Mineral dissolution products drive anammox nitrogen removal via sludge aggregation.

Combined quartz crystal microbalance with dissipation (QCM-D) and generalized ellipsometry (GE) to characterize the deposition of titanium dioxide nanoparticles on model rough surfaces

Impacts of carrier properties, environmental conditions and extracellular polymeric substances on biofilm formation of sieved fine particles from activated sludge

In situ kinetic study of zinc sulfide activation using a quartz crystal microbalance with dissipation (QCM-D)

Phase-transition induced structural changes of 1,2-ditridecanoyl-sn-glycero-3-phosphocholine (DTPC) lipid vesicles adsorbed on a titanium oxide (TiO(2)) surface have been investigated using a quartz crystal microbalance with dissipation (QCM-D) monitoring device. The frequency and energy dissipation responses obtained upon scanning the temperature across the phase-transition temperature were fitted to a Voigt-based viscoelastic model. The phase-transition induced changes of the effective viscosity and effective film thickness were used to define the phase transition temperature, explore hysteresis upon temperature sweeps with different rates and to unravel structural changes during the phase transition. To explore the influence of the vesicle-surface interaction on the phase-transition behavior, salt content and pH were varied. The results reveal less pronounced hysteresis and higher phase-transition temperatures with increasing strength of the surface interaction. The advantage of probing phase-transition induced structural changes without external labels and the validity of the Voigt-based model to represent the QCM-D response for adsorbed lipid vesicles are discussed.

C-reactive protein (CRP), a biomarker for cardiovascular disease, has been reported to have a strong affinity to zwitterionic phosphorylcholine (PC) groups in the presence of calcium ions. In addition, PC-immobilized surfaces have been used as a nonfouling coating to prevent nonspecific protein binding. By appropriately using the features of PC-immobilized surfaces, including specific recognition to CRP and nonfouling surface, it is reasonable to create an antibody-free biosensor for the specific capture of CRP. In this study, PC-functionalized 3,4-ethylenedioxythiophene (EDOT) monomers were used to prepare PC-immobilized surfaces. The density of PC groups on the surface can be fine-tuned by changing the composition of the monomer solutions for the electropolymerization. The density of PC group was confirmed by X-ray photoelectron spectroscopy (XPS). The specific interaction of CRP with PC groups was monitored by using a quartz crystal microbalance with dissipation (QCM-D). The amount of protein binding could be estimated by the reduction in frequency readout. Through the QCM-D measurement, we revealed the nonfouling property and the specific CRP capture from our PC-immobilized surfaces. Notably, the dissipation energy also dropped during the binding process between CRP and PC, indicating the release of water molecules from the PC groups during CRP adsorption. We anticipate that surface-bound water molecules are mainly released from areas near the immobilized PC groups. Based on Hofmeister series, we further examined the influence of ions by introducing four different anions including both kosmotrope (order maker) and chaotrope (disorder maker) into the buffer for the CRP binding test. The results showed that the concentration and the type of anions play an important role in CRP binding. The present fundamental study reveals deep insights into the recognition between CRP and surface-immobilized PC groups, which can facilitate the development of CRP sensing platforms.

A comparative study of biopolymer adsorption on model anisotropic clay surfaces using quartz crystal microbalance with dissipation (QCM-D)

Investigation of SARS-CoV-2 nucleocapsid protein interaction with a specific antibody by combined spectroscopic ellipsometry and quartz crystal microbalance with dissipation

Lignosulfonates obtained from pulping spent liquor are nontoxic and renewable polymers with excellent dispersibility as disperse dye dispersants. In order to reveal its dispersion mechanism on the dye, the adsorption characteristics of sodium lignosulfonate (NaLS) and sodium naphthalenesulfonic acid formaldehyde (NSF) were investigated using a quartz crystal microbalance with dissipation (QCM-D) and an atomic force microscope (AFM). The results showed that the adsorption of dispersant onto the dye film layer was low and unstable without salt, but the adsorption amount of NaSL or NSF onto dye film was increased significantly with the increase in ionic strength. This indicated that hydrophobic effect was the main interaction between dispersant and dye. The adsorption amounts of both dispersants were decreased with the increase in temperature. NaLS exhibited the better dispersion and improved stability at high temperature than NSF due to higher adsorption amount and the viscoelastic adsorption layer.

Protein-surface Interactions and Functional Geometry of Surface-adsorbed Myosin Motor Fragments

The enhancement mechanisms of mucin and lactoferrin on α-amylase activity in saliva: Exploring the interactions using QCM-D and molecular docking

This paper presents a study of supported lipid bilayer (SLB) formation and subsequent protein binding using a sensor that combines localized surface plasmon resonance (LSPR) and quartz crystal microbalance with dissipation (QCM-D) monitoring. The LSPR activity arises from silicon oxide (SiO x ) coated nanometric apertures in a thin gold film, which also serves as the active electrode of a QCM-D crystal. Both transducer principles provide signatures for the formation of a SLB upon adsorption and subsequent rupture of adsorbed lipid vesicles. However, the two techniques are sensitive over different regions of the sample: LSPR primarily inside and on the rim of the holes and QCM-D primarily on the planar areas between the holes. Although the dimension of the lipid vesicles is on the same order as the dimension of the nanoholes, it is concluded from the response of the combined system that vesicle rupture in the nanoholes and on the planar region between the holes is synchronized. Furthermore, by determining the thickness of the SLB from the QCM-D response, the characteristic decay length of the LSPR field intensity could be determined. This made it possible not only to determine the mass and refractive index of the homogeneous SLB but also to postulate a generic means to quantify the LSPR response in terms of mass-uptake also for nonhomogeneous films. This is exemplified by measuring the adsorbed lipid mass during vesicle adsorption, yielding the critical lipid vesicle coverage at which spontaneous rupture into a planar bilayer occurs. The generic applicability and versatility of the method is demonstrated from specific protein binding to a functionalized SLB. From the absolute refractive index of the protein, provided from the LSPR data alone, it was possible to determine both the effective thickness of the protein film and the molecular mass (or number) of bound protein.

Dehydrogenation polymers (DHPs) can be prepared from coniferyl alcohol (CA), but not solely from sinapyl alcohol (SA) when catalyzed by horseradish peroxidase (HRP). However, it has been proven that from a mixture of CA and SA, DHP with SA incorporated can be formed even with HRP. Conventional experiments using this mixed monolignol system required large amounts of monolignols and enzymes. The use of a quartz crystal microbalance with dissipation (QCM-D) can overcome this drawback. In this study, the dehydrogenative copolymerization of small amounts of CA/SA mixtures and HRP was performed on a QCM-D to further explore the benefits of this system. The DHPs were successfully formed from mixed monolignols on the QCM-D system, and the incorporation of the SA unit was verified through differences in DHP formation between binary monolignol systems and the corresponding CA-single systems. The formation of DHP in the presence of the polysaccharide matrix was performed at the same reaction scale, and the promotional effect of partially acetylated xylan on DHP formation was observed, especially at high CA ratios. The QCM-D monitoring system will be a valuable tool for analyses under limited substrates and/or enzymes that may be encountered in the future.

Cell signaling is one of the fundamental processes that control the cell fate. It modulates the cell shape and mechanics. To identify the dynamic signaling pathway in situ, we need tools that are capable of monitor the real-time elasticity and viscosity changes as well as structural rearrangements. Atomic Force Microscopy (AFM) has been demonstrated to be an effective instrument to visualize membrane and cytoskeleton structures on live cells. It can also provide the mechanical stiffness information by recording force displacement curves. Meanwhile, the viscoelasticity change by signaling pathways can be measured as the change of dissipation of a monolayer of cells by means of a Quartz Crystal Microbalance with Dissipation (QCM-D). In the current study, we use the human epidermoid carcinoma A431 cell line as a model system which will be stimulated by epidermal growth factor (EGF). AFM was first used to image the structure of live A431 cells before and after stimulation; force measurement was also performed to analyze the dynamic elasticity change. The change of viscoelasticity of the A431 cell induced by EGF was monitored in real time on a QCM-D in terms of dissipation change and frequency shift. The mechanical property measurements from AFM and QCM-D experiment was analyzed and compared. Quantitative analysis can be performed to obtain the dynamic modulus of the material through theoretical modeling. This novel combination can be complementary to each other. A unified profile can therefore be generated as an effective indicator of signaling pathways such as cell proliferation and apoptosis.

The viscoelastic behavior of surface-tethered poly(N-isopropylacrylamide), or poly(NIPAAm), networks in contact with aqueous solutions was characterized by the quartz crystal microbalance with dissipation (QCM-D). To avoid ambiguities in the data analysis, four integer multiples of the dry thickness (h = k x 36 nm, where k = 1, 2, 3, 4) were analyzed at the third through ninth overtones of the QCM-D signal. At the third overtone, the networks resembled rigid films and the viscoelastic behavior could not be ascertained. With increasing overtones, however, the films showed deviation from the rigid film limit, allowing for analysis of the viscoelastic parameters. As the network collapsed over the temperature range of 15-40 degrees C, the shear modulus of the network increased by a factor of 24 (from 5 to 120 MPa); the shear viscosity, on the other hand, increased only by a factor of 2 (from 40 to 80 cP). The high values of the shear modulus suggest the QCM-D probes a regime where the polymer mesh does not adequately relax, and the high values of the shear viscosity suggest significant polymer-polymer coil overlap above and below the demixing temperature. Finally, the influence of NaCl on the viscoelastic response was measured. Interestingly, NaCl affects the shear modulus of the networks but not the dynamics.

Quartz Crystal Microbalance Studies of Multilayer Glucagon Fibrillation at the Solid-Liquid Interface