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Papers by C. Gehin-Delval
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2014
The rising velocity of air bubbles in surfactant solutions is a sensitive measure for the formati... more The rising velocity of air bubbles in surfactant solutions is a sensitive measure for the formation of a dynamic adsorption layer (DAL) at the bubble surface. Due to a certain surface coverage by adsorbed species the bubble surface starts to become immobilized and the rising velocity is retarded. There is a large difference in the retardation effect in presence of the protein -lactoglobulin (BLG) alone and its mixed solutions with surfactants. In presence of added surfactants BLG forms complexes, which adsorb and retard the bubble rising velocity according to their respective surface activity and adsorption kinetics. While the nonionic surfactant C 12 DMPO does not show significant increase in retardation effects as compared to BLG alone, the ionic surfactants SDS and DoTAB form highly surface active complexes and change the rising velocity much stronger.
Food Hydrocolloids, 2014
ABSTRACT Protein adsorption is one of the most complex and intriguing phenomenon in interfacial s... more ABSTRACT Protein adsorption is one of the most complex and intriguing phenomenon in interfacial science. This phenomenon has been addressed in this paper for a short time range using maximum bubble pressure tensiometer. This study presents the issue of negative surface pressure of proteins which has been much of a speculation, with the thermodynamic model. Here beta-lactoglobulin has been studied at different pHs and the experimental results agree with the theoretical model presented. (c) 2013 Elsevier Ltd. All rights reserved.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2016
The local velocity profile (LVP) of a rising bubble can serve as a fingerprint for the dynamic be... more The local velocity profile (LVP) of a rising bubble can serve as a fingerprint for the dynamic behavior of the adsorption/desorption processes going on at a solution/air interface. The LVP of bubbles in β-lactoglobulin (BLG) solutions proves to be extremely sensitive for the adsorption of BLG at low bulk concentrations. In addition, it can show the impact of pH and ionic strength on the dynamic surface properties of BLG at the solution/air interface. It is observed that the time for establishing an immobile rigid surface layer at the rising bubble surface becomes shorter with increasing pH from 3 to 7. A peculiar behavior is observed at the isoelectric point (IEP) where the LVPs show irregularities. Under dynamic conditions BLG does not exhibit highest surface active at the IEP within the range of BLG concentrations as measured by the rising bubble technique.
The Journal of Physical Chemistry B
Several characteristics of β-lactoglobulin (BLG) layers adsorbed at the air/water interface exhib... more Several characteristics of β-lactoglobulin (BLG) layers adsorbed at the air/water interface exhibit a strong pH dependence, but our knowledge on the underlying structure-property relations is still fragmental. Here, we therefore extend our recent studies by neutron reflectometry (NR) and provide a comprehensive overview through direct measurements of the surface excess Γ and the layers' molecular structure. This enables comparison with available literature data in order to draw general conclusions. The NR experiments were performed at various pH values and within a wide range of protein concentrations, CBLG. Adsorption kinetics measurements in air-contrast-matched-water enabled direct quantification of the dynamic surface excess Γ(t) and are found to be consistent with ellipsometry data. Near the isoelectric point, pI, the rate of adsorption and Γ are maximal, but only at sufficiently high CBLG. NR data collected over a wider Qz-range and in two aqueous isotopic contrasts revealed the structure of adsorbed BLG layers close to equilibrium. Independently of the pH, BLG was found to form dense monolayers with average thicknesses of 1.5 nm, suggesting flattening of the BLG globules upon adsorption as compared to their bulk dimensions (≈ 3.5 nm). Near pI and at sufficiently high CBLG, a thick (≈ 5.5 nm) but looser secondary sublayer is additionally formed adjacent to the dense primary monolayer. The thickness of this sublayer can be interpreted in terms of disordered BLG dimers. The results obtained and notably the specific interfacial structuring of BLG near pI complement previous observations relating the impact of solution pH and CBLG on other interfacial characteristics such as surface pressure and surface dilational viscoelasticity modulus.
Journal of Colloid and Interface Science, 2016
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2014
• -Lactoglobulin alone and mixed with different surfactants were studied.
Food Hydrocolloids, 2014
ABSTRACT Protein adsorption is one of the most complex and intriguing phenomenon in interfacial s... more ABSTRACT Protein adsorption is one of the most complex and intriguing phenomenon in interfacial science. This phenomenon has been addressed in this paper for a short time range using maximum bubble pressure tensiometer. This study presents the issue of negative surface pressure of proteins which has been much of a speculation, with the thermodynamic model. Here beta-lactoglobulin has been studied at different pHs and the experimental results agree with the theoretical model presented. (c) 2013 Elsevier Ltd. All rights reserved.
Progrès en urologie : journal de l'Association française d'urologie et de la Société française d'urologie
This randomized prospective study evaluated the safety and efficacy of a single oral dose of OFL ... more This randomized prospective study evaluated the safety and efficacy of a single oral dose of OFL compared to a single parenteral dose of CTRX prior to TURP. 191 patients (mean age: 68.7 +/- 6.2 years) with bacterial free urine before surgery were enrolled and received either OFL: 400 mg per os (n = 95) or CTRX: 1 g intrasmuscularly (n = 96) at the pre-anaesthetic medication time (two hours prior TURP). Two urine cultures were obtained: on the day of the patient's discharge and within one month after surgery. Blood cultures were performed in case of temperature > 38 degrees 5C. Treatment failure was defined as bacteriuria > 10(5) CFU/ml and/or in case of positive blood culture after surgery. 182 patients were evaluable for efficacy. They were similar with respect to age, prostatic resection, histology, duration of post operative catheterization in the two treatment groups. On discharge from the department, 93.2% of the patients in the OFL group had sterile urines versus 94....
Langmuir, 2005
The adsorption of poly(vinylamine) (PVA) on poly(styrene sulfate) latex particles is studied, and... more The adsorption of poly(vinylamine) (PVA) on poly(styrene sulfate) latex particles is studied, and its consequences on the charging behavior and suspension stability are investigated. The adsorption process is assessed by batch depletion experiments and time-resolved electrophoretic mobility measurements. The adsorption of PVA appears to be basically irreversible. The rate of adsorption decreases with decreasing polymer dose. At low polymer dose, the polymer coverage corresponds to the amount of the polyelectrolyte added, while at high polymer dose, the polymer coverage saturates the surface. Stability ratios are determined by dynamic light scattering, and strongly depend on the polymer dose and salt level. The aggregation is rapid near the isoelectric point (IEP), and it slows down when moving away from it. The charge neutralization is highly nonstoichiometric with charging ratios (CR) larger than unity, meaning that several charges on an adsorbed polyelectrolyte chain are necessary to neutralize a single charge on the particle surface. By comparing the IEP for particles and polyelectrolytes of different charge densities, we find a strong dependence of the CR on the mismatch between the average distances between individual charges on the surface and on the polyelectrolyte. A simple model is proposed to explain this trend.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2014
• -Lactoglobulin alone and mixed with different surfactants were studied.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2014
ABSTRACT The presented drop and bubble micro manipulator (DBMM) is a new experimental tool for th... more ABSTRACT The presented drop and bubble micro manipulator (DBMM) is a new experimental tool for the quantitative analysis of the interaction between two drops or two bubbles or even between a single drop with a bubble in a liquid medium. For each drop or bubble, a coarse and a very fine dosing system allow controlling their size or changing it in respect to a given protocol. An accurate pressure sensor for each drop/bubble can record changes in the capillary pressure with a selected sampling rate in order to follow critical processes between the two liquid menisci, such as coalescence. The stability of liquid films between drops or bubbles can be studied also under external perturbations, i.e. a harmonic oscillation with a given frequency and amplitude can be generated in order to find critical conditions for the coalescence. The described tool can be used in different experimental protocols. Among them there are options to mimic the situation of multilayers and multiple emulsions. Recording of dynamic processes as video with a standard frame rate is possible as well. Alternatively, a fast video camera can be mounted to monitor fast processes, such as the coalescence of two drops or bubbles.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2007
The charging behavior of carboxyl latex surface in the presence of poly(diallyl dimethyl ammonium... more The charging behavior of carboxyl latex surface in the presence of poly(diallyl dimethyl ammonium chloride) (DADMAC) was investigated by means of potentiometric titrations and electrophoretic mobility. The titration curves at different ionic strengths show a common crossing point, which coincides with the point of zero mobility, and can be identified with the point of zero charge (PZC). This characteristic behavior is due to the adsorption of the strong cationic polyelectrolyte on the weak acid particle surface, leading to an additional positive charge, and a corresponding shift of the surface potential. These features can be quantified in terms of modified Stern model and the standard electrokinetic model. This model predicts the PZC very well, while the magnitude of the charge and its ionic strength dependence are reproduced only semi-quantitatively.
Food Hydrocolloids, 2014
ABSTRACT Protein adsorption is one of the most complex and intriguing phenomenon in interfacial s... more ABSTRACT Protein adsorption is one of the most complex and intriguing phenomenon in interfacial science. This phenomenon has been addressed in this paper for a short time range using maximum bubble pressure tensiometer. This study presents the issue of negative surface pressure of proteins which has been much of a speculation, with the thermodynamic model. Here beta-lactoglobulin has been studied at different pHs and the experimental results agree with the theoretical model presented. (c) 2013 Elsevier Ltd. All rights reserved.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2014
The rising velocity of air bubbles in surfactant solutions is a sensitive measure for the formati... more The rising velocity of air bubbles in surfactant solutions is a sensitive measure for the formation of a dynamic adsorption layer (DAL) at the bubble surface. Due to a certain surface coverage by adsorbed species the bubble surface starts to become immobilized and the rising velocity is retarded. There is a large difference in the retardation effect in presence of the protein -lactoglobulin (BLG) alone and its mixed solutions with surfactants. In presence of added surfactants BLG forms complexes, which adsorb and retard the bubble rising velocity according to their respective surface activity and adsorption kinetics. While the nonionic surfactant C 12 DMPO does not show significant increase in retardation effects as compared to BLG alone, the ionic surfactants SDS and DoTAB form highly surface active complexes and change the rising velocity much stronger.
Food Hydrocolloids, 2014
ABSTRACT Protein adsorption is one of the most complex and intriguing phenomenon in interfacial s... more ABSTRACT Protein adsorption is one of the most complex and intriguing phenomenon in interfacial science. This phenomenon has been addressed in this paper for a short time range using maximum bubble pressure tensiometer. This study presents the issue of negative surface pressure of proteins which has been much of a speculation, with the thermodynamic model. Here beta-lactoglobulin has been studied at different pHs and the experimental results agree with the theoretical model presented. (c) 2013 Elsevier Ltd. All rights reserved.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2016
The local velocity profile (LVP) of a rising bubble can serve as a fingerprint for the dynamic be... more The local velocity profile (LVP) of a rising bubble can serve as a fingerprint for the dynamic behavior of the adsorption/desorption processes going on at a solution/air interface. The LVP of bubbles in β-lactoglobulin (BLG) solutions proves to be extremely sensitive for the adsorption of BLG at low bulk concentrations. In addition, it can show the impact of pH and ionic strength on the dynamic surface properties of BLG at the solution/air interface. It is observed that the time for establishing an immobile rigid surface layer at the rising bubble surface becomes shorter with increasing pH from 3 to 7. A peculiar behavior is observed at the isoelectric point (IEP) where the LVPs show irregularities. Under dynamic conditions BLG does not exhibit highest surface active at the IEP within the range of BLG concentrations as measured by the rising bubble technique.
The Journal of Physical Chemistry B
Several characteristics of β-lactoglobulin (BLG) layers adsorbed at the air/water interface exhib... more Several characteristics of β-lactoglobulin (BLG) layers adsorbed at the air/water interface exhibit a strong pH dependence, but our knowledge on the underlying structure-property relations is still fragmental. Here, we therefore extend our recent studies by neutron reflectometry (NR) and provide a comprehensive overview through direct measurements of the surface excess Γ and the layers' molecular structure. This enables comparison with available literature data in order to draw general conclusions. The NR experiments were performed at various pH values and within a wide range of protein concentrations, CBLG. Adsorption kinetics measurements in air-contrast-matched-water enabled direct quantification of the dynamic surface excess Γ(t) and are found to be consistent with ellipsometry data. Near the isoelectric point, pI, the rate of adsorption and Γ are maximal, but only at sufficiently high CBLG. NR data collected over a wider Qz-range and in two aqueous isotopic contrasts revealed the structure of adsorbed BLG layers close to equilibrium. Independently of the pH, BLG was found to form dense monolayers with average thicknesses of 1.5 nm, suggesting flattening of the BLG globules upon adsorption as compared to their bulk dimensions (≈ 3.5 nm). Near pI and at sufficiently high CBLG, a thick (≈ 5.5 nm) but looser secondary sublayer is additionally formed adjacent to the dense primary monolayer. The thickness of this sublayer can be interpreted in terms of disordered BLG dimers. The results obtained and notably the specific interfacial structuring of BLG near pI complement previous observations relating the impact of solution pH and CBLG on other interfacial characteristics such as surface pressure and surface dilational viscoelasticity modulus.
Journal of Colloid and Interface Science, 2016
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2014
• -Lactoglobulin alone and mixed with different surfactants were studied.
Food Hydrocolloids, 2014
ABSTRACT Protein adsorption is one of the most complex and intriguing phenomenon in interfacial s... more ABSTRACT Protein adsorption is one of the most complex and intriguing phenomenon in interfacial science. This phenomenon has been addressed in this paper for a short time range using maximum bubble pressure tensiometer. This study presents the issue of negative surface pressure of proteins which has been much of a speculation, with the thermodynamic model. Here beta-lactoglobulin has been studied at different pHs and the experimental results agree with the theoretical model presented. (c) 2013 Elsevier Ltd. All rights reserved.
Progrès en urologie : journal de l'Association française d'urologie et de la Société française d'urologie
This randomized prospective study evaluated the safety and efficacy of a single oral dose of OFL ... more This randomized prospective study evaluated the safety and efficacy of a single oral dose of OFL compared to a single parenteral dose of CTRX prior to TURP. 191 patients (mean age: 68.7 +/- 6.2 years) with bacterial free urine before surgery were enrolled and received either OFL: 400 mg per os (n = 95) or CTRX: 1 g intrasmuscularly (n = 96) at the pre-anaesthetic medication time (two hours prior TURP). Two urine cultures were obtained: on the day of the patient's discharge and within one month after surgery. Blood cultures were performed in case of temperature > 38 degrees 5C. Treatment failure was defined as bacteriuria > 10(5) CFU/ml and/or in case of positive blood culture after surgery. 182 patients were evaluable for efficacy. They were similar with respect to age, prostatic resection, histology, duration of post operative catheterization in the two treatment groups. On discharge from the department, 93.2% of the patients in the OFL group had sterile urines versus 94....
Langmuir, 2005
The adsorption of poly(vinylamine) (PVA) on poly(styrene sulfate) latex particles is studied, and... more The adsorption of poly(vinylamine) (PVA) on poly(styrene sulfate) latex particles is studied, and its consequences on the charging behavior and suspension stability are investigated. The adsorption process is assessed by batch depletion experiments and time-resolved electrophoretic mobility measurements. The adsorption of PVA appears to be basically irreversible. The rate of adsorption decreases with decreasing polymer dose. At low polymer dose, the polymer coverage corresponds to the amount of the polyelectrolyte added, while at high polymer dose, the polymer coverage saturates the surface. Stability ratios are determined by dynamic light scattering, and strongly depend on the polymer dose and salt level. The aggregation is rapid near the isoelectric point (IEP), and it slows down when moving away from it. The charge neutralization is highly nonstoichiometric with charging ratios (CR) larger than unity, meaning that several charges on an adsorbed polyelectrolyte chain are necessary to neutralize a single charge on the particle surface. By comparing the IEP for particles and polyelectrolytes of different charge densities, we find a strong dependence of the CR on the mismatch between the average distances between individual charges on the surface and on the polyelectrolyte. A simple model is proposed to explain this trend.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2014
• -Lactoglobulin alone and mixed with different surfactants were studied.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2014
ABSTRACT The presented drop and bubble micro manipulator (DBMM) is a new experimental tool for th... more ABSTRACT The presented drop and bubble micro manipulator (DBMM) is a new experimental tool for the quantitative analysis of the interaction between two drops or two bubbles or even between a single drop with a bubble in a liquid medium. For each drop or bubble, a coarse and a very fine dosing system allow controlling their size or changing it in respect to a given protocol. An accurate pressure sensor for each drop/bubble can record changes in the capillary pressure with a selected sampling rate in order to follow critical processes between the two liquid menisci, such as coalescence. The stability of liquid films between drops or bubbles can be studied also under external perturbations, i.e. a harmonic oscillation with a given frequency and amplitude can be generated in order to find critical conditions for the coalescence. The described tool can be used in different experimental protocols. Among them there are options to mimic the situation of multilayers and multiple emulsions. Recording of dynamic processes as video with a standard frame rate is possible as well. Alternatively, a fast video camera can be mounted to monitor fast processes, such as the coalescence of two drops or bubbles.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2007
The charging behavior of carboxyl latex surface in the presence of poly(diallyl dimethyl ammonium... more The charging behavior of carboxyl latex surface in the presence of poly(diallyl dimethyl ammonium chloride) (DADMAC) was investigated by means of potentiometric titrations and electrophoretic mobility. The titration curves at different ionic strengths show a common crossing point, which coincides with the point of zero mobility, and can be identified with the point of zero charge (PZC). This characteristic behavior is due to the adsorption of the strong cationic polyelectrolyte on the weak acid particle surface, leading to an additional positive charge, and a corresponding shift of the surface potential. These features can be quantified in terms of modified Stern model and the standard electrokinetic model. This model predicts the PZC very well, while the magnitude of the charge and its ionic strength dependence are reproduced only semi-quantitatively.
Food Hydrocolloids, 2014
ABSTRACT Protein adsorption is one of the most complex and intriguing phenomenon in interfacial s... more ABSTRACT Protein adsorption is one of the most complex and intriguing phenomenon in interfacial science. This phenomenon has been addressed in this paper for a short time range using maximum bubble pressure tensiometer. This study presents the issue of negative surface pressure of proteins which has been much of a speculation, with the thermodynamic model. Here beta-lactoglobulin has been studied at different pHs and the experimental results agree with the theoretical model presented. (c) 2013 Elsevier Ltd. All rights reserved.