Content uploaded by Eva Kiss
Author content
All content in this area was uploaded by Eva Kiss on Jun 24, 2017
Content may be subject to copyright.
A preview of the PDF is not available
Nanoencapsulation of Antitubercular Drug Isoniazid and Its Lipopeptide Conjugate
Abstract and Figures
Isoniazid (INH) is a first line drug for treatment of the widespread deadly disease caused by Mycobacterium tuberculosis. Peptide conjugate of INH was designed and synthesised for targeted and receptor mediated cellular uptake of INH. Chemical composition, hydrophobicity (n-octanol/water partition coefficient), and membrane affinity (using a Langmuir lipid monolayer as a model system) of the conjugate were characterised. Hydrophilicity of the drug was remarkably decreased by the conjugation which resulted in improved interaction with lipid layer and allowed its efficient encapsulation into polylactic/glycolic acid nanoparticles enhancing the bioavailability of the drug.
Figures - uploaded by Eva Kiss
Author content
All figure content in this area was uploaded by Eva Kiss
Content may be subject to copyright.
... The surface properties of nanocarriers define their behaviour, stability against aggregation, biocompatibility, interaction with membrane, moreover provide the platform for specific targeting by chemical modification [18,[20][21][22]. Hydrophilic polymers such as polyvinyl alcohol or block copolymers, such as PEO-PPO-PEO triblock copolymers (Pluronics) are effective surface modifiers for the most applied biodegradable poly(lactic-co-glycolic acid) (PLGA) drug carrier nanoparticles (NPs) [18,23]. The surface layer on NPs assures the satisfactory colloidal stability, enhanced biocompatibility and possibility of further chemical modification to improve interaction with phospholipid membrane [24]. ...
... The adsorbed POPC amount increases with increasing hydrophobicity of the Pluronic copolymers. This trend corresponds to the relation observed by Hädicke et al. previously for dissolved Pluronic molecules namely PPO blocks favour the binding to liposomes while long PEO chains reduce it by steric effect [23]. The binding of liposomes to C18-HbPG covered surface is similar to that of Pluronic105 with moderate hydrophobicity. ...
The benefit gained by application of nanostructured drug delivery systems is highly influenced by their possible transport in the body. The affinity to cell membrane is a crucial parameter to be optimized by tuning the surface properties of nanoparticles (NPs). Poly(lactic/glycolic acid) (PLGA) NPs designed for drug delivery were stabilized with three different Pluronics (103, 105 and 108) as well as an amphiphilic monoalkyl hyperbranched polyglycerol (C18-HbPG). Their interaction with lipid bilayer was investigated in two types of arrangements using liposomes and polymeric adsorbed layer, while in the other model polymer stabilized PLGA NPs and supported lipid bilayer (SLB) were applied. Degree of adhesion of liposomes and PLGA NPs were characterized by quartz crystal microbalance (QCM) measurements in combination with the visual analysis of the surfaces by atomic force microscopy (AFM). The comparison of the various polymer coatings led to the conclusion that C18-HbPG resulted in the highest membrane affinity, followed by Pluronic105 with medium polarity within the Pluronic series. This finding further supports the results obtained previously regarding colloid stabilization efficacy (Kasza 2017) [1] that amphiphilic hyperbranched polyglycerol is an ideal alternative to Pluronics in the functional surface modification of drug carrier NPs.
... More recently biodegradable polymeric nanoparticles have been investigated as biocompatible alternatives for these materials to be used as stabilizer for medical emulsions [14]. Poly(lactic-co-glycolic acid) (PLGA) nano-and microparticles have been described as convenient platforms to carry drug molecules in the body [15,16,17]. Surface modification of these biodegradable particles with polyethylene oxide containing molecules has been shown to increase the biocompatibility of these systems [18,19,20,21]. ...
... tanh 32 (16) where ε is the dielectric permittivity of the medium, κ −1 is the Debye length, r and Ψ NP are the radius and surface potential of the particle and h is the separation distance. The steric interaction can be approximated with the following formulae [50,51] (17) where h is the separation distance, L is the thickness of the brush that was estimated as L ≈ lN 1/2 , where l is the length of a polymeric segment, 3.7 Å for PEO [52,53], and N is the number of segments, 258 ...
Hypothesis:
Adsorption and localization of nanoparticles at fluid interfaces are key factors in processes like transport through membranes or emulsion stabilization. Adsorption of poly(lactic-co-glycolic acid) (PLGA) and Pluronic coated PLGA nanoparticles (NPs) were studied at three different fluid interfaces. The effect of particle surface modification and type of interface was investigated with the aim of fine tuning interfacial interaction of the nanoparticles.
Experiments:
Surface tension measurements were carried out to determine the surface activity and adsorption kinetics of the particles. Particles layers at the air/water interface were further studied using the Langmuir balance technique by recording the surface pressure-area isotherms. Interfacial rheological measurements were performed to characterize the structural properties of the nanoparticle interfacial films.
Findings:
Interfacial adsorption and its kinetics were explained by the diffusion controlled adsorption theory and considering the energy barrier of particle transport to the interface. Surface modification by Pluronic increased the interfacial activity of nanoparticles at all interfaces. Surface activity of PLGA-Pluronic particles could be described by the contributions of both the PLGA NPs and the effective portion of their Pluronic shell. Both particle films present mainly elastic dilatational properties suggesting that particles are in kinetically separated state.
... To achieve the higher solubility, selectivity, internalization rate, and intracellular efficacy of the antimycobacterial compounds, different delivery vehicles can be used. Targeting peptides can enhance cellular uptake of active agents via receptor-mediated endocytosis, thus, peptidebased drug conjugates can increase the intracellular efficacy of antimycobacterial compounds [29][30][31][32][33][34][35][36]. The development of delivery peptides is also a demanding process (solubility, efficient targeting, and stability as well as cytotoxicity aspects). ...
Mycobacterium tuberculosis is an intracellular pathogen and the uptake of the antimycobacterial compounds by host cells is limited. Novel antimycobacterials effective against intracellular bacteria are needed. New N-substituted derivatives of 4-aminosalicylic acid have been designed and evaluated. To achieve intracellular efficacy and selectivity, these compounds were conjugated to tuftsin peptides via oxime or amide bonds. These delivery peptides can target tuftsin- and neuropilin receptor-bearing cells, such as macrophages and various other cells of lung origin. We have demonstrated that the in vitro antimycobacterial activity of the 4-aminosalicylic derivatives against M. tuberculosis H37Rv was preserved in the peptide conjugates. The free drugs were ineffective on infected cells, but the conjugates were active against the intracellular bacteria and have the selectivity on various types of host cells. The intracellular distribution of the carrier peptides was assessed, and the peptides internalize and display mainly in the cytosol in a concentration-dependent manner. The penetration ability of the most promising carrier peptide OT5 was evaluated using Transwell-inserts and spheroids. The pentapeptide exhibited time- and concentration-dependent penetration across the non-contact monolayers. Also, the pentapeptide has a fair penetration rate towards the center of spheroids formed of EBC-1 cells.
... 6; 122.0; 123.3 nm) show good match. The calculated response function for the diameter (y 1 ) is the following quadratic formula (Equation (2)) with the coefficients: (2) The coefficients >2.42 are significant (conf.int.: 95%) which means that the composition of the organic phase, x 2 and its volume, x 3 have considerable effect on the size of the NPs. The response surface presenting the effect of composition (x 2 ) and volume of organic phase (x 3 ) is displayed in Figure 5. ...
The hardly water-soluble curcumin with low bioavailability was successfully encapsulated into biodegradable
polymeric particles by nanoprecipitation. By using the more hydrophobic poly(ε-caprolactone) (PCL) instead of poly(lactic-
co-glycolic acid) 50:50 (PLGA) significantly increased drug load was achieved. The stronger interaction between curcumin
and PCL than PLGA was supported by Fourier-transform infrared spectroscopy (FTIR) measurements. As efficient
colloid stabilizer, a novel amphiphilic polymer, hyperbranched polyglycerol with one long alkyl chain (C18-HbPG) was
used which has better membrane affinity than the widely used Pluronics, and it enables further functionalization of the drug
carrier as well. A Box-Behnken experimental design was applied to prepare and optimize the properties of curcumin loaded
PCL nanoparticles (NPs) varying the initial drug load, composition of the organic phase and volume ratio of aqueous and
organic phases. The volume of the organic phase was found to be the most relevant parameter for encapsulation, and it can
be used to control the size and drug content of the NPs. The curcumin load of 10 w/w% of the NPs with diameter below
120 nm was observed in the optimal system. Cumulative controlled release of curcumin with strong pH-dependence into
simulated gastric fluids with up to ~80% is found after 8–12 hours.
... The most pertinent parameters that are essentially evaluated in LDC development and characterization are discussed in brief below: i Fourier Transformed nfrared Spectra (FTR): This is needed to characterize the intermediates and final product and establish their identity ( Müller and Olbrich, 2004). ii Partition Coefficient (logP): It is a measure of molecular polarity and is usually determined by shake flask method ( Kiss et al., 2011;Jeffery et al., 1989). iii NMR and Mass Spectra: Both are essential tools to establish molecular identity (Willard et al., 1988) and confirm successful conjugation in the formation of the LDC. ...
Biocompatible and biodegradable polymers such as poly(lactic-co-glycolic acid), PLGA and polycaprolactone, PCL nanoparticles (NPs) have been used successfully as drug carriers in controlled drug release. The main weakness is the generally low drug loading (1–-5%) of the NPs. An option to enhance the drug content of NPs is to find the optimum matrix for a given drug molecule. To reveal the influence of matrix and drug polarity on the favoured encapsulation, polymeric NPs loaded with a series of alkyl-4-hydroxybenzoate (paraben) with increasing alkyl chain length (C1-C8) as model drugs were prepared by nanoprecipitation method. The paraben series represents the drugs with various polarities while the selected matrix polymers show increased hydrophobicity: PLGA with 50% lactic acid content (PLGA50) < PLGA with 75% lactic acid content (PLGA75) < PCL. The drug content of the PLGA NPs was found to significantly increase up to 10% with the hydrophobicity of the parabens, while encapsulation was further boosted by applying PCL. To find the proper fit between drug and matrix and finely tune the polarity of the NPs, as a novel approach, blends of PLGA50 and PCL were applied as matrix polymers. The drug loading of the NPs was proved to be dependent on the systematically changed blend composition. Furthermore, the introduction of PCL into the PLGA50 matrix improves the release kinetics of the active component.
Most therapeutic agents used for treating brain malignancies face hindered transport through the blood-brain barrier (BBB) and poor tissue penetration. To overcome these problems, we developed peptide conjugates of conventional and experimental anticancer agents. SynB3 cell-penetrating peptide derivatives were applied that can cross the BBB. Tuftsin derivatives were used to target the neuropilin-1 transport system for selectivity and better tumor penetration. Moreover, SynB3-tuftsin tandem compounds were synthesized to combine the beneficial properties of these peptides. Most of the conjugates showed high and selective efficacy against glioblastoma cells. SynB3 and tandem derivatives demonstrated superior cellular internalization. The penetration profile of the conjugates was determined on a lipid monolayer and Transwell co-culture system with noncontact HUVEC-U87 monolayers as simple ex vivo and in vitro BBB models. Importantly, in 3D spheroids, daunomycin-peptide conjugates possessed a better tumor penetration ability than daunomycin. These conjugates are promising tools for the delivery systems with tunable features.
Two aspects of biorelevant interfacial phenomena, the surface biocompatibility and membrane affinity of polymeric biomaterials were discussed in the present paper. Surface modifications of biodegradable polyesters, poly(lactic acid) (PLA) and poly(lactic-co-glycolic acid) (PLGA) were developed by forming poly(ethylene oxid), PEO-containing layer. Different polymer layers were studied by XPS and ellipsometry measurements to determine the effect of Pluronic component on bovine serum albumin (BSA) adsorption. Significant increase in surface hydrophilicity was achieved leading to reduced protein adsorption which contributes to enhanced biocompatibility.
Applying surface modifications to polymeric drug delivery nanoparticles (NPs) the macromolecular coverage offers the steric stabilization of the colloidal drug loaded particles. Meanwhile, the tuning of surface properties by changing the chemical composition can improve the membrane affinity of the drug carrier particles. Additionally, providing that significant number of functional groups is available in the surface layer that allows further chemical coupling of various ligands to accomplish targeted drug delivery.
To characterize the membrane affinity of a colloidal drug carrier, Langmuir-balance measurement using lipid monomolecular layers were carried out. These nanocarriers with diameter of 100-150 nm probably show different molecular interactions and transport route than the molecular construction. The adhesion to the membrane surface however, is a first crucial step in the process which is tested in the penetration ability measurement. With the aim to increase the membrane affinity and potential of targeted drug delivery the end group derivative of Pluronics was synthesized in a straightforward way to obtain Pluronic-amines. This method allows modulation of the charge character of the NPs’ surface and provides functional groups for chemical reactions useful for targeting while retaining the aggregation stability of the system. Presence of the positively charged end groups was detectable with electrophoretic mobility measurements. The Pluronic-amine coated NPs showed the highest membrane affinity into the DPPC layer while controllable properties of the surface layer can be achieved by combined application of the Pluronics with different compositions.
Adhesion/adsorption of the biodegradable PLGA NPs were studied at another model cell membrane (SLB) composed of lipid bilayer formed on a solid support. The influence of NPs’ surface properties on the interfacial interactions was evaluated comparing various amphiphilic block copolymers (Pluronics) as well as amphiphilic monoalkyl hyperbranched polyglycerols (Cn-HbPGs). Cn-HbPGs were successfully applied as surface modifiers and stabilizers in the preparation of PLGA NPs with outstanding colloidal stability due to the orienting interaction of the hydrophobic alkyl segment. The Pluronic- and C18-HbPG coated NPs were applied to SLB obtained on quartz crystal microbalance (QCM) sensor surface by liposome spreading. Degree and type of adhesion of NPs were determined by nanogravimetric measurements in combination with the visual analysis of the surfaces using atomic force microscopy (AFM). Comparison of different Pluronic surface coatings led to the conclusion that the length of the PEO chains in the Pluronic molecules has marked effect on the stability of the NPs and their interactions with lipid systems. Stabilization of NPs by C18-HbPG resulted in the highest membrane affinity which is an initial requirement for cellular uptake, followed by Pluronic105 with medium polarity within the Pluronic series applied here.
In parallel to the characterization of the drug carrier nanoparticles, the membrane affinity of various bioactive compounds has also been studied. Using both of the mono- and bilayer lipid model membrane measurements large number of drug candidates were managed to screen and promising compounds were selected acting against Mycobacterium tuberculosis, the pathogen of tuberculosis.
These types of model experiments have also proved useful in the assessment of amphiphilic cationic polymers applied as antibacterial coating on various textile materials. On the basis of the membrane affinity results the chemical structure involving conformational properties of the alkyl chain grafted poly(ethylene imine) derivatives was found to be important in the molecular interactions playing role in antibacterial behaviour of amphipathic cationic polyelectrolytes.
Poly(lactic-co-glycolic acid) drug loaded nanoparticles are applied successfully to increase the distribution and bioavailability of hydrophobic drug molecules, although the generally low drug content implies a limitation. Poly(lactic-co-glycolic acid) nanoparticles were prepared by nanoprecipitation to encapsulate model drugs, a series of alkyl-hydroxy-benzoate (parabens) from methyl-to octyl with increasing hydrophobicity to address the influence of drug property on the encapsulation. The drug content and encapsulation efficiency were found to be substantially different for the various parabens. The analysis of the miscibility of the polymer with parabens using their solubility parameters could not provide satisfactory explanation for the experimental findings.
The treatment of nanoencapsulation however, as a partitioning process involving poly(lactic-co-glycolic acid) and aqueous phase led to a relationship between the drug content of the nanoparticles and the characteristic properties of the drug molecule. According to that both the high hydrophobicity and high aqueous solubility of the drug favour the efficacy of its encapsulation. The actual and also the achievable maximum drug content can be predicted and was tested in several systems. The above approach opens the way for more reasonable design of nanoparticle drug carrier in addition to the possible explanation for the drug content achievable for a given compound.
Tuberculosis is caused by Mycobacterium tuberculosis, an intracellular pathogen that can survive in host cells, mainly in macrophages. An increase of multidrug-resistant tuberculosis qualifies this infectious disease a major public health problem worldwide. The cellular uptake of the antimycobacterial agents by infected host cells is limited. Our approach is to enhance the cellular uptake of the antituberculars by target cell-directed delivery using drug-peptide conjugates to achieve an increased intracellular efficacy. In this study, salicylanilide derivatives (2-hydroxy-N-phenylbenzamides) with remarkable antimycobacterial activity were conjugated to macrophage receptor specific tuftsin based peptide carriers through oxime bond directly or by insertion of a GFLG tetrapeptide spacer. We have found that the in vitro antimycobacterial activity of the salicylanilides against M. tuberculosis H37Rv is preserved in the conjugates. While the free drug was ineffective on infected macrophage model, the conjugates were active against the intracellular bacteria. The fluorescently labelled peptide carriers that were modified with different fatty acid side chains showed outstanding cellular uptake rate to the macrophage model cells. The conjugation of the salicylanilides to tuftsin based carriers reduced or abolished the in vitro cytostatic activity of the free drugs with the exception of the palmitoylated conjugates. The conjugates degraded in the presence of rat liver lysosomal homogenate leading to the formation of an oxime bond-linked salicylanilide-amino acid fragment as the smallest active metabolite.
Interfacial properties of spread monolayers of poly(lactic acid), PLA and poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) block copolymer (Pluronic6400) have been studied at the air–water interface by measuring surface pressure–area isotherms. Film balance experiments were also performed on the mixed layers of PLA and Pluronic6400 over a wide concentration range. Transitions observed of the isotherms compressing the pure Pluronic6400 monolayer could be correlated to conformational changes of other PEO-containing type copolymers interpreted by the scaling theory. In the mixed systems, the Pluronic6400 additive exhibited a concentration-dependent influence on the behaviour and structural changes of the PLA film. The maximum effect on phase transition of PLA monolayer and compressibility was obtained at 100∶60 PLA/Pluronic6400 weight ratio. Analysis of the additivity of the components revealed that the mixed films are miscible and non-ideal systems with high deviation from ideality. The interaction existing in the PLA–Pluronic6400 monolayer results in contraction in the low surface pressure range where the film is characterized by low compressibility, while in the compressed state dynamic effects might also contribute to the expansion of the mixed films.
The ordering of the hydrocarbon chain interior of bilayer membranes has been calculated using the molecular field approximation developed in previous work on liquid crystals. Different statistical averages are evaluated by exact summation over all conformations of a single chain in the field due to neighboring molecules. The internal energy of each conformation, as well as contributions arising from interaction with the molecular field and from a lateral pressure on the chain have been included.The results describe properties of both lipid monolayers and bilayers. For monolayers, the calculated pressure-area relationships are in good agreement with experimental observations. The order parameter for hydrocarbon chains in bilayers (or monolayers) as a function of temperature, lateral pressure and position along the chain, is shown and compared with the available NMR data. Combining the results of calculation and NMR measurements we obtain the value for intrinsic lateral pressure within bilayer membranes, in excellent agreement with direct measurements on surface monolayers.The calculation also gives average length of hydrocarbon chains, thermal expansion coefficient and fraction of bonds in gauche conformations. The effect of cholesterol and proteins within the bilayer is qualitatively described, and the contribution of the bilayer interior to membrane elasticity is determined.
Soybean-Phosphatidylcholine Phospholipon® 100 has a stable gel conformation in the as-prepared state. We observed a main phase transition (chain melting) above 30 °C in the first heating run. This transition is marked 1. by a change of the lamellar repeat distance recorded by small angle X-ray diffraction, and 2. by an increase of the imaginary part of the dielectric constant. After the first heating up to + 90 °C the chains “melt” in a broad temperature range between -60 °C and +90 °C. The high stability of chain conformation in the temperature range -60 °C to +30 °C of the as-prepared state is due to the low water content of the material.
Poly(dl-lactide) (PLA) and two of its random copolymers with glycolic acid, poly(dl-lactide-co-glycolide) (PLGA) with 75/25 and 50/50 component ratios of lactide/glycolide were blended with poly(ethylene oxide)/poly(propylene oxide)/poly(ethylene oxide) (PEO–PPO–PEO) triblock non-ionic surfactants, known by the Pluronic® trade names of PE6100, PE6400 and PE6800. The surface chemical compositions of the blended films were identified by X-ray photoelectron spectroscopy (XPS). Based on the component of the carbon signal assigned to the ether carbon of the Pluronic® molecule, quantification of the surface accumulation of the Pluronic® additive, compared to its bulk concentration, was performed. The data demonstrated that PEO-containing surfaces were prepared by the blending process. A significant surface hydrophilization, characterized by wettability measurements, was obtained by applying the Pluronics® at a concentration of 1.0–9.1 wt% in the blends. The composition of the surface layer and, in accordance with this, the wettability of the film were found to be dependent on the type of Pluronic® and on the composition of the unmodified polymer. Protein adsorption on the polymer films was measured by the FT-IR ATR spectroscopic technique. The adsorbed amount of bovine serum albumin onto PLA was highly reduced when the polymer was blended with a Pluronic®. The increased hydrophilicity and the reduced protein adsorption properties of the PLA and PLGA obtained by blending with PEO compounds might contribute to their applications as drug carrier systems with great potential. Copyright © 2003 John Wiley & Sons, Ltd.
The stability (area loss as a function of time) of dipalmitoylphosphatidylcholine (DPPC) at the air–water interface is an important property in the context of studying its behaviour as a major component of synthetic lung surfactant. However, some Langmuir troughs cannot support a stable monolayer of lung surfactant for long periods of time owing to adhesion between the surfactant and the materials that compose the trough. In this work, the stability has been measured as a function of surface pressure, Wilhelmy plate length and width, compression barrier material and the height of the water surface relative to the edge of the compression barriers on a Nima 601M Langmuir trough. Octadecanoic acid (stearic acid) and a non-amphiphilic porphyrin, 5,10,15,20-tetrakis(3,4-bis[ethylhexyloxy]phenyl)-porphyrinatozinc (Zn EHO) have also been investigated in order to identify the features of area loss which are surfactant material dependent and those which are affected by the properties of the trough itself. Stability of the highly amphiphilic monolayers was greatly improved when using Delrin barriers instead of PTFE barriers but had little effect on the porphyrin monolayers.
The formation of a colloidal suspension of nanoparticles was obtained, in a very simple manner, by transferring a solution of poly--caprolactone in a good solvent (L1) into a non-solvent (L2). Photon Correlation Spectroscopy (PCS) measurements confirmed by microscopic observations were used to determine the morphological aspects of the preparations. The influence of several factors on nanoprecipitation was examined: polymer concentration, L1/L2 ratio, dielectric constant of the final mixture. An experimental model of the phenomenon, which takes into account the flocculation concentration and the L1/L2 ratio, is proposed. It allows the optimal conditions for nanoparticles formation to be determined.
The biodistribution of injected colloidal carriers for targeted delivery will be highly dependent upon their size and surface properties. This paper describes investigations on the preparation of sub-200 nm poly(lactide-co-glycolide) (PLGA) microspheres by the variation of processing parameters using the solvent evaporation technique. Smaller particle sizes were found to be favoured by a two stage emulsification process, a low PLGA concentration and an increased surfactant concentration. In the latter case, it would appear that the viscosity of the continuous phase is a crucial factor. The process of particle size reduction could further be complimented by using a surfactant of lower molecular weight. Employing such procedures, microspheres as low as 90 nm in diameter of low polydispersity were prepared in a reproducible manner.
The aim of the present work was to investigate the preparation of nanoparticles as a potential drug carrier and targeting system for the treatment of inflammatory bowel disease. Rolipram was chosen as the model drug to be incorporated within nanoparticles. Pressure homogenization–emulsification (PHE) with a microfluidizer or a modified spontaneous emulsification solvent diffusion method (SESD) were used in order to select the most appropriate preparation method. Poly(ε-caprolactone) has been used for all preparations. The drug loading has been optimized by varying the concentration of the drug and polymer in the organic phase, the surfactants (polyvinyl alcohol, sodium cholate) as well as the volume of the external aqueous phase. The rolipram encapsulation efficiency was high (>85%) with the PHE method in all cases, whereas with the SESD method encapsulation efficiencies were lower (<40%) when lower surfactant concentrations and reduced volume of aqueous phase were used. Release profiles were characterized by a substantial initial burst release with the PHE method (25–35%) as well as with the SESD method (70–90%). A more controlled release was obtained after 2 days of dissolution with the PHE method (70–90%), no further significant drug release was observed with the SESD method.
Indomethacin-loaded nanocapsules were prepared by deposition of poly-(D,L-lactide) polymer at the o/w interface following acetone displacement from the oily nanodroplets. An attempt was made to elucidate the mechanisms of formation in terms of interfacial turbulence between two unequilibrated liquid phases involving flow, diffusion and surface tension decrease (Marangoni effect).