QCM-D Measurements Research Articles

The effect of probe density coverage on the detection of oenological tannins in Quartz Crystal Microbalance with Dissipation monitoring (QCM-D) experiments.

Polyphenols are a group of compounds found in grapes, musts, and wines. Their levels are crucial for grape ripening, proper must fermentation, and final wine characteristics. Standard chemical analysis is commonly used to detect these compounds, but it is costly, time-consuming, and requires specialized laboratories and operators. To address this, this study explores a functionalized acoustic sensor for detecting oenological polyphenols. The method involves utilizing a Quartz Crystal Microbalance with Dissipation monitoring (QCM-D) to detect the target analyte by using a gelatin-based probe layer. The sensor is functionalized by optimizing the probe coverage density to maximize its performance. This is achieved by using 12-mercaptododecanoic acid (12-MCA) to immobilize the probe onto the gold sensor surface, and dithiothreitol (DTT) as a reducing and competitive binding agent. The concentration of 12-MCA and DTT in the solutions is varied to control the probe density. QCM-D measurements demonstrates that the probe density can be effectively adjusted using this approach, ranging from 0.2×1013 molecules cm-2 to 2×1013 molecules cm-2 . This study also investigates the interaction between the probe and tannins, confirming the sensor ability to detect them. Interestingly, the lower probe coverage achieves higher detection signals when normalized to probe immobilization signals. Moreover, significant changes in mechanical properties of the functionalization layer are observed after the interaction with samples. The combination of QCM-D with gelatin functionalization holds great promise for future applications in the wine industry. It offers real-time monitoring capabilities, requires minimal sample preparation, and provides high sensitivity for quality control purposes. This article is protected by copyright. All rights reserved.

Effects of Counterion on the Formation and Hydration Behavior of α-Form Hydrated Crystals (α-Gels).

α-Form hydrated crystals form a lamellar gel in which the alkyl chains of the amphiphilic molecules are hexagonally arranged within bilayers below the gel-liquid crystal phase transition temperature. In practice, the lamellar gel network with excess water is called an "α-gel", particularly in the cosmetics industry. In this study, the hydration or water sorption of amphiphilic materials in water vapor was assessed using a humidity-controlled quartz crystal microbalance with dissipation monitoring (QCM-D) technique. The amphiphilic materials used in this study were hexadecyl phosphate salts neutralized with L-arginine (C16P-Arg), CsOH (C16P-Cs), KOH (C16P-K), and NaOH (C16P-Na). Small- and wide-angle X-ray scattering measurements revealed that C16P-Arg and C16P-Cs yielded α-form hydrated crystals. Humidity-controlled QCM-D measurements demonstrated that C16P-Arg and C16P-Cs more readily underwent hydration or water sorption than C16P-K and C16P-Na. The key conclusion is that the significant hydration ability of C16P-Arg and C16P-Cs promotes the formation of the corresponding α-form hydrated crystals.

Effect of metal ions on the flotation separation of biotite from quartz using mixed anionic/cationic collectors

Metal cations have great effects on the flotation of silicate minerals whereas the interaction mechanism is unclear. Single mineral flotation demonstrated that the recovery of biotite rose to 94.69% and 96.41%, and that of quartz declined to 1.21% and 2.01% after introducing small amounts of Ca2+ and Mg2+, respectively. Artificial mixed mineral tests indicated that Ca2+ and Mg2+ could increase the Gaudin's selectivity index by 11.98 and 11.37, respectively, compared with 11.53 without metal ions. QCM-D measurements revealed that sodium oleate (NaOL) and dodecylamine (DDA) could co-absorb on the biotite surface, and a rigid DDA layer formed on these surfaces with/without metal ions. Moreover, the adsorption of NaOL on the biotite surface could be enhanced by Mg2+, from dissipated to rigid adsorption, while that on the quartz surface was barely influenced. Surface chemistry analysis confirmed that metal ions acted as adsorption bridges between mineral surfaces and carboxylate, thereby enhancing the adsorption of collectors.

Interaction Mechanisms and Predictions of the Biofouling of Polymer Films: A Combined Atomic Force Microscopy and Quartz Crystal Microbalance with Dissipation Monitoring Study.

Biofouling of polymeric membranes is a severe problem in water desalination and treatment applications. A fundamental understanding of biofouling mechanisms is necessary to control biofouling and develop more efficient mitigation strategies. To shed light on the type of forces that govern the interactions between biofoulants and membranes, biofoulant-coated colloidal AFM probes were employed to investigate the biofouling mechanisms of two model biofoulants, BSA and HA, toward an array of polymer films commonly used in membrane synthesis, which included CA, PVC, PVDF, and PS. These experiments were combined with quartz crystal microbalance with dissipation monitoring (QCM-D) measurements. The Derjaguin, Landau, Verwey, and Overbeek (DLVO) and the extended-DLVO (XDLVO) theoretical models were applied to decouple the overall adhesion interactions between the biofoulants and the polymer films into their component interactions, i.e., electrostatic (El), Lifshitz-van der Waals (LW), and Lewis acid-base (AB) interactions. The XDLVO model was found to predict better the AFM colloidal probe adhesion data and the QCM-D adsorption behavior of BSA onto the polymer films than the DLVO model. The ranking of the polymer films' adhesion strengths and adsorption quantities was inversely proportional to their γ- values. Higher normalized adhesion forces were quantified for the BSA-coated colloidal probes with the polymer films than the HA-coated colloidal probes. Similarly, in QCM-D measurements, BSA was found to cause larger adsorption mass shifts, faster adsorption rates, and more condensed fouling layers than HA. A linear correlation (R2 = 0.96) was obtained between the adsorption standard free energy changes (ΔGads°) estimated for BSA from the equilibrium QCM-D adsorption experiments and the AFM normalized adhesion energies (WAFM/R) estimated for BSA from the AFM colloidal probe measurements. Eventually, an indirect approach was presented to calculate the surface energy components of biofoulants characterized by high porosities from Hansen dissolution tests to perform the DLVO/XDLVO analyses.

Monitoring Growth and Removal of Pseudomonas Biofilms on Cellulose-Based Fabrics.

Biofilms are often tolerant towards routine cleaning and disinfection processes. As they can grow on fabrics in household or healthcare settings, resulting in odors and serious health problems, it is necessary to contain biofilms through eradication strategies. The current study proposes a novel test model for the growth and removal of biofilms on textiles with Pseudomonas fluorescens and the opportunistic nosocomial pathogen Pseudomonas aeruginosa as model organisms. To assess the biofilm removal on fabrics, (1) a detergent-based, (2) enzyme-based, and (3) combined formulation of both detergent and enzymes (F1/2) were applied. Biofilms were analyzed microscopically (FE-SEM, SEM, 3D laser scanning- and epifluorescence microscopy), via a quartz crystal microbalance with mass dissipation monitoring (QCM-D) as well as plate counting of colonies. This study indicated that Pseudomonas spp. form robust biofilms on woven cellulose that can be efficiently removed via F1/2, proven by a significant reduction (p < 0.001) of viable bacteria in biofilms. Moreover, microscopic analysis indicated a disruption and almost complete removal of the biofilms after F1/2 treatment. QCM-D measurements further confirmed a maximal mass dissipation change after applying F1/2. The combination strategy applying both enzymes and detergent is a promising antibiofilm approach to remove bacteria from fabrics.

Comparison of membrane fouling during ultrafiltration with adsorption studied by quartz crystal microbalance with dissipation monitoring (QCM-D)

Even though membrane technology is used in numerous industrial applications, membrane fouling is still a major challenge. Valuable information on the formation kinetics and structure of the fouling layer can be obtained by in situ real-time monitoring. Quartz crystal microbalance with dissipation monitoring (QCM-D) enables the study of adsorptive fouling in situ on a model membrane. However, so far, there has been no in-depth investigation as to what extent observations from QCM-D relate to fouling during membrane filtration. This gap is here approached by comparing membrane fouling during ultrafiltration with QCM-D measurements using the same feed (process water from thermomechanical pulping) and the same material in the polymer film as in the membrane (hydrophilized polysulfone). The performance at two temperatures (25 °C and 50 °C) was studied. Fouling was analyzed by flux measurements, changes in frequency and dissipation over time with QCM-D, and surface characterization of the membrane samples and QCM-D sensors. QCM-D revealed an increase in rigidity of the fouling layer at 50 °C with time, which was consistent with a higher irreversible resistance during ultrafiltration. This was presumably caused by structural changes of hemicelluloses and colloidal wood extractive droplets in the process water at the higher temperature. The study shows that findings from QCM-D on the attachment of foulants on polymer films are comparable to membrane fouling. Thus, QCM-D, together with complementary analytical methods, can provide valuable insights on the development of membrane fouling of e.g., industrial wastewater.

Proteins at polysaccharide-based biointerfaces: A comparative study of QCM-D and electrokinetic measurements

Controlling protein adsorption on biomaterial surfaces requires a thorough understanding of interfacial phenomena. Proteins adhering after implantation influence successful biointegration. Deciphering adsorption mechanisms at biointerfaces is crucial and of high interest. Here, a combination of time-resolved in situ electrokinetic measurements and quartz crystal microbalance with dissipation monitoring (QCM-D) was employed to understand the adsorption phenomena of blood proteins at thin layers of polysaccharide-based biointerfaces. Adsorption kinetics of bovine serum albumin (BSA), fibrinogen (Fg), and γ-globulin (γG) was studied on polydimethylsiloxane (PDMS) coatings functionalised with chitosan-surfactant complex and hyaluronic acid. The functionalised surfaces show a suppressed protein affinity compared to hydrophobic PDMS. Fg exhibits peculiar adsorption behaviour on PDMS, stemming from the highly oriented end-on adsorption with freely moving α chains. BSA demonstrates arbitrary surface orientation, while γG shows preferential surface orientation on PDMS, exposing a higher density of cationic moieties. The combination of the mentioned techniques proved beneficial for the investigation of interactions, orientations, and changes at biointerfaces in real-time. The approach is versatile and promising where research on surfaces and interfaces is in high demand.

Novel diagnostic and prognostic factors for the advanced melanoma based on the glycosylation-related changes studied by biophysical profiling methods

Melanoma is a life-threatening disease due to the early onset of metastasis and frequent resistance to the applied treatment. For now, no single histological, immunohistochemical or serological biomarker was able to provide a precise predictive value for the aggressive behavior in melanoma patients. Thus, the search for quantifying methods allowing a simultaneous diagnosis and prognosis of melanoma patients is highly desirable. By investigating specific molecular interactions with some biosensor-based techniques, one can determine novel prognostic factors for this tumor. In our previous study, we have shown the possibility of a qualitative in vitro distinguishing the commercially available melanoma cells at different progression stages based on the measurements of the lectin Concanavalin A interacting with surface glycans present on cells.Here, we present the results of the quantitative diagnostic and prognostic study of both commercial and patient-derived melanoma cells based on the evaluation of two novel factors: lectin affinity and glycan viscoelastic index obtained from the quartz crystal microbalance with dissipation monitoring (QCM-D) measurements. Two approaches to the QCM-D measurements were applied, the first uses the ability of melanoma cells to grow as a monolayer of cells on the sensor (cell-based sensors), and the second shortens the time of the analysis (suspension cell based-sensors). The results were confirmed by the complementary label-free (atomic force microscopy, AFM; and surface plasmon resonance, SPR) and labeling (lectin-ELISA; and microscale thermophoresis, MST) techniques. This new approach provides additional quantitative diagnosis and a personalized prognosis which can be done simultaneously to the traditional histopathological analysis.

Detection of Oenological Polyphenols via QCM-D Measurements.

Polyphenols are a family of compounds present in grapes, musts, and wines. Their dosage is associated with the grape ripening, correct must fermentation, and final wine properties. Owing to their anti-inflammatory properties, they are also relevant for health applications. To date, such compounds are detected mainly via standard chemical analysis, which is costly for constant monitoring and requires a specialized laboratory. Cheap and portable sensors would be desirable to reduce costs and speed up measurements. This paper illustrates the development of strategies for sensor surface chemical functionalization for polyphenol detection. We perform measurements by using a commercial quartz crystal microbalance with dissipation monitoring apparatus. Chemical functionalizations are based on proteins (bovine serum albumin and gelatin type A) or customized peptides derived from istatine-5 and murine salivary protein-5. Commercial oenological additives containing pure gallic tannins or proanthocyanidins, dissolved in water or commercial wine, are used for the analysis. Results indicate that selected functionalizations enable the detection of the two different tannin families, suggesting a relationship between the recorded signal and concentration. Gelatin A also demonstrates the ability to discriminate gallic tannins from proanthocyanidins. Outcomes are promising and pave the way for the exploitation of such devices for precision oenology.

Solution and interfacial self-assembly of Bacillus subtilis bacterial lipoteichoic acid (LTA): nanoclustering, and effects of Ca2+ and temperature.

Lipoteichoic acid (LTA) is a major structural and functional molecule in the Gram-positive bacteria membrane. Knowledge of LTA adsorption at interfaces and its solution self-assembly is crucial to understanding its role in bacterial adhesion and colonisation, infections and inflammations. Here, we report the self-assembly behaviour of LTA extracted from Bacillus subtilis, a Gram-positive bacterium, in an aqueous solution using cryogenic transmission electron microscopy (Cryo-TEM) and small-angle neutron scattering (SANS) and its adsorption behaviour at the solid-liquid interface using atomic force microscopy (AFM) imaging and quartz crystal microbalance with dissipation monitoring (QCM-D). The Cryo-TEM results indicated the formation of spherical LTA micelles that decreased in size on addition of calcium chloride (CaCl2), attributed to charge neutralisation and possible formation of stable Ca2+-bridges between the phosphate groups on neighbouring LTA chains. Analysis of the SANS data from the polydisperse LTA aggregates in solution using the two Lorentzian model revealed the existence of two correlation lengths, which could respectively account for the presence of LTA micelle clusters and the local structure arising from LTA intra-molecular interactions. In the presence of CaCl2, the decrease in the correlation lengths of the clusters indicated possible disruption of H-bonding by Ca2+, leading to poorer water-LTA interactions. At higher temperatures, the correlation length corresponding to the clusters increased, indicating a temperature assisted growth caused by the fluidization of micellar core and dehydration of the polar LTA chains. AFM imaging showed that adsorption of LTA aggregates at the SiO2-water interface was significantly prompted by the addition of CaCl2, also confirmed by QCM-D measurements. These unprecedented nanoscopic structural details on the morphology of LTA aggregates in solution and at the solid-liquid interface add to our fundamental understanding of its self-assembly behaviour hitherto underexplored.

Adsorption characterization of various modified β-cyclodextrins onto TEMPO-oxidized cellulose nanofibril membranes and cryogels

TEMPO-Oxidized cellulose nanofibrils (toCNF), in the form of highly entangled network such as membrane or cryogels, have proven to be of interest for various applications, including drug release or purification by pollutant adsorption. β-Cyclodextrins (β-CDs) have the ability to form inclusion complexes with large amount of hydrophobic molecules, and are considered as a promising way to bring new functionalities to these materials, by reducing drug burst release effect or improving the pollutant adsorption properties. The study of the adsorption β-CDs onto toCNF is then crucial to design toCNF/β-CDs materials, but is very complex due to the chemical proximity between these compounds. In this study, we develop toCNF cryogels containing various types of β-CDs derivatives by physical adsorption. Different protocols for analyzing the interactions between these compounds, such as Isothermal Titration Calorimetry (ITC), Quartz-Crystal Microbalance with dissipation monitoring (QCM-d) and a Phenolphthalein-based protocol (PhP protocol) have been performed. Adsorption between β-CD and toCNF was proven at two different temperatures with ITC. QCM-d measurements allowed measuring adsorption of different β-CDs derivatives onto toCNF, with higher adsorption measured for the modified β-CDs, and with estimated binding capacity ranging from 13.4 to 47.6 μmol/g toCNF. PhP protocol allowed us to monitor the amount of β-CDs released in aqueous environment, highlighting a lower release for modified β-CDs onto toCNF, and the results were consistent with the estimated binding capacity. This quantification of the binding adsorption capacity of various β-CDs is key results for optimizing the design of toCNF/β-CDs materials.

Identification of high-affinity phage-displayed VH fragments by use of a quartz crystal microbalance with dissipation monitoring

• Selection of phage-displayed antibody fragments selective to PHA legume lectin. • QCM-D as an effective tool for the evaluation of biomolecular interactions. • Multiparameter analysis identifies clone clusters with similar binding properties. • Improvement of the design of label free bioanalytical assays. Phage display has become a powerful tool for antibody discovery in a wide variety of fields. This technology allows specific binders for a given antigen to be selected from combinatorial libraries. A key step in the process is characterizing and evaluating antibody clones thus selected to reliably identify the best antigen binders. Novel characterization methods can provide essential insight into the binding mechanism and supplement the information obtained with conventional techniques. In this work, we used a quartz crystal microbalance with dissipation monitoring (QCM-D) to determine the kinetic and thermodynamic binding parameters for phage-displayed V H antibody fragments. Phytohemagglutinin (PHA), a legume lectin of analytical interest, was used as a complex model antigen to select specific V H fragments from a phage-displayed library. Eight V H fragments with a unique amino acid sequence were identified as PHA binders by using the well-established enzyme-linked immunosorbent assay (ELISA). QCM-D measurements, structural analysis and principal component analysis (PCA) were used to evaluate the antibody fragments and identify clone clusters with similar binding characteristics and molecular interaction mechanisms. This unprecedented study has enabled the identification of high-affinity phage-displayed V H antibody fragments for PHA, which could be useful for PHA analysis (apparent association constant ranged from 10 8 to 10 10 M −1 ). In fact, the proposed methodology provides a useful tool for evaluating and characterizing antibody fragments with capabilities beyond those of conventional techniques.

Low-fouling properties in serum of carboxylic-oligo(ethylene glycol)-based interfaces

In the present work we evaluated the low-fouling feature of a carboxylic-oligo(ethylene glycol) self-assembled monolayer (carboxylic-OEG-SAM) interface using a quartz crystal microbalance with dissipation monitoring (QCM-D). QCM-D measurements allowed us to estimate the amount of protein loading in two different serum dilutions at two different interfaces: bare gold and carboxylic-OEG. The observed amount of protein adsorbed onto bare gold is about twice higher that of carboxylic OEG interface, confirming the low-fouling characteristics of OEG-modified surfaces. Additionally, QCM-D results demonstrated the existence of two protein adsorption regimes, a faster and a slower, with distinct dissipation energies which was modelled by a two-step kinetic model. The faster regime was attributed to the adsorption of proteins into free sites of the carboxylic-OEG-SAM in a rigid binding process, followed by a slower and more viscoelastic adsorption process ascribed to structural conformational changes; this slower step conforms with the filling of remaining free sites associated with the steric hindrance in which protein-protein interactions defines the slower rate constant for the adsorption.

Generation and Characterization of a Polyclonal Human Reference Antibody to Measure Anti-Drug Antibody Titers in Patients with Fabry Disease.

Male patients with Fabry disease (FD) are at high risk for the formation of antibodies to recombinant α-galactosidase A (AGAL), used for enzyme replacement therapy. Due to the rapid disease progression, the identification of patients at risk is highly warranted. However, currently suitable references and standardized protocols for anti-drug antibodies (ADA) determination do not exist. Here we generate a comprehensive patient-derived antibody mixture as a reference, allowing ELISA-based quantification of antibody titers from individual blood samples. Serum samples of 22 male patients with FD and ADAs against AGAL were pooled and purified by immune adsorption. ADA-affinities against agalsidase-α, agalsidase-β and Moss-AGAL were measured by quartz crystal microbalance with dissipation monitoring (QCM-D). AGAL-specific immune adsorption generated a polyclonal ADA mixture showing a concentration-dependent binding and inhibition of AGAL. Titers in raw sera and from purified total IgGs (r2 = 0.9063 and r2 = 0.8952, both p < 0.0001) correlated with the individual inhibitory capacities of ADAs. QCM-D measurements demonstrated comparable affinities of the reference antibody for agalsidase-α, agalsidase-β and Moss-AGAL (KD: 1.94 ± 0.11 µM, 2.46 ± 0.21 µM, and 1.33 ± 0.09 µM, respectively). The reference antibody allows the ELISA-based ADA titer determination and quantification of absolute concentrations. Furthermore, ADAs from patients with FD have comparable affinities to agalsidase-α, agalsidase-β and Moss-AGAL.

Tracking of Glycans Structure and Metallomics Profiles in BRAF Mutated Melanoma Cells Treated with Vemurafenib.

Nearly half of patients with advanced and metastatic melanomas harbor a BRAF mutation. Vemurafenib (VEM), a BRAF inhibitor, is used to treat such patients, however, responses to VEM are very short-lived due to intrinsic, adaptive and/or acquired resistance. In this context, we present the action of the B-Raf serine-threonine protein kinase inhibitor (vemurafenib) on the glycans structure and metallomics profiles in melanoma cells without (MeWo) and with (G-361) BRAF mutations. The studies were performed using α1-acid glycoprotein (AGP), a well-known acute-phase protein, and concanavalin A (Con A), which served as the model receptor. The detection of changes in the structure of glycans can be successfully carried out based on the frequency shifts and the charge transfer resistance after interaction of AGP with Con A in different VEM treatments using QCM-D and EIS measurements. These changes were also proved based on the cell ultrastructure examined by TEM and SEM. The LA-ICP-MS studies provided details on the metallomics profile in melanoma cells treated with and without VEM. The studies evidence that vemurafenib modifies the glycans structures and metallomics profile in melanoma cells harboring BRAF mutation that can be further implied in the resistance phenomenon. Therefore, our data opens a new avenue for further studies in the short-term addressing novel targets that hopefully can be used to improve the therapeutic regiment in advanced melanoma patients. The innovating potential of this study is fully credible and has a real impact on the global patient society suffering from advanced and metastatic melanomas.

Adsorption and Lubrication of α-Gel (α-Form Hydrated Crystal) Dispersion at Solid/Liquid Interfaces.

We characterized the adsorption and desorption of α-gel (α-form hydrated crystal) dispersions in aqueous media using a quartz crystal microbalance with dissipation monitoring (QCM-D) technique. The α-gel was formed from a mixture of N-[3-(dimethylamino)propyl]docosanamide (APA-22) L-lactic acid salt, 1-octadecanol (C18OH), and water. The solid substrate employed in this study as a model for hair was silica. The QCM-D measurements revealed that the α-gel dispersions yielded a rigid adsorption film on the negatively charged silica surface. The adsorption mass decreased with decreasing domain size (on the micrometer scale) of the α-gel dispersions. The adsorption film highly restricted the desorption of the α-gel from the silica surface even after rinsing with water. The adsorption film also exhibited excellent lubrication ability in aqueous media both before and after rinsing with water. We expect that the α-gel formed by APA-22 L-lactic acid is a potential ingredient for formulating an environment-friendly hair conditioner owing to its high adsorption, limited desorption, and excellent lubrication abilities on the solid surface.

Mechanism of lysozyme adsorption onto gold surface determined by quartz crystal microbalance and surface plasmon resonance

In this study, the physicochemical characterization of lysozyme adsorbed on gold was investigated. Through the use of MP-SPR it was possible to establish that the orientation of molecules changes from side-on to between or end-on with increasing surface coverage. The data confirms that the process of adsorption is driven primarily by electrostatic interactions but also by hydrophobic forces. MP-SPR data was compared with the Random Sequential Adsorption model for a molecule with an ellipsoidal shape. Contact angle measurements showed that higher surface coverage also translates in more hydrophilic properties of obtained lysozyme layer. Comparison of CD and PM-IRRAS spectra in solution and adsorbed state respectively showed changes in the secondary structures of lysozyme. These changes are dependent on pH, but fundamentally they go in the direction of the increase of β-turn/random content with a simultaneous decrease in β-sheet fraction, which suggests that aggregation is not occurring. The combination of MP-SPR and QCM-D measurements allowed the estimation of the number of water molecules associated with the lysozymes films. It has been observed that hydration decreases from 70% in pH = 4 to 30% in pH = 11. This data indicates that hydration is driven mainly by the degree of protonation of lysozyme molecules.

Pickering high internal phase emulsion costabilized by a low amount of bio-based rigid surfactant with microsilica via depletion interaction and synergistic effect

A series of green bio-based polyether surfactant were synthesized based on dehydroabietic acid and used to construct Pickering high internal phase emulsions (HIPEs) with microsilica particles which the dispersed phase fraction could up to 90%. Such surfactants have a high surface activity so that the Pickering HIPEs could be stabilized stably at low concentrations with micron-size silica. The microstructure, droplet size and rheology property of Pickering HIPEs could be regulated by varying the microsilica content or dispersed phase fraction. The QCM-D measurements revealed that the nonionic surfactant could adsorb on surface of silica particles, giving rise to the change of wettability of the hydrophilic particles and rendering the particles surface-active. The coated particles were more likely to adsorb at the oil-water interface of droplets. The synergistic effects of hydrophilic silica particles and this nonionic surfactant promoted the formation of stable Pickering HIPEs. Moreover, the depletion interaction between droplets and hydrophilic particles was also the vital factor in the stability of the Pickering HIPEs. Once particles were adsorbed, particles at the interface were inhibited desorption by depletion attraction. This work suggests another possible mechanism for better stability of Pickering HIPEs in nonionic surfactant/particles system, and our strategy to preparing Pickering HIPEs is environmentally friendly by using a bio-based surfactant, which has wide potential application in cosmetics, pharmaceuticals, food, environmental protection, materials, and so on.

Adsorption of aqueous copper chlorophyllin mixtures on model surfaces

Measured were the colloidal and adsorption properties of copper chlorophyllin (CuChl), a complex mixture derived from chlorophyll that is used as a food additive and in other applications. CuChl has an “apparent solubility” (it is a mixture) of 0.1 g/L in PBS buffer. Dynamic light scattering of dilute solutions showed the presence of particles with diameters in the range 10−800 nm. Nanoparticle tracking analysis (NanoSight LM10) showed the majority of nanoparticles had hydrodynamic diameters 100−200 nm. Dialysis experiments revealed that 58 % of a 0.1 g/L CuChl was present as dispersed particles. QCM-D measurements showed that aqueous CuChl adsorbs on surfaces giving a maximum adsorbed coverage, Γmax, that is sensitive to the type of surface; cellulose > polystyrene>> pullulan > silica = 0. No adsorption was observed on silica. Centrifuged CuCe6, a pure chlorin, showed essentially the same adsorption behaviors as centrifuged CuChl mixtures on polystyrene, suggesting that chlorins are the dominant adsorbed species from CuChl mixtures on hydrophobic surfaces. Centrifuged CuChl and CuCe6 usually gave lower Γmax values compared to non-centrifuged samples. In all cases, rinsing with buffer after CuChl or CuCe6 adsorption resulted in the immediate removal of some of the adsorbed chlorins. With cellulose there was no further dissolution, whereas with polystyrene, the adsorbed layer eventually was entirely removed. AFM measurements showed the adsorbed materials included nanoparticles. The surfactants SDS or DTAB could displace CuChl adsorbed on cellulosic filter paper only if the surfactant concentrations were above the critical micelle concentration.

Development of Hospital Formulations Based on Medical Need

Aphthous stomatitis is induced by chemotherapy and radiotherapy. It has been reported that 100% of patients administered high-dose chemotherapy and 80% of patients receiving radiotherapy develop stomatitis. The most serious cases are accompanied by pain and bleeding of the ulcers, which cause significant suffering and reduce patients' quality of life. Rebamipide (RB) was developed in Japan as a treatment for gastric ulcer. In this study, we prepared and evaluated a mouthwash for stomatitis taking into consideration the solubilization of RB. RB nanoparticles were prepared by the wet-milling technique using various forms of hydroxypropyl cellulose (HPC-L, -SL, and -SSL) and sodium lauryl sulfate (SLS). RB nanoparticles sized between 126.6 and 286.8 nm were obtained under various conditions. From the results of zeta potential measurement and evaluation of their dispersibility, it appeared that the prepared nanosuspensions were stable. Furthermore, adhesion of the nanoparticles to the mucous membrane in the oral cavity was evaluated using quartz crystal microbalance with dissipation monitoring (QCM-D) technology. From the changes in the thickness of the gold sensor observed in QCM-D measurement, it was suggested that HPC-SSL molecules interact with mucin mounted on the gold sensor. It appears feasible to utilize RB nanoparticles dispersed in HPC-SSL solution in mouthwash to prevent stomatitis.