Colloids and Interfaces

17 pages, 3356 KiB

Open AccessArticle

Encapsulation of Canola Oil by Sonication for the Development of Protein and Starch Systems: Physical Characteristics and Rheological Properties

by Reynaldo J. Silva-Paz, Celenia E. Ñope-Quito, Thalia A. Rivera-Ashqui, Nicodemo C. Jamanca-Gonzales, Amparo Eccoña-Sota, Natalia Riquelme and Carla Arancibia

Colloids Interfaces 2025, 9(1), 10; https://doi.org/10.3390/colloids9010010 - 22 Jan 2025

Abstract

Canola oil, extracted from Brassica napus, is appreciated for its nutritional profile, but its use in the food industry is limited by its susceptibility to oxidation. This study aimed to evaluate the nanoemulsion of canola oil by sonication to develop stable nanoemulsified [...] Read more.

Canola oil, extracted from Brassica napus, is appreciated for its nutritional profile, but its use in the food industry is limited by its susceptibility to oxidation. This study aimed to evaluate the nanoemulsion of canola oil by sonication to develop stable nanoemulsified gels from protein and starch systems. Two stages were performed. In the first stage, oil-in-water (O/W) nanoemulsions were prepared using soy lecithin and Tween 80 as emulsifiers, analyzing their physical stability by particle size and polydispersity index. The results show that the sonication conditions and emulsifier concentration significantly affected the creaming index and particle size. In the second stage, gels were developed from these nanoemulsions, evaluating their colorimetric and rheological properties. It was observed that the gels presented a viscoelastic behavior suitable for food applications, with a higher luminosity in protein systems. In conclusion, nanoemulsion by sonication improves the stability of canola oil, suggesting its potential use in various food applications. Additional emulsifier combinations and optimization of processing conditions are recommended to further improve the stability and functionality of the encapsulated oil. Full article

(This article belongs to the Special Issue Food Colloids: 3rd Edition)

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19 pages, 4221 KiB

Open AccessFeature PaperArticle

Bio-Based Interpolyelectrolyte Complexes for the Stabilization of Pickering-like Emulsions

by Francisco Joel Guerrero-Vasquez, Francisco Ortega, Ramón G. Rubio and Eduardo Guzmán

Colloids Interfaces 2025, 9(1), 9; https://doi.org/10.3390/colloids9010009 - 22 Jan 2025

Abstract

This work studies the stabilization of Pickering-like emulsions using dispersions of interpolyelectrolyte complexes (IPECs) formed by chitosan (CS) and sodium alginate (ALG), two polymers from natural resources, as the aqueous phase and soybean oil as the oil phase. The ability of these bio-based [...] Read more.

This work studies the stabilization of Pickering-like emulsions using dispersions of interpolyelectrolyte complexes (IPECs) formed by chitosan (CS) and sodium alginate (ALG), two polymers from natural resources, as the aqueous phase and soybean oil as the oil phase. The ability of these bio-based IPECs to form stable emulsions was evaluated by varying the compositional ratio of CS to ALG (Z-ratio) and the oil volume fraction (ϕ_o). Turbidity, zeta potential, and dynamic light scattering measurements revealed the dependence of IPEC properties on the Z-ratio, with phase separation observed near stoichiometric ratios. Phase diagram analysis showed that stable oil-in-water (O/W) and water-in-oil (W/O) emulsions could be obtained under certain combinations of the Z-ratio and ϕ_o. Emulsion stability increased with higher Z-ratios due to increased interfacial activity of the complexes and reduced coalescence. Emulsions with high ϕ_o exhibited transitions from discrete droplets to bicontinuous interfacially jammed emulsion gels (bijels), suggesting tunable morphologies. These results highlight the potential of CHI-ALG IPECs as eco-friendly and efficient stabilizers of Pickering-like emulsions for applications in food, cosmetics and pharmaceuticals. Full article

(This article belongs to the Special Issue State of the Art of Colloid and Interface Science in the Iberian Peninsula)

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10 pages, 1873 KiB

Open AccessFeature PaperArticle

An Imine-Based Two-Dimensional Covalent Organic Framework for Gemcitabine Delivery

by Kajal Kaliya, Neha Bhardwaj, Ruchika and Ankit Saneja

Colloids Interfaces 2025, 9(1), 8; https://doi.org/10.3390/colloids9010008 - 21 Jan 2025

Abstract

A 2D imine-linked covalent organic framework (COF) with good biocompatibility was synthesized using o-Dianisidine and 1,3,5-Triformylbenzene. The synthesized COF was characterized by using the Fourier transform infrared (FTIR), thermogravimetry analysis (TGA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The synthesized COF [...] Read more.

A 2D imine-linked covalent organic framework (COF) with good biocompatibility was synthesized using o-Dianisidine and 1,3,5-Triformylbenzene. The synthesized COF was characterized by using the Fourier transform infrared (FTIR), thermogravimetry analysis (TGA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The synthesized COF was subsequently utilized for the delivery of gemcitabine (Gem), an FDA-approved drug for the treatment of pancreatic cancer. The COF demonstrated a remarkable drug loading of 30 µg/mg and better drug release at pH 5.0. The biocompatibility of the COF was evaluated in the L929 (mouse fibroblast) cell line, while the cytotoxicity of the Gem-loaded COF (COF-Gem) was evaluated against the MIA-PaCa-2 and PANC-1 (pancreatic cancer) cell lines using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. The results indicated that the COF was safe at concentrations up to 200 µg/mL, while the COF-Gem led to superior cytotoxicity as compared to native Gem, with IC₅₀ values of 8.1 ± 1.2 µM in MIA-PaCa-2 cells and 6.0 ± 1.3 µM in PANC-1 cells after 48 h. This study offers a new perspective of utilizing COF as a promising delivery system for Gem delivery. Full article

(This article belongs to the Special Issue Biocolloids and Biointerfaces: 2nd Edition)

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13 pages, 1177 KiB

Open AccessArticle

Transient Diffusiophoresis of a Spherical Colloidal Particle

by Hiroyuki Ohshima

Colloids Interfaces 2025, 9(1), 7; https://doi.org/10.3390/colloids9010007 - 19 Jan 2025

Abstract

A general theoretical approach is introduced to analyze the time-dependent, transient diffusiophoresis of a charged spherical colloidal particle in a symmetrical electrolyte solution when an electrolyte concentration gradient is suddenly applied. We derive a closed-form approximate expression for the relaxation function R( [...] Read more.

A general theoretical approach is introduced to analyze the time-dependent, transient diffusiophoresis of a charged spherical colloidal particle in a symmetrical electrolyte solution when an electrolyte concentration gradient is suddenly applied. We derive a closed-form approximate expression for the relaxation function R(t), which describes the time course of the diffusiophoretic mobility of a weakly charged spherical colloidal particle possessing a thin electrical double layer. The relaxation function depends on the mass density ratio of the particle to the electrolyte solution and the kinematic viscosity. However, it does not depend on the type of electrolyte (e.g., KCl or NaCl). It is also found that the expression for the relaxation function in transient diffusiophoresis of a weakly charged spherical colloidal particle with a thin electrical double layer takes the same form as that for its transient electrophoresis. Full article

(This article belongs to the Special Issue Biocolloids and Biointerfaces: 2nd Edition)

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15 pages, 7577 KiB

Open AccessFeature PaperArticle

Experimental Investigation of Stability of Emulsions Produced by Catastrophic Phase Inversion Using Non-Ionic Surfactants

by Maria Doutsi, Maria C. Vlachou, Christos Koukiotis, Margaritis Kostoglou and Thodoris D. Karapantsios

Colloids Interfaces 2025, 9(1), 6; https://doi.org/10.3390/colloids9010006 - 16 Jan 2025

Abstract

Emulsions stabilized by environmentally friendly surfactants have been at the center of research attention over recent decades. Non-ionic surfactants with good biodegradability, while being non-toxic and non-irritating, have dominated in this area. For a chosen system, the main goal is to engineer its [...] Read more.

Emulsions stabilized by environmentally friendly surfactants have been at the center of research attention over recent decades. Non-ionic surfactants with good biodegradability, while being non-toxic and non-irritating, have dominated in this area. For a chosen system, the main goal is to engineer its properties for smaller droplet sizes and better stability, a process which is mainly derived from the emulsification method. In the present study, Ethylan 1005 and Ethylan 1008 were used as stabilizers, both alone and combined at different ratios, in eco-friendly emulsions produced by paraffin oil and Millipore water, via direct emulsification, catastrophic phase inversion and catastrophic phase inversion in droplets. During the experiments, the emulsions’ rheological behavior, phase separation, and droplet size distribution profiles were measured. Catastrophic phase inversion in droplets resulted in the finest droplet size distributions for both emulsifiers when used alone. As the concentration of Ethylan 1008 increased from 0% to 100% in the surfactant mixtures, the droplets’ mean diameter and range also increased, indicting degradation of emulsion stability. However, phase separation tests revealed the opposite. Explanation was found in the chemical structure of the two emulsions and the steric phenomena caused by this, while a semi-quantitative analysis of these trends was also developed. Full article

(This article belongs to the Special Issue Exclusive Papers of the Editorial Board Members of Colloids and Interfaces 2024)

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26 pages, 44536 KiB

Open AccessArticle

Polydispersity and Composition Stability in a Long-Term Follow-Up of Palmarosa (Cymbopogon Martini) and Tea Tree (Melaleuca Alternifolia) O/W Nanoemulsions for Antibacterial Use

by Erick Sánchez-Gaitán, Vianney González-López and Francisco Delgado

Colloids Interfaces 2025, 9(1), 5; https://doi.org/10.3390/colloids9010005 - 14 Jan 2025

Abstract

There is a growing focus on the design of nanoemulsions because of their valuable properties as an enhanced vehicle for interaction with cells and resistant bacteria. Their potential applications in the health and food industry are numerous. Although they are considered unstable because [...] Read more.

There is a growing focus on the design of nanoemulsions because of their valuable properties as an enhanced vehicle for interaction with cells and resistant bacteria. Their potential applications in the health and food industry are numerous. Although they are considered unstable because of flocculation and coalescence, they are still efficient resources for antibacterial inhibition due to their droplet size. Studies on the interactions between essential oils and an aqueous medium are increasing, in order to efficiently formulate them at the nanometric scale using surfactants, thereby providing them with long-lived droplet size stability. This study used the ultrasonication method for fabrication and Eumulgin as a surfactant to achieve nanometric droplet sizes using two noble essential oils, palmarosa and tea tree. A follow-up for one year tracked a stable droplet size and sustained polydispersity in those emulsions as the most valuable outcome. Moreover, the insights of a thermoresponsive study have been included, also showing a strong stability. The antibacterial properties of the essential oils considered became enhanced, at a comparable scale of an antibiotic, on Salmonella spp. and Bacillus subtilis depending on the nanoscale droplet size. The outcomes suggest the importance of deepening parametric studies of these nanoformulations in terms of concentrations and temperature changes, characterizing their remarkable properties and durability. Full article

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19 pages, 2309 KiB

Open AccessFeature PaperArticle

Micellization and Physicochemical Properties of CTAB in Aqueous Solution: Interfacial Properties, Energetics, and Aggregation Number at 290 to 323 K

by Bappaditya Naskar

Colloids Interfaces 2025, 9(1), 4; https://doi.org/10.3390/colloids9010004 - 9 Jan 2025

Abstract

This work reports a detailed investigation of the micellization of the cationic surfactant cetyltrimethylammonium bromide (CTAB) over the temperature range of 290–313 K. Conductometry, tensiometry, fluorimetry, and isothermal titration calorimetry (ITC) were used to study the overall solution behavior of amphiphilic self-aggregation. The [...] Read more.

This work reports a detailed investigation of the micellization of the cationic surfactant cetyltrimethylammonium bromide (CTAB) over the temperature range of 290–313 K. Conductometry, tensiometry, fluorimetry, and isothermal titration calorimetry (ITC) were used to study the overall solution behavior of amphiphilic self-aggregation. The CMC values showed a trend of first declining and then rising with a minimum temperature of 298 K. The adsorption at the air–water interface and micellization processes of CTAB are both spontaneous. The enthalpy of CTAB micellization is negative at 290 K and increases negatively as the temperature rises. The interfacial parameters—maximum surface excess concentration (Γ_max), minimum area per molecule (A_min), standard free energy of adsorption (A_min), and surface pressure at CMC (Π_CMC)—were calculated using surface tension data. The aggregation numbers (N) of CTAB micelles and others (SDS and CHAPS) determined at different [surfactant]>CMC by the static fluorescence quenching method were used to find out the N values at CMC (or N^CMC). The results revealed that the N^CMC values were 48, 54, and 4 for CTAB, SDS, and CHAPS micelles, respectively. Temperature-dependent N^CMC by the ITC method was also examined for the studied surfactants. Additionally, the ITC-determined specific heat of micellization was used to find out the extent of water penetration into the micelle interior of up to 8, 7, and 3 hydrocarbons for CTAB, SDS, and CHAPS, respectively. Full article

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18 pages, 6011 KiB

Open AccessReview

Application of Porous Materials in Photocatalytic Treatment of Wastewater

by Jian Nan, Xinyu Liu, Di Zhang, Rui Xu and Yong Zhang

Colloids Interfaces 2025, 9(1), 3; https://doi.org/10.3390/colloids9010003 - 3 Jan 2025

Abstract

With the increasing environmental water pollution, there is an increasing demand for efficient and sustainable wastewater treatment technologies. Photocatalysis, as an environmentally friendly oxidation technology, shows significant promise for the degradation and mineralization of organic pollutants in wastewater. Porous structured materials have received [...] Read more.

With the increasing environmental water pollution, there is an increasing demand for efficient and sustainable wastewater treatment technologies. Photocatalysis, as an environmentally friendly oxidation technology, shows significant promise for the degradation and mineralization of organic pollutants in wastewater. Porous structured materials have received much attention from scientists for the photocatalytic treatment of wastewater due to their good dispersibility and high specific surface area. Based on the exploration of the recent research papers about various porous materials in photocatalytic degradation of wastewater, we summarize the synthesis of porous materials and methods of loading catalysts, explore the applications for treating different types of pollutants, and finally present the challenges and prospects of porous materials in photocatalytic wastewater treatment. We hope that this review will inspire more researchers to focus on this important field. Full article

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12 pages, 2616 KiB

Open AccessArticle

Microencapsulation Efficiency of DCOIT Biocide in the TPM/SiO₂ System and a Study of Their Acute Toxicity

by Assem Issayeva, Saule Aidarova, Galiya Madybekova, Seitzhan Turganbay, Alpamys Babayev, Miras Issakhov, Altynay Sharipova, Reinhard Miller and Botagoz Mutaliyeva

Colloids Interfaces 2025, 9(1), 2; https://doi.org/10.3390/colloids9010002 - 31 Dec 2024

Abstract

Biocides are often used in various industries and applications to control microbial growth and prevent the deterioration of materials, and they often have the ability to target a wide range of microorganisms rather than being specific to one type. They are designed to [...] Read more.

Biocides are often used in various industries and applications to control microbial growth and prevent the deterioration of materials, and they often have the ability to target a wide range of microorganisms rather than being specific to one type. They are designed to be highly effective at killing or inhibiting the growth of microorganisms and some biocides have residual activity, meaning they remain active for a period of time after application, providing longer-term protection. Biocides need to be compatible with the materials and surfaces they are applied to without causing damage or adverse effects, and they should remain stable under various environmental conditions, such as temperature and pH, to maintain their efficacy over time. In this study, microcapsules incorporating the biocide 4,5-dichloro-2-n-octyl-4-isotriazolin-3-one (DCOIT) were synthesized, and their effectiveness was evaluated. The investigation focused on several aspects, including colloidal chemical properties such as interfacial tension at pH values of 3, 7, and 9, as well as the size, ζ-potential, and morphology of the microcapsules. To validate the microcapsule production, elemental analysis was performed, and the effects on wettability and toxicological properties were assessed within the DCOIT + trimethoxysilyl propylmethacrylate/silicon dioxide nanoparticle system. Interfacial tension kinetics were measured using the PAT-1 tensiometer. The microcapsules exhibited an average diameter of 146 ± 1 nm following emulsification, with a ζ-potential of −50.2 ± 1 mV, as determined by the Malvern Zetasizer Nano Z. The morphology of the microcapsules was characterized using the SEM Controller 1550. Elemental composition was analyzed via energy-dispersive X-ray microanalysis (EDAX). The study concluded that the DCOIT biocide, when incorporated in the TPM/SiO₂ system, demonstrated non-toxic properties. Full article

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24 pages, 7049 KiB

Open AccessArticle

Remediation of Caffeine from Aqueous Solutions Using Waste-Derived Adsorbents: A Polyaniline/Cuttlefish Bone Nanocomposite for Pollutant Removal

by Esraa Salama, Samar M. Mahgoub, Ahmed A. Allam, Haifa E. Alfassam and Rehab Mahmoud

Colloids Interfaces 2025, 9(1), 1; https://doi.org/10.3390/colloids9010001 - 26 Dec 2024

Abstract

Caffeine is commonly used in pharmaceutical and personal care products, where it serves both therapeutic and cosmetic purposes. However, its widespread presence in wastewater from the pharmaceutical and cosmetic industries has raised concerns about environmental contamination. This study explores the use of a [...] Read more.

Caffeine is commonly used in pharmaceutical and personal care products, where it serves both therapeutic and cosmetic purposes. However, its widespread presence in wastewater from the pharmaceutical and cosmetic industries has raised concerns about environmental contamination. This study explores the use of a polyaniline (PANI)/cuttlefish bone (CB) nanocomposite as an effective adsorbent for the removal of caffeine from aqueous solutions. The nanocomposite was synthesized by incorporating polyaniline (PANI) onto cuttlefish bone (CB) flakes, resulting in a material with a hybrid morphology consisting of layered nanosheets and flaky structures. Adsorption experiments were conducted to determine the optimal conditions for caffeine removal, with results showing the best adsorption efficiency at pH 7 and an adsorbent dosage of 0.1 g/L for the nanocomposite, achieving an 80.73% removal efficiency. The maximum adsorption capacity of the nanocomposite was 108.33 mg/g—significantly higher than for pure CB (55.05 mg/g) and PANI (57.71 mg/g). The adsorption process followed the pseudo-second-order kinetic model and the Langmuir isotherm, indicating a chemisorption mechanism and monolayer adsorption. Additionally, the nanocomposite demonstrated excellent reuse capacity, maintaining over 85% of its initial efficiency after multiple adsorption–desorption cycles, highlighting its potential for sustainable long-term use. This work demonstrates the potential of using waste-derived materials like cuttlefish bone as an effective support for PANI in the development of low-cost, sustainable adsorbents for pollutant remediation in pharmaceutical wastewater. Future studies will explore the adsorbent’s applicability for other contaminants and its potential antimicrobial properties. Full article

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23 pages, 11733 KiB

Open AccessFeature PaperReview

Potentiating Virus-like Particles for Mucosal Vaccination Using Material Science Approaches

by Milad Radiom

Colloids Interfaces 2024, 8(6), 68; https://doi.org/10.3390/colloids8060068 - 12 Dec 2024

Abstract

Virus-like particles (VLPs) exhibit such unique colloidal and structural properties that make them ideal candidates for various bio-nanotechnology applications, among which mucosal vaccination is particularly promising. However, since mucosal surfaces present harsh environments to VLPs, stabilization of VLP capsids or alternative delivery strategies [...] Read more.

Virus-like particles (VLPs) exhibit such unique colloidal and structural properties that make them ideal candidates for various bio-nanotechnology applications, among which mucosal vaccination is particularly promising. However, since mucosal surfaces present harsh environments to VLPs, stabilization of VLP capsids or alternative delivery strategies are necessary. Addressing these challenges requires interdisciplinary research, and the intersection of material science and immunology is presented in this review. Approaches such as crosslinking capsid coat proteins, incorporating VLPs in polymer matrices and hydrogels, or forming crystalline nano-/micro-structures show potential for developing muco-stable VLP vaccines or for delivering these vaccines in a sustainable manner. This review explores recent material science approaches that leverage VLPs as nanotools for various applications and with the potential for translation to mucosal vaccination. Full article

(This article belongs to the Special Issue Biocolloids and Biointerfaces: 2nd Edition)

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17 pages, 8176 KiB

Open AccessArticle

Effect of the Core/Shell Particle Synthesis Method on the Physico–Chemical Properties of Their Shell and Sensory Properties of 3D-Ordered Films

by Olga Iakobson, Elena Ivankova, Svetlana Laishevkina and Natalia Shevchenko

Colloids Interfaces 2024, 8(6), 67; https://doi.org/10.3390/colloids8060067 - 10 Dec 2024

Abstract

In this work, we investigated the influence of the synthetic conditions of core/shell particles on physico–chemical properties of their shells, the process of self-assembly of particles into 3D-ordered structures, and the sensitivity of films based on these particles to the presence of ethanol [...] Read more.

In this work, we investigated the influence of the synthetic conditions of core/shell particles on physico–chemical properties of their shells, the process of self-assembly of particles into 3D-ordered structures, and the sensitivity of films based on these particles to the presence of ethanol and temperature changes. The core/shell particles were prepared by two methods: seed emulsion copolymerization and semi-batch emulsion copolymerization. The cores consisted of polystyrene or its copolymer with methyl methacrylate. Polymer shells of the particles were obtained by copolymerization of methyl methacrylate with several acrylate comonomers: butyl acrylate, butyl methacrylate, propyl acrylate, and ethyl acrylate. The photonic crystal films with the highest sensitivity to ethanol vapors were obtained on the basis of the core/shell particles synthesized by semi-batch emulsion polymerization. It was also established that introducing butyl acrylate or propyl acrylate units into shell copolymers led to an increase in the sensitivity of the resulting photonic crystal films. The films demonstrated a pronounced thermosensitivity only when the corresponding core/shell particles were synthesized as follows: the shell comonomers (methyl methacrylate and butyl acrylate) were introduced into the reaction system during the semi-batch emulsion process in a single step. The intensity of the photonic band gap (PBG) peak for these films decreased by 100% at around 42 °C. Full article

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17 pages, 2972 KiB

Open AccessFeature PaperArticle

Foaming Properties of Chlorella sorokiniana Microalgal Biomass

by Despoina Georgiou, Aggelos Charisis, Athina Theocharidou, Christos Ritzoulis, Georgia Papapanagiotou, Christina Samara, Christos Chatzidoukas and Eleni P. Kalogianni

Colloids Interfaces 2024, 8(6), 66; https://doi.org/10.3390/colloids8060066 - 29 Nov 2024

Cited by 1

Abstract

Chlorella sorokiniana is a well-studied microalga with significant nutritional potential due to its health-promoting nutrients. C. sorokiniana is rich in proteins (~50%), lipids (~14%), vitamins, and other bioactive compounds, making it an attractive ingredient for the food industry. Other properties of C. sorokiniana [...] Read more.

Chlorella sorokiniana is a well-studied microalga with significant nutritional potential due to its health-promoting nutrients. C. sorokiniana is rich in proteins (~50%), lipids (~14%), vitamins, and other bioactive compounds, making it an attractive ingredient for the food industry. Other properties of C. sorokiniana, such as its foaming properties, have not been extensively investigated. The present work examines the foaming properties of C. sorokiniana biomass and of its fractions, namely the foaming properties of the whole-cell biomass, the disrupted-cell biomass, the water-soluble protein-rich extract, and the disrupted-cell biomass residue after oil extraction. The water/air interfacial tension, zeta potential, foaming capacity, foam stability, and foam morphology of C. sorokiniana biomass and its fractions were determined. Furthermore, the effect of the pH on the foaming properties of the water-soluble protein-rich extract was also investigated. The results show that the examined fractions decrease the water-air interfacial tension and form foams. The type of biomass fraction affects strongly the foam characteristics and foam stability. Furthermore, the stability and characteristics of the foam are significantly affected by pH. Overall, the water-soluble protein-rich extract at pH 7 presented the best foam stability, as the foam remained stable for more than 24 h and had a narrow bubble size distribution. The obtained results suggest that fractionated microalgae biomass could be used as an effective foaming agent in different commercial applications. Full article

(This article belongs to the Special Issue Food Colloids: 3rd Edition)

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16 pages, 2729 KiB

Open AccessArticle

Polyelectrolyte-Surfactant Mixture Effects on Bulk Properties and Antibacterial, Cytotoxic Activity of Fine Sulfur Particles

by Seitzhan Turganbay, Saule Aidarova, Assem Issayeva, Zhanar Iskakbayeva, Aitugan Sabitov, Gulsinay Turganbay and Alpamys A. Babayev

Colloids Interfaces 2024, 8(6), 65; https://doi.org/10.3390/colloids8060065 - 28 Nov 2024

Abstract

Elemental sulfur, commonly known for its wide range of biological activities, has a long history of use in protecting all garden and vegetable crops from a range of pests and diseases, including powdery mildew, ascochyta blight, clubroot, plant mites, oidium, anthracnose, and scab. [...] Read more.

Elemental sulfur, commonly known for its wide range of biological activities, has a long history of use in protecting all garden and vegetable crops from a range of pests and diseases, including powdery mildew, ascochyta blight, clubroot, plant mites, oidium, anthracnose, and scab. In the present study, a quick and environmentally friendly approach has been developed for the synthesis of sulfur nanoparticles with antibacterial activity. Fine sulfur particles (FSPs) were prepared by modifying the surface of elemental sulfur using various polyelectrolyte–surfactant mixtures (PSMs) including sodium carboxymethyl cellulose–sodium dodecylbenzene sulfonate (NaCMC-SDBS) and polyhexamethylene guanidine hydrochloride–cetyltrimethylammonium bromide (PHMG-CTAB). The FSPs were characterized by UV–visible spectrophotometry, X-ray diffraction (XRD), thermogravimetric/differential scanning calorimetry analysis (TG/DSC), and scanning electron microscopy (SEM), with the FSPs showing an almost spherical shape with an average size in the range of 150–200 nm. The antibacterial activity of the FSPs was tested against Gram-positive Staphylococcus aureus and Enterococcus faecium and Gram-negative Escherichia coli and Pseudomonas aeruginosa bacteria and one fungus (Aspergillus brasiliensis ATCC 95 16404). Based on this, it could be seen that FSPs exhibited significant antimicrobial activity against Gram-positive bacteria, i.e., S. aureus and E. faecium. The in vitro cytotoxicity of the FSPs-1 and FSPs-2 studied in normal (MeT-5A) and tumorous (MCF-7) human cell lines was assessed in the concentration range from 500 μg/mL to 0.12 mg/mL, from which it was determined as being non-cytotoxic. The received products can be considered for potential application in agriculture and medicine. Full article

(This article belongs to the Special Issue Exclusive Papers of the Editorial Board Members of Colloids and Interfaces 2024)

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13 pages, 2053 KiB

Open AccessFeature PaperArticle

Adsorption Behavior of Fluorocarbon Surfactants on Polytetrafluoroethylene Surface

by Fei Yan, Cheng Ma, Qingtao Gong, Wangjing Ma, Zhiqiang Jin, Zhicheng Xu, Lei Zhang and Lu Zhang

Colloids Interfaces 2024, 8(6), 64; https://doi.org/10.3390/colloids8060064 - 20 Nov 2024

Abstract

By using the sessile drop method, the wetting properties of nonionic fluorocarbon surfactants (FNS-1 and FNS-2) and anionic fluorocarbon surfactant (FAS) solutions on the surface of polytetrafluoroethylene (PTFE) were investigated. Meanwhile, the effects of surfactant concentration on the contact angle, adhesion tension, PTFE–liquid [...] Read more.

By using the sessile drop method, the wetting properties of nonionic fluorocarbon surfactants (FNS-1 and FNS-2) and anionic fluorocarbon surfactant (FAS) solutions on the surface of polytetrafluoroethylene (PTFE) were investigated. Meanwhile, the effects of surfactant concentration on the contact angle, adhesion tension, PTFE–liquid interfacial tension, and work of adhesion of the fluorocarbon surfactant with different structures were detected. The results demonstrate that the adsorption amount of the three fluorocarbon surfactants at the air–liquid interface is 1.5~2 times higher than their adsorption amount at the PTFE–solution interface. Before critical micelle concentration (CMC), the fluorocarbon surfactant molecules rely on their hydrophobic groups to adsorb on the PTFE surface. The smallest molecular size of FNS-2 results in the largest adsorption amount, while electrostatic repulsion and large steric hindrance result in the smallest adsorption amount for FAS. Above CMC, the fluorocarbon surfactants form semi-micelles to adsorb on the PTFE surface. The hydrophilic modification ability of the three fluorocarbon surfactants for the PTFE surface is stronger than that of reported surfactants, and the contact angle can be reduced to about 20° at high concentrations. The order of the hydrophilic modification ability is FNS-2 > FNS-1 > FAS. Hydrophilic EO groups can effectively enhance the hydrophilicity of FNS-1 and FNS-2. Due to the hydrophobic -CH₃ group and the smaller adsorption amount, FNS-1 possesses a weaker hydrophilic modification ability than FNS-2. Investigating the adsorption behavior of fluorocarbon surfactants on the PTFE surface can help us to better utilize fluorocarbon surfactants. This could have broad implications for colloid and interface science. Full article

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18 pages, 8994 KiB

Open AccessArticle

A GNN-Based QSPR Model for Surfactant Properties

by Seokgyun Ham, Xin Wang, Hongwei Zhang, Brian Lattimer and Rui Qiao

Colloids Interfaces 2024, 8(6), 63; https://doi.org/10.3390/colloids8060063 - 19 Nov 2024

Abstract

Surfactants are among the most versatile molecules in the chemical industry because they can self-assemble in bulk solutions and at interfaces. Predicting the properties of surfactant solutions, such as their critical micelle concentration (CMC), limiting surface tension (

γ_{c m c}

), [...] Read more.

Surfactants are among the most versatile molecules in the chemical industry because they can self-assemble in bulk solutions and at interfaces. Predicting the properties of surfactant solutions, such as their critical micelle concentration (CMC), limiting surface tension (

γ_{c m c}

), and maximal packing density (

Γ_{m a x}

) at water–air interfaces, is essential to their rational design. However, the relationship between surfactant structure and these properties is complex and difficult to predict theoretically. Here, we develop a graph neural network (GNN)-based quantitative structure–property relationship (QSPR) model to predict the CMC,

γ_{c m c}

, and

Γ_{m a x}

. Ninety-two surfactant data points, encompassing all types of surfactants—anionic, cationic, zwitterionic, and nonionic—are fed into the model, covering a temperature range of [20–30 °C], which contributes to its generalization across all surfactant types. We show that our models have high accuracy (R² = 0.87 on average in tests) in predicting the three parameters across all types of surfactants. The effectiveness of the QSPR model in capturing the variation of CMC,

γ_{c m c}

, and

Γ_{m a x}

with molecular design parameters are carefully assessed. The curated dataset, developed model, and critical assessment of the developed model will contribute to the development of improved surfactants QSPR models and facilitate their rational design for diverse applications. Full article

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36 pages, 4529 KiB

Open AccessFeature PaperReview

Addressing the Apparent Controversies Between the Contact Angle-Based Models for Estimation of Surface Free Energy: A Critical Review

by Georgi As. Georgiev, Stanislav Baluschev, Petar Eftimov, Mihaela Bacheva and Katharina Landfester

Colloids Interfaces 2024, 8(6), 62; https://doi.org/10.3390/colloids8060062 - 18 Nov 2024

Abstract

The most popular contact angle (CA)-based approaches for determination of solid surface free energy (SFE) are considered: (i) single liquid methods, mainly of Neumann and Chibowski, (ii) the multiple liquids approach of Owens–Wendt–Rabel–Kaelble (OWRK), and (iii) van Oss-Chaudhury–Good (vOCG) acid–base model. Evaluations based [...] Read more.

The most popular contact angle (CA)-based approaches for determination of solid surface free energy (SFE) are considered: (i) single liquid methods, mainly of Neumann and Chibowski, (ii) the multiple liquids approach of Owens–Wendt–Rabel–Kaelble (OWRK), and (iii) van Oss-Chaudhury–Good (vOCG) acid–base model. Evaluations based on Neumann and Chibowski models agree between each other. Under the assumption of equilibrium “wet wetting” (i.e., presence of saturated precursor film ahead of the drop), the model of Chibowski transforms in Lipatov’s interfacial equilibrium rule, i.e., the Antonow rule derived for the ternary point solid–liquid–gas. Very good agreement is observed between single and multiple liquids models where OWRK/vOCG values can be viewed as a mean of the individual SFE adopted by the solid with each of the wetting probes. Both approaches (single and multiple liquids) can be used in conjunction to evaluate SFE dispersion and polar components and to elucidate hydrophobicity and hydrophilicity. The implementation of apparently fully non-polar liquids (diiodomethane, bromonaphthalene) in OWRK and vOCG is practically and theoretically suspect. CA-based estimates represent apparent SFE determined by the interactions of both the solid surface and the probing liquid, which are very useful to elucidate the energy, chemistry and dynamics of the solid surface. Full article

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13 pages, 3087 KiB

Open AccessArticle

Mixed Adsorption Mono- and Multilayers of ß-Lactoglobulin Fibrils and Sodium Polystyrene Sulfonate

by A. G. Bykov, G. Loglio, R. Miller, E. A. Tsyganov, Z. Wan and B. A. Noskov

Colloids Interfaces 2024, 8(6), 61; https://doi.org/10.3390/colloids8060061 - 11 Nov 2024

Abstract

The formation of beta-lactoglobulin (BLG)/sodium polystyrene sulfonate (PSS) complexes decelerates the change in the surface properties of the mixed solutions with the surface age and increases the steady-state dilational surface elasticity in a narrow PSS concentration range. At the same time, the changes [...] Read more.

The formation of beta-lactoglobulin (BLG)/sodium polystyrene sulfonate (PSS) complexes decelerates the change in the surface properties of the mixed solutions with the surface age and increases the steady-state dilational surface elasticity in a narrow PSS concentration range. At the same time, the changes in the surface properties are accelerated in the dispersions of BLG fibrils with and without PSS due to the influence of small peptides coexisting with fibrils. A decrease in the peptide concentration as a result of the dispersion purification leads to slower changes in the surface properties at low PSS concentrations. The increase in the polyelectrolyte concentration results in an increase in the steady-state surface elasticity due to the fibril/PSS complex formation and in very slow changes in the surface properties if the polyelectrolyte exceeds a certain critical value. The latter effect is a consequence of the formation of large aggregates and of an increase in the electrostatic adsorption barrier. The consecutive adsorption of BLG fibrils and PSS leads to the formation of regular multilayers at the liquid–gas interface. The multilayer properties change noticeably with an increase in the number of layers from four to six in agreement with previous results on the multilayers of PSS with an oppositely charged synthetic polyelectrolyte, presumably due to the heterogeneity of the first PSS layer. The dynamic elasticity of the multilayers approaches 250 mN/m, indicating that they can effectively stabilize foams and emulsions. Full article

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37 pages, 3487 KiB

Open AccessFeature PaperArticle

The Entropy of Mixing in Self-Assembly and the Role of Surface Tension in Modeling the Critical Micelle Concentration

by Frank Müh

Colloids Interfaces 2024, 8(6), 60; https://doi.org/10.3390/colloids8060060 - 31 Oct 2024

Abstract

A theory for the micelle formation of nonionic head-tail amphiphiles (detergents) in aqueous solutions is derived based on the traditional molecular thermodynamic modeling approach and a variant of the Flory–Huggins theory that goes beyond lattice models. The theory is used to analyze experimental [...] Read more.

A theory for the micelle formation of nonionic head-tail amphiphiles (detergents) in aqueous solutions is derived based on the traditional molecular thermodynamic modeling approach and a variant of the Flory–Huggins theory that goes beyond lattice models. The theory is used to analyze experimental values for the critical micelle concentration of n-alkyl-ß-D-maltosides within a mass action model. To correlate those parts of the micellization free energy, which depend on the transfer of hydrophobic molecule parts into the aqueous phase, with molecular surfaces, known data for the solubility of alkanes in water are reanalyzed. The correct surface tension to be used in connection with the solvent-excluded surface of the alky tail is ~30 mN/m. This value is smaller than the measured surface tension of a macroscopic alkane–water interface, because the transfer free energy contains a contribution from the incorporation of the alkane or alkyl chain into water, representing the change in free volume in the aqueous phase. The Flory–Huggins theory works well, if one takes into account the difference in liberation free energy between micelles and monomers, which can be described in terms of the aggregation number as well as the thermal de Broglie wavelength and the free volume of the detergent monomer. Full article

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