Aggregation Phenomena Research Articles

Exploring the Assembly of Resorc[4]arenes for the Construction of Supramolecular Nano-Aggregates.

Many biologically active compounds feature low solubility in aqueous media and, thus, poor bioavailability. The formation of the host-guest complex by using calixarene-based macrocycles (i.e., resorcinol-derived cyclic oligomers) with a good solubility profile can improve solubilization of hydrophobic drugs. Herein, we explore the ability of resorc[4]arenes to self-assemble in polar solutions, to form supramolecular aggregates, and to promote water-solubility of an isoflavone endowed with anti-cancer activity, namely Glabrescione B (GlaB). Accordingly, we synthesized several architectures featuring a different pattern of substitution on the upper rim including functional groups able to undergo acid dissociation (i.e., carboxyl and hydroxyl groups). The aggregation phenomenon of the amphiphilic resorc[4]arenes has been investigated in a THF/water solution by UV–visible spectroscopy, at different pH values. Based on their ionization properties, we demonstrated that the supramolecular assembly of resorc[4]arene-based systems can be modulated at given pH values, and thus promoting the solubility of GlaB.

Influence of geographical determinants on the spatial distribution of positioning uncertainties in mobile phone location data

AbstractThe increasing use of mobile phone location (MPL) data in mobility research has provided many insights into people's travel behaviors. Despite these achievements, the spatial distribution of MPL data positioning uncertainties and their influence mechanism are rarely discussed. In this research, we investigate the influence of geographical determinants on the spatial distribution of the positioning uncertainties in MPL data. First, we discuss the spatial distribution trends in the positioning uncertainties of MPL data. Then we apply multiple linear regression and geographical detector (GeoDetector) models to explore the influence mechanism on the spatial distribution of the positioning uncertainties. By applying these methods to MPL data sets from a major operator in Nanjing city, we find a spatial aggregation phenomenon in the positioning uncertainties. Elevation contributes most to the spatial distribution of the positioning uncertainties. Furthermore, the influencing power of geographical factors on the spatial distribution of positioning uncertainties is nonlinearly enhanced after an interaction.

Amphiphile conformation impacts aggregate morphology and solution structure across multiple lengthscales

Although the self-assembly of amphiphiles is well-studied in aqueous solutions, much less is understood about the fundamental driving forces and structure property relationships in non-polar media. In recent work [Journal of Physical Chemistry B, 2020, 124, 10822.] the authors have studied a series of malonomide-based amphiphiles that are relevant to liquid-liquid extraction. That work demonstrated that aggregation is largely driven by local dipole-dipole interactions between molecules. Here, we build upon this observation to develop a more detailed understanding of how the balance of dipole-dipole interactions (controlled by conformation) and molecular architecture influences the morphology of the aggregates across lengthscales. Using constrained molecular dynamics about key degrees of freedom, we demonstrate that the conformation of N,N-dimethyl,N,N-dioctylhexylethoxy malonamide (DMDOHEMA) and N,N-dimethyl,N,N-dibutyltetradecyl malonamide (DMDBTDMA) has a significant impact upon self-association - where appropriate conformational sampling is essential. To quantify the aggregate morphology, several graph theoretic and persistent homology based properties are determined. The former examines the patterns of intermolecular interactions within clusters, while the latter examines the 3-dimensional spatial distribution. Based upon these analyses, we find that the morphology of aggregates, particularly at higher malonamide concentration, depends on a balance of dipole alignment and alkyl tail sterics. Dipole alignment encourages linear patterns of the intermolecular interactions within aggregates, while the alkyl tail steric interactions between the malonamide result in noticeably less linear aggregates for DMDOHEMA than DMDBTDMA. This is reflected in the spatial distribution, where more holes or voids exist between extractants within the DMDOHEMA that distribute within the solution in more of a “swiss cheese” arrangement as opposed to the more filamentous distribution of DMBDTDMA. This study links conformation and molecular structure to the morphology of amphiphile assemblies, and serves as a basis for ongoing study of multicomponent amphiphile solutions with polar and other solutes, and how these impact aggregation phenomena.

The Discovery of Peptide Macrocycle Rescuers of Pathogenic Protein Misfolding and Aggregation by Integrating SICLOPPS Technology and Ultrahigh-Throughput Screening in Bacteria.

The phenomenon of protein misfolding and aggregation has been widely associated with numerous human diseases, such as Alzheimer's disease, systemic amyloidosis and type 2 diabetes, the vast majority of which remain incurable. To advance early stage drug discovery against these diseases, investigation of molecular libraries with expanded diversities and ultrahigh-throughput screening methodologies that allow deeper investigation of chemical space are urgently required. Toward this, we describe how Escherichia coli can be engineered so as to enable (1) the production of expanded combinatorial libraries of short, drug-like, head-to-tail cyclic peptides and (2) their simultaneous functional screening for identifying effective inhibitors of protein misfolding and aggregation using a genetic assay that links protein folding and misfolding to cell fluorescence. In this manner, cyclic peptides with the ability to inhibit pathogenic protein misfolding and/or aggregation can be readily selected by flow cytometric cell sorting in an ultrahigh-throughput fashion. This biotechnological approach accelerates significantly the identification of hit/lead molecules with potentially therapeutic properties against devastating diseases.

Molecular interactions between heavy crude oil and a flow enhancer in a pipeline for pressure drop reduction

Asphaltenes and paraffin are considered the molecules present in heavy crude oils that tend to form aggregates that cause high viscosity values. Understanding the molecular interactions occurring in such aggregation phenomena is essential to apply flow enhancers that effectively reduce viscosity and positively impact power requirements in production fields. In this sense, this work develops a methodology that involves the molecular interaction energies determined by computational chemistry in the obtention of a semiempirical model to predict viscosity reduction. The model was developed based on heavy crude oil (8.88 °API, saturated fraction 33.23%, asphaltene fraction 26.46%, and 156.853 mPa s at 30 °C) dosed with a biodiesel-based flow enhancer which active principle is a fatty acid ester. The model predicted a 50% reduction of viscosity and, according to transport phenomena equations, pressure drop and the pumping power required for transport are also decreased by 50%. The semiempirical results were contrasted against field results, where the reduction expected of pressure drop was obtained. Such an outcome confirms that the assumed asphaltene-ester interaction in the computational study governs the flow enhancer activity in avoiding aggregation performed by asphaltene and paraffin molecules.

Colorimetric detection of Pb2+ ions using curcumin silver nanoparticles

The silver nanoparticles (AgNPs) complexed with curcumin (CUR) extracted from turmeric (TMR) were synthesized and applied for a simple and rapid colorimetric technique for Pb2+ detection. The results reveal that our low-cost and rapid AgNPs-CUR sensor is highly selective for Pb2+ ions with the detection limit of 13.6 µM (2.8 mg.L−1) and can be applied for real water samples. Not only the observed absorption spectrum and the solution color can reveal the contamination of Pb2+ in the sample, but also an orange floccules precipitate can be clearly observed by naked-eye within 20 min. In addition, the results obtained from DFT calculation agree well with the experiments. Density functional theory (DFT), at the M06 level with mixed basis set of 6-31G(d) and def2-tzvp, was applied to propose the binding mechanism of AgNPs with CUR and AgNPs-CUR with Pb2+. Calculated binding energies of the compound of AgNPs with CUR and the AgNPs-CUR with Pb2+ are −145.8 and −361.4 kcal mol−1, respectively, indicating that the AgNPs-CUR is strongly interact with Pb2+ ions through formation of highly stable Pb2+AgNPs-CUR complexes indicating the stable aggregative phenomena which agrees well with FTIR spectrum.

Ruthenium Complexes with 2-Pyridin-2-yl-1H-benzimidazole as Potential Antimicrobial Agents: Correlation between Chemical Properties and Anti-Biofilm Effects.

Antimicrobial resistance is a growing public health concern that requires urgent action. Biofilm-associated resistance to antimicrobials begins at the attachment phase and increases as the biofilms maturate. Hence, interrupting the initial binding process of bacteria to surfaces is essential to effectively prevent biofilm-associated problems. Herein, we have evaluated the antibacterial and anti-biofilm activities of three ruthenium complexes in different oxidation states with 2-pyridin-2-yl-1H-benzimidazole (L1 = 2,2′-PyBIm): [(η6-p-cymene)RuIIClL1]PF6 (Ru(II) complex), mer-[RuIIICl3(CH3CN)L1]·L1·3H2O (Ru(III) complex), (H2L1)2[RuIIICl4(CH3CN)2]2[RuIVCl4(CH3CN)2]·2Cl·6H2O (Ru(III/IV) complex). The biological activity of the compounds was screened against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa strains. The results indicated that the anti-biofilm activity of the Ru complexes at concentration of 1 mM was better than that of the ligand alone against the P. aeruginosa PAO1. It means that ligand, in combination with ruthenium ion, shows a synergistic effect. The effect of the Ru complexes on cell surface properties was determined by the contact angle and zeta potential values. The electric and physical properties of the microbial surface are useful tools for the examined aggregation phenomenon and disruption of the adhesion. Considering that intermolecular interactions are important and largely define the functions of compounds, we examined interactions in the crystals of the Ru complexes using the Hirshfeld surface analysis.

Microplastics through the Lens of Colloid Science.

Microplastics are sub-millimeter-sized fragments of plastics and a relatively new class of pollutant increasingly found in the environment. Due to their size and surface area to volume ratio, the physicochemical characteristics of microplastics can diverge from those of their macroscopic counterparts. This is partly why it is challenging to understand their origin, analyze their behavior, and predict their fates in the environment compared to large pollutants. We believe that adopting a view of microplastics as a colloid provides a holistic framework that connects their physical properties and surface chemistries with observations of their dynamics in the environment. In particular, we discuss the role of fundamental principles of colloid science in interpreting phenomena of wetting, adsorption, aggregation, and transport of microplastics. Colloid and interface science can provide the tools to couple or decouple the physicochemical behaviors of microplastics, which may aid in understanding the environmental challenge both from a fundamental perspective and with respect to practical remediation methods.

Host-to-Guest Energy Transfer and Its Role in the Lower Stability of Solution-Coated versus Vacuum-Deposited Phosphorescent OLEDs

Electroluminescence (EL) degradation mechanisms in solution-coated (SOL) host:guest (H:G) systems commonly used in phosphorescent organic light-emitting diodes (OLEDs) are investigated and compared to their vacuum-deposited (VAC) counterparts. Changes in the EL, photoluminescence (PL), and time-resolved PL (TRPL) characteristics of devices comprising SOL or VAC H:G light-emitting layers (EMLs) made of the same materials and in the same device architectures during prolonged electrical driving are compared and analyzed. Hole-only devices are also utilized to study the effects of charges and excitons, separately and combined. Moreover, devices with double EMLs comprising SOL and VAC components are tested to glean additional insights into the role of host excitons in device degradation. The results indicate that the faster degradation of SOL EML devices relative to their VAC EML counterparts under electrical stress is due–at least in part–to the less efficient host-to-guest (H → G) energy transfer in these systems, which accelerates molecular aggregation in the EML. Interactions between excitons and polarons in the EMLs induce this aggregation phenomenon which occurs more strongly in the case of SOL EMLs compared to their VAC counterparts because of the higher host exciton concentration in the former as a result of the less efficient H → G energy transfer. The findings shed light on one of the root causes of the limited stability of SOL OLEDs.

Boosting the Catalytic Performance of CeO2 in Toluene Combustion via the Ce-Ce Homogeneous Interface.

Catalytic combustion is an advanced technology to eliminate industrial volatile organic compounds such as toluene. In order to replace the expensive noble metal catalysts and avoid the aggregation phenomenon occurring in traditional heterogeneous interfaces, designing homogeneous interfaces can become an emerging methodology to enhance the catalytic combustion performance of metal oxide catalysts. A mesocrystalline CeO2 catalyst with abundant Ce-Ce homogeneous interfaces is synthesized via a self-flaming method which exhibits boosted catalytic performance for toluene combustion compared with traditional CeO2, leading to a ∼40 °C lower T90. The abundant Ce-Ce homogeneous interfaces formed by both highly ordered stacking and small grain size endow the CeO2 mesocrystal with superior redox property and oxygen storage capacity via forming various oxygen vacancies. Surface and bulk oxygen vacancies generate and activate crucial oxygen species, while interfacial oxygen vacancies further promote the reaction behavior of oxygen species (i.e., activation, regeneration, and migration), causing the splitting of redox property toward lower temperature. These properties facilitate aromatic ring decomposition, the important rate-determining step, thus contributing to toluene catalytic degradation to CO2. This work may shed insights into the catalytic effects of homogeneous interfaces in pollutant removal and provide a strategy of interfacial defect engineering for catalyst development.

Moment approximation of individual-based models. Application to the study of the spatial dynamics of phytoplankton populations

The objective of this paper is to analyze the efficiency of a spatial moments model (SMM) in approximating an individual-based model (IBM) dedicated to the study of the aggregation phenomenon in a phytoplankton population. The dynamic system of spatial moments consists of a system of integro-differential equations derived from a phytoplankton IBM. The later is built on the basis of stochastic processes describing the dynamics of phytoplankton cells and their interactions. These processes are: (1) the movement of cells, which takes into account the random dispersion of cells in water and the attraction between cells due to their chemosensory abilities, (2) the demographical process (cell division or cell death) in which, the effect of local competition for nutrient resources on the cell’s division process is taken into account through the use of density dependent division rate.We solve numerically the SMM and then simulate the two models (IBM and SMM), for a set of scenarios chosen to analyze the aggregation and the different interactions in the population. The numerical results have led to the conclusion that in contrast to the mean-field model (MFM), the method of spatial moments is efficient to capture the dynamics of the IBM. Further, the SMM easily permits the prediction of long term behavior of phytoplankton cells and their spatial structure, namely that the aggregation behavior of the cells is very much related to their cellular diffusion and the perceptual radius.Concerning competition on resources, this process has a short and medium-term effect on aggregation, since regardless of its intensity, in the long term the population tends to be stable with formation of aggregates, as a result of the equilibrium between different mechanisms, including reproduction, competition, diffusion and cells attractions due to chemosensory abilities.

Pulmonary Delivery of Curcumin and Beclomethasone Dipropionate in a Multicomponent Nanosuspension for the Treatment of Bronchial Asthma.

Curcumin has shown a potential extraordinary activity as an add-on ingredient in asthma treatment, due to its immunomodulatory and anti-inflammatory mechanism of action. However, its low water solubility and bioavailability lead to a poor therapeutic effect, which can be overcome by its formulation as nanocrystals. The aim of this study was to prepare a multicomponent formulation for the delivery of curcumin (CUR) and beclomethasone dipropionate (BDP) into the lungs as water-based nanosuspensions (NS). Single component formulations (CUR-NS, BDP-NS) and a multicomponent formulation (CUR+BDP-NS) were prepared through a wet ball media milling technique, using P188 as a non-toxic stabilizer. Characterization was carried out in terms of size, size distribution, zeta potential, nanocrystals morphology, and solid-state properties. Moreover, the inhalation delivery efficiency was studied with Next Generation Impactor (NGI, Apparatus E Ph. Eu). CUR-NS was optimized and showed a long-term stability and improved nanocrystals apparent solubility. The three formulations exhibited a nanocrystal mean diameter in the range of 200–240 nm and a homogenous particle size distribution. Aggregation or sedimentation phenomena were not observed in the multicomponent formulation on 90 days storage at room temperature. Finally, the nebulization tests of the three samples showed optimal aerodynamic parameters and MMAD < 5 µm.

Economic and educational factors played roles in the development of regional vision impairment in Shandong province, China

We analyze regional factors and spatial distribution of children's vision impairment in Shandong province, to explore the spatial changes brought by time and their influencing factors, so as to provide scientific basis for prevention of childhood vision impairment. This study covers five complete cross-sectional surveys from 2013 to 2017, involving about 29.24 million students. Spatial autocorrelation and hotspot analysis methods were used to analyze spatial features. The associated factors were analyzed by multinomial logistic regression. The vision impairment prevalence showed a trend of decreasing first and then increasing from 2013 to 2017, with slight changes. In terms of regional spatial differences, Weihai and Yantai have the highest VI rates in all years, and there was a large-scale spatial aggregation phenomenon. The southern low-value clusters, however, showed a trend of weakening from year to year. Further exploration revealed that economic factors and number of full-time teachers were verified as risk factors for regional vision impairment levels. The slight rebound of the prevalence of vision impairment and the high rate in the eastern and northern regions of Shandong province need more attention. It is suggested that relevant departments should focus on the influence of regional economic and educational factors when formulating relevant strategies.

Effect of heat accumulation on the microstructure of Invar alloy manufactured by multi-layer multi-pass laser melting deposition

Invar alloy has an important application in the manufacture of composite forming mould. The laser melting deposition (LMD) technology was utilized to fabricate multi-layer multi-pass deposited samples in this study. The effect of heat accumulation on the microstructure of deposition layer (DL) was investigated through experimental and simulation method. A finite element (FE) model was established to study the temperature field distribution in LMD process. Microstructure of DL was investigated by optical microscope (OM), scanning electron microscope (SEM), and energy dispersive spectrometer (EDS). The thermal cycle curves were extracted for analysis. The accumulation of heat during the deposition process would make the higher location DL reach a higher peak temperature. It could be seen from the observation of the transverse section of the deposited samples that the microstructure consisted of elongated cellular crystals and regular cellular crystals. At the bottom of the DL were columnar crystals grown epitaxially along the maximum temperature gradient and gradually transitioned to equiaxed crystals at the top of the DL. EDS detection results showed that there was no element aggregation phenomenon in the DL. The grains in the remelted zone were coarsened due to suffering a state of overheating.

Insights into the aggregation mechanism of RNA recognition motif domains in TDP-43: a theoretical exploration.

The transactive response DNA-binding protein 43 (TDP-43) is associated with several diseases such as amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) due to pathogenic aggregations. In this work, we examined the dimer, tetramer and hexamer models built from the RRM domains of TDP-43 using molecular dynamics simulations in combination with the protein–protein docking. Our results showed that the formations of the dimer models are mainly achieved by the interactions of the RRM1 domains. The parallel β-sheet layers between the RRM1 domains provide most of the binding sites in these oligomer models, and thus play an important role in the aggregation process. The approaching of the parallel β-sheet layers from small oligomer models gradually expand to large ones through the allosteric communication between the α1/α2 helices of the RRM1 domains, which maintains the binding affinities and interactions in the larger oligomer models. Using the repeatable-superimposing method based on the tetramer models, we proposed a new aggregation mechanism of RRM domains in TDP-43, which could well characterize the formation of the large aggregation models with the repeated, helical and rope-like structures. These new insights help to understand the amyloid-like aggregation phenomena of TDP-43 protein in ALS and FTLD diseases.

An AIEgen–protamine assembly/disassembly based fluorescence turn-on probe for sensing alkaline phosphatase

Alkaline phophatase (ALP) is indispensable for physiological functioning of living systems, and participates in the hydrolysis of monoester phosphate linkage from biological molecules, such as, nucleic acids, proteins etc. The abnormal concentration of ALP in human blood serum is an indicator of many diseases, therefore, ALP acts as a very useful biomarker for diagnosis of several diseases. In this contribution, we have exploited the unique phenomenon of aggregation induced emission (AIE) to design a rapid, easy, sensitive and highly selective fluorescence “Turn-On” probing system for monitoring ALP activity. The sensing units of the probing system are made up of an AIE active dye, di-anionic 1,2-Bis[4-(3-sulfonatopropoxyl)phenyl]-1,2-diphenylethene salt (BSPOTPE) and polycationic protamine sulphate (PrS) that electrostatically interact with each other to make a highly fluorescent BSPOTPE-PrS supra-molecular complex. Subsequently, the fluorescence of BSPOTPE-PrS complex is efficiently quenched by the introduction of sodium hexametaphospahte, (NaPO3)6. A rapid recovery in the fluorescence (turn-on) is obtained by adding ALP in the basic buffer conditions. The method registers LOD of 28.7 (±3) μU/mL of ALP in the linear concentration range of 0–36 mU/mL. The sensor exhibits remarkable specificity for ALP. The potential application of the sensing probe in real samples is demonstrated successfully in human serum samples.

Effect of composition of mono/di-hydroxy organic compounds and temperature on the aggregation behavior and physico-chemical properties of polyvinyl alcohol + TTAB mixture

Herein, the aggregation manners of polyvinyl alcohol (PVA) with tetradecyltrimethylammonium bromide (TTAB) in alcohols/diols media containing various concentrations and at several temperatures were performed using the conductivity measurement technique. Different physico-chemical parameters, such as critical micelle concentration (CMC), fraction of bound counter ions (β) and thermodynamic properties (ΔGo m, ΔHo m, ΔSo m, and ΔCo m) for the TTAB + PVA mixture in aqueous solutions of EtOH (EtOH), 1-propanol (1-PrOH), ethylene glycol (EG), and propylene glycol (PrG), have been determined. The CMC values were found to undergo a decrease in 1-PrOH in comparison to the values obtained in aqueous media, but in EtOH, the CMC value firstly decreases, touches the lowest point, and then exhibits an upsurge with further increase of the percentage of EtOH. The observed greater CMC values in diols media disclose that the micelle formation of TTAB + PVA mixture is delayed in the manifestation of diols. The CMC values of TTAB + PVA mixture have also been observed to vary with the change of study temperature. The negative values of ΔG0 m were obtained for all circumstances suggesting a spontaneous aggregation phenomenon of TTAB + PVA system. The values of ΔH 0 m and ΔS0 m dictate that the PVA molecule interacts exclusively with TTAB through the formation of hydrogen bonding, ion-dipole, and hydrophobic interaction. Furthermore, the standard molar heat capacity (ΔC 0 m), compensation temperature (T c), intrinsic enthalpy gain (ΔH 0,* m), and the thermodynamic properties of transfer (ΔG 0 m.tr, ΔH 0 m.tr. and ΔS 0 m.tr.) for the studied system were assessed and demonstrated with appropriate explanations.

Physics-informed deep learning for modelling particle aggregation and breakage processes

Particle aggregation and breakage phenomena are widely found in various industries such as chemical, agricultural and pharmaceutical processes. In this study, a physics-informed neural network is developed for solving both the forward and inverse problems of particle aggregation and breakage processes. In this method, the population balance equation is directly embedded in the loss function of a neural network so that the network can be trained efficiently and fulfil physical constraints. For the forward problems, solutions of population balance equations are obtained through the optimization of the neural network where the predictions well match the analytical solutions. In the inverse modelling, the data-driven discovery of model parameters of population balance equations is investigated. The sensitivity regarding the selection of different neural network structures is also investigated. The developed population balance equations embedded with neural network approach is promising for solving inverse problems of particle aggregation and breakage processes with noisy observation data.

Filtration of Nanoparticle Agglomerates in Aqueous Colloidal Suspensions Exposed to an External Radio-Frequency Magnetic Field.

The study investigated the phenomenon of the fast aggregation of single-domain magnetic iron oxide nanoparticles in stable aqueous colloidal suspensions due to the presence of a radio-frequency (RF) magnetic field. Single-domain nanoparticles have specific magnetic properties, especially the unique property of absorbing the energy of such a field and releasing it in the form of heat. The localized heating causes the colloid to become unstable, leading to faster agglomeration of nanoparticles and, consequently, to rapid sedimentation. It has been shown that the destabilization of a stable magnetic nanoparticle colloid by the RF magnetic field can be used for the controlled filtration of larger agglomerates of the colloid solution. Two particular cases of stable colloidal suspensions were considered: a suspension of the bare nanoparticles in an alkaline solution and the silica-stabilized nanoparticles in a neutral solution. The obtained results are important primarily for biomedical applications and wastewater treatment.

Gasification of N-rich fibreboard in an air-blown fluidized bed reactor: A study on the fate of tars, NH3 and HCN during oxidative mild Hot Gas Filtration

Wood wastes, such as Medium Density Fibreboard (MDF), are interesting low-cost fuels for gasifiers. The present study examines the effect of oxidative Hot Gas Filtration (HGF) on gasification indicators and pollutants (tars, NH3 and HCN) of producer gas. Pellets of N-rich MDF were gasified in an air-blow bubbling bed reactor at 800 °C coupled with a downstream HGF unit equipped with multilayer metallic filters and operated at mild temperature (400–600 °C). The fate of pollutants was assessed by complementary analytical techniques (HPLC, UV-fluorescence, GC/MS-FID and wet chemical methods for N-compounds). The deposit of the filter was also sampled after gasification trials and characterised by SEM-EDX.For the reference tests, conducted without the HGF unit, tar concentration was 6.5 g/Nm3 (dry gas, benzene-free) while, 43% of Fuel Bounded Nitrogen (FBN) was converted to NH3 and 4% to HCN. Oxidative HGF tests showed that secondary reactions inside the HGF unit undergo in homogeneous (gas-gas) and heterogeneous (gas-solid) phase. At a relatively high secondary air flow rate brought in the HGF unit, the severe oxidation of the dust cake particles led to irreversible melting, aggregation and sintering phenomena of ash deposits on the surface of the filter, as well as, to a drop of 49% in the tar yield. Overall, this work demonstrates that the addition of secondary air inside the HGF unit should be carefully tailored in order to minimise the exothermic oxidation of dust cake particles and, to promote long-term operation of the filter.