA) and the neuraminidase inhibitor Zanamivir (Zan), acting as two mobile ligands binding to the complementary receptors hemagglutinin (HA) and neuraminidase (NA) on the virus surface. From ternary amphiphile mixtures comprising these ligands, the amidines spontaneously self-assemble on top of carboxylic acid-terminated SAMs to form reversible mixed monolayers (rSAMs) that are easily tunable with respect to the ligand ratio. We show that this results in the ability to construct surfaces featuring a very strong affinity for the surface proteins and specific virus subtypes. Hence, an rSAM prepared from solutions containing 15% SA and 10% Zan showed an exceptionally high affinity and selectivity for the avian IAV H7N9 (Kd = 11 fM) that strongly exceeded the affinity for other subtypes (H3N2, H5N1, H1N1). Changing the SA/Zan ratio resulted in changes in the relative preference between the four tested subtypes, suggesting this to be a key parameter for rapid adjustments of both virus affinity and selectivity.

Microcontact-Imprinted Optical Sensors for Virulence Factors of Periodontal Disease

Periodontitis (gum disease) is a common biofilm-mediated oral condition, with around 7% of the adult population suffering from severe disease with risk for tooth loss. Moreover, periodontitis virulence markers have been found in atherosclerotic plaque and brain tissue, suggesting a link to cardiovascular and Alzheimer's diseases. The lack of accurate, fast, and sensitive clinical methods to identify patients at risk leads, on the one hand, to patients being undiagnosed until the onset of severe disease and, on the other hand, to overtreatment of individuals with mild disease, diverting resources from those patients most in need. The periodontitis-associated bacterium, Porphyromonas gingivalis, secrete gingipains which are highly active proteases recognized as key virulence factors during disease progression. This makes them interesting candidates as predictive biomarkers, but currently, there are no methods in clinical use for monitoring them. Quantifying the levels or proteolytic activity of gingipains in the periodontal pocket surrounding the teeth could enable early-stage disease diagnosis. Here, we report on a monitoring approach based on high-affinity microcontact imprinted polymer-based receptors for the Arg and Lys specific gingipains Rgp and Kgp and their combination with surface plasmon resonance (SPR)-based biosensor technology for quantifying gingipain levels in biofluids and patient samples. Therefore, Rgp and Kgp were immobilized on glass coverslips followed by microcontact imprinting of poly-acrylamide based films anchored to gold sensor chips. The monomers selected were N-isopropyl acrylamide (NIPAM), N-hydroxyethyl acrylamide (HEAA) and N-methacryloyl-4-aminobenzamidine hydrochloride (BAM), with N,N'-methylene bis(acrylamide) (BIS) as the crosslinker. This resulted in imprinted surfaces exhibiting selectivity towards their templates high affinity and selectivity for the templated proteins with dissociation constants (K _d) of 159 and 299 nM for the Rgp- and Kgp-imprinted, surfaces respectively. The former surface displayed even higher affinity (K _d = 71 nM) when tested in dilute cell culture supernatants. Calculated limits of detection for the sensors were 110 and 90 nM corresponding to levels below clinically relevant concentrations.