In situ studies of bovine serum albumin adsorption onto functionalized polystyrene latices monitored with a quartz crystal microbalance technique

The adsorbability of bovine serum albumin (BSA) onto poly(styrene‐co‐itaconic acid) (PS–IA), poly(styrene‐co‐hydroxyethyl methacrylate) (PS–HEMA), poly(styrene‐co‐acrylic acid) (PS–AA), and poly(styrene‐co‐methacrylic acid) (PS–MAA) latices were investigated with a quartz crystal microbalance. The amount adsorbed onto the functionalized latices, except for PS–MAA, was greater than that adsorbed onto polystyrene (PS) latex. To explain this result, two kinds of interaction forces were considered, hydrogen bonding and hydrophobic interactions, whereas electrostatic interaction was assumed to be small. When comparing the two extremes of hydrophobic interaction and hydrogen bonding, the latter was stronger. The corrected adsorption mass suggested that the BSA molecules were adsorbed onto the PS–MAA latex in a side‐on mode. However, in the case of the PS, PS–IA, PS–HEMA, and PS–AA latices, the BSA molecules were probably adsorbed in multiple layers. The presence of the BSA in the latex particle surface was verified by attenuated total reflectance/Fourier transform infrared spectroscopy and atomic force microscopy. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42055.     

In situ investigation of lysozyme adsorption into polyelectrolyte brushes by quartz crystal microbalance with dissipation

A well understanding about protein adsorption into charged polymer brushes is of importance in the elucidation of mechanism and important phenomena (such as “chain delivery” effect) in protein adsorption on polymer-grafted ion exchange adsorbents. In this work, quartz crystal microbalance with dissipation (QCM-D) was introduced to in situ investigate lysozyme adsorption on QCM sensors grafted with poly(3-sulfopropyl methacrylate) (pSPM) via atom transfer radical polymerization. It was achieved by analyzing frequency (f) and energy dissipation (D) shift simultaneously on pSPM-grafted sensors. The result showed that an initial decrease in ΔD was typical of lysozyme adsorption on pSPM-grafted sensor and more significant with an increase of chain length and grafting density. It was attributed to significant water release in the hydration layer of protein and polymer chains in lysozyme adsorption into pSPM brushes. On pSPM-grafted sensors with long and dense chains, furthermore, lysozyme transitioned from monolayer to multilayer adsorption and the maximum adsorbed amount was obtained to be 374.0?ng·cm^?2 among all pSPM-grafted sensors in this work. The results in D-f plot further revealed that lysozyme adsorption into pSPM brushes increased the rigidity of adsorbed layer and little structure adjustment of adsorbed lysozyme. It was unfavorable for “chain delivery” effect for facilitated transport of adsorbed protein. This work provided valuable insight into protein adsorption in pSPM brushes and outlined a feasible approach to increasing mass transport in polymer-grafted ion exchange adsorbents.     

A multiscale investigation on controlling bovine serum albumin adsorption onto polyurethane films

Our previous study on castor oil (CO) and poly(ethylene glycol) (PEG)‐based shape memory polyurethane (PU) films indicated that cell spreading on the polymer surface, cell morphology, and adhesion of fibroblast are closely related to the composition of the polymer that influences surface properties. This integrated experimental and computational study is designed to investigate the effect of important parameters such as surface roughness, crystallinity, hydrophilicity, distribution of hard/soft segments, and topology of the surface on protein adsorption for CO‐ and PEG‐based PUs. Analyses indicate that the crystallinity percentage highly promotes bovine serum albumin (BSA) adsorption. Roughness together with topological features determines BSA adsorption rate and concentration. Hydrophilicity and hard segment content seem to have less critical effect on adsorption. Distribution of hard segments into the soft segments emerges as another important factor for protein adsorption. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45669.     

Ultraviolet light treatment of thin high‐density polyethylene films monitored with a quartz crystal microbalance

Ultraviolet (UV) treatment is an effective method for modification of the surface properties of polymeric materials. In this study, the effects of the ozone‐generating UV light treatment of thin high‐density polyethylene (HDPE) films were monitored with the quartz crystal microbalance (QCM) technique both in the presence of ozone and without it. The films were further characterized by X‐ray photoelectron spectroscopy, optical microscopy, and atomic force microscopy. We found that the ozone not only modified the surface properties of the HDPE films but also etched away the polymer layer. An average etching rate of 0.48 nm/min was determined. UV light exposure of the polymer film in an argon atmosphere resulted only in minor degradation of the films; the presence of ozone was needed to cause the destruction and loss of material. The QCM technique was a straightforward method for the monitoring of the kinetics of the ablation induced by the UV–ozone treatment process. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2833–2839, 2004     

In situ analysis of bismuth telluride electrodeposition using combined spectroscopic ellipsometry and electrochemical quartz crystal microbalance

Electrodeposition of bismuth telluride (Bi₂Te₃) in an acidic medium with Arabic gum by galvanostatic polarization has been investigated. Simultaneous in situ spectroscopic ellipsometry and gravimetric measurements have been performed to study the morphological evolution of the compound. A progressive covering stage was demonstrated and revealed that a 40 nm thick film has already acquired morphological and optical behavior similar to that of thicker films. The optical thickness and electrochemical quartz crystal microbalance (EQCM) mass are coherent with a density of 7.06. Combined gravimetric and coulometric data confirm the formation of Bi₂Te₃ by determining the ratio m/z.     

表面带磺酸基团的聚苯乙烯微球的制备及其对蛋白质的吸附

研究了运用分散聚合法,在乙醇/水混合介质中,制备2-丙烯酰胺基-2-甲基丙磺酸(AMPS)与苯乙烯(St)的共聚微球。运用红外、核磁共振、激光光散射和扫描电子显微镜对功能微球进行表征。阐述了该微球对牛血清蛋白(BSA)的吸附量与吸附时间和pH值的关系。结果表明:功能微球对BSA的吸附先随时间的增长而增大,一段时间后达到平衡吸附。当pH值接近BSA等电点(pI=4.7)时,BSA的吸附量达到最大值。     

Electrochemical quartz crystal microbalance studies of a palladium electrode oxidation in a basic electrolyte solution

Anodic oxidation of Pd in basic solutions (0.1 M KOH_aq and 0.1 M NaOH_aq) has been examined via cyclic voltammetry (CV) and an electrochemical quartz crystal microbalance (EQCM). Admittance tests show that Pd(II) layer behaves as a rigid one. The anodic vertex potential influences mass response during formation of the Pd(II) layer. For low anodic vertex potentials, obtained absolute mass per mole values suggest Pd(OH)₂ or PdO·H₂O to be oxidation products. At this stage of the oxidation process, contribution from adsorbed H₂O/OH⁻ in Pd(II) layer formation could explain the lower-than-expected mass gain, although the extent of H₂O/OH⁻ adsorption is unclear. The mass gain decreases with further increase in the anodic vertex potential, eventually reaching the value of ca. 8 g mol⁻¹ at about 700 mV vs. SCE. Comparing the influence of vertex potential in CV experiments on the mass and reduction potential of the Pd(II) species points to the formation of PdO at higher oxidation potentials. At this stage of the process, a fraction of the PdO species is generated during transformation of previously formed Pd(OH)₂/PdO·H₂O. A shift of the main Pd(II) reduction potential peak depends on both the anodic vertex potential and on the composition of the Pd(II) film. The order of the Pd(II) reduction process is the opposite of that observed for the oxidation process. The Pd(IV) species formed at E ≥ 500 mV vs. SCE and those reduced between 50 and 350 mV are hydrated or contain hydroxyl groups.     

A viscometric study for adsorption of bovine serum albumin onto the inner surface of glass capillary

Viscosities of aqueous solutions of bovine serum albumin (BSA) at different temperatures were carefully measured in a common glass capillary Ubbelohde viscometer in the concentration range from dilute down to extremely dilute concentration regions. The adsorption effect occurred in viscosity measurements were theoretically analyzed and discussed. The theory based on the Langmuir isotherms could adequately describe the existing data. The influence of temperature on the adsorption of BSA solution was discussed and a simple adsorption model was proposed. The conformational change of BSA macromolecules happened both in the bulk solution and on the inner surface of glass capillary. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

In situ reactive compatibilization of aramid/polystyrene blends using amine‐functionalized polystyrene

High molecular weight aramid chains (Ar) were synthesized from aromatic diamine and diacid chloride. Amine functionality was introduced to polystyrene (PS) in two steps i.e., nitration followed by reduction producing amino functional polystyrene (APS) which serves as a reactive compatibilizer, being reactive with the Ar end‐groups. APS was characterized by FTIR, NMR spectral data, and exploited in the preparation of Ar/APS blends, and the effect of reactive compatibilization on blend morphology and interfacial adhesion was explored. Two blend systems Ar/PS and Ar/APS were investigated over a range of PS or APS ratios. To assess the effect of amine units incorporated in PS, on the compatibility with Ar; morphology, thermal, and mechanical properties were probed. Incorporation of reactivity into the system has resulted in significant refinement of the blend morphology and augmentation of thermal stability. The in situ generation of APS‐g‐Ar copolymers during solution mixing of APS and Ar was evaluated using spectroscopic analysis. In addition to stabilizing the microstructure, in situ compatibilization was found to alter the mechanical properties of the Ar/APS interface. Ar/APS blend containing 10 wt% APS was found to demonstrate optimum mechanical reinforcement as complemented by the optimal thermal and morphological profiles of 10 wt% Ar/APS blend. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Studying mechanical microcontacts of fine particles with the quartz crystal microbalance

To study micromechanical adhesion, glass particles were deposited on a quartz crystal microbalance (QCM). Beforehand, a 160 nm-thick film of polystyrene (PS) had been spin-coated on the gold surface of the QCM. Shifts in the resonance frequency were monitored versus the oscillation amplitude. The aim was to analyse how QCM experiments reflect the state of adhesion. During oscillation, the motion of the particles and the induced frequency shift of the QCM are governed by a balance between inertial and contact forces. In order to vary the relative strength of the two, the diameter of the particles was varied between 5 and 20 μm. The adherence of the particles could be increased by annealing the PS film at 150 °C. Annealing led to the formation of a PS meniscus. For a semi-quantitative interpretation we have to take into account that the particles show a distribution of coupling constants.The vibration of the QCM changes the micromechanical contact between QCM surface and particles. There is an instantaneous and a long-term effect. Instantaneously, the oscillation induces partial slip. Under an oscillating load, part of the contact ruptures, which decreases the effective stiffness of the contact. In addition, there are long-term memory effects. The vibration of the QCM can lead to a consolidation and an increased coupling. However, it can also break the contact and even lead to detachment. Particles deform the PS surface and induce damage due to inertial forces.     

Electrochemistry of methanofullerene films: Simultaneous cyclic voltammetry and electrochemical quartz crystal microbalance studies

Electrochemical properties of eight methanofullerene films, prepared on electrodes by casting, were examined by means of cyclic voltammetry and electrochemical quartz crystal microbalance (EQCM) technique in acetonitrile solution. Compared with C₆₀ film, the film stability with respect to dissolution is associated with the length of the alkyl chains introduced into C₆₀ cage and is strongly dependent on the nature of the cation of the supporting electrolyte. TBA⁺, Li⁺, K⁺, and Na⁺ were selected to observe the effect of countercations on the electrochemical behavior of methanofullerene films. In TBAPF₆ solution, when short chains, such as formic ether or butyl butyrate groups, were introduced into C₆₀ cage, the film stability was less than that of C₆₀. When the length of the alkyl chain was extended to butyl 12 alkanoate group, the film would not dissolve until the third reduction process because the long alkyl chain could inflect and encase the cations into the film. In KPF₆ or NaClO₄ solution, however, the solubility of the salt formed by K⁺ or Na⁺ with methanofullerene anion was higher than that formed by TBA⁺ with methanofullerene anion. Li⁺ (alkali metal) affected the behavior of the films in different ways. The possible electron‐transfer mechanisms of methanofullerene films in various supporting electrolyte solutions were presented. Furthermore, the film images observed by atomic force microscopy indicated that TBA⁺ and Li⁺ affected the behavior of the methanofullerene films in different ways. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3634–3640, 2006     

Adsorption of bovine serum albumin onto glass powder surfaces coated with polyvinyl alcohol

The adsorption of bovine serum albumin (BSA) was carried out onto polyvinyl alcohol–coated glass powder surfaces. The adsorbed amount was about four times more than that on uncoated glass. The kinetics of the adsorption process was followed colorimetrically, and kinetic parameters, such as adsorption coefficient, rate constants for adsorption and desorption, diffusion constant, and penetration rate constant, were evaluated. The effects of experimental conditions, such as pH, presence of salts, addition of aliphatic alcohols, and variation in the dielectric constant of the medium, on the amount of adsorbed BSA were investigated. The effect of temperature on adsorption was also studied, and several thermodynamic parameters, such as standard free energy change (ΔG°), heat of reaction (ΔH°), and entropy change (ΔS°), were evaluated. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 933–940, 2000     

Electrochemical quartz crystal nanobalance and chronocoulometry studies of phenylalanine adsorption on Au

The interfacial adsorption behaviour of the amino acid, phenylalanine (Phe), was studied at a polycrystalline Au surface in 0.05 M KClO₄ using cyclic voltammetry, chronocoulometry (CC) and electrochemical quartz crystal nanobalance (EQCN) frequency measurements. The frequency was observed to decrease with increasing concentration of Phe, indicating that the frequency measurements were following analyte adsorption directly. Both CC and EQCN frequency measurements showed a two-stage adsorption process, consistent with the molecule being adsorbed in the horizontal position at negative potentials, but rearranged to the more upright position at potentials more positive to the potential of zero charge. From the slopes at the onset of each of these two regions in plots of change in mass from the EQCN frequency measurements versus the surface charge density from CC measurements, the calculated molar mass corresponded to that of Phe displacing adsorbed water molecules for EQCN measurements made with small bulk concentrations of Phe (i.e., <1 × 10⁻⁴ mol L⁻¹).The adsorption process from CC measurements for Phe, described using the Henry adsorption isotherm, gave Gibbs energies of adsorption (ΔG_ADS) ranging from −18 to −35 kJ mol⁻¹ over the potential range of −0.6 to 0.6 V. The observed decrease in frequency of the EQCN measurements with additions of aliquots of amino acid and the substantial ΔG_ADS values suggests that Phe adsorbs onto the surface via chemisorption. Surface concentrations (1.2 × 10⁻¹⁰ mol cm⁻²) were in excellent agreement between the EQCN and CC measurements for small bulk concentrations of Phe (4.0 × 10⁻⁵ mol L⁻¹), in very good agreement with previously published results at the Au(1 1 1) surface. Thus, for small bulk concentrations of analyte, these electrochemical techniques complement one another to enhance our knowledge of the behaviour of thin organic films at electrode surfaces.     

Arsenic species interactions with a porous carbon electrode as determined with an electrochemical quartz crystal microbalance

The interactions of arsenic species with platinum and porous carbon electrodes were investigated with an electrochemical quartz crystal microbalance (EQCM) and cyclic voltammetry in alkaline solutions. It is shown that the redox reactions in arsenic-containing solutions, due to arsenic reduction/deposition, oxidation/desorption, and electrocatalyzed oxidation by Pt can be readily distinguished with the EQCM. This approach was used to show that the arsenic redox reactions on the carbon electrode are mechanistically similar to that on the bare Pt electrode. This could not be concluded with just classical cyclic voltammetry alone due to the obfuscation of the faradaic features by the large capacitative effects of the carbon double layer.For the porous carbon electrode, a continual mass loss was always observed during potential cycling, with or without arsenic in the solution. This was attributed to electrogasification of the carbon. The apparent mass loss per cycle was observed to decrease with increasing arsenic concentration due to a net mass increase in adsorbed arsenic per cycle that increased with arsenic concentration, offsetting the carbon mass loss. Additional carbon adsorption sites involved in arsenic species interactions are created during electrogasification, thereby augmenting the net uptake of arsenic per cycle.It is demonstrated that EQCM, and in particular the information given by the behavior of the time derivative of the mass vs. potential, or massogram, is very useful for distinguishing arsenic species interactions with carbon electrodes. It may also prove to be effective for investigating redox/adsorption/desorption behavior of other species in solution with carbon materials as well.     

Thermodynamic aspects of the bovine serum albumin adsorption onto N,N′‐ diethylaminoethyl dextran microbeads

Adsorption of proteins on solid surfaces is widely studied because of its importance in various biotechnological, medical, and technical applications, e.g., biosensor cardiovascular implants and chromatography. Adsorption thermodynamics has been studied on the microbeads of N,N′‐diethylaminoethyl (DEAE) dextran anion exchanger for bovine serum albumin at 25, 30, 35 40, and 45°C. As a result some thermodynamic parameters like Freundlich constants, thermodynamic equilibrium constant (K_D), standard free energy changes (ΔG_assoc), standard entropy changes (ΔS_assoc), and standard enthalpy change (ΔH_assoc) have been evaluated. Using the linear Van't Hoff plot, the ΔH_assoc value of the system for the interaction of BSA adsorbed crosslinked DEAE dextran microbeads was determined as 12.5 kJ/mol. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Usage of quartz crystal microbalance technique to study the polyaniline films formation in the presence of p-phenylenediamine

Polyaniline (PANI) was prepared using chemical method in the presence and absence of p-phenylenediamine (PPDA) and Ammonium peroxydisulfate (APS) was used as oxidizing agent. The effect of PPDA concentrations on the PANI films formation were monitored using quartz crystal microbalance (QCM) technique. It was found that the presence of PPDA affect the growth rate (G_r) and the reaction time. As the PPDA concentration increases reaction time decreases and the G_r increases. UV–VIS absorption spectra for the in situ PANI films deposited onto glass supports was used for justification the data obtained from QCM. The presence of PPDA has no effect on the structure and crystallinity of PANI and that confirmed using FTIR and X-ray.     

A quartz crystal microbalance study of the kinetics of interaction of benzotriazole with copper

The kinetics of interaction of benzotriazole (C₆H₅N₃, BTAH) with the surface of copper in salt water were studied using an electrochemical quartz crystal microbalance and X-ray photoelectron spectroscopy (XPS). Upon injecting BTAH into the electrolyte, three regions appear in the time response of the microbalance. Region I (at short time of few minutes), exhibits rapid linear growth of mass with time, which is attributed to the formation of a protective Cu(I)BTA complex. Region II reveals attachment of BTAH at a slower rate onto the inner Cu(I)BTA complex. Region III is a plateau indicating that the BTAH film attains an equilibrium mass and thickness, which increase with the concentration of BTAH. The intensity of the N1s peak in the XPS spectra increases with the time of immersion, indicating more BTAH on the surface. The results suggest a duplex inhibitor film composed of an inner thin layer of Cu(I)BTA and an outer layer of physically adsorbed BTAH which increases in thickness with time and BTAH concentration. They also offer an explanation for the much documented findings of simultaneous increase of the polarization resistance and decrease of double layer capacity with inhibitor concentration and time of immersion.     

Study on photocatalytic deposition of bismuth onto nanocrystalline TiO2 by quartz crystal microbalance and electrochemical method

In situ techniques of quartz crystal microbalance (QCM), differential pulse voltammetry (DPV) and amperometric measurement were employed to investigate the adsorption Bi(III) ions and the photocatalytic deposition Bi process at the surface of nanocrystalline TiO₂. It was obtained that the adsorption of Bi(III) ions onto nanocrystalline TiO₂ accords with the pseudo-second-order reaction and the reaction rate constant k was about 13.3 g mol⁻¹ min⁻¹. In addition, the photocatalytic deposition of Bi onto the surface of TiO₂ was further investigated. It was found that photocatalytic deposition rate at the surface of TiO₂ was enhanced by increasing pH value or initial concentration of Bi(III) ions. The influence of organic hole-scavegeners on the photocatalytic deposition of Bi was also investigated, and it was obtained that formic acid may be the best for the photocatalytic reduction of Bi. The mass ratio between the Bi(III) and Bi metal deposition was calculated as 7.48:1. Therefore, it can be concluded that QCM, DPV and amperometric measurement may be effective and reliable for the investigation of the photocatalytic deposition of Bi onto the surface of nanocrystalline TiO₂.     

Electrochemical quartz crystal microbalance study on carbon oxides adsorption in the presence of electrosorbed hydrogen on Pd alloys with Pt and Rh

CO₂ and CO adsorption on Pd-Pt and Pd-Rh alloys has been studied by cyclic voltammetry (CV) and the electrochemical quartz crystal microbalance (EQCM). Adsorbed CO₂ inhibits partially hydrogen adsorption on Pt and Rh surface atoms but does not block significantly hydrogen absorption into alloy bulk. In the presence of adsorbed CO both hydrogen adsorption and absorption are strongly suppressed. On electrodes covered with adsorbed CO the oxidation of previously absorbed hydrogen is significantly shifted into higher potentials. The EQCM response in CO₂/CO adsorption experiments is affected by both the effects connected with the changes in mass attached to the resonator and the non-mass effects including changes in metal-solution interactions and variation of solution density and viscosity in the vicinity of the electrode. Differences in the EQCM behavior suggest that the products of CO₂ and CO adsorption on the alloys studied are not totally identical.