Quartz Crystal Microbalance Analysis Research Articles

Megalin‐related mechanism of hemolysis‐induced acute kidney injury and the therapeutic strategy

AbstractHemolysis‐induced acute kidney injury (AKI) is attributed to heme‐mediated proximal tubule epithelial cell (PTEC) injury and tubular cast formation due to intratubular protein condensation. Megalin is a multiligand endocytic receptor for proteins, peptides, and drugs in PTECs and mediates the uptake of free hemoglobin and the heme‐scavenging protein α1‐microglobulin. However, understanding of how megalin is involved in the development of hemolysis‐induced AKI remains elusive. Here, we investigated the megalin‐related pathogenesis of hemolysis‐induced AKI and a therapeutic strategy using cilastatin, a megalin blocker. A phenylhydrazine‐induced hemolysis model developed in kidney‐specific mosaic megalin knockout (MegKO) mice confirmed megalin‐dependent PTEC injury revealed by the co‐expression of kidney injury molecule‐1 (KIM‐1). In the hemolysis model in kidney‐specific conditional MegKO mice, the uptake of hemoglobin and α1‐microglobulin as well as KIM‐1 expression in PTECs was suppressed, but tubular cast formation was augmented, likely due to the nonselective inhibition of protein reabsorption in PTECs. Quartz crystal microbalance analysis revealed that cilastatin suppressed the binding of megalin with hemoglobin and α1‐microglobulin. Cilastatin also inhibited the specific uptake of fluorescent hemoglobin by megalin‐expressing rat yolk sac tumor‐derived L2 cells. In a mouse model of hemolysis‐induced AKI, repeated cilastatin administration suppressed PTEC injury by inhibiting the uptake of hemoglobin and α1‐microglobulin and also prevented cast formation. Hemopexin, another heme‐scavenging protein, was also found to be a novel ligand of megalin, and its binding to megalin and uptake by PTECs in the hemolysis model were suppressed by cilastatin. Mass spectrometry‐based semiquantitative analysis of urinary proteins in cilastatin‐treated C57BL/6J mice indicated that cilastatin suppressed the reabsorption of a limited number of megalin ligands in PTECs, including α1‐microglobulin and hemopexin. Collectively, cilastatin‐mediated selective megalin blockade is an effective therapeutic strategy to prevent both heme‐mediated PTEC injury and cast formation in hemolysis‐induced AKI. © 2024 The Pathological Society of Great Britain and Ireland.

Eliminating extracellular autoinducing peptide signals inhibits the Staphylococcus aureus quorum sensing agr system

An accessory gene regulator (agr) in the quorum sensing (QS) system in Staphylococcus aureus contributes to host infection, virulence factor production, and resistance to oxidative damage. Artificially maintaining the inactive state of agr QS impedes the host infection strategy of S. aureus and inhibits toxin production. The QS system performs intercellular signal transduction, which is activated by the mature autoinducer peptide (AIP). It is released from cells after AgrD peptide processing as an intercellular signal associated with increased bacterial cell density. This study evaluated the effectiveness of inhibiting agr QS wherein AIP trap carriers were made to coexist when culturing Staphylococcus aureus. Immersing a nitrocellulose (NC) membrane in Staphylococcus aureus ATCC 12600 culture inhibited QS-dependent α-hemolysin production, which significantly reduced the hemolysis ratio of sheep red blood cells by the culture supernatant. A quartz crystal microbalance analysis supported AIP adsorption onto the NC membrane. Adding the NC membrane during culture was found to maintain the expression levels of the agr QS gene agrA and α-hemolysin gene hla lower than that when it was not added. Eliminating extracellular AIP signals allowed agr QS to remain inactive and prevented QS-dependent α-hemolysin expression. Isolating intercellular signals secreted outside the cell is an effective strategy to suppress gene expression in bacterial cells that collaborate via intercellular signaling.

Self-assembly of metal-polyphenolic network on biomass for enhanced organic contaminant capturing from water with a high cost-to-benefit ratio

Nanomaterials present a vast potential as functional materials in environmental engineering. However, there are challenges with nanocomplex for recyclability, reliable/stable, and scale-up industrial integration. Here, a versatile, low-cost, stable and recycled easily metal-polyphenolic-based material carried by wood powder (bioCar-MPNs) adsorption platform was nano-engineered by a simple, fast self-assembly strategy, in which wood powder is an excellent substrate serving as a scaffold and stabilizer to prevent the nanocomplex from aggregating and is easier to recycle. Life cycle analysis highlights a green preparation process and environmental sustainability for bioCar-MPNs. The metal-polyphenolic nanocomplex coated on the wood surface in bioCar-MPNs presents a remarkable surface adsorption property (1829.4 mg/g) at a low cost (2.4 US dollars per 1000 g bioCar-MPNs) for organic dye. Quartz crystal microbalance analysis (QCM) demonstrates an existing strong affinity between polyphenols and organic dyes. Furthermore, Independent Gradient Model (IGM) and Hirshfeld surface analysis reveal the presence of the electrostatic interactions, π-π interactions, and hydrogen bonding. Meanwhile, adsorption efficiency of bioCar-MPNs maintains over 95% in the presence of co-existing ions (Na+, 0.5 M). Importantly, the reasonable utilization of biomass for water treatment can contribute to achieving the high-value and resource utilization of biomass materials.

Mechanism of mitigating organic fouling on an electro-conductive membrane under anaerobic conditions and cathodic operation

Anaerobic electroconductive membrane (ECM) bioreactors are promising wastewater treatment technology, yet their organic antifouling mechanism remains unclear. This research investigated the impact of reactive oxygen species (ROS) oxidation, pH alteration, and electrostatic repulsion on carbon nanotube-based ECM organic fouling. Using a decoupled anode–cathode filtration system ensured unbiased results from the anode while studying distinct conditions near the cathodic ECM surface. The results demonstrated a 50 % reduction in transmembrane pressure (TMP) onset applying potential due to electroosmosis, emphasizing its importance in fouling studies. Fouling experiments using alginate in synthetic wastewater solution showed substantial organic fouling at open circuit potential, −1 and −1.5 V, as the TMP increased by about 2.5 times than the initial value. Fouling decreased significantly at −2.5 V (vs. Ag/AgCl), as indicated by the stable TMP. Analysis of ROS effects and fouling experiments at pH 7–––12 found no influence on organic fouling. Simplified force balance analysis and filtration tests suggested electrostatic repulsion as the antifouling mechanism. At potentials below −2.5 V, electrostatic repulsion maximizes closer to the ECM surface, causing fouling from short-range attractive forces. Electrochemical quartz crystal microbalance analysis at 0.1 V (vs. Ag/AgCl) proposed that a smooth ECM surface can reduce organic fouling at lower potentials.

A Comprehensive Study on the Ion-Selective Behavior of MnOx for Electrochemical Deionization

Manganese oxide is an effective active material in several electrochemical systems including batteries, supercapacitors, and electrochemical deionization (ECDI). This work conducts a comprehensive study on the ion-selective behavior of MnOx to fulfill the emptiness in the energy and environmental science field. Furthermore, it broadens the promising application of MnOx in the ion-selective ECDI system. With the support of a microfluidic cell and the electrochemical quartz crystal microbalance (EQCM) analysis, we proposed a time-dependent multi-mechanism ion-selective behavior with the following guidelines. (1) Hydrated radius is the most critical factor for ions with the same valence, and MnOx tends to capture cations with a small hydrated radius. (2) The importance of charge density rises when comparing cations with different valences, and MnOx prefers to capture divalent cations with a large hydrated radius but a strong electrostatic attraction. In addition, ion-swapping may occur where divalent cations replace monovalent cations in this circumstance. (3) NH4 + triggers MnOx dissolution, leading to performance and stability decay. The clear EQCM evidence has directly verified the proposed mechanisms. Moreover, the EQCM data provide a novel but simple method to judge ion selectivity preference. The overall ion selectivity sequence is Ca2+ > Mg2+ > K+ > NH4 + > Na+ > Li+ with the highest βCa//Li and βCa//Na values around 3 at the deionization time = 10 min.

Coverage Effects in Quartz Crystal Microbalance Measurements with Suspended and Adsorbed Nanoparticles.

Quartz crystal microbalance (QCM) biosensors often deal with nanoparticles suspended in the solvent at tens of nanometers above the resonator while being linked to some molecular receptor (DNA, antibody, etc.). This work presents a numerical analysis based on the immersed boundary method for the flow and QCM impedance created by an ensemble of spherical particles of radius R at varying surface coverage Θ and particle-surface gap distance Δ. The trends for the frequency Δf and dissipation ΔD shifts against Θ and Δ are shown to be determined by modifications in the structure of the perturbative flow created by the analytes. Simulations are in good agreement with a relatively large experimental database collected from the literature. Qualitative differences between the adsorbed (Δ ≈ 0) and suspended states (Δ > 0) are highlighted. In the case of adsorbed particles, deviations from the linear scaling Δf ∝ Θ are observed above Θ > 0.05 and largely depend on the specific analyte-substrate combination. Moreover, in general, ΔD(Θ) is not monotonous and usually presents a maximum around Θ ∼ 0.2. In the case of suspended analytes, the agreement with the numerical results is quantitative, indicating that the predicted scalings are universal and determined by hydrodynamics. Up to high coverage, the suspended particles present Δf ∼ Θ and ΔD ∼ Θβ, where β ≈ 0.85 is not largely dependent on R. The present findings should help forecast molecular configurations from QCM signals and have implications on QCM analyses, e.g., in the case of suspended ligands (Δf ∝ Θ), it is safe to use Δf to build Langmuir isotherms and estimate equilibrium constants. Open questions on the transition from the suspended-to-adsorbed state are discussed.

Li Plating/Stripping Efficiency in Ether‐based Dilute Electrolyte for Anode‐free Lithium‐metal Batteries: Effect of Operating Potential Range on Subsequent SEI Layer Structure

AbstractAnode‐free lithium‐metal batteries (AFLMBs) are regarded as a promising candidate for next‐generation batteries due to a great enhancement of energy density over lithium‐metal anode batteries. However, unstable solid‐electrolyte interface (SEI) formation accompanied by lithium dendrite growth and electrolyte decomposition causes low Coulombic efficiencies. This study explores the effect of different operating potential ranges on SEI layer structure and further on Li plating/stripping efficiency in the dilute LiTFSI/TEGDME electrolyte in an AFLMB anode half‐cell configuration. Cyclic voltammetry analyses reveal the existence of an “oxidative subsequent SEI” formation process (named as OSS) and the improved Li plating/stripping efficiency by blocking reaction OSS, which is further verified by quartz crystal microbalance analysis regarding the insight of such an improvement. XPS depth‐profile analysis confirms the formation of the Li2O‐ and lithium‐sulfur compounds‐based subsequent SEI layers when the OSS process is blocked, which guarantees the improved stability of Li plating/stripping. A hypothesis is proposed to discuss possible electrochemical reactions via OSS process by combining in situ surface‐enhanced Raman spectroscopy analysis. These results together suggested the importance of adjusting operating potential range in a proper manner to achieve a better performance in Li plating/stripping in AFLMB configuration.

Comprehensive Study on the Ion-Selective Behavior of MnOx for Electrochemical Deionization.

Manganese oxide is an effective active material in several electrochemical systems, including batteries, supercapacitors, and electrochemical deionization (ECDI). This work conducts a comprehensive study on the ion-selective behavior of MnOx to fulfill the emptiness in the energy and environmental science field. Furthermore, it broadens the promising application of MnOx in the ion-selective ECDI system. We propose a time-dependent multimechanism ion-selective behavior with the following guidelines by utilizing a microfluidic cell and the electrochemical quartz crystal microbalance (EQCM) analysis. (1) Hydrated radius is the most critical factor for ions with the same valence, and MnOx tends to capture cations with a small hydrated radius. (2) The importance of charge density rises when comparing cations with different valences, and MnOx prefers to capture divalent cations with a strong electrostatic attraction at prolonged times. Under this circumstance, ion swapping may occur where divalent cations replace monovalent cations. (3) NH4+ triggers MnOx dissolution, leading to performance and stability decay. The EQCM evidence has directly verified the proposed mechanisms, and these data provide a novel but simple method to judge ion selectivity preference. The overall ion selectivity sequence is Ca2+ > Mg2+ > K+ > NH4+> Na+ > Li+ with the highest selectivity values of βCa//Li and βCa//Na around 3 at the deionization time = 10 min.

A-082 Measuring Peroxynitrite as an Early Biomarker for Cystic Fibrosis Using Organoselenide-Modified Glassy Carbon Electrode

Abstract Background Cystic fibrosis (CF) is a genetic disease that affects the respiratory, digestive, and reproductive systems. One of the issues associated with CF is oxidative stress, which is an imbalance between the production of reactive oxygen species (ROS) and the ability of the body to neutralize them. Peroxynitrite, a member of ROS, is a very noxious molecule formed from the reaction of nitric oxide (NO) and superoxide and can damage cellular components such as proteins, lipids, and DNA. Studies have shown that peroxynitrite levels are elevated in people with CF and that this increased oxidative stress can contribute to the development of lung damage, airway obstruction, and other symptoms associated with the disease. Therefore, understanding the role of peroxynitrite in the pathogenesis of CF is important for developing new therapeutic strategies to reduce oxidative stress and improve the quality of life for people with this disease. Methods In this study, we have quantified peroxynitrite levels, which could serve as an early biomarker for CF. A modified glassy carbon electrode (GCE) with a series of organoselenide compounds was adopted using the electro-grafting method to measure peroxynitrite levels in situ. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) were used to examine the structure and surface chemistry of organoselenide. Quartz Crystal Microbalance (QCM) analysis was used to determine the thickness of the electrodeposited selenium on the GCE surface. Results Our organoslenide GCE allowed for the application of low positive potential, which enhances the separation of peroxynitrite from other analytes sensitive to higher potentials. Cyclic voltammetry and amperometry showed sensitivity at 110 nA/mol, and the detection limit was recorded at 10 micromolar. This electrochemical technique of our modified electrodes can be miniaturized to detect peroxynitrite at the cell line. The sensitive probe, which was constructed, can be utilized to target the ratiometric changes in several lung slices, from healthy to lung inflammation and cystic fibrosis, via peroxynitrite fluctuation. In addition, ratiometric alterations and the prevalence of cystic fibrosis have a strong linear association, resulting in good potential in predicting the progression of cystic fibrosis in the early stage and improving effective treatment. Conclusion The study aimed to quantify peroxynitrite levels in cystic fibrosis (CF) patients as a potential early biomarker for the disease. We have used a modified glassy carbon electrode with organoselenide compounds and adopted an electro-grafting method to measure peroxynitrite levels. The modified electrodes showed sensitivity and a limit of detection of 10 micromolar, which can be miniaturized to detect peroxynitrite in the cell line. The results suggest that peroxynitrite’s sensors could serve as an early biomarker for CF by understanding its role in the pathogenesis, which can improve the quality of life for people with this disease.

Greening Industrially Applied Toxic Cadmium Plating with γ‐Ni2Zn11 Alloy in Deep Eutectic Solvents: Promising Electroplating Efficiency and Chemical Corrosion Resistance

Cadmium is an industrially applied plating metal used in aerospace applications, but electrodeposition of cadmium is toxic, and current production method will soon be banned. Therefore, electrodeposition of alternative alloys in environmentally friendly solutions is an attractive research area. An additive‐free, nonaqueous, deep eutectic solvent (DES) containing Ni and Zn halide salts is developed in a greener environmental method. Gamma‐phase nanocrystalline Ni2Zn11 is coated onto hot‐rolled mild steel via pulse reverse current (PRC) in the developed nonaqueous solvent. The employed DES’ relatively low viscosity and sufficient conductivity enable the simultaneous reduction of Ni2+ and Zn2+ cations on microelectrode. Electrochemical quartz crystal microbalance (eQCM) analysis proves the absence of the commonly reported problem of electrode blocking during electrodeposition, revealing an efficiency of 86.07%. Appropriate PRC parameters are applied for scaled macroelectrode deposition. The plating profile exhibits 20 μm‐thick alloy deposition without cracks around 3 h. Scanning electron microscopy–electron‐dispersive spectroscopy and X‐ray diffraction analyses reveal that 15.5 wt% Ni is in the nanograin phase, and all crystal planes belong to the γ‐Ni2Zn11 phase, which is needed as an alternative to cadmium plating. Hardness and corrosion tests performed on the γ‐Ni2Zn11 coating reveal better hardness and corrosion resistance with supporting morphological evidence.

Label-free genosensing of dengue serotypes with an electrodeposited reduced graphene oxide-tris(bipyridine)ruthenium(II)

Constructing a label-free electrochemical transducer platform without compromising inherent biocompatibility against specific bioreceptor remains challenging, particularly probing nucleic acid hybridization at electrode interface without external redox-mediator. Here, we show that electrochemically reduced graphene oxide-tris(bipyridine)ruthenium(II) (ErGO-TBR) nanosheets electrodeposited on carbon screen printed electrode can quantify hybridization of clinically important target sequences specific to serotypes of dengue virus (DENV) non-structural 1 (NS1) protein. Different variables including deposition potential, time, and electrolytic composition were optimized for fabrication of label-free transducer platform. Structural and electrochemical properties of ErGO-TBR/SPE were comprehensively elucidated using microscopic and spectroscopic techniques. Electrochemical quartz crystal microbalance (EQCM) analysis reveals the growth of electrodeposited redox-active species on the electrode interface. Surface functional group investigations suggested that TBR deposited on the basal and edges of ErGO substrate via electrostatic and π-π interactions. Functionalization of bio-affinity layer (B) on ErGO-TBR/SPE enables better loading of probe DNA (PDNA) toward specific detection of DENV target DNA (TDNA) with an ultralow detection limit promising for clinical diagnosis. Scalable chronoamperometry-based redox-active surface growth, customizable bioactivation strategy and external mediator-less probing of nucleic acid hybridization make the present system suitable for other translational application in healthcare diagnosis.

67-kDa laminin receptor mediates oolonghomobisflavan B-induced cell growth inhibition in melanoma

BackgroundOolonghomobisflavans are unique polyphenols found in oolong teas. Oolonghomobisflavan B (OHBFB), a dimer of (–)-epigallocatechin-3-O-gallate (EGCG), is an active compound found in green tea. PurposeOHBFB has been reported to exert an inhibitory effect on lipase enzyme activity. However, little is known regarding its intercellular signaling induction effect. Further, there are no reports describing the anti-cancer effects of OHBFB. MethodsThe effect of OFBFB on B16 melanoma cells was evaluated by cell counting, and its mechanisms were determined by western blot analysis with or without protein phosphatase 2A (PP2A) inhibitor treatment. Intracellular cyclic adenosine monophosphate (cAMP) levels were evaluated by time-resolved fluorescence resonance energy transfer analysis. Quartz crystal microbalance (QCM) analysis was performed to assess the binding of OHBFB to 67LR. ResultsCell growth assay and western blot analyses showed that OHBFB inhibited melanoma cell growth, followed by myosin phosphatase target subunit 1 (MYPT1) and myosin regulatory light chain (MRLC) dephosphorylation via protein phosphatase 2A (PP2A)-dependent mechanisms. These effects are mediated by intracellular cAMP- and protein kinase A (PKA) A-dependent mechanisms. QCM analysis identified the 67-kDa laminin receptor (67LR) as an OHBFB receptor with a Kd of 3.7 µM. We also demonstrated for the first time that OHBFB intake suppresses tumor growth in vivo. ConclusionsTaken together, these results indicate that the cAMP/PKA/PP2A/MYPT1/MRLC pathway is a key mediator of melanoma cell growth inhibition following OHBFB binding to 67LR and that OHBFB suppresses tumor growth in vivo.

Temperature and concentration dependence of the electrochemical PtHg4 alloy formation for mercury decontamination

New and improved methods to remove toxic mercury from contaminated waters and waste streams are highly sought after. Recently, it was shown that electrochemical alloy formation of PtHg4 on a platinum surface with mercury ions from solution can be utilized for decontamination, with several advantages over conventional techniques. Herein, we examine the alloy formation process in more detail by mercury concentration measurements using inductively coupled plasma mass spectrometry in batch measurements as well as electrochemical quartz crystal microbalance analysis both in batch and in flowing water with initial mercury concentrations ranging from 0.25 to 75000 µg L−1 Hg2+. Results show that mercury is effectively removed from all solutions and the rate of alloy formation is constant over time, as well as for very thick layers of PtHg4. The apparent activation energy for the electrochemical alloy formation was determined to be 0.29 eV, with a reaction order in mercury ion concentration around 0.8. The obtained results give new insights that are vital in the assessment and further development of electrochemical alloy formation as a method for large scale mercury decontamination.

Effect of pretreatment severity on the inhibitory behaviors of larch lignins in enzymatic hydrolysis

To explore the underlying reasons for the decreased enzymatic hydrolysis yields of the acid pretreated softwood under the higher pretreatment severity, the residual bulk lignins, as one type lignin fraction with stronger inhibition, were isolated from larch (softwood) pretreated with different pretreatment severity in this study. The lignin structure changes during the pretreatment were comprehensively investigated by nuclear magnetic resonance (NMR) analysis. The larch lignins addition decreased the enzymatic hydrolysis of Avicel from 68.43% to 25.9–39.3%. The pretreatment intensified the inhibition of isolated lignins on enzymatic hydrolysis of Avicel. Furthermore, quartz crystal microbalance (QCM) analysis was applied to investigate the interaction between enzyme and lignins, distinguishing the reversible and irreversible enzyme adsorption. It demonstrated that the obviously higher irreversible adsorption of enzyme was observed on lignins from pretreated substrates with the higher severity. Additionally, the correlation between structure and inhibition of residual lignins in the enzymatic hydrolysis was then investigated with Pearson’s correlation heatmap. The findings can be used to develop theoretical guidelines for alleviating the residual lignin inhibition in the enzymatic hydrolysis of acidic pretreated softwood.

Impact of pH on the Formation and Properties of Whey Protein Coronas around TiO2 Nanoparticles.

In aqueous media, titanium dioxide (TiO2) nanoparticles can interact with proteins in their environment and form a protein corona. The pH of the aqueous media affects the structure and properties of the protein corona, and currently there is a lack of understanding of the effects of pH on the characteristics of protein coronas. In this study, we examined the impact of pH (2-11) on the structural and physicochemical properties of whey protein coronas formed around TiO2 nanoparticles. The pH of the solution influenced the structure of whey protein molecules, especially around their isoelectric point. Thermogravimetric and quartz crystal microbalance analyses showed that the adsorption capacity of the whey proteins was the largest at their isoelectric points and the lowest under highly acidic or alkaline conditions. The majority of the proteins were tightly bound to the nanoparticle surfaces, forming a hard corona. The influence of solution pH on protein corona properties was mainly attributed to its impact on the electrostatic forces in the system, which impacted the protein conformation and interactions. This study provides useful insights into the influence of pH on the formation and properties of protein coronas around inorganic nanoparticles, which may be important for understanding the gastrointestinal and environmental fates.

Electropolymerized Melamine on Electrochemically Reduced Graphene Oxide: Growth Mechanistics, Electrode Processing, and Amperometric Sensing of Acyclovir.

Metal-free, cost-efficient, redox-active electrode materials, combining graphene derivatives with nitrogen-rich polymelamine (PM), are widely explored as an interface layer for electrocatalysis and an electrochemical sensor platform. However, conventional chemical routes often yield derivatives of PM suffering from impaired redox behavior, restricting their electron-transfer kinetics. Herein, an optimal potentiodynamic method has been established to electrodeposit PM on electrochemically reduced graphene oxide (ErGO). A supporting electrolyte, containing Cl-, enhances the formation of intermediates NH3+ and ═NH2+ at the monomeric melamine, eventually interacting with the residual oxygenated functional groups of ErGO to form PM. In situ Raman spectrum analysis revealed the influence of the defective area and the graphitization ratio on the ErGO surface during the course of electropolymerization of melamine. Under optimal electrodeposition conditions (E = 0-1.6 V; ν = 0.1 V/s), the amount of electrodeposited PM on the ErGO surface was determined to be 16.5 μg/(cycle·cm2), using electrochemical quartz crystal microbalance analysis. An ErGO-PM-modified glassy carbon electrode (GCE) and a screen-printed electrode exhibit the direct electrooxidation of acyclovir (ACV). Amperometric analyses of ErGO-PM-modified electrodes exhibited the lowest detection limit of 137.4 pM with analytical robustness, rapid steady state, and reproducibility promising for ACV detection in complex biological matrices.

Assembly of zein/propylene glycol alginate nanoparticles in aqueous ethanol and the binding kinetics

The interaction between zein and propylene glycol alginate (PGA) in aqueous ethanol was investigated to fabricate novel zein-based nanoparticles. The results indicated that electrostatic attraction could occur between the two polyelectrolytes in aqueous ethanol. The interaction was insensitive to temperature variation but was weakened in high total biopolymer concentrations, and the optimum conditions were pH 5.0, zein to PGA mass ratio 2:1, total solid concentration 0.2% (w/v), and ethanol concentration 70% (v/v) in the absence of salts, which could yield positively charged zein/PGA nanoparticles of 120 nm according to atomic microscope observation. Isothermal titration calorimetry, quartz crystal microbalance analysis, and microscale thermophoresis revealed that zein exhibited much lower stoichiometry but greatly higher affinity in binding PGA than in the zein/PGA nanoparticles prepared by the conventional anti-solvent and pH cycling methods. Hence, the self-assembly in 70% ethanol was a feasible way to fabricate novel zein/PGA nanoparticles with homogeneous structure and enhanced stability in a single step.

Surface reaction mechanism of atomic layer deposition of niobium oxide: In situ characterization and first-principle study

We report the surface reaction mechanism of the atomic layer deposition (ALD) of niobium oxide films by combining experimental and theoretical studies. Tert-butylimido tris(dimethylamido)niobium [tBuN=Nb(NMe2)3] and ozone (O3) were studied as the precursor and co-reactant. The in situ quartz crystal microbalance (QCM) analysis predicted that two HNMe2 molecules or one H2NtBu molecule were released at 200 °C per one molecule tBuN=Nb(NMe2)3. Since the QCM alone could not distinguish two possible reaction pathways, we compared two pathways by density functional theory (DFT) calculations. We simulated the chemisorption of the precursor molecule on the –OH terminated T-Nb2O5 substrate. The release of two –NMe2 ligands was favorable due to low activation energies of 0.71 and 0.63 eV for the first and second releases. On the other hand, the release of =NtBu was not favorable due to the high activation energy of 1.50 eV. Therefore, the amido and imido ligands were actor and spectator ligands during the first half-reaction of the ALD of niobium oxide films. The combination of QCM and DFT could successfully reveal the surface reaction mechanism of the ALD process using a heteroleptic precursor.

Modification of the antigenicity of cancer cells by conjugates consisting of hyaluronic acid and foreign antigens.

Tumor-specific cytotoxic T-lymphocytes (CTLs) recognize tumor-associated antigens presented on major histocompatibility complex (MHC) class I molecules. However, it is difficult to induce potent CTLs by vaccination because the antigenicity is not so high, compared with that of foreign antigens derived from viruses and microbes. The affinity of binding to MHC class I molecules is proportional to the antigenicity of the antigen that they are presenting. Here, we prepared several conjugates consisting of hyaluronic acid (HA) as a carrier to cancer cells and ovalbumin (OVA) as a foreign protein and changed the antigens on cancer cells from intrinsic antigens to OVA fragments. The conjugate containing multiple HA and OVA molecules (100k4HA-3OVA) adopted a highly condensed structure and was well recognized by recombinant CD44 molecules in quartz crystal microbalance analysis and incorporated into cancer cells (CT26 cells). A mixture of CT26 cells treated with 100k4HA-3OVA and splenocytes including OVA-specific CTLs induced abundant secretion of IFN-γ into the supernatant. At 48 h after mixing with the CTLs, almost all CT26 cells had died. These results indicate that 100k4HA-3OVA is actively internalized into the cells through interaction between HA and CD44. Subsequently, CT26 cells present not only self-antigens, but also OVA fragments on MHC class I molecules and are recognized by OVA-specific CTLs. We thus succeeded in modifying the antigenicity from self- to non-self-antigens on cancer cells. Therefore, this foreign-antigen delivery using HA to cancer cells, followed by antigen replacement, could be used as a novel strategy for treating cancers.

Electropolymerized methylene blue on graphene oxide framework for the direct voltammetric detection of gallic acid

Electropolymerized materials are cost efficient, sensitive and durable for sensor applications. Herein, the cationic dye, methylene blue, electropolymerized on graphene oxide framework using cyclic voltammetry and processed for voltammetric sensor platform. The surface chemistry, topology and wettability of the prepared electrode material was comprehensively studied with Raman spectroscopy, field-emission scanning electron/atomic force microscopes and contact angle measurement. The electrochemical quartz crystal microbalance analysis was done to quantify the mass adsorbed on the graphene oxide framework. Cyclic voltammetric study of the prepared methylene blue-graphene oxide framework electrode exhibits a reversible redox behavior at the electrode-electrolyte interface, following surface confined process with a coefficient determination of 0.99. Electrochemical sensing ability of the prepared electrode material was tested against the clinically important phytomedicine, gallic acid. Linear sweep voltammetric analysis enabled that methylene blue-graphene oxide framework is highly sensitive and selective toward electrooxidation of gallic acid, exerting a detection limit of 49.2 μM in the studied experimental concentration range from 50 μM to 1 mM. Real sample validation with commercial herbal tablet extracts of Euphorbia prostrata containing spiked gallic acid suggest that the prepared sensor platform could be a potential analytical probe for herbaceutical testing.