Surface Groups Research Articles

A comparison of char fuel properties derived from dry and wet torrefaction of oil palm leaf and its techno-economic feasibility

In this study, the chars were derived through dry and wet torrefaction (DT and WT) of oil palm leaf (OPL), and techno-economic feasibility for char production was evaluated. DT was performed at 200 to 300 °C for 30 min under CO2 atmosphere. WT was performed at 180 to 220 °C for 30 min over process water (PW) reuse. Fuel properties of the DT-char and WT-char products, including mass yield, physiochemical characteristics, fuel properties, thermal stability, surface chemical functional groups, and surface structure were investigated. The study results indicated that DT affected OPL characteristics rather than WT, where the char with outstanding fuel properties was derived through DT. WT affected the fuel properties of OPL marginally. OPL chars with the highest HHV (28.67 MJ/kg), HHV improvement (0.48) and energy yield (131.78 %) could be derived via the DT. The O/C and H/C ratios of the DT-char were reduced and similar to those of lignite coal. PW reuse in WT slightly affected the char fuel properties, thus it is the outstanding method of PW utilization. Techno-economic feasibility analysis results determined that DT is the profitable process for converting OPL to char fuel, and its simple payback period is 14.13 years. These results recommended that DT constitutes a dominant technology for producing char fuel from OPL.

Bismuth-Based BiOBrxI1–x/Ti3C2 MXene Schottky Nanocomposites for Hg2+ Photoelectrochemical Sensors

BiOBrxI1–x/Ti3C2 Schottky heterojunction nanocomposites were prepared through a simple electrostatic adsorption and self-assembly method. The Schottky heterojunction was used as a sensitive material in the fabrication of a photoelectrochemical (PEC) sensor for mercury ion detection. Due to the large specific surface area, excellent electrical conductivity, and abundant surface chemical groups of the 2D nano Ti3C2 in the Schottky heterojunction, the in situ growth of solid solution BiOBrxI1–x on its surface enabled the nanocomposites to form a high Schottky barrier to improve the sensitivity of the PEC response. The addition of glutathione (GSH) caused it to adhere to the surface of the nanocomposites where it hindered the transfer of electrons and reducing the photocurrent by reacting with the bismuth ions on their surface through its carboxyl groups. During the Hg2+ assay, Hg2+ ions reacted to GSH on the surface of the heterojunction nanocomposites, and then captured more GSH in a solution to form a complex with 3D structure. This complex further hindered electron transfer and led to a sharp decrease in photocurrent. A trace amount of Hg2+ was detected based on the change of photocurrent, with a linear range of 1.0 × 10–10 mol/L to 1.0 × 10–6 mol/L and a detection limit of 4.21 × 10–11 mol/L. This method was one of the most sensitive methods reported for Hg2+ detection. The sensor had been applied to determine trace mercury in environmental water samples.

Nitrogen-Doped Porous Carbon from Biomass with Efficient Toluene Adsorption and Superior Catalytic Performance.

The chemical composition and surface groups of the carbon support affect the adsorption capacity of toluene. To investigate the effect of catalyst substrate on the catalytic performance, two different plant biomasses, banana peel and sugarcane peel, were used as carbon precursors to prepare porous carbon catalyst supports (Cba, Csu, respectively) by a chemical activation method. After decorating PtCo3 nanoparticles onto both carbon supports (Cba, Csu), the PtCo3-su catalyst demonstrated better catalytic performance for toluene oxidation (T100 = 237 °C) at a high space velocity of 12,000 h-1. The Csu support possessed a stronger adsorption capacity of toluene (542 mg g-1), resulting from the synergistic effect of micropore volume and nitrogen-containing functional groups, which led to the PtCo3-su catalyst exhibiting a better catalytic performance. Moreover, the PtCo3-su catalyst also showed excellent stability, good water resistance properties, and high recyclability, which can be used as a promising candidate for practical toluene catalytic combustion.

Improving the anti-collapse performance of water-based drilling fluids of Xinjiang Oilfield using hydrophobically modified silica nanoparticles with cationic surfactants

Wellbore instability, especially drilling with water-based drilling fluids (WBDFs) in complex shale formations, is a critical challenge for oil and gas development. The purpose of this paper is to study the feasibility of using hydrophobically modified silica nanoparticle (HMN) to enhance the comprehensive performance of WBDFs in the Xinjiang Oilfield, especially the anti-collapse performance. The effect of HMN on the overall performance of WBDFs in the Xinjiang Oilfield, including inhibition, plugging, lubricity, rheology, and filtration loss, was studied with a series of experiments. The mechanism of HMN action was studied by analyzing the changes of shale surface structure and chemical groups, wettability, and capillary force. The experimental results showed that HMN could improve the performance of WBDFs in the Xinjiang Oilfield to inhibit the hydration swelling and dispersion of shale. The plugging and lubrication performance of the WBDFs in the Xinjiang Oilfield were also enhanced with HMN based on the experimental results. HMN had less impact on the rheological and filtration performance of the WBDFs in the Xinjiang Oilfield. In addition, HMN significantly prevented the decrease of shale strength. The potential mechanism of HMN was as follows. The chemical composition and structure of the shale surface were altered due to the adsorption of HMN driven by electrostatic attraction. Changes of the shale surface resulted in significant wettability transition. The capillary force of the shale was converted from a driving force of water into the interior to a resistance. In summary, hydrophobic nanoparticles presented a favorable application potential for WBDFs.

RIS Grouping Based Index Modulation for 6G Telecommunications

In this letter, a novel reconfigurable intelligent surface (RIS) grouping based index modulation (RGB-IM) is proposed to enhance spectral efficiency and improve bit error rate (BER). The idea is to divide an RIS into several number of group-surfaces (GR). Furthermore, the incoming data bits are modulated to spatial symbol, which represents the index of one of the available GR that will be activated at a particular time. In addition, the impact of RIS imperfect channel estimation is investigated in this letter. Both spectral efficiency and BER of the proposed system are simulated and validated with theoretical result. The computer simulation results indicate that the RGB-IM outperform a relay-assisted spatial modulation (SM).

Analysis of Boron Removal By Capacitive Deionization

Climate change and water overextraction are some of the reasons for a growing global water stress, with seawater desalination being the leading solution worldwide. The state-of-the-art technology for seawater desalination is reverse osmosis (RO), utilizing mechanical pressure to push seawater through membranes, leaving the dissolved species in the brine. However, boron, which is considered toxic in high concentrations, is poorly removed by RO. This is because under normal conditions boron is present as boric acid, a small neutrally-charged compound. The most common technique to overcome this problem includes multiple RO stages combined with chemical dosage of the effluent, ensuring boron is present as borate, a charged species, present in high pH conditions.Capacitive deionization (CDI) is an emerging membraneless technique for water treatment and desalination, based on electrosorption of salt ions into microporous electrodes. Large internally-generated pH gradients develop during CDI operation, and thus CDI can potentially remove boron without chemically adjusting the feed pH. Here, we present a novel theoretical framework predicting the adsorption of boron in micropores, while considering pH-dependent chemical surface groups in the micropores, ion transport in the macropores, and local electrolyte pH. Moreover, we account for association and dissociation reactions of boron-consisting compounds in the electrolyte[1].We analyzed the effects electrodes order have on pH dynamics, where panels a. and b. in the attached figure present spatiotemporal plots of the pH for the case where cathode is placed upstream (panel a., cat-an) and the anode placed upstream (panel b., an-cat). This analysis shows that higher pH in the anode are expected for the an-cat configuration, counter to common-wisdom in the field. Panel c. follows this trend, by presenting the removed boron as a function of scaled flow velocity for both configurations. The results show, both experimentally and theoretically, that an-cat configuration should be preferred. Similarly, we found that an optimum charging voltage exists, even without accounting for parasitic reactions. Moreover, we found that also the discharging voltage significantly affects boron removal. Overall, CDI is a promising technology for boron removal, but a deep theoretical understanding of the problem is crucial towards future optimization.

Surface Chemical Groups of Flocs Are Key Factors for the Growth of Flocs in Sweep Coagulation: A Case Study of Surface Occupation by Humic Acid

Coagulation is one of the most common processes in water treatment. Charge neutralization and sweep flocculation are recognized as the primary coagulation mechanisms. However, in-depth understanding on floc growth, breakage, and regrowth is still unclear. In this study, the formation, breakage, and regrowth of alum flocs with humic acid (HA) added either before coagulant addition or during the floc breakage stage were investigated. The floc size continuously decreased with the increase in floc breakage events, and eventually, to a stable value. The floc growth was not affected by the addition of HA before coagulant addition. However, it was prevented as HA was added during the breakage stage, and the prevention extent increased with HA dose. Similar results were also found for natural organic matter (NOM) from real surface water. These results suggested that HA/NOM can cover the active site on the floc surface, and the coverage differed for fresh flocs (newly precipitated) and old flocs (after breakage), which, respectively, represent the case in conventional coagulation and sludge recirculation. Based on these findings, the illustration of floc growth, breakage, and regrowth processes was put forward. We concluded that the charge neutralization and sweep flocculation mechanisms only explained the possibility of flocs approaching each other; whether flocs can connect to each other depends on the activated functional groups on the floc surface. The results in this study revealed the underlying mechanism of “collision effectiveness” in coagulation, complementing the existing understanding of the coagulation process.

Study on the control of condensable particulate matter by spraying activated carbon combined with electrostatic precipitator

Condensable particulate matter (CPM) is a primary particulate matter that exists in the form of gas or vapor phase before discharge, but after discharge, it rapidly turns into a particulate substance due to cooling and dilution. The composition of CPM is very complex, and it poses a threat to the environment and human health. However, there is a lack of research on the control of CPM. Therefore, this study investigated the effects of activated carbon (AC) injection coupled with low-low temperature electrostatic precipitator on the adsorption of CPM in the flue gas of a 300 MW ultra-low emission coal-fired power plant. The sampling system was conducted according to ISO 23210–2009 and U.S. EPA method 202. Results shows that the adsorption removal efficiency of CPM by ACs ranged from 14% to 33%, and the adsorption removal effect of AC on inorganic components in CPM was better than that of organic components. AC had significant adsorption effects on Cl− and NH4+ but had weak adsorption effect on NO3− in CPM. AC with larger specific surface area, more abundant pore structure, and richer surface chemical functional groups has better adsorption effect on metal elements such as Na, Ca, Mg, K, and Al in CPM is better than that of Fe. As for the organic components in CPM, the adsorption effect of AC for esters was considerable, but its adsorption on organosilicon was limited.

Engineering Electro- and Photocatalytic Carbon Materials for CO2 Reduction by Formate Dehydrogenase.

Semiartificial approaches to renewable fuel synthesis exploit the integration of enzymes with synthetic materials for kinetically efficient fuel production. Here, a CO2 reductase, formate dehydrogenase (FDH) from Desulfovibrio vulgaris Hildenborough, is interfaced with carbon nanotubes (CNTs) and amorphous carbon dots (a-CDs). Each carbon substrate, tailored for electro- and photocatalysis, is functionalized with positive (−NHMe2+) and negative (−COO–) chemical surface groups to understand and optimize the electrostatic effect of protein association and orientation on CO2 reduction. Immobilization of FDH on positively charged CNT electrodes results in efficient and reversible electrochemical CO2 reduction via direct electron transfer with >90% Faradaic efficiency and −250 μA cm–2 at −0.6 V vs SHE (pH 6.7 and 25 °C) for formate production. In contrast, negatively charged CNTs only result in marginal currents with immobilized FDH. Quartz crystal microbalance analysis and attenuated total reflection infrared spectroscopy confirm the high binding affinity of active FDH to CNTs. FDH has subsequently been coupled to a-CDs, where the benefits of the positive charge (−NHMe2+-terminated a-CDs) were translated to a functional CD-FDH hybrid photocatalyst. High rates of photocatalytic CO2 reduction (turnover frequency: 3.5 × 103 h–1; AM 1.5G) with dl-dithiothreitol as the sacrificial electron donor were obtained after 6 h, providing benchmark rates for homogeneous photocatalytic CO2 reduction with metal-free light absorbers. This work provides a rational basis to understand interfacial surface/enzyme interactions at electrodes and photosensitizers to guide improvements with catalytic biohybrid materials.

In-situ growth strategy of ZIF-8 nanocrystals on carbon fibers achieved high-efficient interface enhancement

The unique imidazole bridge structure of ZIF-8 nanocrystals makes it flexible and low elastic modulus, which can withstand more flexible crystal deformation and have superior bearing capacity and anti-wear effect. In this work, an in-situ growth strategy of ZIF-8 nanocrystals on the surface of carbon fibers (CFs) was used for the enhancement of interfacial combination and out-of-plane properties between CFs and Poly(hexahydrotriazine)s (PHT) matrix. The introduction of ZIF-8 nanocrystals functionalized CFs to disperse and transfer more load and energy, and the interface performance between two phases were characterized via mechanical and tribological tests. The results indicated that the tensile strength of ZIF-8 grafted on CFs increased due to the improved rough surface, bonding area and active chemical groups of CFs. The fracture mechanism of ZIF-8 based composites were investigated by morphology observation on the interface. In addition, the wear rate of ZIF-8 based composites reduced by 43.7% when compared to neat CF. The improvement of mechanical and tribological properties depends on the introduction of ZIF-8 which improves the interfacial adhesion between CFs and resin matrix, and further facilitates the load transfer from interface to CFs.

Electrochemical impedance spectroscopy (EIS) reveals the role of microbial fuel cell-ceramic membrane bioreactor (MFC-CMBR): Electricity utilization and membrane fouling

Ceramic membrane has become a major concern due to creasing cost and competitive efficiency. Microbial fuel cell-ceramic membrane bioreactor (MFC-CMBR) is considered alternative technology for larger-scale industrial application because of its advantages of convenient detecting and control of membrane fouling. However, MFC-CMBR are highly susceptible to membrane fouling and harsh operating requirements in these wastewaters of different compositions. This research critically discusses that electrochemical response in different types of MFC-CMBRs and control of electricity utilization on ceramic membrane fouling. The experimental results indicated that the application of sludge acclimated in coupling system with higher external resistance could ensure that lower costs (electricity utilization and membrane cleaning) provided enough membrane fouling control. The improved performance of MFC-CMBR-1 could be attributed to its enhanced nitrification/denitrification activity and capacity of electrons migration between electrode and sludge mixture. The coupling system alleviated membrane fouling and impedance increasing by improving the characteristics of sludge (increased particle size, decreased adsorption adhesion free energy), EPS (decreased hydrophobicity, molecular weight distribution regulation). And filtration tests showed that roughness and contact angle for the MFC-CMBR tend for better development compared to CMBR, dependent on the changes in the chemical surface groups as a result of electric distribution ratio. In addition, correlation analysis and filtration experiments showed that the extracellular polymer substances (EPS) enhanced the charge transfer resistance (Rct), and the protein substance in EPS was the main fouling substance when external resistance was close to the internal resistance of MFC. In summary, the low internal resistance of ceramic membrane lead to obvious better fouling control and electricity utilization than organic membrane, and the paper provides insight into the MFC-CMBR systems for a wide range of detecting membrane fouling and applications of membrane fouling mitigation.

Recent progress in MXene layers materials for supercapacitors: High‐performance electrodes

AbstractIn 2011, Gogotsi et al. discovered a new type of two‐dimensional transition metal carbides and nitrides, called MXenes, which have become a dazzling new star in the energy storage industry. MXenes are endowed with a series of fascinating properties due to their unique structures and tunable surface chemical functional groups. The application of MXenes in electrochemical energy storage has attracted special attention, especially showing great potential in supercapacitor applications. Compared with other materials, MXenes have high mechanical flexibility, high energy density, and good electrochemical performance, so they are especially suitable as electrode materials for supercapacitors. However, similar to other 2D materials, due to the strong van der Waals forces, MXene layers inevitably undergo stacking agglomeration, resulting in severe loss of electrochemically active sites. If the self‐stacking of MXenes layers can be effectively suppressed, their electrochemical performance will be enhanced. Structural optimization of MXenes and composite doping of MXenes with other materials are two strategies with significant effects. This review summarizes recent advances in MXene synthesis, fundamental properties, and composite materials, focusing on the latest electrochemical performance of MXene‐based electrodes/devices, and puts forward the challenges and new opportunities that MXenes face in this emerging energy storage field.

Fabrication of laminated composite filter with nonwoven fabrics for oil/water separation

Various materials have been prepared and applied for the oil-water mixture separation, but there are some problems such as high cost, complicated formulation process and inferior durability. Nonwoven fabrics are widely used in industrial fields because of their low production cost and high economic benefit. In this study, a sandwich-structure filter was prepared for oil/water separation based on laminated nonwovens. Spunbond-meltblown-spunbond (SMS) nonwoven treated with silica and fluorine resin was selected for the hydrophobic top layer. The spunlaced viscose (VS) impregnated with citrate was used for the hygroscopic core layer while spunbond polypropylene (PP) prepared for the bottom substrate. These three layers were reinforced on an ultrasonic-bonding machine and tested for oil-water separation. Surface morphology and chemical group changes of treated fiber were recorded by scanning electron microscope (SEM), atomic force microscope (AFM), energy dispersive spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR). The effect of surface hydrophobicity and core hydrophilicity on separation efficiency was analyzed. The durability after recycles was evaluated and discussed. The possible separation mechanism was proposed. The results demonstrated that coating and spraying methods achieved uniform distribution of silica and fluorine resin onto the fiber surface. The suitable conditions for the preparation of composite filter were obtained as follows: the surface SMS layer was coated with silica, then sprayed with fluorine resin for a 6.0%weight gain to get a hydrophobic layer. The core layer viscose fiber impregnated with 3.0% citrate to enhance its hygroscopicity. The three layers were laminated and reinforced for the composite filter. Improving the hydrophobicity of top layer and the hydrophilicity of core layer both contributed to the enhance of separation efficiency and stability. The pore size of composite filter was mainly in the range of 9-11μm with a 35% distribution. After 15 times recycles, the water recovery ratio remains over 95% while water contact angle decreased from 150° to 135°. After layers laminated and bonding, the hydrophobic surface trapped oil and water in the mixture, hygroscopicity layer enabled a connection with the water in mixture through SMS layer and formed a capillary water channel. The water transferred to the sublayer by gravity and capillary action to actualize oil-water separation. These results provided new insights for the application of nonwoven fabrics on oil-water separation.

Fabrication of Transparent Silica/PEG Smooth Thin Coatings on Polymeric Films for Antifogging Applications.

Fog accumulation on surfaces typically has a negative effect by reducing their transparency and efficiency. Applications such as plastic packaging, agricultural films, and particularly many optical devices suffer from these negative effects. One way to prevent fogging is to coat the substrate with an antifogging coating having a smooth surface and hydrophilic surface chemical groups. This causes the fog water droplets that come into contact with the substrate to completely flatten across its surface, thus retaining transparency. These coatings are mostly relegated to laboratory research due to their insufficient stability and costly synthetic processes. We proposed the use of organically modified silica particles consisting of a mixture of tetraethyl orthosilicate and methacryloxypropyltriethoxysilane, which were grown in situ in the presence of a corona-activated polyethylene film, thus providing a thin siloxane coating containing activated double bonds. An additional coating of poly(ethylene glycol) diacrylate was then spread on the coated film and polymerized via UV curing. The in situ process and UV curing anchored the coating to the substrate through covalent bonds, which provided additional stability. This coating exhibited low surface roughness and contact angle, which resulted in excellent antifogging properties when exposed to a hot-fog test. Furthermore, the antifogging coating retained its properties after 10 hot-fog cycles, indicating the high coating stability. Additionally, the coating was found durable to immersion in aqueous pH levels 1–13 and detergent solutions as well as to tape test applications and sand test. This coating was compared to a commercially available antifogging spray, which was used to coat a polyethylene film. This resulted in excellent initial antifogging properties, which decreased after exposure to durability tests. The results of the in situ coating process indicate its potential uses for industrial applications.

Exploration of alternative cellulosic natural fiber from the stem of Malva Slyvestris

ABSTRACT The present work is planned to research the properties of fibers extracted from the stem of Malva sylvestris in detail. Cellulose and hemicellulose contents, surface atomic concentrations, surface chemical bonds and functional groups of Malva sylvestris fibers were determined by means of chemical characteristics. X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) were utilized to further analyze the fibers. Fiber density measurement and single fiber tensile test were performed. Malva sylvestris fibers were found to be thermally stable until 301 C which is a key parameter when processing with thermoplastic polymers. Thermal analysis also showed a char yield of 30.31%. The relatively lower density (1.104 g/cm3) can make it usable for light-weight applications. The crystallinity index (60.9%), cellulose content (75.7%) and maximum degradation temperature (355 C) are comparable with both common and new natural cellulosic fibers. Morphological observations confirmed its rough surface in untreated form. Malva sylvestris fibers are confirmed to be an appropriate material in manufacturing of green composites as reinforcement and/or additive.

Mechanical Properties Evolution and Damage Mechanism of Kevlar Fiber under Ozone Exposure in Near-Space Simulation

The stratospheric airship, a long-term floating vehicle in near-space, has become a new hotspot in aerospace exploration. The airship’s envelope material is vulnerable to ozone exposure in near-space and degrades. This paper used typical Kevlar fiber as the research material for an ozone exposure experiment in a near-space simulated environment. The results showed that the elongation of the Kevlar fiber decreased and the elastic modulus increased after ozone exposure. The tensile strength of fiber decreased gradually with an increase in ozone concentration and exposure time. When ozone concentration increased from 0 pphm to 1000 pphm, the tensile strength of fiber decreased from 2397 MPa to 2059 MPa. With increasing ozone exposure time from 0 h to 1000 h under ozone concentration 1000 pphm, the tensile strength of fiber decreased from 2332 MPa to 1954 MPa. The hydrogen bonds and partial amide groups in the fiber structure were damaged, and the surface chemical functional groups of the Kevlar fiber were reassembled under ozone exposure. Low molecular weight oxidation products, including -COO- structures, formed on the surface of the Kevlar fiber. This work explores the ground simulation method in a near-space environment and enriches the service data of airship envelope materials.

Z-scheme heterojunction ZnSnO3/rGO/MoS2 nanocomposite for excellent photocatalytic activity towards mixed dye degradation

In this work, a novel (ZnSnO3/rGO/MoS2) nanocomposite was prepared and its photocatalytic performances were investigated. The synthesised ZnSnO3 spheres were well dispersed over the surface of rGO sheet and MoS2 layers (ZSGM). The structural, morphological and elemental properties of the composites were examined by XRD, SEM, HRTEM and EDS. The surface chemical composition and functional groups of the elements interlinked in the composites were identified from XPS and FTIR analysis. BET and Raman analysis indicate the effective formation between MoS2/rGO/ZnSnO3 ternary heterostructure nanocomposite. The suppressed photogenic charge carrier's recombination rate was investigated by PL analysis. From UV analysis, the bandgap of ZSGM nanocomposite was successfully tuned from 3.13 eV to 2.70 eV, leading to high photocatalytic performance by mixed dye pollutant under UV-visible light illumination. The ZSGM photocatalyst achieved highest removal rate of 0.0131 min−1 for Rh B degradation, and 0.0153 min−1 for MB dye degradation and efficiency was 78% (Rh B) and 86% (MB), respectively in 100 min, which shows dramatically enhanced activity than other samples. In the presence of rGO/MoS2 in ZS, ZSGM photocatalysts exhibit higher catalytic activity due to a lower bandgap, more absorption in the visible region, and suppressed recombination rate of photogenerated e−/h+ pairs.

Performance Evaluation of Physically and Chemically Modified Pumice on Removal of Cu(II) from Aqueous Solution

Modification by physical and chemical treatments was evaluated to increase the adsorption capability of natural pumice in the removal of Cu(II) from aqueous solution. The treatments were heating at temperatures of 300, 450 and 600 ℃ for physical and soaking in acid solutions (HCl, H2SO4 and HNO3) for chemical treatment. The adsorption was performed in the batch system at the optimum condition (5 of pH solution, < 63 µm of adsorbent diameter, 3 g/L of adsorbent dose, 5 mg/L of Cu(II) concentration and 30 min of contact time). The results showed the removal efficiency and Cu(II) uptake increased using modified pumice from 71.19 % and 1.19 mg/g to 84.45 % and 1.41 mg/g. The highest removal efficiency and Cu(II) uptake were obtained from 300℃ of heating temperature and HCl for the acid solution. The application of physical and chemical treatments in modification has the potential to increase the removal efficiency and heavy metal uptake of the natural pumice.
 HIGHLIGHTS
 
 Various methods have been evaluated for the modification of pumice to improve their sorption capacity
 Physical and chemical treatment to pumice may modify the surface areas, pore structures, and chemical functional group on the surface of the pumice
 
 GRAPHICAL ABSTRACT

Mechanisms of Change in Emulsifying Capacity Induced by Protein Denaturation and Aggregation in Quick-Frozen Pork Patties with Different Fat Levels and Freeze-Thaw Cycles.

Herein, we discuss changes in the emulsifying properties of myofibrillar protein (MP) because of protein denaturation and aggregation from quick-frozen pork patties with multiple fat levels and freeze–thaw (F–T) cycles. Protein denaturation and aggregation were confirmed by the significantly increased surface hydrophobicity, turbidity, and particle size, as well as the significantly decreased solubility and absolute zeta potential, of MPs with increases in fat levels and F–T cycles (p < 0.05). After multiple F–T cycles, the emulsifying activity and emulsion stability indices of all samples were significantly reduced (p < 0.05). The emulsion droplets of MP increased in size, and their distributions were dense and irregular. The results demonstrated that protein denaturation and aggregation due to multiple F–T cycles and fat levels changed the distribution of surface chemical groups and particle sizes of protein, thus affecting the emulsifying properties.

Inhibiting Protein Aggregation by Small Molecule-Based Colloidal Nanoparticles

ConspectusProtein aggregation is associated with different human diseases such as Alzheimer’s, Huntington’s, Parkinson’s, diabetes type II, and cataracts. Currently no effective treatment exists for many of these diseases, particularly for neurological disorders. Ongoing research focuses on understanding the origin of protein aggregation, nucleation–growth mechanism of protein aggregation, origin of cytotoxicity of protein aggregates, cellular response of toxic protein aggregates, progress of diseases at intra/extracellular space, and drug developments for respective diseases. Key issues are the identification of molecular drugs that can inhibit protein aggregation at early stage, lowering of toxicity due to protein aggregates, delivery of drugs to remote organ and intracellular space, clearing matured protein aggregates from cell/extracellular space/brain, and design of effective therapeutic strategy.Chemists and materials scientists have identified a wide variety of antiamyloidogenic small molecules, macromolecules, and nanomaterials. It is shown that antiamyloidogenic molecules prevent protein oligomerization via binding to protein, masking metal ions (via chelating with metal ions) that are responsible for protein aggregation via generating reactive oxygen species (ROS), and lowering protein–protein interaction via macromolecular crowding effect. Similarly, nanoscale materials with curved surface and multiple chemical functional groups act as adsorption/binding sites of proteins, modulate nucleation–growth kinetics of protein aggregation, and delay/inhibit protein aggregation in many cases. However, performance of all these antiamyloidogenic materials needs significant improvement, and proper therapeutic strategies are required for effective drug development.In this Account, we describe that the performance of antiamyloidogenic molecules can be greatly improved via appropriate design into colloidal and nanoparticle form. We first discuss different human diseases that are linked with protein aggregation, location and mechanism of protein aggregation, adverse effect of protein aggregates on cell functions, and progress of different diseases due to these effects. Next, we discuss different classes of antiamyloidogenic materials, their mechanism of inhibiting protein aggregation, and existing approaches for their utilization under in vitro/in vivo conditions. Further, we show that antiamyloidogenic performance of small molecules can be enhanced as high as 100 000-times if they are transformed into appropriately designed colloidal nanoparticles. In particular, we explain that such enhanced performance is due to increased bioavailability at intra/extracellular space, modular binding property with protein, and higher brain delivery option in nanoparticle form. Next, we discuss different strategies for the preparation of colloidal nanoparticle where antiamyloidogenic molecules are terminated or loaded with nanoparticle and polymer micelle and their mechanism of action. Finally, we discuss that a wide variety of colloidal nanoparticles can be designed either for inhibiting or disintegrating or clearing of protein aggregates. The Account ends with a “Conclusions and Outlook” section that discuss a vision for development of therapeutic nanodrug for protein aggregation-related diseases.