scholarly journals Influence of Hydrophilic Surfactants on the W1–W2 Coalescence in Double Emulsion Systems Investigated by Single Droplet Experiments

2021 ◽  
Vol 5 (2) ◽  
pp. 21
Author(s):  
Nico Leister ◽  
Heike P. Karbstein
Keyword(s):  
Double Emulsion ◽  
Water Phase ◽  
Single Droplet ◽  
Fast Evaluation ◽  
Double Emulsions ◽  
Low Concentrations ◽  
Emulsion Systems ◽  
The Stability ◽  
Single Droplets ◽  
And Diffusion

Double emulsions are a promising formulation for encapsulation and targeted release in pharmaceutics, cosmetics and food. An inner water phase is dispersed in an oil phase, which is again emulsified in a second water phase. The encapsulated inner water phase can be released via diffusion or via coalescence, neither of which is desired during storage but might be intended during application. The two interfaces in a double emulsion are stabilized by a hydrophilic and a lipophilic surfactant, to prevent the coalescence of the outer and the inner emulsion, respectively. This study focuses on the influence of the hydrophilic surfactant on the release of inner water or actives encapsulated therein via coalescence of the inner water droplet with the outer O–W2 interface. Since coalescence and diffusion are difficult to distinguish in double emulsions, single-droplet experiments were used to quantify differences in the stability of inner droplets. Different lipophilic (PGPH and PEG-30 dipolyhydroxylstearate) and hydrophilic surfactants (ethoxylates, SDS and polymeric) were used and resulted in huge differences in stability. A drastic decrease in stability was found for some combinations, while other combinations resulted in inner droplets that could withstand coalescence longer. The destabilization effect of some hydrophilic surfactants depended on their concentration, but was still present at very low concentrations. A huge spread of the coalescence time for multiple determinations was observed for all formulations and the necessary statistical analysis is discussed in this work. The measured stabilities of single droplets are in good accordance with the stability of double emulsions for similar surfactant combinations found in literature. Therefore, single droplet experiments are suggested for a fast evaluation of potentially suitable surfactant combinations for future studies on double-emulsion stability.

scholarly journals Effect of Selected Stabilizers and Processing Aids on the Stability of a Double Emulsion Encapsulating Bitter Gourd Extract

2021 ◽  
Author(s):  
Urmila Choudhary ◽  
Latha Sabikhi
Keyword(s):  
Double Emulsion ◽  
Gum Arabic ◽  
Sodium Caseinate ◽  
Bitter Gourd ◽  
Whey Protein Concentrate ◽  
Physical Parameters ◽  
Sedimentation Stability ◽  
Double Emulsions ◽  
The Stability ◽  
Emulsion Matrix

Effect of three variables in differing concentrations [NaCl (3-5%), polyglycerol polyricinoleate (PGPR) (2-4%) and dairy protein-polysaccharide complexes (Whey protein concentrate(WPC-80)-gum Arabic(GA) and sodium caseinate(SC)-gum Arabic in 1:2 ratio)] on the stability of W1/O/W2 emulsion matrix that was used to encapsulate bitter gourd extract was evaluated. The double emulsion matrix was characterized by apparent viscosity, zeta potential, turbidity and sedimentation stability by visual appearance. The physical parameters of the double emulsion matrix were very highly significantly (p < 0.001) affected by all variables such as the concentration of salt, PGPR and complex (WPC-GA and SC-P) as well as their interactions. The double emulsions prepared with WPC-GA became unstable immediately after preparation or after one day of preparation. SC-GA stabilized double emulsions were found more stable than WPC-GA stabilized emulsions. A double emulsion containing 5% NaCl, 2% PGPR and 16.5% SC-GA were found most stable (10 days at 37°C) in comparison to other combinations used.

scholarly journals Addition of Trans-Resveratrol-Loaded Highly Concentrated Double Emulsion to Yoghurts: Effect on Physicochemical Properties

2021 ◽  
Vol 23 (1) ◽  
pp. 85
Author(s):  
Rocío Díaz-Ruiz ◽  
Amanda Laca ◽  
Marta Sánchez ◽  
Manuel Ramón Fernández ◽  
María Matos ◽  
...  
Keyword(s):  
Antioxidant Capacity ◽  
Droplet Size ◽  
Storage Time ◽  
Control Sample ◽  
Double Emulsion ◽  
Colour Variation ◽  
Double Emulsions ◽  
Appreciable Increase ◽  
Different Types ◽  
The Stability

Trans-resveratrol (RSV) needs to be encapsulated to maintain its beneficial properties on the human body. This is due to its extreme photosensitivity, short biological half-life, and easy oxidation. In this study, the use of double emulsions for RSV encapsulation and their further application on functional yoghurts was studied. Different types of yoghurts were prepared: with and without RSV and with two types of volumetric emulsion formulations (20/80 and 30/70). In order to study the influence of the addition of double emulsions to the physical properties of the prepared yoghurts, they were characterised fresh and after a month under storage at 4 °C, in terms of droplet size, morphology, stability, rheology, texturometry, colorimetry, and antioxidant capacity. Results obtained showed that the presence of emulsion in the yoghurts produced a generalised decrease in the predominant droplet size (from 48 µm to 15–25 µm) and an increase in the stability. Additionally, a predominantly elastic character was observed. The firmness values obtained were very similar for all the yoghurts analysed and did not suffer important modifications with time. A slight colour variation was observed with storage time in the control sample, whereas a more notable variation in the case of emulsion yoghurts was observed. An appreciable increase of the antioxidant capacity of the final functional yoghurt (100 g) was observed when it contained 5–8 mg of RSV. Encapsulated RSV added to yoghurts presented a larger protection against RSV oxidation compared with free RSV, presenting a larger antioxidant inhibition after one month of storage. Moreover, the antioxidant capacity of yoghurts with encapsulated RSV was not affected under storage, since slight reductions (3%) were registered after one month of storage at 4 °C.

scholarly journals Evaluating the Stability of Double Emulsions—A Review of the Measurement Techniques for the Systematic Investigation of Instability Mechanisms

2020 ◽  
Vol 4 (1) ◽  
pp. 8
Author(s):  
Nico Leister ◽  
Heike P. Karbstein
Keyword(s):  
Measurement Techniques ◽  
Double Emulsion ◽  
Systematic Investigation ◽  
Model Systems ◽  
Scanning Calorimetry ◽  
Contrast Model ◽  
Double Emulsions ◽  
Analysis Methods ◽  
The Stability

Double emulsions are very promising for various applications in pharmaceutics, cosmetics, and food. Despite lots of published research, only a few products have successfully been marketed due to immense stability problems. This review describes approaches on how to characterize the stability of double emulsions. The measurement methods are used to investigate the influence of the ingredients or the process on the stability, as well as of the environmental conditions during storage. The described techniques are applied either to double emulsions themselves or to model systems. The presented analysis methods are based on microscopy, rheology, light scattering, marker detection, and differential scanning calorimetry. Many methods for the characterization of double emulsions focus only on the release of the inner water phase or of a marker encapsulated therein. Analysis methods for a specific application rarely give information on the actual mechanism, leading to double emulsion breakage. In contrast, model systems such as simple emulsions, microfluidic emulsions, or single-drop experiments allow for a systematic investigation of diffusion and coalescence between the individual phases. They also give information on the order of magnitude in which they contribute to the failure of the overall system. This review gives an overview of various methods for the characterization of double emulsion stability, describing the underlying assumptions and the information gained. With this review, we intend to assist in the development of stable double emulsion-based products.

scholarly journals Influence of Aqueous Phase Composition on Double Emulsion Stability and Colour Retention of Encapsulated Anthocyanins

Foods ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 34
Author(s):  
Damien A. Sebben ◽  
Stephanie V. MacWilliams ◽  
Long Yu ◽  
Patrick T. Spicer ◽  
Vincent Bulone ◽  
...  
Keyword(s):  
Phase Composition ◽  
Aqueous Phase ◽  
Emulsion Stability ◽  
Double Emulsion ◽  
Storage Period ◽  
Size Analysis ◽  
Structural Behaviour ◽  
Double Emulsions ◽  
The Stability ◽  
Emulsion Rheology

Water-in-oil-in-water (W1/O/W2) emulsions (double emulsions) have often been used for the encapsulation of bioactive compounds such as anthocyanins. Instability of both anthocyanins and double emulsions creates a need for a tailored composition of the aqueous phase. In this work, double emulsions with a gelled internal water phase were produced and monitored over a 20-day storage period. The effect of the electrolyte phase composition (varying electrolyte components, including adipic acid, citric acid, and varying concentration of potassium chloride (KCl)) on anthocyanin and double emulsion stability was analysed using colour analysis, droplet sizing, and emulsion rheology. The effect of electrolytes on colour retention was shown to differ between the primary W1/O emulsion and the secondary W1/O/W2 emulsion. Furthermore, droplet size analysis and emulsion rheology highlighted significant differences in the stability and structural behaviour of the emulsions as a function of electrolyte composition. In terms of colour retention and emulsion stability, a citrate-buffered system performed best. The results of this study highlight the importance of strict control of aqueous phase constituents to prevent anthocyanin degradation and maximise double emulsion stability. Additional experiments analysed the effect of pectin chemistry on the anthocyanin colour retention and leakage, finding no conclusive difference between the unmodified and amidated pectin.

scholarly journals SURFACE FUNCTIONALIZED EMULSION FOR SELECTIVE DRUGS TRANSPORT

2019 ◽  
Vol 62 (8) ◽  
pp. 113-119
Author(s):  
Agata Metera ◽  
Ewa Dłuska ◽  
Agnieszka Markowska-Radomska ◽  
Barbara Tudek ◽  
Konrad Kosicki
Keyword(s):  
Drug Transport ◽  
Physical Adsorption ◽  
Phase 1 ◽  
Double Emulsion ◽  
Rotational Frequency ◽  
Surface Proteins ◽  
Water Phase ◽  
Titration Calorimetry ◽  
Step Method ◽  
Double Emulsions

This paper presents the results of functionalization of surfaces of double emulsions drops for selective drug transport and selection of antibodies for targeting brain tumor cells - glioblastoma multiforme (GBM). The functionalization involved physical adsorption of antibodies: anti-CD15 (Hodgkin's disease marker) on oil drops of the emulsion. The interactions between molecules of antibodies and compounds of the oil drops were measured using isothermal titration calorimetry (ITC). Double emulsions were prepared by a one-step method, in a helical flow contactor. The ITC analysis showed that antibodies interacted with emulsion compounds. The change in the heat rates reflecting molecular interactions proved that proteins adhered to oil drops interfaces. Additionally, surface proteins (antibodies) were identified and analyzed for targeting specific GBM cell lines: U87MG, LN229, T98G. The multiple emulsions were created under conditions: the size of the annular gap between the coaxial cylinders was 1.5 mm, the rotational frequency of the inner cylinder was 2162 rpm, the volumetric flow rates of internal water phase to membrane oil phase 1:1 and membrane oil phase to external water phase 1:15. The method of double emulsions preparation has been described more precisely in our previous papers. The sizes of the internal phase drops and the membrane phase drops were determined based on analyzing images captured during microscopic observation of the double emulsion samples.

Kinetics of Various 99mTc-Sn-Pyrophosphate Compounds in the Rat

1977 ◽  
Vol 16 (04) ◽  
pp. 157-162 ◽  
Author(s):  
C. Schümichen ◽  
B. Mackenbrock ◽  
G. Hoffmann
Keyword(s):  
Normal Saline ◽  
Half Life ◽  
Compound A ◽  
Short Half Life ◽  
Low Concentrations ◽  
The Stability ◽  
Kinetics Of ◽  
In Vitro Stability

SummaryThe bone-seeking 99mTc-Sn-pyrophosphate compound (compound A) was diluted both in vitro and in vivo and proved to be unstable both in vitro and in vivo. However, stability was much better in vivo than in vitro and thus the in vitro stability of compound A after dilution in various mediums could be followed up by a consecutive evaluation of the in vivo distribution in the rat. After dilution in neutral normal saline compound A is metastable and after a short half-life it is transformed into the other 99mTc-Sn-pyrophosphate compound A is metastable and after a short half-life in bone but in the kidneys. After dilution in normal saline of low pH and in buffering solutions the stability of compound A is increased. In human plasma compound A is relatively stable but not in plasma water. When compound B is formed in a buffering solution, uptake in the kidneys and excretion in urine is lowered and blood concentration increased.It is assumed that the association of protons to compound A will increase its stability at low concentrations while that to compound B will lead to a strong protein bond in plasma. It is concluded that compound A will not be stable in vivo because of a lack of stability in the extravascular space, and that the protein bond in plasma will be a measure of its in vivo stability.

scholarly journals Assessment of Micral-Test Microalbuminuria Test Strip in the Laboratory and in Diabetic Outpatients

1992 ◽  
Vol 29 (1) ◽  
pp. 96-100 ◽  
Author(s):  
Denis R Jury ◽  
Donald J Mikkelsen ◽  
Deborah Glen ◽  
Peter J. Dunn
Keyword(s):  
Screening Method ◽  
Urine Osmolality ◽  
Test Strip ◽  
Albumin Concentration ◽  
Creatinine Concentration ◽  
Urine Albumin ◽  
Low Concentrations ◽  
Colour Development ◽  
The Stability ◽  
Sodium And Potassium

We have evaluated a semi-quantitative dry immunochemical screening method (Micral-Test) for the detection of low concentrations of albumin in urine. The stability of Micral-Test strips on storage was good, especially with regard to temperature, light and humidity. Changes in urine osmolality (urea and creatinine concentration), pH and sodium and potassium concentration did not have a significant analytical effect on the Micral-Test measurement; extremes of temperature altered the rate of colour development. The depth of dipping the strip into the sample and the timing of reading colour development were critical. We measured the albumin concentration in 184 urine samples from diabetic outpatients by the Micral-Test and by our in-house immunoturbidimetric method; a Micral-Test result of 20 mg/L had a sensitivity of 91% and specificity of 97% to predict a discriminating urine albumin concentration > 30 mg/L by the in house method. The Micral-Test is suitable for use by non-laboratory personnel and is capable of producing analytically acceptable results for use in diabetes clinics and by general practitioners.

Global Hopf Bifurcation in a Phytoplankton–Zooplankton System with Delay and Diffusion

2021 ◽  
Vol 31 (08) ◽  
pp. 2150114
Author(s):  
Ming Liu ◽  
Jun Cao ◽  
Xiaofeng Xu
Keyword(s):  
Hopf Bifurcation ◽  
Global Existence ◽  
Upper And Lower Solutions ◽  
Positive Periodic Solutions ◽  
Global Hopf Bifurcation ◽  
System With Delay ◽  
Local Hopf Bifurcation ◽  
Distribution Of Eigenvalues ◽  
The Stability ◽  
And Diffusion

In this paper, the dynamics of a phytoplankton–zooplankton system with delay and diffusion are investigated. The positivity and persistence are studied by using the comparison theorem and upper and lower solutions method. The stability of steady states and the existence of local Hopf bifurcation are obtained by analyzing the distribution of eigenvalues. And the global existence of positive periodic solutions is established by using the global Hopf bifurcation result given by Wu [1996]. Finally, some numerical simulations are carried out to illustrate the analytical results.

Stability of the PEG Fatty Acid Glycerides Based O/W Emulsions

2021 ◽  
Vol 58 (4) ◽  
pp. 271-277
Author(s):  
Zihan Wang ◽  
Liangliang Lin ◽  
Hujun Xu
Keyword(s):  
Droplet Size ◽  
Lauric Acid ◽  
Volume Ratio ◽  
Water Volume ◽  
Optimal Conditions ◽  
Rotational Rheometer ◽  
Emulsion Systems ◽  
Oil Water ◽  
The Stability ◽  
Emulsifier Concentration

Abstract In the present work, oil-in-water (O/W) emulsion systems were prepared by using the PEG-7 lauric acid glycerides as the emulsifiers and the liquid paraffin as the oil phase. The influence of processing parameters such as emulsification temperature, stirring speed, emulsifier concentration, oil-water volume ratio and polymer addition on the stability of the emulsion systems was investigated. In order to determine the optimal conditions for the preparation of the emulsion systems based on PEG-7 lauric acid glycerides, a laser drop size analyser and a rotational rheometer were used. As the stability of the O/W emulsion systems increased, the average droplet size of the O/W emulsions measured by the laser droplet size analyser became smaller and the viscosity, storage modulus and loss modulus of the O/W emulsions measured by the rotational rheometer became larger. The following optimal conditions were determined in this study: emulsification temperature 80°C, stirring speed 500 r/min, emulsifier concentration 5 wt%, oil-water volume ratio 1:1 and added amount of xanthan gum 0.2 wt%. The droplet morphology of the O/W emulsion prepared under the optimal conditions, which was characterised by a super high magnification microscope, is small. Furthermore, the long-term stability of the emulsion system prepared under the optimal conditions was investigated over a period of time (4 weeks). The O/W emulsion proves to be well stable even after 4 weeks, with a water separation rate of 0%.

Effects of Delay and Diffusion on the Dynamics of a Leslie–Gower Type Predator–Prey Model

2014 ◽  
Vol 24 (04) ◽  
pp. 1450043
Author(s):  
Jia-Fang Zhang ◽  
Xiang-Ping Yan
Keyword(s):  
Periodic Solutions ◽  
Positive Constant ◽  
Neumann Boundary ◽  
Predator Prey ◽  
Predator Prey Model ◽  
Constant Equilibrium ◽  
Homogeneous Neumann Boundary Condition ◽  
Delayed System ◽  
The Stability ◽  
And Diffusion

In this paper, we consider the effects of time delay and space diffusion on the dynamics of a Leslie–Gower type predator–prey system. It is shown that under homogeneous Neumann boundary condition the occurrence of space diffusion does not affect the stability of the positive constant equilibrium of the system. However, we find that the incorporation of a discrete delay representing the gestation of prey species can not only destabilize the positive constant equilibrium of the system but can also cause a Hopf bifurcation at the positive constant equilibrium as it crosses some critical values. In particular, we prove that these Hopf bifurcations' periodic solutions are all spatially homogeneous if the diffusive rates are suitably large, which has the same properties as periodic solutions of the corresponding delayed system without diffusion. However, if the diffusive rates are suitably small, then the system will generate spatially nonhomogeneous periodic solutions. The results in this work demonstrate that diffusion plays an important role in deriving complex spatiotemporal dynamics.

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