Change In Droplet Size Research Articles

Spray drying of emulsions: Influence of the emulsifier system on changes in oil droplet size during the drying step

The goal of this study was to investigate the influence of the emulsifier system on the changes in oil droplet size occurring during the drying step of spray drying of emulsions. Atomization and spray drying experiments were performed with emulsions stabilized with whey protein isolate (WPI) alone or in combination with low molecular weight emulsifiers (lecithin, mono- and diglycerides (MoDi), and citrem). Oil droplet coalescence was observed for the systems WPI/Citrem and WPI/MoDi, as the d90,0 increased from 0.86 ± 0.16 and 1.67 ± 0.35 µm after atomization to 1.83 ± 0.24 and 1.90 ± 0.17 µm after drying, respectively. Oil droplets stabilized with WPI or WPI/Lecithin remained stable during drying. Measurements of dilatational rheology of the interfacial film showed that phase angle values increase in the order WPI/Lecithin < WPI < WPI/Citrem = WPI/MoDi. Therefore, in the studied system oil droplet coalescence during drying increases when the elastic behavior of the interfacial film decreases. Practical applications Spray drying of emulsions is a widely used process in the food industry for production of, for example, infant formula, dairy powders, and encapsulated aroma and coloring compounds. The oil droplet size in the resulting powder determines sensory aspects and stability of the final product. This study deepens the understanding of the changes in oil droplet size occurring during spray drying as affected by the formulation components, allowing therefore a better control of the quality of spray dried food emulsions.

A Study on Liquid Spray Evaporation into a High Temperature Gas Stream.(Dept.M)

An analytical model has been developed for the process of liquid spray evaporation into a high temperature gas stream. In this model, the calculation scheme utilizes the cellular approach in-which each cell is regarded as a control volume and the gas-droplet interaction is considered. Based on an experimental data, droplets of a liquid spray are classified into several size distribution groups, The conservation laws of mass, momentum and energy are applied to each group considering the evaporation and diffusion of droplets, Predictions of gas-droplet Flow-field, trajectories of the Individual droplets, rate of evaporation and change of size distribution of the spray droplets have been obtained. An experimental verification of the prediction results has been carrid out. An optical arrangement is used for measurements of sire distribution of spray droplets into a high temperature gag stream. The comparison shows a reasonable agreement of the results based on the analytical model with the experimental measurements for each of droplet size distribution and changes of Sauter Dean diameter at different axial distances from the injection nozzle plane.

New Modified Equations to Estimate the Percentage of Over Three Emulsifiers in Emulsifier Mixture to Form a Stable Emulsion

AbstractThis research aims to deduce new simple empirical equations for applying Griffin's method for the Hydrophilic–Lipophilic Balance (HLB) to calculate the percentages of three to five emulsifiers used as an emulsifier mixture to form a stable emulsion. To achieve this aim, various types of oils, emulsifiers, and other additives (i.e. corrosion inhibitor and biocide) were used in emulsions formation for use in various purposes such as cosmetic chemistry, metalworking fluid (MWF), and emulsion polymerization fields. Dynamic light scattering (DLS) was used to measure the change of droplet size with time to assess the stability of emulsions. The emulsifiers were chosen based on their physical properties, chemical structure, and HLB value. The use of the deduced equations was restricted to the chemical structure and the HLB values of the emulsifiers used, the required HLB (RHLB) values of the oil and oil mixtures used, and the synergy in chemical structure between the hydrocarbon chain of oil(s) and the lipophilic moiety of the emulsifiers used. The results demonstrated that increasing the number of emulsifiers for a mixture of more than two emulsifiers increased the stability of the emulsion formed.

Temperature induced dynamics of water confined between graphene and MoS2.

Water trapped between MoS2 and graphene assumes a form of ice composed of two planar hexagonal layers with a non-tetrahedral geometry. Additional water does not wet these ice layers but forms three-dimensional droplets. Here, we have investigated the temperature induced dewetting dynamics of the confined ice and water droplets. The ice crystals gradually decrease in size with increasing substrate temperature and completely vanish at about 80 °C. Further heating to 100 °C induces changes in water droplet density, size, and shape through droplet coalescence and dissolution. However, even prolonged annealing at 100 °C does not completely dry the interface. The dewetting dynamics are controlled by the graphene cover. Thicker graphene flakes allow faster water diffusion as a consequence of the reduction of graphene's conformity along the ice crystal's edges, which leaves enough space for water molecules to diffuse along the ice edges and evaporate to the environment through defects in the graphene cover.

A comparative study of the self-propelled jumping capabilities of coalesced droplets on RTV surfaces and superhydrophobic surfaces

Understanding the mechanism of coalescence-induced self-propelled jumping behavior provides distinct insights in designing and optimizing functional coatings with self-cleaning and anti-icing properties. However, to date self-propelled jumping phenomenon has only been observed and studied on superhydrophobic surfaces, other than those hydrophobic surfaces with weaker but fairish water-repellency, for instance, vulcanized silicon rubber (RTV) coatings. In this work, from the perspective of thermodynamic-based energy balance aspect, the reason that self-propelled jumping phenomenon does not happen on RTV coatings is studied. The apparent contact angles of droplets on RTV coatings can be less than the theoretical critical values therefore cannot promise energy surplus for the coalesced droplets onside. Besides, on RTV and superhydrophobic surfaces, the droplet-size dependent variation characteristics of the energy leftover from the coalescence process are opposite. For the droplets coalescing on RTV coatings, the magnitudes of energy dissipations are more sensitive to the increase in droplet size, compared to that of released surface energy. While for superhydrophobic coatings, the energy generated during the coalescence process can be more sensitive than the dissipations to the change in droplet size.

Breakup and Coalescence of Oil Droplets in Protein-Stabilized Emulsions During the Atomization and the Drying Step of a Spray Drying Process

The goal of this study was to investigate the changes in oil droplet size in whey protein–stabilized emulsions during the atomization and the subsequent drying step of a spray drying process. For this purpose, experiments were performed in an atomization rig and a pilot spray dryer with two commercial pressure swirl atomizers. By comparing the oil droplet size before atomization, after atomization, and after spray drying, the changes in oil droplet size during each process step were quantified. The effect of oil droplet breakup during atomization was isolated by atomizing emulsions with 1 wt.% oil content and a protein to oil concentration ratio of 0.1. At 100 bar, the Sauter mean diameter of oil droplet size was reduced from 3.13 to 0.61 μm. Directly after breakup, coalescence of the oil droplets was observed for emulsions with a high oil content of 30 wt.%, leading to a droplet size after atomization of 1.15 μm. Increasing the protein to oil concentration ratio to 0.2 reduced coalescence during atomization and oil droplets with a mean diameter of 0.92 μm were obtained. Further coalescence was observed during the drying step: for an oil content of 30 wt.% and a protein to oil concentration ratio of 0.1 the mean droplet size increased to 1.77 μm. Powders produced at high oil contents showed a strong tendency to clump. Comparable effects were observed for a spray drying process with a different nozzle at 250 bar. The results confirm that droplet breakup and coalescence during atomization and coalescence during drying have to be taken into consideration when targeting specific oil droplet sizes in the product. This is relevant for product design in spray drying applications, in which the oil droplet size in the powder or after its redispersion determines product quality and stability.

The Effect of Inert Salts on Explosive Emulsion Thermal Degradation

AbstractAmmonium nitrate fuel oil (ANFO) explosive emulsions are comparatively safe, effective and low‐cost products for mining operations. They consist of a supersaturated ammonium nitrate solution dispersed as droplets in a continuous fuel phase. Here we apply a previously developed bench‐top Nuclear Magnetic Resonance (NMR) Pulsed Field Gradient (PFG) technique to monitor the emulsion droplet size distribution in ANFO explosive emulsions as a function of time stored at an elevated temperature of 50 °C; we thus investigate the subtle effect of adverse storage conditions on emulsion stability. Storage at 50 °C for 12 weeks lead to a ∼60 % increase in mean droplet size, whereas a sample stored at 21 °C experienced no change in mean droplet size. The addition of inert salts (calcium nitrate or sodium nitrate) to the ammonium nitrate solution was also considered in terms of their ability to enable stable storage of the emulsions at 50 °C. An addition of 5 wt% calcium nitrate to the aqueous phase was required to suppress any thermal degradation of the explosive emulsions whilst a much lower dosage of only 1 wt% sodium nitrate was required to realise the same stabilizing effect.

Inter-species variabilities of droplet transport, size change, and deposition in human and rat respiratory systems: An in silico study

To speculate on human responses from animal studies, scale-up factors (body weight, lung volume, or lung surface area ratios) are currently used to extrapolate aerosol lung deposition from animal to human. However, those existing scale-up methods between animals and humans neglected two important inter-subject variability factors: (1) the effect of anatomical differences in respiratory systems from mouth/nose to peripheral lungs between human and rat, and (2) the effect of spatial distributions and temporal evolutions of temperature and relative humidity (RH) on droplet size change dynamics between the two species. To test the above-mentioned inter-species variability effects on droplet fates in pulmonary routes and generate correlations as a precise scale-up method for lung deposition estimation, this study simulated the transport of pure-water droplets in both human and Sprague-Dawley (SD) rat respiratory systems. Employing an experimentally validated Euler-Lagrange based Computational Fluid-Particle Dynamics (CFPD) model, simulations were performed for droplets with Stk/Fr between 8.36 × 10−5 and 1.25 × 10−2. Droplets were inhaled through human and rat nostrils under resting breathing conditions. Numerical results indicate that RH becomes uniformly distributed in rat airways sooner than in human airways, which significantly influences droplet size change dynamics and the resultant droplet trajectories in pulmonary routes. Using the Stokes-Froude dimensionless number group (i.e., Stk/Fr) as the independent variable, the regional deposition fractions (DFs) and evaporation fractions (EFs) in both rat and human respiratory systems collapsed into unified correlations. Such correlations can be used for the new rat-to-human scale-up method, estimating the lung depositions with consideration of anatomical differences. Furthermore, the necessity to employ realistic RH and temperature boundary conditions (BCs) at airway walls was also confirmed for the accurate prediction of droplet size change using CFPD model. Employing idealized BCs leads the droplets to evaporate slower and deposit more than using realistic RH and temperature BCs.

Characterization of Flow-Focusing and Flow-Blurring Modes of Atomization

This paper presents a characterization of flow-blurring (FB) and flow-focusing (FF) modes of atomization using a new atomizer, which enables continuous transition from FB to FF regimes by controlling the recess of a liquid tube. The atomizer has optical access and features flexibility in controlling the Weber number (We) and the air/liquid mass flow ratio (ALR). The Phase Doppler Particle Analyzer (PDPA) technique is employed here along with long-distance microscopic and direct imaging to observe and characterize the atomization regime. Experiments were carried out with water and air as the working fluids at room temperature and in an atmospheric pressure environment. The results show that operation in the FB regime generates smaller droplet sizes in the spray core compared to the FF regime. However, the benefit of FB decays with increasing We, and eventually the difference between both regimes decreases. Among the distinctive features of FB sprays found only in the near-field region are: a more noticeable change in the mean droplet size with the radial direction, more pronounced polydispersity, larger centerline axial velocity and larger axial and radial velocity fluctuations. Liquid tube recess was also found to be an important parameter in controlling the spray behavior in the FB regime. It was found to impact the droplet size, the values and shape of the axial velocity variation curves, as well as the range of radial velocity values. It is also shown that, at a high enough We, effective differentiation between FB and FF atomization regimes became harder and rather limited to the visual confirmation of the presence of a bubble in the liquid tube.

Molecular Dynamics Simulation of the Leidenfrost Effect

Results of the molecular dynamics simulation of the contact between an argon droplet and an overheated copper surface (with the temperature exceeding critical for argon) are presented. The direct contact of argon (supercritical fluid) and the overheated surface is observed in the numerical experiment. Dynamics of the droplet size change is described by a simple equation.

Droplet Evaporation Dynamics of Low Surface Tension Fluids Using the Steady Method.

Droplet evaporation governs many heat- and mass-transfer processes germane in nature and industry. In the past 3 centuries, transient techniques have been developed to characterize the evaporation of sessile droplets. These methods have difficulty in reconciling transient effects induced by the droplet shape and size changes during evaporation. Furthermore, investigation of evaporation of microdroplets residing on wetting substrates, or fluids having low surface tensions (<30 mN/m), is difficult to perform using established approaches. Here, we use the steady method to study the microdroplet evaporation dynamics of low surface tension liquids. We start by employing the steady method to benchmark with water droplets having base radii (20 ≤ Rb ≤ 260 μm), apparent advancing contact angle (45° ≤ θa,app ≤ 162°), surface temperature (30 < Ts < 60 °C), and relative humidity (40% < ϕ < 60%). Following validation, evaporation of ethanol (≈22 mN/m), hexane (≈18 mN/m), and dodecane (≈25 mN/m) were studied for 90 ≤ Rb ≤ 400 μm and 10 < Ts < 25 °C. We elucidate the mechanisms governing the observed behavior using heat and mass transport scaling analysis during evaporation, demonstrating our steady technique to be particularly advantageous for microdroplets, where Marangoni and buoyant forces are negligible. Our work not only elucidates the droplet evaporation mechanisms of low surface tension liquids but also demonstrates the steady method as a means to study phase change processes.

Electropermanent magnet-driven droplet size modulation for two-phase ferromicrofluidics

A new ferrofluidic droplet generator is demonstrated using an electropermanent magnet to change the viscosity of the ferrofluid oil phase in a flow-focusing junction, which enables control of the aqueous droplet size. Electropermanent magnets are capable of fast switching (< 100 $$\upmu$$ s) and have magnetic field strengths comparable to those of permanent magnets. When switched on, the magnetoviscous effect increases the viscosity of the ferrofluid, thus increasing the channel’s fluidic resistance, slowing the flow rate of the oil-based phase and changing the droplet diameter. We have demonstrated on-demand droplet size modulation as large as 44% at speeds fast enough to modulate the size of a single droplet in a stream. Due to compliance in the supply tubing and Polydimethylsiloxane (PDMS) microfluidic channels, the change in droplet size relaxes with a time scale of seconds. An application of droplet size modulation was demonstrated by integrating a passive size-based magnetic droplet sorting stage.

Particle-stabilized oil-in-water emulsions as a platform for topical lipophilic drug delivery

Low-environmental-impact emulsion systems for transdermal drug delivery in topical treatment have gained increasing interest. However, low stability and adverse systemic side effects severely decrease their efficiency. This study proposed a stable oil-in-water (O/W) emulsion loaded with bifonazole (BFZ) as a lipophilic drug stabilized by poly(2-isopropoxy-2-oxo-1,3,2-dioxaphospholane)-modified cellulose nanocrystals (CNC-g-PIPP) as vehicles for topical delivery of lipophilic drugs. We fully characterized stability, BFZ-loaded particle-stabilized emulsions (PEs) for morphology, droplet size, and its distribution. In addition, we evaluated the in vitro drug-releasing capacity and in vitro skin permeation of BFZ in a porcine skin animal model using a side-bi-side® diffusion cell. An O/W BFZ-loaded emulsion stabilized with CNC-g-PIPP particles (BFZ-loaded CP-PE) with a small mean droplet size of 2.54 ± 1.39 μm was developed and was stable for > = 15 days without a significant change in droplet size. The BFZ-loading efficiency in PEs was 83.1 %. BFZ was slowly released over an extended period, and the releasing ratio from BFZ-loaded CP-PE was only 17 % after 48 h. The BFZ-loaded CP-PE showed a ∼4.4-fold increase in BFZ permeation and penetration compared to a conventional surfactant-stabilized emulsion and BFZ control solution. Fluorescence-labeling studies showed that BFZ-loaded CP-PE could well penetrate skin layers from the stratum corneum (SC) to the dermis. In addition, histopathology studies of porcine skin treated with the PE formulation showed an intact SC with unaltered adjacent structures and no observed signs of inflammation. Therefore, the proposed CP-PE shows great potential as a transdermal drug carrier for enhancing lipophilic drug permeation.

A Study on Aerosol Spray Characteristics of Different Size Atomizers

In this study, the variations of spray characteristics are tested with air-assisted siphon type different size liquid atomizers. The spray characteristics are analyzed considering three atomizers having the same inlet diameter, with different constricted areas and exit diameters for the flow rates of 42, 57, and 71l pm. Three different mixtures of Oleic Acid with Ethanol, and three different mixtures of Di-Octyl Phthalate (DOP) with Ethanol are employed as working fluids along with the six different suction heights. Experimental outcomes show that, for the same flow rates, solution, and suction height, the droplet size changes by varying the diameter of the constricted area and exit area. The change of any area in atomizer changes the level of turbulence in flow that results in the variation of droplet size and its distribution. The increasing flow rate also assists in increasing the droplet size. Since the droplet size distribution decreases with the increasing viscosity, the use of DOP and Ethanol mixture increases the droplet size as it is more viscous than the Oleic Acid and Ethanol mixture. It is also noticed that at a constant airflow rate, Number Median Aerodynamic Diameter (NMAD), and liquid consumption rate are inversely proportional, whereas the Geometrical Standard Deviation (GSD) and Mass Median Aerodynamic Diameter (MMAD) is directly proportional to the suction height.

Theoretical analysis on droplet vaporization at elevated temperatures and pressures

Droplet vaporization has a great impact on combustion of liquid fuels and might greatly affects the engine performance. Physical understanding and theoretical interpretation of the droplet vaporization behavior are decisive to constitute appropriate models for spray combustion. In this work, we proposed a fully transient formulation for the droplet vaporization at wide ranges of temperature and pressure. The governing equations are solved analytically by means of suitable coordinate transformations. The droplet surface temperature and mass fraction of fuel vapor are determined by the matching conditions at the liquid-gas interface. Accordingly, a theoretical model, characterizing the time change of droplet size during its vaporization, is proposed in terms of the unsteadiness factor and droplet vaporization lifetime. The theoretical model successfully reveals the conventional recognition of droplet vaporization characteristics, and its predicted droplet size history agrees well with experimental results reported in the literature. Besides, based on the present theoretical analysis, the experimentally observed dual effect of pressure upon droplet vaporization is analyzed with help of an explicit formula for enthalpy of vaporization indicating its temperature-dependence.

Formulation and Preparation of Water-In-Oil-In-Water Emulsions Loaded with a Phenolic-Rich Inner Aqueous Phase by Application of High Energy Emulsification Methods.

Currently, industry is requesting proven techniques that allow the use of encapsulated polyphenols, rather than free molecules, to improve their stability and bioavailability. Response surface methodology (RSM) was applied in this work to determine the optimal composition and operating conditions for preparation of water-in-oil-in-water (W/O/W) emulsions loaded with phenolic rich inner aqueous phase from olive mill wastewater. A rotor-stator mixer, an ultrasonic homogenizer and a microfluidizer processor were tested in this study as high-energy emulsification methods. Optimum results were obtained by means of microfluidizer with 148 MPa and seven cycles input levels yielding droplets of 105.3 ± 3.2 nm in average size and 0.233 ± 0.020 of polydispersity index. ζ-potential, chemical and physical stability of the optimal W/O/W emulsion were also evaluated after storage. No droplet size growth or changes in stability and ζ-potential were observed. Furthermore, a satisfactory level of phenolics retention (68.6%) and antioxidant activity (89.5%) after 35 days of storage at room temperature makes it suitable for application in the food industry.

Radiation-Induced Condensational Growth and Cooling of Cloud-Sized Mist Droplets

AbstractA laboratory-experimental and theoretical-modeling investigation was conducted of isobaric, radiative cooling of cloud-like water mists to a remote heat sink, similar to what can happen at the tops of clouds. For mist initially at 20°C cooled by a radiative sink at −20°C, the mean (D43) mist droplet diameter grew from 5.5 to 8.4 μm and the mist temperature decreased from 20° to 3°C in just 80 s. Modeling showed that conventional assumptions were able to predict the measured temperature decrease reasonably well but not droplet size changes, suggesting that bulk radiative cooling was being reasonably well modeled but not detailed, droplet-size-dependent behavior. In a theoretical analysis, Lewis-number near unity was exploited to obtain an analytic expression for quasi-steady supersaturation that agrees with what Davies reported in 1985 but is simpler and is a function of only droplet size distribution, surface tension, and solute parameters and not radiative transfer. A simpler expression for the corresponding time constant was also found that is a function of only the binary diffusion coefficient and D31 moment of the droplet diameter distribution. The time constant was found to be in milliseconds and not seconds. Simply modifying quasi-steady supersaturation (i.e., applying droplet cooling effects uniformly to all droplet sizes) was shown not to be an acceptable substitute for including droplet-specific radiation terms in the droplet growth equation. These results confirm that radiative cooling at cloud top can have a significant effect on droplet size evolution and temperature change and provide data and analytical simplifications for use in further needed investigations of radiation modeling assumptions and parameterizations.

Influence of the Emulsifier System on Breakup and Coalescence of Oil Droplets during Atomization of Oil-In-Water Emulsions

Spray drying of whey protein-based emulsions is a common task in food engineering. Lipophilic, low molecular weight emulsifiers including lecithin, citrem, and mono- and diglycerides, are commonly added to the formulations, as they are expected to improve the processing and shelf life stability of the products. During the atomization step of spray drying, the emulsions are subjected to high stresses, which can lead to breakup and subsequent coalescence of the oil droplets. The extent of these phenomena is expected to be greatly influenced by the emulsifiers in the system. The focus of this study was therefore set on the changes in the oil droplet size of whey protein-based emulsions during atomization, as affected by the addition of low molecular weight emulsifiers. Atomization experiments were performed with emulsions stabilized either with whey protein isolate (WPI), or with combinations of WPI and lecithin, WPI and citrem, and WPI and mono- and diglycerides. The addition of lecithin promoted oil droplet breakup during atomization and improved droplet stabilization against coalescence. The addition of citrem and of mono- and diglycerides did not affect oil droplet breakup, but greatly promoted coalescence of the oil droplets. In order to elucidate the underlying mechanisms, measurements of interfacial tensions and coalescence times in single droplets experiments were performed and correlated to the atomization experiments. The results on oil droplet breakup were in good accordance with the observed differences in the interfacial tension measurements. The results on oil droplet coalescence correlated only to a limited extent with the results of coalescence times of single droplet experiments.

CRISPR/Cas9 knockout plin1 enhances lipolysis in 3T3-L1 adipocytes

We used CRISPR/Cas9 to delete plin1 of 3T3-L1 preadipocyte, to observe its effect on lipolysis in adipocytes and to explore regulatory pathways. We cultured 3T3-L1 preadipocytes, and the plin1 knockout vectors were transfected by electroporation. Puromycin culture was used to screen successfully transfected adipocytes, and survival rates were observed after transfection. The optimized "cocktail" method was used to differentiate 3T3-L1 preadipocytes. The glycerol and triglyceride contents were determined by enzymatic methods. The changes in lipid droplet form and size were observed by Oil red O staining. The protein expression of PLIN1, PPARγ, Fsp27, and lipases was measured by Western blotting. RT-PCR was used to measure the expression of PLIN1 and lipases mRNA. After the adipocytes in the control group were induced to differentiate, the quantity of tiny lipid droplets was decreased, and the quantity of unilocular lipid droplets was increased and arranged in a circle around the nucleus. Compared with the control group, the volume of unilocular lipid droplets decreased, and the quantity of tiny lipid droplets increased after induction of adipocytes in the knockout group. The expression of PLIN1 mRNA and protein in the adipocytes was significantly inhibited (P<0.05); glycerol levels increased significantly (0.098 4±0.007 6), TG levels decreased significantly (0.031 0±0.005 3); mRNA and protein expression of HSL and ATGL increased (P<0.05); PPARγ and Fsp27 expression unchanged in adipocytes. The above results indicate that the knockout of plin1 enhances the lipolysis of 3T3-L1 adipocytes by exposing lipids in lipid droplets and up-regulating lipases effects.

Zeta potential changing nanoemulsions based on phosphate moiety cleavage of a PEGylated surfactant

The aim of this study was to develop and evaluate a zeta potential changing nanoemulsion (NE) containing polyoxyethylene (9) nonylphenol monophosphate ester (PNPP) as emulsifier.2% (v/v) of PNPP and 0.18% (5 μM) of cetyltrimethylammonium bromide (CTAB) were incorporated into the lipophilic NE preconcentrate (PEG-40 castor oil, glyceryl tricaprylate/tricaprate, propylene glycol dicaprylocaprate, propylene glycol monolaurate, highly purified diethylene glycol monoethyl ether; 20/20/10/30/20, v/v). After diluting the lipophilic preconcentrate, resulting NE was analyzed regarding droplet size, polydispersity index (PDI), storage stability and zeta potential change after incubation with intestinal alkaline phosphatase (IAP). Phosphate release due to cleavage by IAP was quantified by malachite green assay and toxicity as well as cellular uptake behavior on Caco-2 cells was determined. The NE containing PNPP and CTAB displayed a droplet size of 113 nm and a PDI of 0.20. It was stable over 4 h. A zeta potential change from −33.7 to +8.2 mV was observed due to cleavage of phosphate groups by isolated IAP. PNPP could be identified as non-toxic up to concentrations of 0.01% (v/v). Furthermore, an enhanced cellular uptake of the NE changing its zeta potential on Caco-2 cells was determined. Therefore, PNPP seems to be a promising tool for the development of zeta potential changing NE.